Effect of Impact Energy in ESSO Test (Part 3: Experimental Validation for New Validity Criteria of Impact Condition Giving Constant Evaluation in ESSO Test)

Abstract In our second report, whether the impact had an important effect on the results or not depended on the critical condition that was proposed by calculating the ratio of the values of Kd both for where impact was considered and where it was not considered. This proposal was shown as a look-up figure where “effect” or “no effect” conditions were shown as regions illustrated on a graph, revealing the relationship between nondimensional impact energy and arrested crack length. In order to validate the criteria included in this proposal, some experiments under high impact energy conditions were carried out by using a steel plate with a known value of brittle crack arrest toughness under ordinary conditions. The experiments were conducted near the critical boundary that divides the area of “affect” and that of “not affect” on the evaluation. It was found that the experimentally evaluated plots closely followed the relationship of existing properties under low impact energy conditions of the same material on the Arrhenius plot. Hence, the proposed validity criteria can be interpreted as being made on the safe side. In addition, if the impact energy is larger than the specified condition, it may have an important effect on the test results. In this case, the results have to be treated as reference data in spite of being an expensive test. However, these criteria can only be determined after actual testing because the criteria include arrested crack length. Therefore, the authors also tried to make a simple recommendation for obtaining valid data that can be investigated before ESSO tests and without the effect of impact.