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珠光体组织的疲劳裂纹扩展方式可分为A,B,C三种类型。A型为裂纹同时横切多层铁素体片和渗碳体片而扩展;B型为裂纹逐层切割铁素体片和渗碳体片扩展;C型为裂纹只沿一层铁素体片或其界面扩展。A型出现的几率最大,B型的扩展阻力最大,C型的扩展阻力和出现的几率都最小。在疲劳裂纹扩展过程中它们的断口特征和比例都不同。在疲劳裂纹慢速扩展区,珠光体组织的疲劳裂纹扩展方式为A型加部分C型或B型。在疲劳裂纹稳态扩展区以A型和B型为主,可见明显的疲劳条纹,在快速扩展区以解理或韧窝为主。
The pearlite fatigue crack growth mode can be divided into A, B, C three types. Type A cracked at the same time transversely multi-layered ferrite sheet and cementite sheet expansion; B-type crack layer by layer cut ferrite sheet and cementite sheet expansion; C-type crack along only a layer of ferrite Expansion of the film or its interface. Type A has the highest probability of occurrence, Type B has the largest expansion resistance, and Type C has the smallest expansion resistance and chance of occurrence. Their fracture characteristics and proportions are different during fatigue crack propagation. In the slowly expanding zone of fatigue crack, the mode of fatigue crack propagation in pearlite is A type plus C type or B type. In the steady state fatigue crack growth zone, type A and type B are the main ones. Obvious fatigue streaks are observed. In the rapid expansion zone, cleavage or dimples are dominant.