Residual stress evaluations of thermally sprayed coatings by a modified Almen method

<正>Based on the Almen method,the authors have modified this test method so that the results of the simple testcan be correlated to the absolute values of residual stress measured fy conventional methods such as X-ray diffraction ormechanical techniques.The technique utilizes changes in the strain of standardized test substrates, which is measured byBHP-700℃ temperature-compensated reststance strain gauges, as an indication of the level of residual stress in thesprayed coatings. Based on the concept that the sprayed coating on the surface of substrate with residual stresses acts aforce (N) and bending momeat (M) on the test piece,the calculating equation of residual stress in the coatings hasbeen proposed. The results of the test method showed that the technique is potentially reliable and accurate, althoughdeficiencies and many controversies are still exist.