Quantitative Evaluation of the Damaged Layer by Machining Using a Scanning Acoustic Microscope

点击翻译按钮获取中文摘要

The mechanical and physical properties of base metals deteriorate during machining. A nondestructive evaluation of surface integrity provides information for these determination of the conditions in certain manufacturing processes.For this kind of inspection, the X-ray diffraction method, eddy current electromagnetics, ultrasonic techniques and other methods have conventionally been employed. In particular, the ultrasonic technique utilizing the Rayleigh surface wave has been used for the in-process measurement of the nonumiformity of materials and the internal cracks in machined parts. However, the resolution by this method was not sufficient to detect a radical change in the extent of damage within a layer immediately beneath the surface. This disadvantage has been overcome by the development of the Scanning Acoustic Microscope (SAM) which utilizes a focussed acoustic beam.Microscopic identification of a damaged layer, produced by machining, was performed by a Scanning Acoustic Microscope. From the series of experiments, the following points have been clarified. 1) The sum of the principal stress has been able to detect and the information related to the hardness could be obtained by a SAM. 2) The wave strength by a SAM is possible to detect the variation of Young's modulus caused by the deformation. This was verified by using a polycarbonate film as a specimen which has a significant material nonlinearity. 3) The degeneration in the metallurgically-damaged layer can be evaluated by the Rayleigh wave velocity, and the total reflection power on the Fourier transform of the V(z) curve.