crackv.破裂；砸开；发出爆裂声；撞击；破解；变嘶哑；崩溃；制裁；<非正式>开玩笑n.裂缝；裂痕；爆裂声；猛击；尝试；俏皮话adj.训练有素的crack hand一流好手

1. Grain size had some effect on the rate of crack propagation.
   晶粒尺寸大小对裂纹扩展速率也有影响。
2. In this paper, various influencing factors of the crack propagation rate of superalloy are concluded, including external factors and internal factors.
   总结了高温合金的裂纹扩展速率的各种影响因素，包括外部因素和内部因素两大类。