Development of the Hybrid Laser-Speckle and Image-Analyzing Method for Measuring Deformation and Strain at Very High Temperature.

利用连续Ar激光器、电视装置和图像处理器，研制了一套电子散斑干涉（ESPI）系统，并将其应用于高温下自由热膨胀应变的测量。ESPI提供了在预选方向上分辨的面内位移的分布。电子散斑干涉技术具有表面处理少、不与表面接触、干涉条纹实时显示等优点。这就使得电子散斑干涉法在很高的温度下进行测量成为可能。在这种情况下，主要问题是高温物体周围的热空气中的湍流、来自物体的背景辐射以及由于氧化而导致的物体表面微观结构的变化。这些都造成了条纹可见度的降低。采用真空室解决了热空气湍流问题。样品上的条纹更加稳定，测量值的散射量在真空室中比在空气中少。在电视摄像机前端安装干涉滤光片，大大抑制了背景辐射。由于氧化，散斑图案的相关性降低。这在腔室中约4-10托的低压下是不可避免的。测量了四种高温金属的热应变。条纹在1200 ° C下可观察到，其间距通过FFT计算以避免人为误差。低压下的电子散斑干涉测量结果与900 ℃下的空气散斑照相测量结果及已发表的数据基本一致。SUS 430、Inconel 601和镍铬合金的线膨胀系数在反常点附近随温度迅速增加。难熔金属钽氧化严重。

A electronic-speckle-pattern-interferometry (ESPI) system using a cw Ar-laser, television equipment and an image processor has been developed and applied to the strain measurement on free thermal expansion at very high temperature. ESPI provides the distribution of in-plane displacement resolved in a preselected direction. ESPI retains the merits of little or no surface preparation, no contact with the surface, and the real-time presentation of interference fringes. These permited the measurement by ESPI at very high temperature. In this case the main problems were the turbulence in the hot air surrounding a high temperature object, the background radiation from the object and the change in the microstructure of the object surface due to oxidation. These caused the reduction of fringe visibility. The problem on hot air turbulence was resolved by using a vacuum chamber. The fringes on specimens were much more stable and the amount of scatter in measured values was less in a vacuum chamber than in air. The background radiation was supressed considerably by a interference filter which was placed at the front of TV camera. The correlation of speckle patterns was reduced due to oxidation. This couldn't be avoided in low pressure about 4-10 Torr in the chamber. The thermal strains on four kinds of high-temperature metals were measured. The fringes were observable to 1200ﾟC, which spacings were calculated by FFT to avoid human error. The results measured by ESPI in low pressure were neary equal to those to 900ﾟC by speckle photography in air and the data which have already been published. The linear coefficient of thermal expansion of the alloys such as sus 430, inconel 601 and nickel chromium increased rapidly with temperature, near the anomaly point. Tantalum of refractory metal oxidized heavily.