ME2254-STRENGTH OF MATERIALS Questions Bank 2014

Anna University, Chennai

QUESTION BANK

ME2254-STRENGTH OF MATERIALS DEPARTMENT OF MECHANICAL ENGINEERING

SRINIVASAN ENGINEERING COLLEGE- PERAMBALUR

UNIT- I

STRESS STRAIN DEFORMATION OF SOLIDS

1. A rod of 150 cm long and diameter 2.0cm is subjected to an axial

pull of 20 KN. If the modulus of elasticity of the material of the rod is 2x

105 N/mm2 Determine 1. Stress 2. Strain 3. the elongation of the rod

(16)

2. The extension in a rectangular steel bar of length 400mm and thickness

10mm is found to 0.21mm .The bar tapers uniformly in width from

100mm to 50mm. If E for the bar is 2x 105 N/mm2 ,Determine the axial

load on the bar (16)

3. Find the young’s modulus of a rod of diameter 30mm and of length

300mm which is subjected to a tensile load of 60 KN and the extension of the rod is equal to 0.4 mm

(16)

4. The extension in a rectangular steel bar of length 400mm and thickness

3mm is found be 0.21mm .The bar tapers uniformly in width from

20mm to 60mm E for the bar is 2x 105 N/mm2 Determine the axial load on the bar. (16)

5. The ultimate stress for a hollow steel column which carries an axial load of 2Mn is 500 N/mm2 .If the external diameter of the column is

250mm, determine the internal diameter .Take the factor of safety as 4.0

(16)

6. A steel rod of 20mm diameter passes through a brass tube of 30 mm inside diameter and 40mm outside diameter . Two nuts one on each side are tightened until a stress of 10 n/mm2 is induced in the rod. F1.2xind the stresses in the rod and the tube if the assembly is heated through 600C. Take

Es = 2x105N/mm2, αs =1.2x10-5/0C

Eb = 0.8x105N/mm2, αb =1.2x10-5/0C

7. A solid steel rod of 5 m length and 10 mm diameter is subjected to an axial load of 5 kN . Find the stress induced in the rod if the load is applied (a) gradually,(b) suddenly and (c) impact after falling from a height of 150 mm. Also find the strain energy stored in the rod under given conditions. Take E= 200 kN/mm2.

8. A rod of diameter 10 mm and length 1.5 mm hangs vertically from the ceiling of a roof. A collar is attached at its lower end on which a load of 250 N falls from a height of 200 mm. Find the strain energy absorbed and the instantaneous deflection of the rod. Take E = 200 kN/ mm2.

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UNIT II

BEAMS – LOADS AND STRESSES

1. Three planks of each 50 x200 mm timber are built up to a symmetrical I section for a beam. The maximum shear force over the beam is 4KN. Propose an alternate rectangular section of the same material so that the maximum shear stress developed is same in both sections. Assume then width of the section to be 2/3 of the depth. (16)

2. A beam of uniform section 10 m long carries a udl of KN/m for the entire length and a concentrated load of 10 KN at right end. The beam is freely supported at the left end. Find the position of the second support so that the maximum bending moment in the beam is as minimum as possible. Also compute the maximum bending moment (16)

3. A beam of size 150 mm wide, 250 mm deep carries a uniformly distributed load of w kN/m over entire span of 4 m. A concentrated load 1 kN is acting at a distance of 1.2 m from the left support. If the bending stress at a section 1.8 m from the left support is not to exceed 3.25

N/mm2 find the load w. (16)

4. A cantilever of 2m length carries a point load of 20 KN at 0.8 m from the fixed end and another point of 5 KN at the free end. In addition, a u.d.l. of 15 KN/m is spread over the entire length of the cantilever. Draw the S.F.D, and B.M.D. (16)

5. A Simply supported beam of effective span 6 m carries three point

loads of 30 KN, 25 KN and 40 KN at 1m, 3m and 4.5m respectively from the left support. Draw the SFD and BMD. Indicating values at salient points.

(16

)

6. A Simply supported beam of length 6 metres carries a udl of

20KN/m throughout its length and a point of 30 KN at 2 metres from the right support. Draw the shear force and bending moment diagram.Also find the position and magnitude of maximum Bending moment.

(16)

7. A Simply supported beam 6 metre span carries udl of 20 KN/m for left half of span and two point loads of 25 KN end 35 KN at 4 m and 5 m from left support. Find maximum SF and BM and their location drawing SF and BM diagrams.

(

16)

8. A horizontal beam of 10 m long is carrying a usdl load of 1 kN/m. The beam is supported on two supports 6 m apart. Find thee position of the supports so that the bending moment on the beam is as small as possible. Also draw the shear force and bending moment diagram.

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UNIT- III TORSION

1. Determine the diameter of a solid shaft which will transmit 300 KN at 250 rpm. The maximum shear stress should not exceed 30 N/mm2 and twist should not be more than 10 in a shaft length 2m.

Take modulus of rigidity = 1x 105N/mm2. (16)

2. The stiffness of the closed coil helical spring at mean diameter 20 cm is made of 3 cm diameter rod and has 16 turns. A weight of 3 KN is dropped on this spring. Find the height by which the weight should be dropped before striking the spring so that the spring may be compressed

by 18 cm. Take C= 8x104 N/mm2. (16)

3. It is required to design a closed coiled helical spring which shall deflect 1mm under an axial load of 100 N at a shear stress of 90 Mpa. The spring is to be made of round wire having shear modulus of 0.8 x

105 Mpa. The mean diameter of the coil is 10 times that of the coil wire.

Find the diameter and length of the wire. (16)

4. A steel shaft ABCD having a total length of 2400 mm is contributed by three different sections as follows. The portion AB is hollow having outside and inside diameters 80 mm and 50 mm respectively, BC is solid and 80 mm diameter. CD is also solid and 70 mm diameter. If the angle of twist is same for each section, determine the length of each portion and the total angle of twist. Maximum permissible shear stress is 50 Mpa and shear modulus

0.82 x 105 MPa (16)

5. The stiffness of close coiled helical spring is 1.5 N/mm of compression under a maximum load of 60 N. The maximum shear stress in the wire of the spring is 125 N/mm2. The solid length of the spring (when the coils are touching) is 50 mm. Find the diameter of coil, diameter of wire and number of coils.

C = 4.5 (16)

6. A solid shaft of length 3.5 m and diameter 25 mm rotates at a frequency of

40 Hz. Find the maximum power to be transmitted by the shaft, assuming the maximum shear stress in the shaft is limited to 40 Mpa and angle of twist does not exceed 60. Take G = 80 Gpa

7. Find the maximum torque that can be applied safely to a shaft of diameter

300 mm. The permissible angle of twist is 1.50 in a length of 7.5 m and a maximum shear is limited to 42 Mpa. Take G = 84.4 Gpa.

8. A solid steel shaft has to transmit 100 kW at 160 r.p.m. Taking allowable shear stress as 70 Mpa, find the suitable diameter of the shaft. The maximum torque transmitted in each revolution exceeds the mean by 20%.

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UNIT-IV BEAMDEFLECTION

1. A simply supported beam of 10 m span carries a uniformly distributed load of 1 kN/m over the entire span. Using Castigliano’s theorem, find the slope at the ends. EI = 30,000 kN/m2.

(16)

2. A 2m long cantilever made of steel tube of section 150 mm external diameter and10mm thick is loaded. If E=200 GN/m2 calculate (1) The value of W so that the maximum bending stress is 150 MN/m (2) The maximum deflection for the loading (16)

3. A beam of length of 10 m is simply supported at its ends and carries two point loads of100 kN and 60 kN at a distance of 2 m and 5 m respectively from the left support. Calculate the deflections under each load. Find also the maximum deflection. Take I = 18 X 108 mm4 and E =

2 X 105. (16)

4. i) A column of solid circular section, 12 cm diameter, 3.6 m long is hinged at both ends. Rankine’s constant is 1 / 1600 and σc = 54 KN/cm2. Find the buckling load. ii) If another column of the same length, end conditions and rankine constant but of 12 cm X 12 cm square cross- section, and different material, has the same buckling load, find the value of σc of its material. (16)

5. A beam of length of 6 m is simply supported at its ends. It carries a uniformly distributed load of 10 KN/m as shown in figure. Determine the deflection of the beam at its mid-point and also the position and the maximum deflection. Take EI=4.5 X 108 N/mm2. (16)

6. An overhanging beam ABC is loaded as shown is figure. Determine the deflection of the beam at point C. Take I = 5 X 108 mm4 and E = 2 X

105 N/mm2. (16)

7. A cantilever of length 2 m carries a uniformly distributed load of 2.5

KN/m run for a length of 1.25 m from the fixed end and a point load of 1

KN at the free end. Find the deflection at the free end if the section is rectangular 12 cm wide and 24 cm deep and E=1 X 104 N/mm2

(16)

8. A cantilever of length 2m carries a uniformly distributed load 2 KN/m over a length of 1m from the free end, and a point load of 1 KN at the free end. Find the slope and deflection at the free end if E = 2.1 X 105 N/mm2 and I = 6.667 X 107 mm4 . (16)

9. Determine the section of a hollow C.I. cylindrical column 5 m long with ends firmly built in. The column has to carry an axial compressive load of 588.6 KN. The internal diameter of the column is 0.75 times the

external diameter. Use Rankine’s constants. a = 1 / 1600, σc = 57.58

KN/cm2 and F.O.S = 6. (16)

(10). A cantilever beam of length L carries a udl of intensity w per unit length over its entire span and a point load P at its free end. Find the maximum deflection of the beam using castingliano’s theorem.

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UNIT-V

ANALYSIS OF STRESSES IN TWO DIMENSIONS

1. A Thin cylindrical shell 3 m long has 1m internal diameter and 15 mm metal thickness. Calculate the circumferential and longitudinal stresses induced and also the change in the dimensions of the shell, if it is subjected to an internal pressure of1.5 N/mm2 Take E = 2x105

N/mm2 and poison’s ratio =0.3. Also calculate change in volume. (16)

2. A closed cylindrical vessel made of steel plates 4 mm thick with plane ends, carries fluid under pressure of 3 N/mm2 The diameter of the cylinder is 25cm and length is 75 cm. Calculate the longitudinal and hoop stresses in the cylinder wall and determine the change in diameter, length and Volume of the cylinder. Take E =2.1x105 N/mm2 and 1/m =

0.286.

