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试件厚度B是断裂力学研究中的一个重要参数。北京钢铁研究总院已故著名断裂力学学者陈篪同志等在大量实验的基础上,总结并提出了在测试金属材料平面应变断裂韧性K_(1c)中,满足平面应变条件的试件厚度B的标准应为: B≥6 S其中S为剪切边宽度。本文通过对小范围屈服条件下裂纹前缘塑性区的计算,根据平面应力和平面应变两种状态下裂纹扩展能量率G_1的比值,从能量的观点推导了满足平面应变条件的试件厚度B与剪切边宽度S的关系为: B≥4.32 S 这一结果与实验的总结基本吻合。这样,就从理论上说明了B依赖于S的关系要比B≥2.5(K_(1C)/σ_S)~2更具有科学性,它将有益于工作的的K_(1C)测试和实验研究。
Specimen thickness B is an important parameter in fracture mechanics research. On the basis of a large number of experiments, the famous researcher of fracture mechanics of Beijing Institute of Iron and Steel Research summarized and proposed the thickness B of the specimen satisfying the plane strain condition in the plane strain fracture toughness K_ (1c) of the test metal material The standard should be: B ≥ 6 S where S is the width of the sheared edge. Based on the calculation of the plastic zone of crack front under a small range of yield conditions and according to the ratio of the crack propagation energy ratio G 1 under both plane stress and plane strain, the thickness B of the specimen satisfying the plane strain condition is derived from the energy point of view The relationship between the sheared edge width S is: B≥4.32 S This result is basically consistent with the conclusion of the experiment. Thus, it is theoretically proved that the dependence of B on S is more scientific than that of B ≧ 2.5 (K 1C / σ S) 2, which will be beneficial to the K 1 C test and experimental research.