摘要
为得到弹塑性材料裂纹扩展的阻力曲线,采用较大外径和较大韧带直径的周边切口在自行研制的间接杆杆型冲击拉伸试验装置上进行了动态断裂和起裂止裂试验.采用数值分析提出的修正方法得到韧带面上的载荷,结合测得的裂纹嘴张开位移(CMOD),推广Rice远场J积分公式来计算动态J积分;依据柔度变化率法确定起裂点,从而获得动态起裂韧度JID.利用柔度标定法得到裂纹扩展轨迹;提出了周边切口拉伸试件裂纹扩展阻力的动态^JM(t)积分表征的修正形式,从而得到了弹塑性材料裂纹扩展至止裂前的阻力曲线,并对相关问题进行了讨论.试验结果表明:修正的^JM(t)可以作为裂纹扩展阻力的表征参量,不仅适用小量稳态扩展过程,裂纹扩展较大时也适用;对弹塑性材料裂纹扩展阻力曲线是惟一的,与裂纹初始长度无关.
To obtain the resistance curve of crack growth of an elastic-plastic material, a test for dynamic crack initiation and arrestment is carried out on a self-designed bar-bar tensile impact apparatus by using larger diameter short specimens with deep circumferential notches and larger ligament diameters. Dynamic J-integral is calculated by extending the J-integral formula of Rice and using the load on ligament plane and the crack mouth opening displacement（CMOD） through direct measuring. The load is obtained by using the modified method proposed by previous FEA work. The time of crack initiation is determined by the compliance changing method and corresponding dynamic crack initiation toughness JID is obtained. Crack growth path is determined by the calibration curve method. The modified formula of crack growth JM（t） about tensile specimens with deep circumferential notches is proposed, and then the material resistance curve is obtained. Some relative problems are discussed. The results show that modified JM（t） as a characteristic parameter of crack initiation and growth is not only applicable to small stable crack growth but to larger crack growth as well. The material resistance curve is unique and independent on crack initial lengths.
关键词
弹塑性
动态断裂
周边切口
裂纹扩展
止裂
J积分
elastie-plastic
dynamic fracture
circumferential notch
crack growth
arrestment
J-integral
