On the plastic deformation in steel specimens produced by an impact compression. 2nd report Effect of contact surface and specimen length for two piled specimens.

Abstract

When an impact load is imposed to a finite body, the dynamic stress state generated in it is very complicated and different from the static loading case. The purpose of this paper is to study the effect of the contact condition and specimen length on the size of the yielding zone generated by an impact compression in prismatical steel specimens, which were piled to a total height 60 m. The lengths of the respective specimens were 20, 30 and 40 mm. An impact compression was imposed on a pile of specimens by a drop weight superposed upon a static compression load at 3, -72 and -184°C respectively. The strain-time diagrams were measured by a strain gauge and discussed based on a one-dimensional stress wave propagation model taking into account the reflection and transmission at the contact surface. The yielding zone was generated near the upper end, the lower end and the contact surface of the specimens. The length of the yielding zone was larger for a large static load superposed, and smaller at a lower temperature. Swelling over the yielding zone was observed by an interferometer and distribution of hardness on the specimen surface was also examined.