(16)

3. A rectangular block of material is subjected to a tensile stress of 110

N/mm2 on one plane and a tensile stress of 47 N/mm2 on the plane at right angle to the former plane and a tensile stress of 47 N/mm2 on the

plane at right angle to the former. Each of the above stress is

accompanied by a shear stress of 63 N/mm2 Find (i) The direction and

magnitude of each of the principal stress (ii) Magnitude of greatest shear stress (16)

4. At a point in a strained material, the principal stresses are100 N/mm2 (T) and 40 N/mm2 (C). Determine the resultant stress in magnitude and

direction in a plane inclined at 600 to the axis of major principal stress. What is the maximum intensity of shear stress in the material at the point? (16)

5. A rectangular block of material is subjected to a tensile stress of 210

N/mm2 on one plane and a tensile stress of 28 N/mm2 on the plane at right angle to the former plane and a tensile stress of 28 N/mm2 on the

plane at right angle to the former. Each of the above stress is

accompanied by a shear stress of 53 N/mm2 Find (i) The direction and

magnitude of each of the principal stress (ii) Magnitude of greatest shear stress (16)

6 .A closed cylindrical vessel made of steel plates 5 mm thick with plane ends, carries fluid under pressure of 6 N/mm2 The diameter of the cylinder is 35cm and length is 85 cm. Calculate the longitudinal and hoop stresses in the cylinder wall and determine the change in diameter, length and Volume of the cylinder. Take E =2.1x105 N/mm2 and 1/m =

0.286.

(16)

7. At a point in a strained material, the principal stresses are 200 N/mm2 (T) and 60 N/mm2 (C) Determine the direction and magnitude in a plane inclined at 600 to the axis of major principal stress. What is the maximum intensity of shear stress in the material at the point

(16)

8. At a point in a strained material, the principal stresses are 100 N/mm2 (T) and 40 N/mm2 (C) Determine the direction and magnitude in a plane inclined at 600 to the axis of major principal stress. What is the maximum intensity of shear stress in the material at the point

(16)

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ME2254-STRENGTH OF MATERIALS Two Marks Questions With Answers 2014

Anna University, Chennai

2 MARK QUESTIONS WITH ANSWERS

ME2254-STRENGTH OF MATERIALS DEPARTMENT OF MECHANICAL ENGINEERING SRINIVASAN ENGINEERING COLLEGE-PERAMBALUR

UNIT- I

STRESS STRAIN DEFORMATION OF SOLIDS

1. Define stress.

When an external force acts on a body, it undergoes deformation. At the

same

time the body resists deformation. The magnitude of the resisting force

is numerically equal to the applied force. This internal resisting force per unit area is called stress. Stress σ= Force/Area, P/A Unit N/mm2

2. Define strain

When a body is subjected to an external force, there is some change of

dimension in the body. Numerically the strain is equal to the ratio of change in length to the original length of the body

Strain = Change in length/Original length

e = ∂L/L

3. State Hooke’s law.

It states that when a material is loaded, within its elastic limit, the stress

is directly proportional to the strain.

E=σ/e

E= Stress / Strain, unit is N/mm2

Where,

E - Young‟s modulus

σ - Stress e - Strain

4. Define shear stress and shear strain.

The two equal and opposite force act tangentially on any cross sectional

plane of the body tending to slide one part of the body over the other part. The stress induced is called shear stress and the corresponding

strain is known as shear strain.

5. Define Poisson’s ratio.

When a body is stressed, within its elastic limit, the ratio of lateral strain

to the longitudinal strain is constant for a given material. Poisson‟ ratio (μ or 1/m) = Lateral strain /Longitudinal strain

6. State the relationship between Young’s Modulus and Modulus of

Rigidity.

E = 2G (1+1/m)

Where, E – Young’s Modulus, K - Bulk Modulus, 1/m – Poisson’s ratio

7. Define strain energy

Whenever a body is strained, some amount of energy is absorbed in the

body. The energy which is absorbed in the body due to straining effect is known as strain energy.

8. Give the relationship between Bulk Modulus and Young’s

Modulus.

E = 3K (1-2ν)

Where, E – Young’s Modulus, K - Bulk Modulus, ν – Poisson’s ratio

9. What is compound bar?

A composite bar composed of two or more different materials joined

together

such that system is elongated or compressed in a single unit.

10. Define- elastic limit

Some external force is acting on the body, the body tends to

deformation. If the

force is released from the body its regain to the original position. This is called elastic limit

11. Define – Young’s modulus

The ratio of stress and strain is constant with in the elastic limit.

E = Stress/Strain

12. Define Bulk-modulus

The ratio of direct stress to volumetric strain.

K = Direct stress/Volumetric strain

13. Define- lateral strain

The strain right angle to the direction of the applied load is called lateral

strain.

13. Define- longitudinal strain

When a body is subjected to axial load P, The length of the body is

increased. The axial deformation of the length of the body is called longitudinal strain.

14. What is principle of super position?

The resultant deformation of the body is equal to the algebraic sum of

the deformation of the individual section. Such principle is called as principle of super position

15. Define- Rigidity modulus

The shear stress is directly proportional to shear strain.

N = Shear stress/Shear strain

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UNIT II

BEAMS - LOADS AND STRESSES

1. Define beam?

BEAM is a structural member which is supported along the length and

subjected To external loads acting transversely (i.e) perpendicular to the center line of the beam.

2. What is mean by transverse loading on beam?

If a load is acting on the beam which perpendicular to the central line of

it then it is called transverse loading.

3. What is Cantilever beam?

A beam one end free and the other end is fixed is called cantilever beam.

4. What is simply supported beam?

A beam supported or resting free on the support at its both ends.

5. What is mean by over hanging beam?

If one or both of the end portions are extended beyond the support then

it is called over hanging beam.

6. What is mean by concentrated loads?

A load which is acting at a point is called point load.

7. What is uniformly distributed load.

If a load which is spread over a beam in such a manner that rate of

loading „w‟ is uniform through out the length then it is called as udl.

8. Define point of contra flexure? In which beam it occurs?

Point at which BM changes to zero is point of contra flexure. It occurs in

overhanging beam.

9. What is mean by positive or sagging BM?

BM is said to positive if moment on left side of beam is clockwise or

right side of the beam is counter clockwise.

10. What is mean by negative or hogging BM?

BM is said to negative if moment on left side of beam is

counterclockwise or right side of the beam is clockwise.

11. Define shear force and bending moment?

SF at any cross section is defined as algebraic sum of all the forces

acting either side of beam. BM at any cross section is defined as algebraic sum of the moments of all the forces which are placed either

side from that point.

12. When will bending moment is maximum?

BM will be maximum when shear force change its sign.

13. What is maximum bending moment in a simply supported beam

of span ‘L’ subjected to UDL of ‘w’ over entire span?

Max BM =wL2 /8

14. In a simply supported beam how will you locate point of maximum bending moment?

The bending moment is max. When SF is zero. Write SF equation at that

point and equating to zero we can find out the distances „x‟ from one end .then find maximum bending moment at that point by taking all

moment on right or left hand side of beam.

15. What is shear force?

The algebraic sum of the vertical forces at any section of the beam to the

left or right of the section is called shear force.

16. What is shear force and bending moment diagram?

It shows the variation of the shear force and bending moment along the

length of the beam.

17. What are the types of beams?

1. Cantilever beam

2. Simply supported beam

3. Fixed beam

4. Continuous beam

5. over hanging beam

18. What are the types of loads?

1. Concentrated load or point load

2. Uniform distributed load

3. Uniform varying load

19. In which point the bending moment is maximum?

When the shear force change of sign or the shear force is zero

20. Write the assumption in the theory of simple bending?

1. The material of the beam is homogeneous and isotropic.

2. The beam material is stressed within the elastic limit and thus obey

Hooke’s law.

3. The transverse section which was plane before bending remains plains after bending also.

4. Each layer of the beam is free to expand or contract independently

about the layer, above or below.

5. The value of E is the same in both compression and tension.

21. Write the theory of simple bending equation?

M/ I = F/Y = E/R

M - Maximum bending moment

I - Moment of inertia

F - Maximum stress induced

Y - Distance from the neutral axis

E – Young’s modulus R – Radius of curvature

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UNIT – III TORSION

1. Define Torsion

When a pair of forces of equal magnitude but opposite directions acting

on body, it tends to twist the body. It is known as twisting moment or torsion moment or simply as torque.

Torque is equal to the product of the force applied and the distance

between the point of application of the force and the axis of the shaft.

2. What are the assumptions made in Torsion equation

The material of the shaft is homogeneous, perfectly elastic and obeys

Hooke’s Law.

Twist is uniform along the length of the shaft

The stress does not exceed the limit of proportionality

The shaft circular in section remains circular after loading

Strain and deformations are small.

3. Define polar modulus

It is the ratio between polar moment of inertia and radius of the shaft. =

J/R polar moment of inertia = J Radius R

4. Write the polar modulus for solid shaft and circular shaft.

polar moment of inertia = J Radius R

J = D4 / 32

5. Why hollow circular shafts are preferred when compared to solid circular shafts?

The torque transmitted by the hollow shaft is greater than the solid shaft.

For same material, length and given torque, the weight of the hollow shaft will be less compared to solid shaft.

6. Write torsion equation

T/J=Cθ/L=q/R

T-Torque, θ-angle of twist in radians

J- Polar moment of inertia

C-Modulus of rigidity

L- Length

q- Shear stress R- Radius

7. Write down the expression for power transmitted by a shaft

P=2NT/60

N-speed in rpm

T-torque

8. Write down the expression for torque transmitted by hollow shaft

T= (/16) (D4-d4)/d4

T-torque

q- Shear stress

D-outer diameter d- Inner diameter

9. Write down the equation for maximum shear stress of a solid circular section

in diameter ‘D’ when subjected to torque ‘T’ in a solid shaft.

