针对平面应变断裂韧度测试中试样厚度条件的选择问题, 以760 ℃亚温淬火45钢紧凑拉伸试样断裂韧度试验为例, 分析讨论了试样厚度对断裂韧度的影响以及试验获得平面应变断裂韧度有效值的约束条件。结果表明: 传统断裂韧度试验的厚度要求不一定适合作为亚温淬火45钢试样尺寸的要求依据; 对于亚温淬火45钢脆性材料的试样, 若断裂破坏以正断为主, 其厚度已经满足平面应变条件的要求, 从而可以测出断裂韧度。

According to the evaluated criterion of specimen thickness in the plane-strain fracture toughness test, the fracture toughness tests for 45 steel quenching at 760 ℃ were experimentally investigated. The effect of specimen thickness on the fracture toughness and the criterion to get the valid plane-strain fracture toughness was analyzed and discussed. The results show that: the thickness criterion for the traditional fracture toughness test may not suit for the fracture tough test for subcritical quenching 45 steel; for the brittle material specimens of subcritical quenching 45 steel, if the fracture type was mainly the traction fracture, then their thickness had already met the thickness criterion, and the fracture toughness could be measured.