X-Ray Study on the Behavior of Carbon Steels under Static and Impact Compressions

Abstract

In this experiment, residual stresses and half-value breadths were measured by the X-ray method, on the specimens of carbon steels with circular notches, by application of static or impact loads, followed by application of combined static-impact loads. For impact loading a simple apparatus of drop hammer type was used, and the applied compressive strains at the notch root (0.2 to 0.9%) were measured with a synchroscope. The X-ray measurements were carried out by the film method using CrKα radiations at the notch root, and on the Lüders band at three locations.The experimental results obtained are summarized as follows. In the case of separate loading, both residual tensile stresses and half-value breadths increased with the applied strains, and the increase in the latter was remarkably larger in the case of impact load. In the case of combined loading of the same kind, the increases in half-value breadth were smaller and, on the contrary, the residual lattice strains were larger as compared with the case of individual loading. On the other hand, in the case of combined loading of different kind, the change in the sequence of loading gave the inverse tendency. On the Lüders band, the residual compressive stresses as well as the increases in half-value breadth showed larger values at points located nearer to the end point. The etching experiment revealed that the residual stresses are restricted within the utmost thin layers from the surface, and that the region of lattice distortions is assumed to penetrate the deeper layers under impact load.