T=/16 D3 Where T-torque, q-Shear stress and D-diameter

10. Define tensional rigidity

Product of rigidity modulus and polar moment of inertia is called

torsional rigidity

11. What is composite shaft?

Some times a shaft is made up of composite section i.e. one type of shaft

is sleeved over other types of shaft. At the time of sleeving, the two shafts are joined together, that the composite shaft behaves like a single shaft.

12. What is a spring?

A spring is an elastic member, which deflects, or distorts under the

action of load and regains its original shape after the load is removed.

13. State any two functions of springs.

1. To measure forces in spring balance, meters and engine indicators.

2. To store energy.

14. What are the various types of springs?

i. Helical springs

ii. Spiral springs iii. Leaf springs

iv. Disc spring or Belleville springs

15. Classify the helical springs.

1. Close – coiled or tension helical spring.

2. Open –coiled or compression helical spring.

16. What is spring index (C)?

The ratio of mean or pitch diameter to the diameter of wire for the spring

is called the spring index.

17. What is solid length?

The length of a spring under the maximum compression is called its

solid length. It is the product of total number of coils and the diameter of wire.

Ls = nt x d Where, nt = total number of coils.

18. Define spring rate (stiffness).

The spring stiffness or spring constant is defined as the load required per

unit deflection of the spring. K= W/y

Where W –load and y – Deflection

19. Define pitch.

Pitch of the spring is defined as the axial distance between the adjacent

coils in uncompressed state. Mathematically

Pitch=free length/ n-1

20. Define helical springs.

The helical springs are made up of a wire coiled in the form of a helix

and are primarily intended for compressive or tensile load.

21. What are the differences between closed coil & open coil helical

springs?

The spring wires are coiled very closely, each turn is nearly at right

angles to the axis of helix The wires are coiled such that there is a gap between the two consecutive turns. Helix angle is less than 10o Helix angle is large (>10o)

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UNIT-IV BEAMDEFLECTION

1. What are the methods for finding out the slope and deflection at a section?

The important methods used for finding out the slope and deflection at a

section

in a loaded beam are

1. Double integration method

2. Moment area method

3. Macaulay‟s method

The first two methods are suitable for a single load, where as the last one is suitable for several loads.

2. Why moment area method is more useful, when compared with double integration?

Moment area method is more useful, as compared with double

integration method because many problems which do not have a simple mathematical solution can be simplified by the ending moment area

method.

3. Explain the Theorem for conjugate beam method?

Theorem I :“The slope at any section of a loaded beam, relative to the

original

axis of the beam is equal to the shear in the conjugate beam at the

corresponding section”

Theorem II: “The deflection at any given section of a loaded beam,

relative to the

original position is equal to the Bending moment at the corresponding

section of the conjugate beam”

4. Define method of Singularity functions?

In Macaulay’s method a single equation is formed for all loading on a beam, the equation is constructed in such away that the constant of

Integration apply to all portions of the beam. This method is also called

method of singularity functions.

5. What are the points to be worth for conjugate beam method?

1. This method can be directly used for simply supported Beam

2. In this method for cantilevers and fixed beams, artificial constraints need to be supplied to the conjugate beam so that it is supported in a manner

consistent with the constraints of the real beam.

6. What are the different sections in which the shear stress distribution is to be obtained?

Rectangular section

Circular section

I- section

T- section

Miscellaneous section

7. What do you mean by shear stress in beams?

The stress produced in a beam, which is subjected to shear forces is

known as stresses.

8. What is the formula to find a shear stress at a fiber in a section of a beam?

The shear stress at a fiber in a section of a beam is given by

F = shear force acting at a section

A = Area of the section above the fiber

Y = Distance of C G of the Area A from Neutral axis

I = Moment of Inertia of whole section about N A

b = Actual width at the fiber

9. What is the shear stress distribution rectangular section?

The shear stress distribution rectangular section is parabolic and is given by

q = F/2I [d2 /4 – y2]

d = Depth of the beam

y = Distance of the fiber from NA

10. What is the shear stress distribution Circular section?

q = F/3I [R2-y2]

11. State the main assumptions while deriving the general formula for shear sresses.

The material is homogeneous, isotropic and elastic

The modulus of elasticity in tension and compression are same. The shear stress is constant along the beam width

The presence of shear stress does not affect the distribution of bending stress.

12. Define: Shear stress distribution

The variation of shear stress along the depth of the beam is called shear

stress distribution

13. What is the ratio of maximum shear stress to the average shear stress for the

rectangular section?

Qmax is 1.5 times the Qavg.

14. What is the ratio of maximum shear stress to the average shear stress in the case of solid circular section?

Qmax is 4/3 times the Qave.

15. What is the shear stress distribution value of Flange portion of the I-section?

q= f/2I * (D2/4 - y)

D-depth

`y- Distance from neutral axis

16. What is the value of maximum of minimum shear stress in a rectangular cross

section?

`Qmax=3/2 * F/ (bd)

17. What is the shear stress distribution for I-section?

The shear stress distribution I-section is parabolic, but at the junction of

web and flange, the shear stress changes abruptly. It changes from F/8I [D2 –d2] to B/b x F/8I [D2 –d2] where D = over all depth of the section

d = Depth of the web

b = Thickness of web

B = Over all width of the section.

18. How will you obtained shear stress distribution for unsymmetrical section?

The shear stress distribution for Unsymmetrical sections is obtained after

calculating the position of N A.

19 Where the shear stress is max for Triangular section?

In the case of triangular section, the shear stress is not max at N A. The

shear stress is max at a height of h/2

20. Where shear stress distribution diagram draw for composite section?

The shear stress distribution diagram for a composite section, should be

drawn by calculating the shear stress at important points.

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UNIT V

ANALYSIS OF STRESSES IN TWO DIMENSION

1. State principle plane.

The planes, which have no shear stress, are known as principal planes.

These planes carry only normal stresses.

2. Define principle stresses and principle plane.

Principle stress: The magnitude of normal stress, acting on a principal plane is known as principal stresses.

Principle plane: The planes which have no shear stress are known as

principal planes.

3. What is the radius of Mohr’s circle?

Radius of Mohr‟s circle is equal to the maximum shear stress.

4. What is the use of Mohr’s circle?

To find out the normal, resultant stresses and principle stress and their

planes.

5. List the methods to find the stresses in oblique plane?

1. Analytical method

2. Graphical method

6. Define thin cylinder?

If the thickness of the wall of the cylinder vessel is less than 1/15 to 1/20

of its

internal diameter, the cylinder vessel is known as thin cylinder.

7. What are types of stress in a thin cylindrical vessel subjected to internal pressure?

These stresses are tensile and are know as Circumferential stress (or

hoop stress ) and Longitudinal stress.

8. What is mean by Circumferential stress (or hoop stress) and

Longitudinal stress?

The stress acting along the circumference of the cylinder is called

circumferential stress (or hoop stress) whereas the stress acting along the length of the cylinder is known as longitudinal stress.

17. What are the formula for finding circumferential stress and longitudinal stress?

Circumferential stress (f1) is given by as f1 = p x d / 2t x η1 and the

longitudinal stress (f2) is given by f2 = p x d / 2t x ηc

.

18. What are maximum shear stresses at any point in a cylinder? Maximum shear stresses at any point in a cylinder, subjected to internal fluid pressure is given by f1 –f2 / 2 = pd / 8t

19. What are the formula for finding circumferential strain and longitudinal strain?

The circumferential strain (e1) and longitudinal strain (e2) are given by

e1 = pd / 2tE (1- 1/2m), e2 = pd / 2tE (1/2 – 1/m).

20. What are the formula for finding change in diameter, change in length and change volume of a cylindrical shell subjected to internal fluid pressure p?

d = pd2 /2tE (1 – 1/2m),

L = pdL /2tE (1/2 – 1/m),

V = pd /2tE (5/2 – 2/m) x volume,

21. What are the formula for finding principal stresses of a thin cylindrical shell Subjected to internal fluid pressure p and a torque?

Major Principal Stress = f1 + f2 / 2+ {(f1 - f2 /2)2 + fs2}

Minor Principal Stress = f1 + f2 / 2 + {(f1 - f2 /2)2 + fs2}

Maximum shear stress = ½ [Major Principal Stress - Minor Principal

Stress]

Where f1 = Circumferential stress, f2 =Longitudinal stress,

fs =shear stress due to torque.

ME2253 ENGINEERING MATERIALS AND METALLURGY Questions Bank 2014

Anna University, Chennai

PART B UNIT -1

1) Draw the Iron – Carbon Diagram neatly (MAY /JUNE 2006) (NOV/DEC 2006) ( MAY/JUN 2007) ( APR/MAY 2010 ) ( APR/MAY 2011)

2) Using the iron – carbon diagram predict the micro structure at room temperature of the carbon steel that contains 0.4%when cooled in furnace ?(MAY /JUNE 2006)

3) Elements A and B melt at 7000c and 10000c respectively. Draw a typical isomorphous phase diagram between the elements A and B(MAY /JUNE 2006)

4) Elements A and B melt at 7000c and 10000c respectively . They form a euetectic at

35% A at temperature 5000c. Draw the typical phase diagram between A and B (MAY

/JUNE 2006)

5) Estimate the carbon content of carbon steel whose microstructure in the annealed condition shows 75% pearlite and 25% ferrite ? (NOV/DEC 2006)

6) Metal A has melting point of 10000c. Metal B has melting point of 5000c. draw Phase diagram (between the elements of A and B ) for each of the following conditions (NOV/DEC 2006)

i) The two elements exhibit unlimited solid solubity ?

ii) The alloy system shows formation of two terminal solid solutions and eutectic reaction point, at 50% A and at 7000c

iii) The alloy system shows formation of an intermettalic phase with the chemical formula A2B.

