| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for predicting the damage of a metal die with which the damage (large cracking or initial cracking) caused by brittle fracture as an important factor affecting the service life of the metal die for performing the plastic working of metal, such as a forging die, as the typical example, is predicted and the predicted value for serving to the metal die designing, such as the selection of material and hardness of the metal die and the decision of the die shape, etc., can be obtained. SOLUTION: The metal die designing is performed by selecting conditions, in which the brittle fracture predicted values F<SB>c1</SB>-F<SB>c3</SB>calculated with following formulas 1-3 do not exceed the critical values decided according to the material. The above-mentioned formulas 1-3 are as the followings: [Formula 1] F<SB>c1</SB>=(σ<SB>m</SB>/σ<SB>eq</SB>), [Formula 2] F<SB>c2</SB>=(σ<SB>m</SB>/σ<SB>1max</SB>) and [Formula 3] F<SB>c3</SB>=(σ<SB>1max</SB>/σ<SB>eq</SB>). Wherein,σ<SB>m</SB>is hydrostatic-pressure stress loaded to tension side of the metal die,σ<SB>eq</SB>is equivalent stress of Von Misese, andσ<SB>1max</SB>is the maximum main stress. COPYRIGHT: (C)2007,JPO&INPIT
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