Avaliação da Tenacidade à Fratura e da Resistência à Fadiga de Dois Aços Utilizados em Eixos de Carros Torpedos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Fatigue and fracture of railway shafts are technical problems that have been treated in studies of mechanical behavior of materials. The pugh car shafts fracture during operation causes production losses and high cost to replace them. In this work, it has been studied the fracture toughness through CTOD parameter and the fatigue crack growth da / dNxΔK , of two steel types applied in pugh car shafts of a steel plant: the ASTM A21 grade H and AISI/SAE 4130 quenched and tempered. The main difference between these two steel types is their chemical composition. C(T) specimens, with B =12,5mm thickness and W =50mm width in L-R orientation were used in the experiments. The testing frequency was f=30Hz at stress ratio of R =0,1. Results revealed that the maximum admissible crack size to fracture toughness testing was 70,3% higher to AISI/SAE 4130 material, associated with 20,6% higher mechanical tensile strength. In the region I of sigmoid curve log(da / dN)xlog(ΔK) , the value of stress intensity threshold th ΔK was 6% higher to ASTM A21 grade H material, being more resistant to fatigue crack growth. In the other hand, it has been seen an identical behavior of fatigue crack propagation rate in the regions II and III. In both types of steel, the fatigue crack closure mechanism is predominantly induced by rugosity, and stronger in ASTM A21 grade H steel type.

ASSUNTO(S)

ctod fracture toughness fatigue engenharias ctod tenacidade à fratura fadiga

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