7) Two elements A and B have melting points 8000c and 6000c respectively

i) Draw a phase diagram between A and B if they exhibit unlimited solid solubility ii) Draw a Phase digram between A and B if a eutectic reaction occurs at composition 40%B and at temperature 4000c. Assume that the maximum solid solubity in either case is 5% and the room temperature solubity in either case is

1%( MAY/JUN 2007)

8) What will be the microstructure of a 2.5%C steel at room temperature ? ( MAY/JUN

2007)

9) Metals A and B having melting points respectively 2700c. and 3200c are assumed to be completely soluble in the liquid state and completely in soluble in solid state. They form euetectic at 1400c. containing 40%B( NOV/DEC 2007 )

i) Draw these equilibrium diagram and label all lines and areas and

ii) For an alloy containing 30%A give the temperature of initial and final solidification and relative amounts of phase present at 180

10) With the help of the Fe- C equilibrium diagram describe completely the change that takes place during the slow cooling of 0.5% carbon steel from liquid state. ( NOV/DEC

2007 )

11) What are the micro- constituents of iron ? Discuss them briefly ?( APR /MAY 2008)

12) How are solid solutions classified ? Give two examples for each . ( APR /MAY 2008)

13) Draw the Fe- Fe3C equilibrium diagram and discuss the different phases and reactions that takes place in it. ( APR /MAY 2008) ( MAY/ JUN-2009 ) ( APR/MAY 2010 ) ( NOV/DEC-2010 ) ( NOV/DEC-2010 )

14) With the ideal phase diagram, cooling curves and examples, explain the following binary systems. Also name the system: ( MAY/ JUN-2009 )

i) Two components completely soluble in liquid and completely insoluble in the solid state

ii) Two components completely soluble in these liquid and completely soluble in the solid state.

15) Discuss Hume – rothery rules for the formation of solid solutions ( APR/MAY 2010 )( APR/MAY 2010 )

16) Draw a typical isomprphous phase diagram and explain the structural changes of an alloy ( say 50%% A & say 50% B ) .Apply lever rules at some temperature in the alpha +

liquid portion for this alloy.( APR/MAY 2010 )

17) Discuss the composition, properties and application of the following cast iron : ( APR/MAY 2010 )

i) Malleable cast iron ii) Spheroidal cast iron

18) What is the solid solution? Explain the Humerothery rules governing substitutional solid solution. Draw the isomorphous phase diagram ? ( NOV/DEC-2010 )

19) Explain the classification of steels along with applications? ( NOV/DEC-2010 )

20) What are the different types of cast iron ? Draw the micro structure of any four type of cast iron. Give any one applications for each ( APR/MAY 2011)

---

UNIT -2

1) Draw a schematic CCT diagram for a carbon steel containing 0.8% carbon. Using this diagram, Expalin how different cooling curves lead to the

i) Annealing heat treatment (NOV/DEC 2009)(APR/MAY 2010)

ii) Normalising heat treatment ( NOV/DEC 2007)

iii) Hardening heat treatment

iv) Spheroidising (MAY/ JUNE 2006) ( MAY/JUNE 2007) ( NOV/DEC 2007) ( APR/MAY 2011)

2) Explain How jominy end quench test is used for determining the hardenability of steels (MAY/ JUNE 2006) (NOV/ DEC2006) ( MAY/JUNE 2007) ( NOV/DEC 2007) (MAY/JUNE 2009)(NOV/DEC 2009) ( APR/MAY 2011)

3) Explain the steps in case carburising of steels (MAY/ JUNE 2006)

4) Draw the schematic isothermal transformation diagram corresponding to 0.8% carbon steel (NOV/ DEC2006) (MAY/JUNE 2009) ( APR/MAY 2011)

5) Explain the Hardening and tempering process with respect to heat treatment procedure, microstructure and mechanical properties (NOV/ DEC2006)( APR/MAY 2008)

(NOV/DEC 2009) ( APR/MAY 2010) ( APR/MAY 2011)

6) With the help of TTT diagram explain the following heat treatments applied to an euetectoid steel

i) Austempering ii) Martempering

iii) Hardening ( NOV/DEC 2007) (APR/MAY 2008) (NOV/DEC 2009) ( APR/MAY

2010) ( MAY/JUNE 2007)

7) Distinguish between diffusion and thermal surface hardening treatments ( NOV/DEC

2007)

8) EXPLAIN in detail the flame hardening and induction hardening (NOV/DEC 2009)

9) Discuss the different types of annealing process ? ( APR/MAY 2010)

10) WHAT IS CASE HARDENING ? explain the following process :

i) Carburizing

ii) Nitriding (APR/MAY 2010)

11) What is hardenability? Describe a test that is used for determination of hardenability of steel? ( APR/MAY 2010)

12) Give the process details of full annealing treatment for steels( APR/MAY 2010)

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UNIT – 3

1) Write a short notes on compositions and properties of the steels :

i) Austenitic stainless steels ii) High speed steels

iii) Martensitic stainless steels

iv) Maraging steels (MAY/JUNE 2006) ( MAY/JUNE 2007) (APR/MAY 2011)

2) How will you classify brasses based on the composition of zinc ? Explain the properties and applications of the main types of brasses? (MAY/JUNE 2006)

3) Explain the steps involved in precipitation hardening?(MAY/JUNE 2006) ( NOV/DEC

2006) (MAY/JUNE 2007) (NOV/DEC 2007) (MAY/JUNE 2009) ( APR/MAY 2010) (APR/MAY 2011)

4) Discuss the austenitic stainless steels and martensitic stainless steel with respect to composition, properties and application( NOV/DEC 2006) (MAY/JUNE 2007)

5) Discuss the strengthening mechanism, composition and properties of anyone types of maraging steels ( NOV/DEC 2006)

6) What are the alpha brasses and alpha- beta brasses? What are their properties and applications? ( NOV/DEC 2006) (MAY/JUNE 2007)

7) Explain how a malleabilising heat treatment will convert a white cast iron to a malleable cast iron (MAY/JUNE 2007)

8) Ferritic stainless steels- composition, properties, Applications (MAY/JUNE 2007)

9) What are the stainless steels ? what are the main characteristics of stainless steels ? Name different types of stainless steels and their main application ? ( NOV/DEC 2007)( APR/MAY 2010)

10) What are the HSLA steels? How can high strength and toughness be obtained in them ? (NOV/DEC 2007) ( APR/MAY 2010)

11) Describe the properties and applications of the following Cu-Zn Brasses, Naval Brass and Muntz metal (NOV/DEC 2007) ( APR/MAY 2010)

12) Discuss the characteristics of Aluminium and also mention its alloys their properties and uses ? ( APR/MAY 2008)

13) Discuss the influence of each of the following alloying elements on the properties of steel:

i) Molybdeum ii) Chromium iii) Manganeses iv) Vanadium

v) Titanium

vi) Tungsten

vii) Silicon (MAY/JUNE 2009)( APR/MAY 2008)

14) Give the composition, property and uses of S.G iron,18-4-1 HSS and Monelmetal

(MAY/JUNE 2009)

15) State the composition, properties and uses of bearing alloys. (MAY/JUNE 2009) (APR/MAY 2010) ( NOV/DEC 2010)

16) Explain the effects of alloying elements in steels (MAY/JUNE 2009)

17) Discuss about the grey cast iron? (MAY/JUNE 2009)

18) Discuss the composition, properties, application --- Malleable cast iron, Spheroidal cast iron ( APR/MAY 2010)

19) Discuss the composition, properties, application --- Stainless steels, Tool steel

( APR/MAY 2010)

20) Discuss the composition, properties, application --- Cupro – Nickel, Bronze ( APR/MAY

2010)

21) Classify the ferrous material with respect to alloying elements, microstructure and properties and write the effect of alloying addition in steels ( NOV/DEC 2010)

22) Write a short notes on light weight nonferrous alloys and discuss the aluminium and its alloy with respect alloying and heat treatments ( NOV/DEC 2010)

23) What are important alloying elements in steels? Discuss the purpose for which alloying elements are added? ( NOV/DEC 2010)

24) Discuss briefly the different types of cast irons ( NOV/DEC 2010)

25) Mention any three copper base alloys. Give the composition, properties, Application.

26) What are the effects of Si,Ni,Mn and Cr in steel and also in Fe-c diagram. (APR/MAY

2011)

27) Discuss any two copper base, any two aluminium base alloys. Give at least one applications for each(APR/MAY 2011)

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UNIT – 4

1) Decsribe the molecular structure, properties and applications of the following polymers i) Polyvinyl chloride( PVC) (MAY/ JUNE 2007) (NOV/DEC 2007)

ii) Polystyrene(PS) (NOV/DEC 2007)

iii) Polyethylene Terephthalate (PET)

iv) Polycarbonate ( PC) (MAY/ JUNE 2006)

2) Discuss the properties and applications of the following ceramic materials i) Alumine ( MAY/JUNE 2009)

ii) Silicon carbide ( MAY/JUNE 2009) iii) Silicon Nitride ( MAY/JUNE 2009) iv) Sialon(NOV/ DEC 2006)

v) Silica ( MAY/JUNE 2009)

3) Discuss the Structure, properties and application of the following polymeric materials i) Polymethyl methacrylate

ii) Polyterafluoroethylene (MAY/ JUNE 2007) (NOV/DEC 2007) (NOV/DEC 2010) ( NOV/DEC 2010)

iii) Polyethyylene terephthalate (MAY/ JUNE 2007) iv) Acryonitrile butadiene styrene(NOV/ DEC 2006) v) Polypropylene (MAY/ JUNE 2007)

4) Write a short notes about the different types of matrix materias and reinforcement materials used to make polymermatrix composites (MAY/ JUNE 2007)

5) Discuss the properties and applications of Al2 O3 and SiC ceramics (NOV/DEC 2007) (NOV/DEC 2010)

6) Compare and contrast the difference between polyprpelene and polyethylene

(NOV/DEC 2007)

7) Compare the difference between

i) Acrylotrile – butadiene – styrene (NOV/DEC 2007)

ii) Stabilized zirconia iii) Sialon

8) Describe these different types of reinforced used in polymer composites (NOV/DEC

2007)

9) Discuss the properties and applications of ceramics materials in industries ( APR/MAY

