摘要
部分地这个系列的Ⅰ，在 EPFM (有弹性塑料的破裂力学) 的试验性的调查被讨论了。在这篇论文，试验性的调查 inLEFM (线性有弹性的破裂力学) 被给。破裂坚韧测试在三不同力量钢上被执行了，用有不同 a/W 比率的彻底地击碎的标本和有可变裂缝尺寸和形状的半椭圆的击碎的标本。当时，结果证明破裂坚韧 K_(IC ) 与减少的 a/W 增加 a/W 【0。3 因为为 a/W 】 的 three-point-bendspecimens，和那 0.3， a/W 独立。浅裂缝标本，击碎 boththrough 、击碎表面，给了显著地更高的价值比深深地 notched 标本。然而，破裂坚韧上的裂缝形状的效果是可以忽略的。结果也证明折断的那条 theLEFM 途径不为 a_c 经常是很小的设计压力是守得住的，远不到 2.5 (K_(IC )/ σ _ y )~ 2。
In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.
