Engineering Physics - Ultrasonic , Application of Ultrasonic and SONAR
Learning Objectives :
On completion of this topic you will be able to understand :
1. Application of ultrasonic waves in various fields e.g., engineering, medical, metallurgical, physical, chemical, etc
2. SONAR
Ultrasonic waves have a wide range of applications in various fields e.g., engineering, medical, metallurgical, physical, chemical, etc. Some of their uses are discussed in below
Ultrasonic Drilling and Cutting
Ultrasonic are used for making holes in very hard materials such as glass, diamond etc., When ultrasonic are passed through these materials it creates air bubbles. This air bubbles collapses within short span of time, thereby a larger amount of pressure and temperature which are used for cutting and drilling.
Ultrasonic Cleaning
Ultrasonic cleaning is an environmentally friendly alternative for the cleaning of continuous materials, such as wire and cable, tape or tubes. The effect of the cavitations generated by the ultrasonic power removes lubrication residues like oil or grease, soaps, stearates or dust. In addition, the pollution particles are dispersed into the cleaning liquid. By that, a new adhesion to the material to be cleaned is avoided and the particles are flushed away.
By the use of an innovative proprietary ultrasonic technology, very strong cavitations fields are generated, so that very good cleaning results at high line speeds can be accomplished. As the cleaning effect is based on the physical cleaning effects of the ultrasound, it can be used for any ferrous and non-ferrous material, e.g. stainless steel, copper, aluminum, but also plastic or
glass. Most commonly ultrasonic cleaning machines are used for drawn wire, e.g. before cladding or extrusion. By the concentration of the ultrasonic power to a low liquid volume, a very compact design can be realized. This can be easily integrated into existing or new production lines, e.g. directly after drawing or reel payoff.
Cavitation is an effect that is generated in liquids by intensive ultrasonic waves. The resulting pressure waves create vacuum bubbles that implode subsequently. As a result of these implosions, very high pressures and temperatures occur in combination with liquid jets of up to 1000km/h. At surfaces, these mechanical forces loosen impurities, so they can be flushed away with the cleaning liquid. For an intensive cavitation - and by that for an intensive cleaning - high amplitudes and a low ultrasonic frequency (approx. 20 kHz) are needed. Ultrasonic Cleaners are used in various industries for a number of applications.
Some of the Ultrasonic Cleaning applications are:
1. Ultrasonic Cleaners in Scientific Labs
Lab Glassware, Test Tubes, Pipettes, Optical & Contact Lenses, Eyeglass Frames, Scientific Instruments, Components
2.Ultrasonic Cleaners in Industrial Manufacturing
Switches, Relays & Motors, Gears, Precision Bearings, Metal & Plastic Parts, Assemblies
3. Ultrasonic Cleaners in Electronics Manufacturing
PC Boards, SMDs, Ceramic Substrates, Capacitors, Lapping Heads, Packaging Components, Quartz Crystals, High-resolution Glass Plates
4. Ultrasonic Cleaners in Medical & Dental Labs
Cannulae, Syringe Parts, Surgical Instruments, Blood Oxygenators, Dental Instruments, Burs, Dentures, Caps, Plates
5. Ultrasonic Cleaners in Jewelry Manufacturing
Watches, Clock Movements, Precious Metals & Gemstones, Intricate Settings, Chains, Charms, Coins
Ultrasonic Welding Applications
Ultrasonic metal-welding is an advanced technical process for combining nonferrous metals, stranded wire and many metal-alloys. It is a cold-phase friction welding technique; there is no melting, no high-temperature buildup. The surfaces being joined are subjected to high- frequency mechanical oscillations while being rubbed together under pressure. The molecules of the surfaces begin to swirl and intermingle with one another, creating a firm and lasting bond. Improvements in quality and efficiency, reduced energy requirements and positive environmental factors are the decisive advantages of this new technology.
SONAR
The word Sonar is an American term first used in World War II, it is an acronym for SOund, NAvigation and Ranging. The British also call Sonar, ASDICS, which stands for Anti- Submarine Detection Investigation Committee. Later developments of Sonar included the echo
sounder, or depth detector, rapid-scanning Sonar, side-scan Sonar, and WPESS (within- pulseectronic-sector-scanning) Sonar.