2008) ( NOV/DEC 2010)

10) Describe the mechanical behaviour of polymers ( APR/MAY 2008)

11) With the schematic diagram illustrate the the processing of reinforced composites

(APR/MAY 2008)

12) What are the special properties of plastics that make them useful engineering material(MAY/JUNE 2009)

13) How do thermoplastics differ from thermosetting materials . Explain ? ( APR/MAY

2008)(APR/MAY 2011)

14) Write short notes on particle reinforced composites and fibre reinforced composites

( MAY/JUNE 2009) ( NOV/DEC 2010)

15) Write short notes on 1) ceramics ) formaldehyde (NOV/DEC 2009)

16) What is PMMA ? Describe it in detail (NOV/DEC 2009)

17) Explain in detail engineering polymers (NOV/DEC 2009)

18) State the properties and uses of reinforced concrete (NOV/DEC 2009)

19) What are the different types of polymers ? give any four polymers, their properties and applications(APR/MAY 2010)

20) What are the different types of engineering ceramics ? give any four ceramics, their properties and applications (APR/MAY 2010)

21) Write down the composition and applications of the following metals i) Stainless steel

ii) Tool steel(APR/MAY 2010)

22) What is the precipitation hardening ? Iilustrate this with an examples? (APR/MAY 2010)

23) Enumerate the composition and applications of the following alloys i) Cupro – nickel

ii) Bronze

iii) Bearing alloy (APR/MAY 2010)

24) State the effects of the following alloying elements in steel i) Chromium

ii) Molybdenum (APR/MAY 2010)

25) Write the properties and applications of the following polymers and discuss anyone fabrication methods of polymers

i) PE ( NOV/DEC2010) ( NOV/DEC 2010)

ii) PEEK ( NOV/DEC2010)

iii) ABS ( NOV/DEC2010)

26) List the important engineering ceramics and its application. Discuss the properties and application of Si3N4 AND SiC ( NOV/DEC 2010) (APR/MAY 2011)

27) What are different types of plastics? Explain with examples and applications ( NOV/DEC

2010)

28) Discuss the properties and application of the following four ceramics

Zirconia, Silica, Cubic boron nitride (APR/MAY 2011)

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UNIT – 5

1) Explain the mechanism of plastic deformation of metals by slip and twinning ? (MAY/ JUNE 2006)

2) Explain the characteristic of ductile fracture and brittle fracture ? explain the testing

(MAY/ JUNE 2006) (NOV/ DEC2006) (NOV/DEC-2007) ( MAY/JUNE 2009)

3) Procedure for Vickers hardness testing (MAY/ JUNE 2006) (NOV/ DEC2006) (NOV/ DEC2010) (APR/MAY 2011)

4) Explain the testing procedure for charpy impact testing (MAY/ JUNE 2006) (MAY/ JUNE

2007) (APR/MAY2008 )

5) What are the slip and twinning ?What are the charateristics ? (NOV/ DEC2006)

6) Write a short notes about different types of metallic fracture (MAY/ JUNE 2007)

7) Explain the testing procedure for determining the following properties i) Brinell hardness

Number ii) Creep strength (MAY/ JUNE 2007)

8) Explain the mechanism of plastic deformation of metals by slip (NOV/DEC-2007)

9) Draw S-N curve for mild steel and aluminium and explain its features . Explain for procedures used to obtain S-N diagram (NOV/DEC-2007)

10) What are the salient features of Rockwell –hardness test? What are the precautions to be taken while determining hardness by this method (NOV/DEC-2007) (NOV/ DEC2010)

11) List the types of fracture and factors influencing them (APR/MAY2008 ) (APR/MAY

2011)

12) Give the griffith crack model for the mechanism of fracture (APR/MAY2008 )

13) What does impact test signify ? Explain impact Izod test with neat sketches( MAY/JUNE

2009) (APR/MAY 2011)

14) What is fatigue failure ?How fatigue test is carried out ? explain ( MAY/JUNE 2009) (APR/MAY 2010) (NOV/ DEC2010) (APR/MAY 2011)

15) What do you mean by engineering stresses and true stresses ( MAY/JUNE 2009)

16) Explain the mechanism of plastic deformation ( NOV/DEC 2009)

17) Write short notes on creep ? ( MAY/JUNE 2009) (APR/MAY 2010)

18) Describe the procedure of tensile test for metals ( MAY/JUNE 2009)

19) Write a short notes on hardness testing ( MAY/JUNE 2009)

20) Discuss the mechanism of slip taking place in metals using edge dislocation and screw dislocation(APR/MAY 2010)

21) Explain the following terms i) Mechaniclal Behaviour ii) Thermal Behaviour iii)Electrical

behaviour (APR/MAY 2010)

ME2253 ENGINEERING MATERIALS AND METALLURGY Two Marks Questions With Answers 2014

Anna University, Chennai

CONSTITUTION OF ALLOYS AND PHASE DIAGRAMS

1. What is an alloy?

A metal alloy, or simply an alloy, is a mixture of two or more metals or a metal and a nonmetal.

2. What is meant by Base Metal?

In an alloy, the element which is present in the largest proportion is called the base metal.

3. What are alloying elements?

In an alloy, all elements other than the base metal are called the alloying elements

4. Differentiate between substitutional and interstitial solid solutions

In a substitutional solid solution, the solute atoms substitute for parent solvent atoms in a crystal lattice.

In interstitial solid solution, the solute atoms fit into the space between the solvent or parent atoms.

5. What are intermetallic compounds?

The compounds formed by two or more metals in apparently stoichiometric proportion is called intermetallic compounds

6. What are the effects of crystal structure and atomic radii on formation of solid solution between two metallic elements? (MAY/JUNE 2006)

Hume Rothery’s Rules

1. Crystal structure: The two metallic elements that form solid solution must have the same crystal structure. Otherwise, there is some point at which a transition occurs from one phase to a second phase with a different structure

2. Atomic radii: The solute and solvent elements atoms must be of similar size, with less than a 15% difference in atomic radius

7. Define Peritectic and Eutectoid reactions. (MAY/JUNE 2006)

In Peritectic reaction, upon cooling, a solid and a liquid phase transformation isothermally and reversibly to a solid phase having a different composition.

Liquid + Solid 1 cooling Solid 2

Heating

8. State the conditions under which two metallic will exhibit unlimited solid solubility. (NOV/DEC 2006)

To exhibit unlimited solid solubility, the solute and solvent elements should obey the following general rules of Hume Rothery

1. Size factor: The atoms must be of similar size, with less than the 15% difference in atomic radius

2. Crystal structure: The materials must have the same crystal structure.

3. Valance: The atoms must have the same valence

4. Electronegativity: The atoms must have the approximately the same electronegativity

9. Define the term “ferrite” and “austenite” in iron – carbon alloy system. (NOV/DEC

2006)

Ferrite is primary solid solution based on α iron having BCC structure. Austenite is a primary solid solution based on ϒ iron having FCC structure. Both are interstitial solid solutions of carbon in iron.

10. What do you understand by “allotropy of iron?”

Allotropy refers to the possibility of existence of two or more different crystal structure for a substance depending upon temperature.

11. Why carbon solubility is more in an austenite?

Austenite is a primary solid solution based on ϒ iron having FCC structure. Carbon solubility is more in austenite is an interstitial solid structure of carbon in iron.

12. What is steel?

steel.

The ferrous alloy having the carbon composition ranging from 0.008 to 2 % is known as

13. Distinguish between hypoeutectic and hypereutectic cast irons.

Cast irons that contain less than 4.3 % carbon are termed as hypoeutectic whereas cast iron that contains more than 4.3 % carbon are termed as hypereutectic cast irons.

14. What are cooling curves?

Cooling curves are obtained by plotting the measured temperatures at equal intervals during the cooling period of a melt to a solid.

15. State Gibb’s phase rule.

Gibb’s phase rule is given by

F= C – P + 2

Where,

F – Degrees of freedom of system or the no. of variables that may be changed independently without altering the equilibrium.

C – No. of components forming the system

P – Number of phases present in the system

16. What are intermediate phases?

If an alloying element is added in excess of the limit of solid solubility, a second phase appears along with the primary solution. If the second phase is differs in both crystal structure and properties from primary solid solution, than it is known as an intermediate phases.

17. What is an equilibrium phase diagram?

A phase diagram can be defined as a plot of the composition of phases as a function of temperature in any alloy system under equilibrium condiions.

18. Define phase.

A phase is defined as any physically distinct, homogeneous, and mechanically separable portions of a substance. Three different kinds of phases are solid, liquid and vapour.

19. How do cast irons differ from steels in terms of carbon content?

Composition from 0.008 to 2% carbon represent steel, and those above 2% carbon represent cast iron

20. What do you mean by invariant reaction?

The eutectic reaction is also called an invariant reaction since it occurs under equilibrium conditions at a specific temperature and alloy composition that cannot be varied.

HEAT TREATMENT

1. Define the term heat treatment.

Heat treatment may be defined as an operation or combination of operations involving heating and cooling of a metal in solid state to obtain desirable properties

2. What are the purposes of the processing heat treatments?

To relieve internal stresses To improve machinability To refin grain size

To soften the metal

3. List some of the important heat treatment operations widely used.

Annealing Normalizing Hardening Tempering Austempering

Martempering Case Hardening

4. what is meant by annealing

Annealing is defined as a softening process consisting of heating he steel to a temperature at or a near the critical point, holding there for a proper time and then allowing it to cool slowly in the furnace itself

5. What are the purpose of annealing?

To remove stresses

To induce softness

To refine grain structure

To remove gases

6. List the different types annealing

Full annealing

Process annealing

Stress relieve annealing

Recrystallization annealing

Spheroidise annealing

7. What is meant by Normalizing?

Normalizing means similar to full annealing, but cooling is established in still air rather than in the furnace

8. What is quenching.stages for quenching?

Quenching refers accelerated cooling

Vapour –jacket stage

Vapour-transport cooling stage

Liquid cooling stage

9. What is TTT diagram?

The TTT diagram is a plot of temperature versus he logarithm of time for a steel alloy of definite composition. It is a tool used by heat treaters to predict quenching reactions in steels

10. What is a CCT diagram?

The CCT diagram is a plot of temperature versus the logarithm of time for steel alloy of definite composition. It is used to indicate when transformations occur as the initially austenitised material is continuously cooled at a specified rate. In addition, it is also used to predict the final microstructure and mechanical charecteristics.

