欠陥を有する鋳造材料に対する強度評価法の提案: Si添加難燃性合Mg合金による検討(<小特集>自動車技術を支える材料力学)

In order to evaluate a casting material which has scatter tensile strength, a strength evaluation method was proposed. Tensile tests were carried out by specimen with a particular artificial defect as a fracture origin. The size of the fracture origin could be controlled using the proposed evaluation method. Therefore the tensile test results which have a little scatter were obtained. However shape of the artificial defect is different from one of casting defect and the effects of each defect on the tensile strength might be different. Then both of the stress intensity factors at the beginning of unstable fracture were compared, it was clarified that the artifical defect and the casting defect have the same effect on the tensile strength. By this method, a Si-added noncombustible Mg alloy which has large casting defects could be evaluated. It was clarified that there is no difference of tensile strength between 1% and 2% Si-added noncombustible Mg alloy, and it is obtained that the relationship between tensile strength and temperature.