The method for reliability estimation of the machine elements under low temperature conditions

The subject considered are the theoretical dependences between parameters in a small scale yielding zone length, and a plastic zone at cave-in spherical indentor. The loadings of a spherical (D=5 mm) indenter in the range from 147 to 11875 N within absolute temperature range 77-293 K were applied. According to this model, fracture conditions occur when the stress sigma z in the centre of ball impression exceeds critical stress of brittle fracture of. Then the indentation energy, corresponding to condition HM =sigma f, where HM and sigma f are the Meyer 's hardness and the material 's critical cleavage fracture stress, was calculated. The comparison of fracture toughness K Ic, and specific energy of plastic deformation on depth of a plastic zone at introduction spherical indentor up values reveals linear relation-ships KIc(up) for all steels in all the investigated temperature range. For the purposes of non-destructive Sk estimation, the relation-ship between S k and misses stress sigma i, in the centre of impression at the temperature 77 K was established. At last fracture toughness values can be calculated from the single unified equation for all investigated steels. The model proposed can be used for predicting the cracking resistance of the machine elements in a low temperature range.