11. What is significance of the critical cooling rate?

The critical cooling rate is most important in hardening. In order to obtain a 100% martensitic structure on hardening, the cooling must be much higher than the critical cooling rate.

List some of the surface hardening techniques employed for altering surface chemistry

Diffusion methods

(a)Carburizing (b)Nitriding (c)Cyaniding (d) Carbonitriding

Thermal methods

(a)Flame hardening (b)Induction hardening

12. What do you mean by the term case hardening

In many applications, it is desirable that the surface of the components should have high hardness, while the inside or core should be soft. The treatments given to steels to achieve this are called surface heat treatments or surface hardening

13. In what ways flame hardening differs from induction hardening

The mechanism and purpose of induction hardening are the same as for flame hardening. The main difference is hat induction hardening the source of heat input is an induced electric current instead of using flame

14. In what ways cyaniding differs from carburizing

The salt both composition for cyaniding gives a case high in nitrogen, whereas carburizing gives a case rich in carbon

15. Case carburizing heat treatment is not generally carried out for medium carbon steels. Why (MAY/JUNE 2006)

The carburizing process is a diffusion treatment process. For diffusion take place the host metal must have a low concentration of the diffusing species and there must be a significant concentration of the diffusing species at the surface in the host metal. Since the medium carbon steels lack the above said criteria, they are not generally carburized

16. What is the critical cooling rate in hardening of steels (NOV/DEC 2006)

The slowest rate of cooling of austenite that will result in 100% martensite transformation is known as the critical cooling rate

17. Name and explain any one subcritical case hardening treatment (MAY/JUNE 2009)

Nitriding is a subcritical case hardening treatment

Nitriding is a process of introducing nitrogen atoms, to obtain hard surface of steel components

18. Mention few applications of induction hardening (April/May 2008)

The induction hardening is employed for hardening he surfaces of gears, tools, wrist pins, crank shaft bearings, machine tool ways and pump shafts

19. Advantages of austempering

Improved ductility

Increased impact strength and toughness Decreased distortion of the quenched metal Less danger of quenching cracks

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UNIT-III

MECHANICAL PROPERTIES AND TESTING

1. What is meant by mechanical properties of materials?

Mechanical properties are whose characteristics of material that describe its behavior

under the action of external forces.

2. Distinguish between elasticity and plasticity.

Elasticity is the property of the material by virtue of which it is able to retain its original

shape and size after the removal of load.

Plasticity is the property of the material by virtue of which a permanent deformation takes place whenever it is subjected to the action of external forces.

3. What are the factors affecting mechanical properties?

Grain size,

Heat treatment, Atmospheric exposure, Low and high temperature.

4. Define the terms Slip and Twinning.

Slip may be defined as the sliding of blocks of the crystal over one another along definite crytsollographic planes called Slip planes.

Twinning is the process in which the atoms in a part of a crystal subjected to

stress, rearrange themselves so that one part of the crystal becomes a mirror image of the other part.

5. Differentiate between ductility and malibility.

Ductility is the property of the material by virtue of which it can be drawn into wires before rupture takes place.

Malleability is the property of the material by virtue of which it can withstand deformation under compression without rupture.

6. Define the terms brittleness and hardness.

Brittleness is the property of the material by virtue of which it can withstand deformation under compression without rupture.

Hardness is the property of the material by virtue of which it is able to resist abrasive indentation, machining, scratching.

7. What do you mean by toughness and stiffness?

Toughness is the property of the material by virtue of which it can absorb maximum energy before fracture takes place.

Stiffness is the property of the material by virtue of which it resists deformation.

8. List any four technological properties of metals.

Machinability, Castability, Weldability,

Formability or Workability.

9. What is meant by fracture?

Fracture is the mechanical failure of the material which will produce the separation or fragmentation of a solid into two or more parts under the action of stresses.

10. List the different types of fracture in a material.

Brittle Fracture, Ductile Fracture, Fatigue Fracture, Creep Fracture.

11. What are the factors affecting the creep?

Grain,

Thermal stability of the micro structure, Chemical reactions,

Prior strain.

12. List some important destructive tests carried out on a material.

Tensile test, Impact test,

Fatigue test, Bend test, Torsion test, Creep test.

13. Define the term notch sensitivity.

The notch sensitivity refers to the tendency of some normal ductile material to behave like brittle material in the presence of notches.

14. Define endurance limit in fatigue test. ( May / June 2006)

Endurance limit is defined as the value of stress below which the material will not fail even when it is loaded for infinite no. of cycles.

15. What are the properties are determined from tension testing of metallic products? ( May / June 2006)

Limit of proportionality

Yield strength

Maximum tensile strength Breaking strength Percentage elongation Modulus of elasticity

16. How will you express the deformation charecteristics of a material through tension test? ( May / June 2007)

The deformation charecteristics of a material through tension test expressed as

the stress-strain curve. With the help of stress strain curve, the various tensile properties such as elastic stress, strain yield strength, youngs modulus, etc are calculated.

17. Why are impact specimens notched? (NOV/DEC 2007)

The impact specimens are notched because the impact test also indicates the notch sensitivity of a material.

The notch sensitivity refers to the tendancy of some normal ductile materials to behave the like a brittle material in the presence of notches.

18. What are slip bands? (April/May 2008)

Slip bands are made up of several slip planes. They indicate that the atomic planes within the crystal have sheared with respect to each other.

19. What is creep? (May/June 2009)

The creep is defined as the property of material by virtue of which it deforms continuously under a steady load.

20. What are the different types of loadings available for fatigue testing? (April/May 2008) Shock or impact load

Static load

Random load

Repeated or reversed load.

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UNIT-IV

FERROUS AND NON FERROUS METALS

1. what are metals. Classify engineering marterials

Metals are elemental substances. Metals are composed of elements which readily give up electrons to provide a metallic bond and electrical conductivity

Types of metals:1.Ferrous metals.2.Non-Ferrous meals

2. State three reasons why ferrous alloys are used extensively

Iron based components are relatively abundant and are widely distributed throughout the world

Ferrous materials can be produced very economically

Ferrous materials are versatile. Therefore wide range of mechanical and physical properties of ferrous matterials can be achieved

3. State three charecteristics of ferrous alloys that limit their utilization

Heavy in weight, lower electrical and thermal conductivity, lower resistance to corrosion

4. Why is alloying done?

To increase strength To improve hardness To improve toughness

To improve machinability

5. What are alloy steels.How are alloy steels classified Alloy steels mean may steels other than steels Alloy steels can be divided into two main groups

1.Low alloy steels:These contain upto 3 to 4% of alloying elements

2.High alloy steels:These contain more than 5% of alloying elements

6. List four important alloying elements added in alloy steels

The most commonly used alloying elements are chromium, nickel, molybdenum, vanadium, tungsten, cobolt, boron, copper and others

7. What are the required properties of a tool steel

Good toughness

Good wear resistance Very good machinability Resistance to softening on heating

8. What is meant by 18-4-1 high speed steel

A widely used high speed tool steel is 18-4-1 high speed steel. This steel contains

18% tungsten, 4% chromium, 1% vanadium. It is considered to be one of the best of all purpose tool steels

9. What are HSLA steels

HSLA steels are nothing but high strength low alloy steels. HSLA steels also known as micro alloyed steels, are low carbon steels containing small amounts of alloying elements.

10. What are maraging steels?

Maraging steels are low carbon, highly alloyed steels. These are very high strength materials that can be hardened o obtain tensile strengths of upto 1900Mpa

11. What are the effects of carbon on the properties of cast iron?

If a cast iron contains more of the brittle cementite, then it is mechanical properties will be a poor

12. What is the chemical composition of grey cast iron

Carbon-2.5 to 4% Silicon-1 to 3% Manganese – 0.4 to 1% Phosphorus-0.15 to 1% Sulphur -0.02 to 0.15% Remaining is iron

13. list some bronze alloys

Bell bronze, phosphor bronze, aluminum bronze, silicon bronze, coinage bronze, and leaded bronze

14. What are cupronickels? What is the use of monel metal

Cupronickels are alloys of copper and nickel

Uses of Monel metal: For making propellers, pump fittings, condenser tubes, steam turbine blades, sea water exposed parts, tanks, and chemical and food handling plants.

15. What is meant by precipitation hardening

precipitation hardening, also known as age hardening, is the most important method of improving the physical properties of some of the non-ferrous alloys by solid state reaction.

16. What is the main strengthening mechanism in high strength aluminum alloys. (MAY/JUNE 2006)

Precipitation strengthening treatment, also known as age hardening is the main strengthening mechanism in high strength aluminum alloys.

17. What are the effect of chromium and molybdenum in low alloy steels? (NOV/DEC 2006)

The effect of chromium in low alloy steels are to: Increase corrosion and oxidation resistance Increase hardenability

Increase high temperature strength

Resist abrasion and wear

The effect of molybdenum in low alloy steels are to: Improve high temperature creep resistance Increase hardenability

Stabilize carbides

18. Mention any two aluminium base alloys and their applications (NOV/DEC 2007)

1. Duralumin: Used for aircraft and automobile industries

For making electric cables, in surgical and orthopedic implements etc.

2. Y-alloy: Used for making pistons of engines, cylinder heads, gear boxes, propeller blades.,

19. What is carbonitriding? (April / May 2008)

Carbonitriding is a surface hardening process that involves the diffusion of both nitrogen and carbon into the steel surface.

20. What are super alloys?

Super alloys is a general term used to describe the nickel base and cobolt base alloys which have been developed for use at elevated temperatures

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UNIT – V

NON METALLIC MATERIALS

1. What are polymers?

Polymers are composed of a large number of repeating units of small molecules called monomers.

