26-02-2013, 11:41 AM
A SEMINAR ON NON DESTRUCTIVE TESTING
DESTRUCTIVE TESTING.ppt (Size: 633.5 KB / Downloads: 61)
INTRODUCTION
As the name indicates NDT means testing of materials without destroying them its purpose is to detect or evaluate any defect and predict the strength and the serviceability of the part.
NDT play an important role not only in the quality control of finished product but also during various stages of manufacturing
ULTRASONIC SYSTEM
Sound with a frequency above the limit of audibility is called 'ultrasonic'. It ranges with a frequency of 0.2 MHz to 800 MHz.
Ultrasonic techniques are very widely used for the detection of internal defects in materials.
Ultrasonic inspection operates on the principle of 'transmitted' & 'reflected' sound wave
A - scan
In the A-scan, shown in fig, the first echo is from the front surface of the material and the second echo is from the rear surface of the material
If there was a flaw within the material, you would see a small peak somewhere between the front wall and back wall
ADVANTAGES OF NDT
Tests are made directly on objects. 100% testing on actual components is possible.
Many NDT methods can be applied on the applied on the same part and hence all properties of interest can be measured.
In service testing is possible.
very little preparation is sufficient
Most test methods are rapid
Repeated checks over period of time are possible
CONCLUSION
Probably the aerospace industry is leading in the world for innovation of new materials and fabrication technique regularly to improve safety, efficiency & reduce cost.
For instance, with increasing use of composites in latest commercial aircraft construction has motivated rapid development in ultrasonic technique C scan presentation.
It can detect defects deep inside composites producing 3 dimensional images of the structures & any irregularities within the test item.