Gunji Shinoda, Tatsurô Watari and Sadao Yamashiro
A compressive load was applied from y-direction to an ESD pipe and the resulting surface stress was measured at the lateral surface, i. e. the intersection of x-axis and the surface of the pipe, the centre of the pipe being taken as the origin of the coordinate, using Cu Kα X-ray. Photographs were taken from the both directions of perpendicular and 45° oblique to the specimen and obtained the following results: The stresses obtained from X-ray data coincide with those calculated from ordinary stress analysis and the applied load. But as soon as the applied load exceeds the yield point of the material, i. e. about 50 kg/mm2, the stress calculated from X-ray data begins to decrease and even tends to zero for the photographs taken from the directions perpendicular to the surface (i. e. in the perpendicular photographs). When the plastic deformation begins, the effect of the hydrostatic tension begins to appear and as this tension becomes zero at the surface, the stress at this place must be lower than the average one. As to the perpendicular photographs, among the crystal grains which have slip planes whose directions coincide with that of the maximum shearing stress, there exist the planes (511) which are oriented so as to be capable of reflecting Cu Kα radiation. Therefore, as soon as a load exceeding the yield point is applied, the slipping takes place at these grains and the positions of the X-ray lines tend to restore to the original positions of no load. Of course, there must exist the grains which share the increased load, but as these grains have no planes which are capable of reflecting X-ray to the back direction, the stress calculated from X-ray data shows as being diminished apparently.
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