Papers by Keyword: Caustic Method

Abstract: Static and dynamic loading fracture experiments were conducted on magnesium alloy under equal and unequal biaxial stress. Cross shape specimens with a crack on their center were used for tests. Fracture behavior was observed by two methods; the caustic and the one point gauge method. From the observation, the stress intensity factors and the fracture toughness values were calculated. It was found that the one point gauge method was not suitable for calculating the stress intensity factor with a strain gauge widely available. The fracture toughness values obtained under equal biaxial stress were 1.2~2.3 times greater than those of magnesium alloy naturally inherited. Moreover, plate thickness was negatively related to the fracture toughness value.

Abstract: Dynamic crack propagation in PMMA was studied using the method of caustics in combination with a Cranz-Schardin type high-speed camera. Three different types of specimen geometries were employed to achieve the crack acceleration, deceleration and re-acceleration process in one fracture event. Dynamic stress intensity factor KID and the crack velocity were evaluated in the course of crack propagation to obtain the relationship between KID and the velocity The effect of crack acceleration and deceleration on the KID -velocity relations was examined.

Abstract: In this study, dynamic behaviors of cracks under dynamic biaxial stress were investigated. We conducted static and dynamic loading fracture experiments on a magnesium alloy (AZ31B-O) under equitable and inequitable biaxial stress by using a hydraulic high-speed biaxial experimental machine. We processed specimens as the cross type with a crack. Different kinds of cracks were defined by their crack angles. We analyzed the results using the caustic method. The experiments revealed some important findings; there is a negative relation between the fracture toughness value and the plate thickness of the magnesium alloy sheet specimen; the fracture toughness value decreases when the crack has an angle different from the loading direction; the fracture toughness value decreases significantly under inequitable biaxial stress.

Abstract: In this study, dynamic behavior of the crack under dynamic biaxial stress was investigated concerning of these situations. Specimen shape was assumed to be a biaxial fracture, and the load device was with a hydraulic high-speed biaxial experiment device, which this laboratory had developed. Dynamic stress intensity factors and strain behaviors in the crack tip, angle of the pre-crack and crack propagation direction, and relate about the dynamic fracture toughness value under a dynamic biaxial stress was studied.