FATIGUE ANALYSIS OF FORGING DIE

In the present study, the repeated forging experiments were conducted using the real forging machine. For supplement of the experiments, forging simulation was also conducted to evaluate the forging load vs. stroke relation during the forging process. Further, stress intensity factor K at the fatigue crack-tip initiated in the real forging tool was evaluated using the new method proposed in the present study. Conclusions obtained are summarized as follows: (1) The cracked portions found in both the real forging-die and -punch are places where the maximum equivalent stresses occur during the forging process; (2) the data (da/dN, K) evaluated for the real forging die and punch corresponds well with the experimental relation da/dN vs. K obtained in laboratory air; and (3) the proposed simulation method is useful for estimating lifetimes of the forging die and punch.