材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
円筒鋼材の残留応力の測定について
Sachs' 法で求められた残留応力分布とX線応力測定法で求められた表面応力の値との比較
下田 秀夫荒木田 豊
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1963 年 12 巻 123 号 p. 875-881

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Sachs' method is generally used as a means to explore the residual stress distribution of various cylindrical steel, but this method is practically inapplicable to the steel products, as it is a destructive method. This is a serious drawback from a practical viewpoint. It is generally said that some kind of residual stress affects the fatigue strength of machine parts. Therefore, it is particularly desirable to resort to a non-destructive method in order to explore the residual stress distribution inside the steel that forms machine parts. As one of the non-destructive methods, there is stress measurement by X-rays, and the surface stress of any product can be measured directly by this means. But the stress measurement by X-rays alone is not adequate yet to know the value of residual stress inside of the steel that forms machine parts.
The authers have reported previously the method of calculating residual stress which is incidental to the heat treatment inside cylindrical steel with the phase transformations in consideration. If the value of the surface residual stress is obtained by the X-ray method and is used as a measure of quantitative check of such calculation results, such a calculation method will have practical utility. But it is sometimes necessary to use Sachs' method to ascertain experimentally the truth of the result reached by the X-ray method. What is the relation then between the surface stress value obtained by the X-ray method and the stress distribution obtained by Sachs' method? Is there good agreement between both the results obtained by X-rays and Sachs' method?
In this report are mentioned some experiments which have been made on this problem and the results there of. Conclusively, it may be stated as follows;
(1) Test was made of reproducibility of the average value obtained from the four values measured by the X-ray method. Although the two average values of the two independent measurements show good agreement, there is considerable scattering among the values individually measured which is considered not to be attributed only to technical error but also to crystalline inhomogenity.
(2) There is some disagreement between the the surface stress value obtained by X-ray method (at 0.25mm depth from outer surface) and the surface stress value obtained by Sachs' method (at 2.5mm depth from outer surface). It is shown in this test that |σS|>|σX| This discrepancy is not to be approved in the procedure of testing materials.
(3) The above mentioned disagreement can only be accounted for by the hypothesis either that some specially steep stress gradient occurs due to heat treatment of the material or that there is some essential difference which inhibits treating σS and σX as the quantity of the same class. This problem requires further experiments to be made with high precision and more data to be collected therefore.

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