Sonar is a system that uses transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distances underwater. It has been used for submarine and mine detection, depth detection, commercial fishing, diving safety and communication at sea. The Sonar device will send out a subsurface sound wave and then listens for returning echoes, the sound data is relayed to the human operators by a loudspeaker or by being displayed on a monitor.
As early as 1822, Daniel Colloden used an underwater bell to calculate the speed of sound underwater in Lake Geneva, Switzerland. This early research led to the invention of dedicated sonar devices by other inventors. Lewis Nixon invented the very first Sonar type listening device in 1906, as a way of detecting icebergs. Interest in Sonar was increased during World War I when there was a need to be able to detect submarines.
In 1915, Paul Langévin invented the first sonar type device for detecting submarines called an "echo location to detect submarines" using the piezoelectric properties of the quartz. He was too late to help very much with the war effort; however, Langévin's work heavily influenced future sonar designs.
The first Sonar devices were passive listening devices - no signals were sent out. By 1918, both Britain and the U.S had built active systems, in active Sonar signals are both sent out and then received back. Acoustic communication systems are Sonar devices where there is both a sound wave projector and receiver on both sides of the signal path. The invention of the acoustic transducer and efficient acoustic projectors made more advanced forms of Sonar possible. There are two major kinds of sonar, active and passive.
Active sonar creates a pulse of sound, often called a "ping", and then listens for reflections of the pulse. The pulse may be at constant frequency or a chirp of changing frequency. If a chirp, the receiver correlates the frequency of the reflections to the known chirp. The resultant processing gain allows the receiver to derive the same information as if a much shorter pulse of the same total power were emitted. In general, long-distance active sonars use lower frequencies. The lowest have a bass "BAH-WONG" sound. To measure the distance to an object, one measures the time from emission of a pulse to reception.
Passive sonars listen without transmitting. They are usually military (although a few are scientific). Passive sonar systems usually have large sonic databases. A computer system frequently uses these databases to identify classes of ships, actions (i.e. the speed of a ship, or the type of weapon released), and even particular ships.
Basic concept of SONAR
Sonar is based on the echo-sounding technique of ultrasound. When an ultrasonic wave is transmitted through water, it is reflected by the objects in the water and will produce an echo signal. By noting the time interval between the generation of the ultrasonic pulse and the reception of the echo signal (t), the depth of the object can be easily calculated. Since the ultrasonic velocity “v’ in sea water is known, the depth of sea is calculated as follows Depth of sea (distance between surface and bottom of the sea) = vt/2
The same procedure is also used to find the distance of submarine or iceberg from the surface of the sea and the distance between two ships in the sea.
Check your understanding :
1. What are the applications of ultrasonic in industry?
Ans: Ultrasonics are used in cutting, drilling, welding, soldering etc
2. What is meant by cavitation?
Ans : Cavitation is the processes of creation and collapse of bubbles, due to the principle of negative local pressure created inside the bubble.
3. What is SONAR
Ans : SONAR is an acronym for “Sound Navigation and Ranging”.
4. What are the applications of SONAR?
Ans : SONAR is used to (i) find the depth of sea (ii) guide the submarine or ships in seas, and (iii) locate the shoal of fish
Summary :
On completion of this topic you have learned
1. Ultrasonic waves have a wide range of applications in various fields e.g., engineering, medical, metallurgical, physical, chemical, etc.
2. SONAR is an acronym for “Sound Navigation and Ranging”. The principle of SONAR is based on the echo sounding technique of ultrasonic. It is the acoustical technique for locating the objects like submarine or iceberg in sea, by transmitting a high frequency sound pulse and receiving it after reflection from that object.
Suggested Reading
1. “Engineering Physics” by Dr.P.K.Palanisamy, Scitech Publications (India) pvt, Ltd, Chennai
2. “Engineering Physics” by Dr.G.SenthilKumar, VRB Publishers Pvt Ltd, Chennai.
ρ is the density of material of the rod. 
