Abstract
The present study was undertaken to investigate the chipping behaviour frequently found on blanking punch, since no systematic research about this behaviour has been established. The punches made of SKD-1 steel were used to reproduce the chipping-phenomena by simulation. The punches, after this test, were examined by means of electron fractography and optical microscopy.(1) The critical limit value of side direction stress to occur the chipping-fracture is exist.(2) This critical limit value depends on hardness of punch.(3) Life time of punch is depends on hardness of punch and with value of side direction stress.(4) On the case of low side stress, many small fatigue cracks joined with each other and grow up the long crack, and chipping fracture results from the crack growth. But on the case of havy side stress, a small fatigue crack immediately grow to the chipping fracture.
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