2. List any four attractive charecteristics of polymers

Low density

Good thermal and electrical insulaion properties

High resistance to chemical attack

Ease of fabrication

Relatively low cost

3.What is mean by isomerism

Isomerism is a phenomenon wherein different atomic configurations are possible for the same configuration

4.Why are additives added to polymers .

Filler materials Flame retardants Colorants

Reinforcements Plasticizers

Stabilizers Lubricants

5.Differentiate commodity plastics with engineering plastics.

The plastics which are not generally used for engineering applications are known as commodity plastics. The plastics which are used in engineering applications are known as engineering plastics.

6.Classify polymers

1.Plastics 2.Elastomers 3.Adhesives 4.Coatings 5.Fibers

7.Name any four commodity plastics and engineering plastics

Commodity plastics:Polyethylene, Polypropylene, Polystyrene, Polyvinyl chloride

Engineering plastics: Ethenic, Polyamides, Cellulosics, Acetals

8.What are the sources of raw materials for plastics? Animal and vegetable by products

Coal by products

Petroleum by products

9.Write short notes on nylons

Polyamides also known as nylons are the product of condensation reaction between an amine and an organic acid

10.What are engineering ceramics?

Engineering ceramics, are also known as technical/industrial ceramics, are those ceramics that are specially used for engineering applications or in industries

11.Name any four engineering ceramics

Alumina Silicon carbide Silicon nitride Sialons

12. What are composites?

Composites are produced when two are more materials are joined to give a combination of properties that cannot be attained in the original materials.

13. What is the role of matrix material in a composite?

The matrix usually provides the major control over electrical properties, the chemical behavior, and elevated temperature use of the composite.

14. Write the general mechanical properties of ceramics? (May / June 2009) Ceramics are strong, hard and brittle.

They are good thermal and electrical insulators.

They have high compressive strength but are weak in tension.

15. What do you meant by copolymers? (Apr. / May 2008)

Copolymers are polymers which are obtained by adding different types of monomers

16. How are refractories classified? (Apr. / May 2008) Fire clay refractories

Silica refractories Basic refractories Special refractories

17. Give two examples of particulate reinforced metal matrix composites. (May / June 2007) Sintered Aluminium Powder (Al/Al2O3)

Cermet

18. What are Cermets and applications?

Ceramic metal composite containing between 80 and 90% of ceramics are known as

Cermets.

Cutting tools, Slip gauge, wire drawing dies, rocket motor and jet engine parts.

19. What are the constituents of composites?

Composites are composed of two phases.

Matrix phase, Dispersed phase

20. Name any four engineering polymers.

Ethenic, Polyamids, Silicones, Polyimides.

ME2252 MANUFACTURING TECHNOLOGY II Questions Bank 2014

Anna University, Chennai

 

THEORY OF METAL CUTTING

1. 1.Explain orthogonal cutting and oblique cutting with its neat sketches and compare?

2. Define the various tool parts of a single point cutting tool with a neat sketches?

3. what is a chip? what are different types of chips? How are they formed?

4. 4.Explain the types of chip formed during machining process?

5. What are the different types of cutting fluids used in machining process?

6. What is the use of a chip breaker? Discuss the various types of chips produced during metal machining process?

7. Explain the basic actions of cutting fluids?

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UNIT – 2

CENTRE LATHE AND SPECIAL PURPOSE LATHES

1. Describe some of the methods and equipments for holding work on a lathe?

2. Explain with neat sketches the various methods of turning a taper?

3. Write down the differences between a capstan lathe and turret lathe?

4. Explain the tool layout for the production of a Hexagonal bolt in a capstan lathe?

5. Explain with neat sketch the working of a swiss type automatic lathe?

6. Difference between parallel action and progressive action multi- spindle automatics?

7. Describe the working principle of multi-spindle automatics? Give its advantages and application?

OTHER MACHINE TOOLS

1. Describe with neat sketch whit-worth quick return mechanism used in shaper?

2. Explain the hydraulic drive of a horizontal shaper with neat sketches?

3. Describe with neat sketch crank and slotted link quick return mechanism used in shaper?

4. Difference between the shaper and planer machine?

5. How do you specify a planer?

6. Make a note on different types of work holding devices used in a slotting machine?

7. Explain different types of milling cutters?

8. Explain simple indexing , compound indexing and differential indexing with suitable examples?

9. Sketch and explain the working principle of upright drilling machine?

10. Explain Gang milling machine?

11. Explain with neat sketch of Radial drilling machine?

12. Explain the working principle of continuous broaching machines?

13. Explain horizontal boring machine?

14. Explain vertical boring machine?

15. Explain the various types of broaches with necessary sketch?

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UNIT – 4

ABRASIVE PROCESSES AND GEAR CUTTING

1. How do you classify cylindrical grinders? what is the difference between “plain

and universal” cylindrical grinder?

2. Explain the salient features of a centreless grinding machine and discuss the different operations that can be carried out in it.mention some advantages?

3. Briefly discuss about the different types of abrasives used in a grinding wheel?

4. Describe the use of cutting fluids in grinding?

5. Difference between gear forming and generating?

6. Explain the principle of operation of gear hobbing operation what are the advantages of gear hobbing?

7. Give the advantages and limitations of gear hobbing?

8. compare gear hobbing with gear shaping?

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UNIT – 5

CNC MACHINE TOOLS AND PART PROGRAMMING

1. Discuss about the following with neat sketch and with suitable example closed loop system and open loop system.

straight line system line system and continuous system

2. Discuss the major elements of CNC machine tools?

3. Describe with neat sketch various steps in computer assisted part programming?

4. compare NC and CNC and DNC?

5. Write short notes on: (i) NC machines

(ii) APT programming

(iii) G and M codes

(iv) CNC machine Vs conventional machine

6. write short notes on APT language?

7. Discuss the advantages of CNC?

8. Discuss major elements of CNC machine tools?

ME2252-MANUFACTURING TECHNOLOGY II Two Marks Questions With Answers 2014

Anna University, Chennai

ME2252-MANUFACTURING TECHNOLOGY II

UNIT -1

THEORY OF METAL CUTTING

TWO MARKS QUESTIONS:

1. What is rake angle? What is the effect of nose radius in tools?

The angle between the tool face and the line parallel to the base of the tool is known as side rake angle. It is used to control chip flow.

2. What is tool?

The various angles of tools are mentioned in a numerical number in particular order. That is known as tool signature.

3. Explain the nose radius?

It is the joining of side and end cutting edges by means of small radius in order to increase the tool life and better surface finish on the work piece.

4. Name the factors that contribute to poor surface finish in cutting?

· Cutting speed

· Feed

· Depth of cut.

5. What is orthogonal cutting?

The cutting edge of tool is perpendicular to the work piece axis

6. Define oblique cutting?

Oblique cutting: - The cutting edge is inclined at an acute angle with normal to the cutting velocity vector is called oblique cutting process

7. What is cutting force?

The sheared material begins to flow along the cutting tool face in the form of small pieces . The compressive force applied to form the chip is called cutting force

8. What is chip reduction co-efficient ?

The reciprocal of chip thickness ratio is called chip reduction co-efficient.

K=1/r

9. What is the function of chip breakers?

The chip breakers are used to break the chips into small pieces for removal, safety and to prevent both the machine and work damage

10. Define machinability of metal?

Machinability is defined as the ease with which a material can be satisfactorily machined

11. How tool life is defined?

Tool life is defined as the time elapsed between two consecutive tool resharpening. During this period the tool serves effectively and efficiently

12. Write Taylor’s tool life equation?

n

Taylor’s tool life equation, VT =C

Where, V= Cutting speed in m/min.

T= Tool life in minute

C= Constant

N= Index depends upon tool and work.

13. What are the factors affecting tool life?

Cutting speed

Feed and depth of cut

Tool geomentry Tool material Cutting fluid Work material

Rigidity of work, tool and machine

14. What are the four important characteristics of materials used for cutting tools?

Hot hardness

Wear resistance

High thermal conductivity Resistance to thermal shock Easy to grind and sharpen .

Low mechanical and chemical affinity for the work material

15. Name the various cutting tool materials.

Carbon tool steel High speed steel Cemented carbides Ceramics Diamonds

16. What are the functions of cutting fluids?

It is used to cool the cutting tool and work piece.

It lubricates the cutting tool and thus reduces the co-efficient of friction between tool and work.

It improves the surface finish as stated earlier. It causes the chips to break up into small parts. It protects the finished surface from corrosion.

It washes away the chips from the tool. It prevents the tool from fouling. It prevents corrosion of work and machine

17. What are the factors responsible for built-up edge in cutting tools?

During cutting process, the interface temperature and pressure are quite high and also high friction between tool chip interfaces causes the chip material to weld itself to the tool face near the nose. This is called built up edge

18. List the essential characteristics of a cutting fluid?

It should have good lubricating properties to reduce frictional forces and to decrease the power consumption.

High heat absorbing capacity.

It should have a high specific heat, high heat conductivity and high film co- efficient.

High flash point.

It should be odorless

It should be non –corrosive to work and tool.

19. What are the causes of wear?

The tool is subjected to three important factors such as force, temperature and sliding action due tool.

20. Briefly, differentiate between orthogonal cutting and oblique cutting?

Sl. No.	Orthogonal cutting	Oblique cutting
1.	The cutting edge of the tool is perpendicular to the cutting velocity vector.	The cutting edge is inclined at an acute angle with the normal to the cutting velocity vector
2.	The chip flows over the tool face and the direction of chip-flow velocity is normal to the cutting edge.	The chip flows on the tool face making an angel with the normal on the cutting edge.
3.	The cutting edge clears the width of the work piece on either ends.(i.e No side flow)	The cutting edge may or may not clear the width of the work piece.
4.	The maximum chip thickness occurs at its middle.	The maximum chip thickness may not occur at the middle.

21. Give two examples for orthogonal cutting.

Turning, facing, thread cutting and parting off

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UNIT – 2

CENTRE LATHE AND SPECIAL PURPOSE LATHES

1. What is swing diameter?

The largest diameter of work that will revolve without touching the bed and is twice the height of the center measured from the bed of the lathe.

