• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.649-655
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• 2019

Fracture behaviors of SCM435 high strength bolt have been studied including macroscopic and microscopic fracture observation, Energy Dispersive X-ray Spectroscopy, Vickers hardness test and applied stress evaluation. cracks (ratchet marks) were generated by the repetitive loads acting on the bolts, initial stress of bolt and the stress concentration. The applied stress was found to be slightly higher than the fatigue limit of the material. The initial stress of bolt must be removed, and the mold temperature during the process must be maintained by room temperature. Bolts are recommended to be peened to improve fatigue limit.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.317-326
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• 2004

This study investigated tile local austenite grain size (AGS) distribution In rolling of SCM435 steel which is commonly used for high strength bolt. To investigate AGS distribution, round-oval (R-O) and square-diamond (S-D) rolling experiments were carried out with pilot mill. In round-oval rolling, local AGS has a tendency to increase when it goes to outward. In square-diamond rolling, local AGS has a tendency to increase when it goes to free surface. To investigate relation between AGS and process parameter, three dimensional FE analysis was carried out along with rolling experiment. To validate accuracy of FE analysis, we compared deformed geometry with FE result. The AGS prediction combined AGS model with numerical analysis was also carried out for center node of S-D rolling. Although this study brought experimental observation and its qualitative analysis into focus and quantitative AGS prediction will be done as a further work.