PSI - Issue 19

Keiji Yanase et al. / Procedia Structural Integrity 19 (2019) 504–512 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

512

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a comparison of S-N diagrams of Material A and Material B. This figure clearly shows that the Material A has an ad vantage over Material B from the viewpoint of the fatigue life that is controlled by the shear-mode fatigue-crack initiation and propagation. Since the static strength of Material A is higher than that of Material B, this result seems reasonable. In practice, however, Material B provides better fatigue reliability for the high speed rolls partly because of its less sticking property in comparison with Material A. Given a noticeable difference exhibited in Fig.13, the realization of S N diagram with the present testing method has merit in the engineering point of view. For example, the inherent fatigue property associated with shear-mode crack growth can be quantitatively evaluated separately from the anti-sticking prop erty. Furthermore, the testing method, as presented in this study, is so simple as to provide the necessary data economi cally within a short period, and therefore, and it would be beneficial to make a right design decision for the development of roll materials with higher spalling resistance. Indeed, further studies are necessary to identify and incorporate the real influencing factors, as those determine the fatigue reliability of the rolls in service, into the proposed fatigue testing method.

4. Concluding remarks

In this study, the torsional fatigue load with superimposed static compression was applied to the roll materials. It was found that the shear-mode crack propagation behavior can be adequately observed and analyzed with this testing method. In particular, the comparison of the S-N diagram is easy and useful to check the influence of microstructure. The proposed testing method is beneficial to the rapid development of roll materials with higher spalling resistance. Further studies are necessary to identify and incorporate the real influencing factors into the proposed method.

References

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