Sir, i have a doubt. In earlier days a basic NDT tool for testing of material is by tapping it by hand and can be ablle to identify whether the material is good or bad based on the sound heard.what is the physical principle behind it. Is it due to the abosorption of sound in the material and accordingly output or is it based on resonance principle. please clarify my doubt.
My second question is what is SLAM/SAM/C-SAM or Acoustic microscopy ? Principle and applications.
Third question is Physical significance of SIGMA 6-SIGMA etc Thank you, GOWRISHANKAR