Unit 4 ae testing
- 1. UNIT-4 ACOUSTIC EMISSION(AE) TESTING COURSE OUTLINE… Introduction Basic principle Signal propagation The ae process chain Advantage & limitation of AE testing Er. Devendra Kumar Sain Asst. Prof. Jodhpur Institute Of Engineering College, Jodhpur
- 2. HISTORY… Probably the first practical use of AE was by pottery makers. As early as 6,500 BC, potters were known to listen for audible sounds during the cooling of their ceramics, to asses the quality of there products. Today, AE Non-Destructive Testing used practically in all industries around the world for different types of structures and materials.
- 3. INTRODUCTION TO ACOUSTIC EMISION TESTING… The father of modern AE testing was Josef Kaiser of Germany. KAISER EFFECT: 1. Material emits minute pulses of elastic energy when placed under stress. 2. Once a given load was applied and the acoustic emission from that noise had ceased, no further emission would occur until the previous stress level was exceeded, even if the load was removed and later reapplied The acoustic emission (AE) testing method where the material being inspected generates signals that warn of impending failure. Solid materials emit sonic or ultrasonic acoustic emissions when they are mechanically or thermally stressed to the point where deformation or fracturing occurs. During plastic deformation, dislocations move through the material’s crystal lattice structure producing low-amplitude AE signals, which can be measured only over short distances under laboratory conditions.
- 4. BASIC PRINCIPLE & MECHANISMS..... The class of phenomena whereby transient elastic waves are generated by the rapid release of energy from localized sources within a material,, or the transient elastic waves so generated. Sources : Crack, Leak, Friction/Wear, Property Changes, Fracture
- 5. AE SOURCE MECHANISMS… PLASTIC DEFORMATIONS: Dislocations motion, twining etc. FRACTURE: ductile,brittle,fatigue,creep etc. Composites (matrix cracking, delaminations, fiber breakage,debonding etc.) PHASE TRANSFORMATION: martensite deformations, melting/ freezing, sintering, curing etc.
- 6. SIGNAL PROPAGATION… A short, transient AE event is produced by a very fast release of elastic energy for a specific dislocation movement. This local dislocation is the source of the elastic wave that propagates in all directions and cannot be stopped. On flat surfaces, the wave propagates as concentric circles around the source and multiple installed sensors can detect it.
- 7. THE AE PROCESS CHAIN…
- 8. CONTINUE.. 1.Test object and application of load: produce mechanical tensions2. 2. Source mechanisms: releasing elastic energy 3.Wave propagation: from the source to the sensor 4.Sensors: converting a mechanical wave into an electrical AE signal 5.Acquisition of measurement data: converting the electrical AE signal into an electronic data set 6.Display of measurement data: plotting the recorded data into diagrams 7.Evaluation of the display: from diagrams to a safety-relevant interpretation Mechanical stress has to be produced within the test object, which is usually done by applying external forces, such as pressuring a tank or heating its contents. Material properties and environmental
- 9. APPLICATIONS… 1.WELD MONITORING During the welding process temperature changes induce stresses between the weld and the base metal. These stresses are often relieved by heat treating the weld.