A Study on Experimental Evaluation of CED in an Arbitrary Direction Based on Load-Displacement Curves

The CED (crack energy density) in an arbitrary direction, ε_φ, is expected to be a parameter to describe not only elastic fracture but also elastic-plastic fracture of a mixed mode crack. This ε_φ is related to load-displacement curves of specimens and it was shown in the elastic region that ε_φ can be evaluated from experimentally obtained load - displacement curves with practically sufficient accuracy based on the relation. In this paper, the applicability of the method to elastic-plastic fracture problems is examined. That is, the load-displacement curves of specimens with a notch (or crack) inclined to the loading axis are obtained by experiments in the elastic-plastic region, and ε_φ is evaluated from those curves. The results are compared with those of finite element analyses, and the availability of evaluation method based on experimentally obtained load-displacement curves is demonstrated. Moreover, the method is applied to a fracture problem and it is shown that the method can be a powerful tool to evaluate the critical value of ε_φ (fracture toughness).