Impact fatigue of low-alloy steels and their welded joints at low temperature

Abstract

A method is described and the basic results of fatigue testing are presented for two grades of low-alloy steels and their butt welded joints under the conditions of impact and sinusoidal loading at low climatic (−60°C) and room temperatures. It has been found that with a drop in temperature from room temperature down to −60°C the cyclic strength of specimens with stress concentrators from the base material and specimens with a weld increases under sinusoidal loading and decreases under impact loading. This decrease is greater the higher the stress concentration factor is. The low temperature negative effect on the experimentally established cyclic strength suggest that, firstly, one of the reasons of the increase in the frequency of crack initiation in machine parts, particularly in those with welded joints, and in the frequency of their fracturing during operation in winter in cold climates is the reduction of their fatigue resistance. Secondly, the serviceability of structures in winter time is better characterized by the results of low-temperature testing of specimens under impact loading rather than under sinusoidal loading.