Modern Situation in Photoacoustic and Thermoelastic Stress Analysis in Application to the Problem of Mechanical Stress Measurements

Abstract

The performance of any component to a great extent is determined by residual stress, resulting from virtually all manufacturing processes. Therefore the problem of residual stress detection and measurement is urgent in modern engineering, mechanics and material physics. A good deal of effort has been undertaken in developing different methods for the residual stress detection. Optical, ultrasonic, magnetic methods, Raman spectroscopy, X-ray and neutron diffraction are effectively applied for detection of residual stresses in many cases. Thermoelastic stress analysis (TSA) is also now a well-known experimental technique (Pitarresi and Patterson [1]) providing information on the surface stress fields in structures. Two common systems based on TSA are developed at present. Stress pattern analysis by measurement of thermal emission (SPATE) has a single detector, while DELTATHERM® systems have a staring array of detectors. These techniques have been already implemented effectively for the residual stress detection. It was experimentally demonstrated that mechanical stresses modify the thermal emission signal. Hole drilling and compliance methods are also actively investigated at present for residual stress detection. Recently holographic or speckle interferometry in conjunction the hole-drilling method has attracted serious attention for solution of this problem. Unfortunately, as a rule many of these methods have limited fields of application. For example, Raman spectroscopy is mainly used in science and technology of semiconductors for which the phonon lines have a relatively simple structure and their shifts with stress are well known. SPATE, DELTATHERM® and holographic interferometry are of more general applicability, but have comparatively low spatial resolution.