Papers by Keyword: Caustics Method

Abstract: The dynamic fracture experiments were conducted on the heat treated magnesium alloys; AZ31B-O, AZ31B-200 °C, and AZ31B-430 °C. Cross shaped specimens with the crack on their center were used for the experiments. Dynamic fracture behavior near a crack tip under equal and unequal biaxial stress was observed by the caustics method. From the observation, the stress intensity factor and the fracture toughness value were calculated. As a result, the effect of heat treatment was found. However, no clear relation such as correlation between dynamic stress intensity factor and heat treatment temperature was deduced.

Abstract: The dynamic fracture properties of polypropylene/nylon-6 (PP/PA6) blends, with different weight fractions and different compatibilizars, are investigated by reflected dynamic caustics experiments. According to the shadow spot patterns around a moving crack tip, which are recorded during the dynamic fracture process, dynamic fracture toughness and crack growth velocity can be estimated to evaluate the fracture properties of polymer blends. Moreover, combined with microscopic observation, the damage mechanism of the polymer blends is discussed.

Abstract: The crack, which occurs because of fatigue, should often consider not only the single crack but also plural cracks occurring. In this paper, the material strength when two or more cracks occurred because of fatigue etc. was examined by calculating stress intensity factor K value by using caustics method and the photoelasticity. In general, plural cracks are known KI value decreases compared with the single crack. Therefore, the influence on K value was experimentally examined from the point of the distance between the cracks, the angle, and the crack length and the mode change. As a result, KI value influences destruction in plural in exist only mode I and the mixed mode of mode I and mode Ⅱ like this research cracks. When the crack length becomes long if the distance between the cracks narrows, the decrease of KI value grows. In addition, it has been understood that the decrease of KI value is influenced by a/w on the boundary of d/a=1 (the distance between the cracks is equal to the crack length).

Abstract: In this study, the dynamic behaviors of cracks under dynamic biaxial stress are investigated. We conduct dynamic loading fracture experiments on the aluminum (2024-T3) and the magnesium alloy (AZ31B-O) under equitable biaxial stress with a hydraulic high-speed biaxial experimental machine. The processed specimens are cruciform with a crack. Different kinds of cracks are defined by their crack angles. We analyze the results by the caustic method. We obtained the stress intensity factor and the fracture toughness value in the neighborhood of the crack tip under dynamic biaxial stress. We analyzed the obtained data, and then, we compared results.