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传统的工程习惯,认为冲击值越大越好,这样就不会引起脆性破坏,因此在工程技术上就片面追求α_k值,可是α_k值往往和σ_b、σ_s相矛盾,为了追求高的α_k值,就势必牺牲强度性能。人们必须在这二者之中作出一种选择,由于以往人们对脆性破坏认识的不足,因此往往作出提高α_k降低强度的选择,可是这种选择往往并不理想,相反,α__k虽然比较低,强度比较高,或者不是高级的材料,在实际使用中却能胜任工作,例如现在广泛采用球墨铸铁做内燃机车、汽车、拖拉机和轮船等大马力柴油机曲轴,其α_k值只有1.2～1.5,一般不超过2,可是却使用得很好;又如凿岩机活塞,苏联原用的是12Cr2Ni4渗碳淬火,
Traditional engineering practice, that the larger the impact value the better, so that it will not cause brittle failure, so one-sided in the engineering and technology to pursue α_k value, but α_k value and σ_b, σ_s often contradictory, in pursuit of high α_k value Is bound to sacrifice the strength of performance. People must make a choice between the two. Because of the lack of understanding of brittle failure in the past, people often make the choice of lowering the strength of α_k. However, this choice is often not ideal. On the contrary, although α__k is relatively low, the strength For instance, ductile iron is widely used as a crankshaft for high-horsepower diesel engines such as diesel locomotives, automobiles, tractors and ships, and its α_k value is only 1.2 to 1.5 and generally does not exceed 2, but it is used well; Another example is the rock drill piston, the Soviet Union is used 12Cr2Ni4 carburizing and quenching,