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Toyama-shi, Japan

Ishihara S.,University of Toyama | Yoshifuji S.,University of Toyama | McEvily A.J.,University of Connecticut | Kawamoto M.,Tanaka Seimitsu Kogyo Co. | And 2 more authors.
Fatigue and Fracture of Engineering Materials and Structures | Year: 2010

High speed steels, such as the alloy H-13, when used as forging dies are subjected to both wear and cyclic loading, and both of these factors can affect the useful life of such dies. It follows that it is of some importance to determine the fatigue characteristics of such steels. However, fatigue studies of such alloys are limited, especially with respect to fatigue crack propagation (FCP) behaviour as a function of mean stress, and therefore more detailed studies are necessary. In the present study, the fatigue lifetimes and the crack propagation behaviour of a high speed steel were experimentally investigated in laboratory air under different stress ratios, R. A modified linear-elastic fracture mechanics (LEFM) approach was applied to analyze the experimentally-obtained FCP behaviour. The predicted S-N curves and crack growth behaviour for a wide range of R ratios agree well with the experimental data, and the modified LEFM approach is therefore considered to be useful for evaluation of the fatigue behaviour of this class of high strength steels. © 2010 Blackwell Publishing Ltd. Source

Horita A.,University of Toyama | Ishihara S.,University of Toyama | Goshima T.,University of Toyama | Kawamoto M.,Tanaka Seimitsu Kogyo Co. | And 3 more authors.
Journal of Thermal Stresses | Year: 2012

In the present study, the repeated forging experiments were conducted using the real forging machine. For supplement of the experiments, forging simulation was also conducted to evaluate the forging load vs. stroke relation during the forging process. Further, stress intensity factor K at the fatigue crack-tip initiated in the real forging tool was evaluated using the new method proposed in the present study. Conclusions obtained are summarized as follows: (1) The cracked portions found in both the real forging-die and -punch are places where the maximum equivalent stresses occur during the forging process; (2) the data (da/dN, K) evaluated for the real forging die and punch corresponds well with the experimental relation da/dN vs. K obtained in laboratory air; and (3) the proposed simulation method is useful for estimating lifetimes of the forging die and punch. © 2012 Copyright Taylor and Francis Group, LLC. Source

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