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、电视设备和图像处理器研制了电子散斑干涉测量系统，并将其应用于高温下自由热膨胀应变的测量。ESPI提供在预选方向上解析的面内位移的分布。ESPI保留了表面处理很少或不需要表面处理、不与表面接触以及实时显示干涉条纹的优点。这些都允许在很高的温度下用ESPI进行测量。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，物体的背景辐射，以及由于氧化而引起的物体表面微结构的变化。这导致了条纹能见度的降低。利用真空室解决了热风湍流问题。样品上的条纹要稳定得多，在真空室中的散射量比在空气中小得多。放置在摄像机前端的干涉滤光片对背景辐射有较大的抑制作用。由于氧化作用，散斑图像的相关性降低。在4-10Torr的低气压下，这是不可避免的。测量了四种高温金属的热应变。条纹可以在1200ﾟC下观察到，这些间距是通过快速傅立叶变换计算的，以避免人为错误。用电子散斑干涉法在低压下测得的结果与空气中散斑照相法的结果和已发表的数据相差不大，仅为90 0ﾟC。SUS 430、Inconel601和镍铬等合金的线膨胀系数随着温度的升高而迅速增大，在异常点附近。难熔金属的钽被严重氧化。

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.