2. write the specifications of a typical lathe?

I, The length of bed.

ii, maximum distance between dead and live centres. iii, Types of bed( i,e) straight, semi gap or gap type. iv, The height of dead centres.

v, swing over the bed. vi, width of the bed. vii, spindle bore.

viii, spindle speed.

ix, H.P. of main motor and rpm. x, Number of spindle speeds.

xi, spindle nose diameter. xii, Feeds .

lathe centres, catch plates, carriers, chucks, mandrels and rests.

4. What are the operations can be performed on a lathe?

Turning, facing, forming, knurling, chamfering, thread cutting, drilling, boring, recessing, tapping, grooving etc.

5. Write down the names of any four lathe accessories?

lathe centres, catch plates, carriers, chucks, mandrels and rests.

6. What are the functions of feed rod and lead screw?

Feed rod:

It is used to guide the carriage in a straight line when it moves along the bed. Lead screw:

It is used to move the carriage while thread cutting operation is carried out. It also ensures the proper speed of work relative to the tool thread cutting operation.

7.Mention four types of chucks used in a machine shop?

i, Three jaw chuck (or) self centering chuck ii, Four jaw chuck (or) independent chuck. iii, magnetic chuck.

8. What is the application of Air operated chuck?

Heavy work piece are mounted with the help of air operated chucks because they will require more power to hold the work piece.

9. What is the purpose of mandrel? How many types of mandrels is there in common use?

Mandrels are used for holding hollow work pieces.

1. plain mandrel

2. collar mandrel

3. cone mandrel

4. special mandrel

5. step mandrel

6. Expansion mandrel

7. Gang mandrel

10. What is thread cutting operation?

Thread cutting is the operation of producing continues helical groove on a cylindrical work piece.

11.Name any four work holding devices?

1, collets

2, chucks

3, Fixtures

4, power chucks

Automatic machine or simply automats are machines tools in which all the operations required to finish off the work piece are done automatically with out the attention of an operator.

13. What are the advantages of automatic lathes?

a, Mass production of identical parts. b, High accuracy is maintained.

c, Time of production is minimized.

d, The bar stock is feed automatically.

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UNIT – 3

OTHER MACHINE TOOLS

1. Compare hydraulic shaper with mechanical shaper?

SL.NO	Hydrulic shaper	Mechanical shaper
1. 2. 3. 4.	smooth cutting operation changing of cutting speed is easy Higher cutting to return ratio can be obtained Stroke length can be easily adjusted without stopping the machine	Rough and noisy cutting operation changing of cutting speed is difficult Lower cutting to return ratio Change of stroke length is not possible with out stopping the machine.

2. Write down any four operations performed by a shaper?

Machining horizontal surfaces. Machining vertical surfaces. Machining inclined surfaces. Machining irregular surfaces.

3. Mention the operation performed by planer?

The following operations generally performed in a planer are a.Planning horizontal surface b.Planning vertical surface c.Planning curved surface d.Planning of an angle

4. What is the function of clapper block in a planer?

During cutting stroke, the tool block fits inside the clapper block rigidly. During the return stroke, the tool block lifts out of the clapper block to avoid rubbing of the tool on the job.

5. State the difference between a vertical shaper and a slotter?

vertical shaper	slotter
1. vertical shapers generally fitted with rotary table to machine curved surfaces 2. Rotary table along with tools will remove. 3. vertical shaper is not fixed in the vertical plane	1.The slides are fitted 2.slides will move to perform slotting. 3. slotter is fixed in the vertical plane.

6. What are the common work holding devices used on milling machines?

a.‘v’ blocks. b.machine vises. c.milling fixtures. d.Dividing heads

7. What is a shell mill?

A shell mill is a large type of face or end mill that mounts onto an arbor, rather than having an integral shank. Typicaly, there is a hollow or recess in the center of the shell for mounting hardware onto a separate arbor.

8. What is meant by up-milling and down milling?

In up milling, cutters rotates opposites to the direction of a feed of the work piece whereas in down milling, the cutter rotates in the same direction of travel of the workpiece.

9. What are the differences between up milling and down milling?

SL.NO	EVENT OF OPERATION	UP MILLING	DOWN MILLING
1. 2. 3.	Direction of Travel Chip thickness cutting force	Cutter rotates against the direction of travel of workpiece. Minimum at the beginning of cut Greeches max when the cut terminates. Increases from zero to max per tooth	Cutter rotates in the same direction of travel of workpiece Maximum at the beginnining Greeches min at terminates Decreases from max to zero per tooth.

10. What is thread milling?

A thread milling has no chamfer. The mill is inserted into the hole along the axis of the spindle, deep enough to produce full thread depth required

11. write down the rule for gear ratio in differential indexing

Rule for gear ratio in differential indexing: Gear ratio = (A-N)/A

A- Selected no which can be indexed by plain indexing and approximately equal to N.

N- Required no. of divisions to be indexed.

12. How do specify radial drilling machine?

A drilling machine is specified by the job following items.

1. Maximum size of the drill in mm that the machine can be operate.

2. Table size of maximum dimension of a job can mount on a table in square meter.

3. maximum spindle speed and range of spindle speeds in r.p.m

13. Write down any four operations that can be performed in a drilling machine?

1. Drilling

2. counter sinking

3. Tapping

4. reaming.

14. What is meant by “sensitive hand feed”?

In drilling machines, manual sensing of the hand does feeding of the tools towards the work piece. it is called as sensitive hand feed

15. What is broaching?

Broaching is a process of machining a surface with a special multipoint cutting tool called “broach” which has successively higher cutting edges in a fixed path.

16. Why is sawing a commonly used process?

1. Easy handling of machines and spindle construction

2. Fast operation and cost of machinery is less

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UNIT – 4

ABRASIVE PROCESSES AND GEAR CUTTING

1. What are the types of surfaces that could de produced using plain cylindrical grinders?

Plain cylindrical parts, cylindrical parts, cylinders, tapers, shoulders, fillets, cams, crankshaft etc.

2. State the abrasives sed in manufacture of grinding wheels?

a, corundum (75 to 90% crystalline Al2O3 +IRON OXIDE)

b, Diamond Artificial abrasives: a, Aluminium oxide b, silicon oxide

3. What do you mean by loading of grinding whells?

During the operation , the chips formed get entrapped in the linner granular space of abrasive particles. This is called loading.

The surface of the wheel becomes smooth and gets a glassy appearance. This is known as glazing wheel.

4. What is meant by dressing and truing?

Dressing is the process of loading and breaking away the glazed surface so that new sharp abrasive particles are again present to work for efficient cutting.

Truing is the process of trimming the cutting surface of the wheel to true with the axis.

5. Mention four important factors that influence the selection of grinding wheel?

1. constant factors

i. physical properties of material to be ground ii. Amount and rate of stock to be removed. iii. Area of contact.

iv. Type of grinding machine

2. variable Factors i.work speed.

ii. wheel speed.

iii. condition of the grinding machine iv. personal factor

6. What for lapping is used?

a, Removing small amounts of material from the surfaces of tools.

b, Removing small defects and surface cracks left during previous operations

c, Eliminating small distortion.

7. What is meant by honing?

An abrading process of finishing previously machined surfaces is known as honing.

8. What are the advantages of honing process?

1. Simple process which can be done on any general purpose machines such as lathes and drilling machines.

2. This process can be applied for both internal cylindrical and flat surfaces.

3. Honing enables the maximum stock removing capacity out of entire surface finishing operations.

9. What is meant by dressing and truing?

Dressing is the process of loading and breaking away the glazed surface so that new sharp abrasive particles are again present to work for efficient cutting.

Truing is the process of trimming the cutting surface of the wheel to run true with the axis.

10. What is roller burnishing process?

Roller burnishing is a method of cold working metal surfaces in which hardened sphere or cylindrical roller is pressed against the work to be processed. For example, in roller burnishing on a lathe, the burnishing tool is moved across the surface to be spanned.

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UNIT – 5

CNC MACHINE TOOLS AND PART PROGRAMMING

1. Define NC?

Controlling a machine tool by means of a prepared program is known as numerical control or NC.

2. what are the classifications of NC machines?

1.point to point NC system

2. straight cut NC system

3.Contouring NC system

3. What are G-codes and M-codes? Give examples.

G-codes are preparatory function codes which prepare the machine are for different modes of movement like positioning, contouring, thread cutting etc.

Eg. G00 – Point to point positioning

G01 – linear interpolation

M- codes are miscellaneous function codes which denote the auxillary or switching information such as coolant on/off, spindle speed etc.

Eg. M00 – Program stop

M01 – Optional stop.

4. What is the role of computer for NC machine tool?

computer numerical control is an NC system that utilizes stored program to perform basic numerical control functions. mini or micro computer based controller unit is used.

5. Name the various elements of CNC machines?

1.Tape reader

2.Mini computer

3. servos and interface logic

4. Motion feedback

6. What is the role of computer for NC machine tool?

computer numerical control is an NC system that utilizes stored program to perform basic numerical control functions. mini or micro computer based controller unit is used.

7.What is point –to- point (PTP) system?

It is also called positioning system. The objectives of the machine tool control is to move the cutting tool to a predefined location. The speed or path is not important in this system

8. Mention the main differencebetween CNC and DNC?

CNC system can do operations on only one machine at a time. But direct numerical control involves that at a time a large central computer to direct the operations of a number of separate NC machines

9. List the commonly used co – ordinate system of CNC machine tools?

Cantilever construction Bridge construction Column construction Gantry construction

10. What is the difference between incremental and absolute system?

In absolute programming, the distance at my point at any instant will be measured from the origin ( X=0, Y=0).

Whereas in incremental programming, the instant point will be noted as (X=0,Y=0). Further measurement will be made from the particular point only.

11. Write down the types of statements in APT language.?

1. Geometric statements

2. Motion statements

3. postprocessor statement

4. special control or Auxiliary statements

12. Define subroutine?

If the same machining operations, which was carried out already, is to be performed at many different positions on the work piece, it can be executed by means of a program called as subroutines