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

在机械加工过程中，基体金属的机械和物理性能会恶化。表面完整性的非破坏性评估为确定某些制造过程中的条件提供了信息。对于这种检查，通常采用X射线衍射法、涡流电磁法、超声技术和其他方法。特别是，利用瑞利表面波的超声波技术已被用于在加工过程中测量材料的不均匀性和机械加工零件的内部裂纹。然而，这种方法的分辨率不足以检测到表面下一层内损坏程度的根本变化。这一缺点已被克服的扫描声显微镜（SAM）的发展，利用聚焦声beam.Microscopic识别的损伤层，由机械加工产生的，是由扫描声显微镜进行。通过一系列的实验，阐明了以下几点。1)SAM可以检测出主应力之和，并获得与硬度相关的信息。2)SAM的波强度可以检测由变形引起的杨氏模量的变化。通过使用具有显著材料非线性的聚碳酸酯膜作为试样来验证这一点。3)损伤层中的退化可以通过瑞利波速度和V（z）曲线的傅立叶变换上的全反射功率来评估。

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.