RELATIONSHIP BETWEEN TEMPERING TEMPERATURE AND CRACK INITIATION LIFE FOR 40Cr STEEL

The relationship between tempering temperature andcrack initiation life for 40Cr steel is investigated by system analysismethod in this paper. The samples at three tempering temperatures are examined in three-point bending fatigue tests. The results showthat there are two stages of crack initiations varing with tempertemperatures: (1) from 20^\circC\sim450^\circC, the crackinitiation life increases remarkably; (2) from 450^\circC\sim580^\circC, the crackinitiation life increases insignificantly. The results also show that thesystem analysis method is effective in the measurement of crack initiation lifenumerically.