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给出了带裂纹橡胶零件的开裂判据Ｊ≥ＪＣ。由标准橡胶试件的实验发现， 试件拉断时的最大载荷和裂纹开始启裂时的临界载荷， 均与裂纹相对深度ａ／ ｗ 呈线性关系， 且随着裂纹相对深度的增加而减小。利用载荷位移曲线上的裂纹启裂点拟合出了裂纹启裂迹线， 进而采用裂纹启裂迹线法测定了油田常用橡胶的临界Ｊ积分值（ 断裂韧性） ， 计算时去除了远离裂尖区域所吸收的能量， 得到４ 种橡胶的临界Ｊ积分值， 即２４０ 号橡胶的ＪＣ＝ ７－１５ ×１０ － ３Ｊ／ｍｍ２ ； ８０２ 号橡胶的ＪＣ＝４－７８ ×１０－ ３Ｊ／ｍｍ２ ； ８１３ 号橡胶的ＪＣ＝ ３－８５ ×１０ － ３Ｊ／ｍｍ２ ； ８１４ 号橡胶的ＪＣ＝ ３－６９×１０ － ３Ｊ／ｍｍ２ 。
The cracking criterion of cracked rubber parts is given as J≥JC. It is found from the experiment of standard rubber specimens that the maximum load at breakage of specimen and the critical load at crack initiation are linear with the relative crack depth a / w and decrease with the increase of relative crack depth . The crack initiation trace was fitted by using the crack initiation point on the load displacement curve, and then the critical J integral (fracture toughness) of the commonly used rubber in the oilfield was determined by using the crack initiation trace method. When calculating, the crack tip away from the crack tip Area of the absorption of energy, the four kinds of rubber to obtain the critical J integral value, that is 240 rubber JC = 7-15 × 10 - 3J / mm2; 802 rubber JC = 4-78 × 10-3J / mm2; 813 JC = 3-85 × 10 - 3J / mm2 rubber; JC = 839 rubber = 3-69 × 10-3J / mm2.