The Influence of the Specimen Surface on the Measurement of Residual Stress by X-Rays
The Influence of the Specimen Surface on the Measurement of Residual Stress by X-Rays
复制标题
试样表面对X射线残余应力测量的影响
DOI：
10.2472/jsms.12.882
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发表时间：
1963
期刊：
影响因子：
--
通讯作者：
K. Kato
中科院分区：
文献类型：
--
作者：
M. Motoyama;Toyoichiro Enami;H. Horizawa;K. Kato
利用X射线测量应力的方法在许多实验室得到了广泛的应用，这是近年来一个显着的趋势。然而，也是一个事实，一些关心这种测量的实验人员仍然对它的准确性有一些怀疑。去年在本学会关于X射线应力测量的特刊上报道的在我实验室进行的实验结果表明，这种测量具有很高的精度。这种高的精度被认为是由于确认了样品表面状况对X射线应力测量的准确性有重要影响，这是我们实验室通过大量调查获得的。然而，一些关于X射线应力测量的文献对表面状况的影响处理得很少。因此，为了阐明这一点，我们使用了不同表面条件的试件进行了实验。结果表明，表面细小的试件所测得的应力与载荷应力吻合较好，而表面粗糙的试件所测得的应力与载荷应力相差较大。此外，对于残余应力，表面细小的试件的测量值大于表面粗糙的试件的测量值。两者测量值之间的差异随着残余应力的增大而增大，其原因可能是与X射线的穿透深度有关。在试件表面粗糙的情况下，X射线的浅穿透可能得不到真实的应力值，因为投影区的应力被消除了。因此，样品表面必须始终是平坦和光滑的，但我们使用的大多数样品远远不能满足这一条件。因此，抛光方法是为了获得光滑的表面，但在抛光过程中引入了应力，导致了真实应力值的移动。为了消除加工中的这种应力，到目前为止，已经采用了通过盐酸或硝酸等化学物质进行刻蚀的方法。然而，化学腐蚀表面的实验结果并不理想。因此，在我们实验室，考虑到加工过程中去除应力后样品表面的平坦度，采用了电解抛光方法，正如本学会关于X射线应力测量的特刊中所报道的那样。此外，我们还研制了一种能够在短时间内消除任何试件加工过程中的应力的电解抛光装置，并用于本实验室。本文报告了以Cr-Kα射线作为特征X射线的情况下所获得的结果。如果所用的Co-Kα射线的穿透深度与Cr-Kα射线的穿透深度不同，则结果可能与本文报道的有所不同。但试件表面应平整光滑仍是一个普遍要求。关于样品表面Co-Kα射线粗糙度之间的关系，作者将进一步研究，并等待另一次机会报告结果。
It is a recent remarkable tendency that the method of X-ray stress measurement by means of X-rays has come to be widely utilized in many laboratories. It is also a fact, however, that some experimenters concerned with this measurement have still some doubts about its accuracy.The results of the experiments carried out in our laboratory, as was reported last year in the special issue of this society pertaining to the measurement of stress by X-rays, showed a high accuracy in the measurement. This high accuracy is considered to have been established as a result of the confirmation that the condition of the specimen surface has an important effect on the accuracy in the measurement of stress by X-rays, which was obtained through a number of investigations in our laboratory.Some literature concerning the measurement of stress by X-rays, however, treat the influence of the surface condition lightly. Accordingly, in order to make this point clear, experiments were carried out using the specimens with various surface conditions. As a result, it was found that the stress measured in the specimens with fine surfaces is in good agreement with the load stress, while that of the specimens with rough surfaces show discrepancies. Besides, as regards the residual stress, the measured values of the specimens with fine surfaces were found to be larger than those of the specimens with rough surfaces. The difference between both the measured values became larger as residual stress increased.The reason why the measured values show differences according to the conditions of the specimen surface might be ascribed to the circumstance that they may have some connection with the depth of penetration of X-rays. In case the specimen surface is rough, the real stress value may not be obtained for the shallow penetration of X-rays, because the stress in the projected area is relieved. Therefore, the specimen surface must always be flat and smooth However most specimens in our use are far from satisfying this condition. Consequently, polishing method is used to obtain a smooth surface, but in the course of polishing stress is introduced, resulting in the shift of the true stress value. In order to eliminate this stress in processing, etching methods by means of chemicals such as hydrochloric or nitric acid have been employed so far. Experiments, however, have shown no good results on the chemically etched surfaces.In our laboratory, therefore, taking the flatness of the specimen surface after the removal of stress in processing into consideration, electrolytic polishing method has been adopted, as was reported in the special issue of this society concerning the measurement of stress by X-rays. Besides, an electrolytic polishing apparatus was manufactured which is capable of eliminating the stress in processing in any specimen in a short time and which is used in our laboratory.This report contains the results obtained for the case in which Cr-Kα rays were employed as characteristic X-rays. If Co-Kα rays with a different penetration depth from that of Cr-Kα rays were used, the results might be somewhat different from this report. But it remains a common requirement that the specimen surface should be flat and smooth. As regards the relation between the roughness of the specimen surface Co-Kα rays, the authors will further their researches and await another opportuuity to report the result.