Micro-and macro-analysis of the fatigue crack growth in pearlitic steels

• Autor(a) principal: Toribio,Jesús
• Data de Publicação: 2008
• Outros Autores: González,Beatriz, Matos,Juan-Carlos
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://scielo.pt/scielo.php?script=sci_arttext&pid=S0870-83122008000100010
• topic: Pearlitic Steel; High Strength Steel; Fatigue Microdamage; Paris’ Law

This paper deals with the influence of the manufacturing process on the fatigue behaviour of pearlitic steels with different degrees of cold drawing. The analysis is focussed on the region II (Paris) of the fatigue behaviour in which da/dN=C (∆K)m, measuring the constants (C and m) for the different degrees of drawing. From the engineering point of view, the manufacturing process by cold drawing improves the fatigue behaviour of the steels, since the fatigue crack growth rate decreases as the strain hardening level in the material increases. In particular, the coefficient m (slope of the Paris laws) remains almost constant and independent of the drawing degree, whereas the constant C decreases as the drawing degree rises. The paper focuses on the relationship between the pearlitic microstructure of the steels (progressively oriented as a consequence of the manufacturing process by cold drawing) and the macroscopic fatigue behaviour. It is seen that the fatigue crack growth path presents certain roughness at the microscopic level, such a roughness being related to the pearlitic colony boundaries more than to the ferrite/cementite lamellae interfaces.