Experimental investigations of the influence of thickness and mixed mode loading on the crack initial angle in LC4-CS aluminum

会议名称：《ICEM 2001 The 3～(rd) International Conference on Experimental Mechanics》

会议日期：2001年

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

关 键 词：Mixed mode crack initiation fracture criterion thickness effect aluminum alloy 

摘      要：正 Mixed mode fracture is one of the most common failure forms of materials in practical engineering. In the past, 2D crack initiation problems under mixed-mode I and II loading conditions have attracted much attention. Through many investigations, a number of fracture criteria for predicting the onset of fracture and the direction of crack initiation tinder mixed-mode I and II crack tip loading conditions have been well established, including the maximum tangential stress criterion （MTS-criterion）, the maximum energy release rate criterion, the minimum strain energy density factor criterion, and the maximum stress triaxiality criterion （M-criterion）. Nonetheless, there is lack of systematic studies on the relation between the crack initial angle and plate thickness insufficiently understood. In this paper, crack initial angle in LC4-CS aluminum plates is investigated experimentally using compact-tension-shear type specimens with various thickness 2, 4, 8 and 14 mm, respectively. The aim is to elucidate the effect of thickness on crack initial angle in aluminum plates and provide a good experimental foundation for revealing three-dimensional failure law and establishing three-dimensional fracture criterion of aluminum alloy under mixed mode loading *** specimen was loaded in a displacement-controlled MTS 810 100kN testing machine at a constant crosshead rate of 0.4 mm/min. Clip-gauge was mounted for measurement of crack opening displacement （CMOD） during final loading. Traces of load versus opening displacement were recorded for each test. Data were captured using the TestStar computer-testing system which triggered every 0.05 mm of displacement. After broken specimens were sectioned into halves at the mid-thickness, crack initiation directions were measured with a universal bevel *** results of the crack initial angle for various thickness plates and mixed load modes were obtainted and compared with theoretical predictions from MTS-cr