IMPROVEMENT OF FATIGUE LIFE BY REDUCING THE FORMATION OF CRACK DURING EDM PROCESS | ||||
| The International Conference on Applied Mechanics and Mechanical Engineering | ||||
| Article 31, Volume 13, 13th International Conference on Applied Mechanics and Mechanical Engineering., May 2008, Page 26-34 PDF (1.17 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/amme.2008.39062 | ||||
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| Authors | ||||
| TAI T. -Y.1; LEE H. -T.2; HSU F. -C.3 | ||||
| 1Assistant professor, Dpt. of Mechanical Engineering, Southern Taiwan University, Tainan, Taiwan. | ||||
| 2Professor, Dpt. of Mechanical Engineering, National Cheng-Kung University, Tainan, Taiwan. | ||||
| 3Engineer, Metal Industries Research & Development Centre (MIRDC), Kaohsiung, Taiwan. | ||||
| Abstract | ||||
| ABSTRACT The present study performs an experimental investigation to identify the EDM processing parameters which suppress the formation of surface cracks in the machined surface of SKD11 tool steel specimens. The rapid heating and cooling effects inherent in the electro-discharge machining (EDM) process result in the formation of a brittle recast layer on the machined surface. This layer increases the surface roughness of the machined component and is characterized by globules of debris, shallow craters, pockmarks, voids and cracks. In the EDM trials, the specimens are machined using pulse currents of 4A, 16A or 32A with pulse-on durations of either 4μs or 16μs. The various specimens are then fatigue tested at loads ranging from 150~245 Kg in order to determine their respective fatigue lives. A polished SKD11 specimen is also fatigue tested for comparison purposes. The results show that the EDM processing parameters have a significant effect on the surface cracking characteristics. Specifically, when the EDM process is performed using a pulse current of 4A and a pulse-on duration of 16μs, the machined surface is found to have a high surface crack density and some of the cracks penetrate as far as the parent material. With processing parameters of 16A /4μs and 32A/16μs, a recast layer is formed on the surface of the machined specimen, but no surface cracks are observed. Hence, it can be inferred that increasing the pulse current and reducing the pulse-on duration provides an effective means of suppressing the surface cracking phenomenon. Higher values of the pulse current and pulse-on duration (i.e. 32A and 16μs, respectively) are found to increase the average thickness of the recast layer and to prompt a corresponding reduction in the fatigue life of the machined specimen. | ||||
| Keywords | ||||
| Electro-discharge Machining (EDM); Fatigue life; Surface Crack | ||||
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