• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.7-12
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• 2010

In this work, optimization analysis has been accomplished to find important process factors for realization of vertical wall around holes punched by the punchless piercing process. Taguchi method was used for optimization analysis. Lemaitre damage theory, one of the ductile fracture models, was also adopted to simulate numerically formation of vertical wall. From the results of analysis the most influencing factor that affects the vertical wall has been revealed to be 'Corner Radius of Die'.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.929-934
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• 2009

In this work, the punchless piercing process with application of alternate high pressure has been proposed as a method to obtain pierced holes having nearly vertical wall over thin metal plates. The numerical simulation considering Lemaitre damage model has been accomplished for the proposed method. The simulated results have been compared with those by conventional one-way punch less piercing process. It has been revealed that the fractured section made by pressure alternation method shows nearly steep wall where the deviation angle from the vertical line is as small as $3.6^{\circ}$.