The Use of Miniaturized Tests to Predict Flow Properties and Estimate Fracture Toughness in Deformed Steel Plates

Prediction of failure in a structure requires knowledge of the mechanical properties of the materials involved. In the case of serious accidents, such as derailments of railroad tank cars carrying hazardous materials, prediction of failure in damaged components is impeded by difficulties in determining the deformed material fracture toughness, the cracks induced by the accident, and the stress state in the damaged region. This paper addresses the problem of determining fracture toughness. Miniaturized shear punch tests on virgin, strained, and deformed steel plates (typical of railroad tank car construction) were conducted over a wide range of test temperatures. These data were compared with tensile properties measurements on identical materials. The use of these data coupled with micromechanical models of fracture allows estimation of the deformed material fracture toughness. Comparisons of the predicted fracture toughness with actual measurements are made.