Method of predicting damage of dies

Abstract

Disclosed is a method of predicting damage of dies for plastic processing of metallic materials, typically, forging dies, by predicting brittle fracture (“great crack” or “initial crack”) dominating die lives contribute to die design including choice of materials, hardness and configuration of the die. The method is characterized in that the die design is carried out by choosing the condition that none of the anticipated values of brittle fracture, F c1 to F c3 , calculated by the formulae 1 to 3 below exceed the critical values depending on the material used. F c1 =(σ m /σ eq )  [formula 1] F c2 =(σ m /σ 1 max )  [formula 2] F c3 =(σ 1max /σ eq )  [formula 3] σ m : mean normal stress loaded to the tensile side of the die σ eq : Von Misese's equivalent stress σ 1max : maximum principal stress

1 . A method of predicting damage of dies used for plastic processing of metallic materials by predicting “great crack” caused by brittle fracture dominating the die lives so as to contribute to die design including choice of die materials, hardness of the material and determination of die shape, which comprises carrying out the die design by selecting the conditions that none of the anticipated brittle fracture values F c1  to F c3  calculated by the formulae below exceed the critical values depending on the materials:  
         F   c1 =(σ m /σ eq )  [formula 1]   F   c2 =(σ m /σ 1 max )  [formula 2]   F   c3 =( s   1max   /s   eq )  [formula 3] 
     where, 
 σ m : mean normal stress loaded to the tensile side of the die  
 σ eq : Von Misese's equivalent stress  
 σ 1max : maximum principal stress.  
 
   
   
       2 . The method of predicting damage of die according to  claim 1 , wherein the material of the die is SKD61 steel and F c1 =0.7, F c2 =0.5 and F c3 =1.25.