Lifespan of relaxed high toughness spheroidal-graphite cast iron after retightening under conditions of variable high temperature and plasticity

The relaxing-retightening characteristics and the lifespan prediction of the high toughness spheroidal graphite cast iron under the conditions of variable high temperatures and plasticity were investigated experimentally. A model for its relaxing-retightening lifespan prediction was built and the calculation analyses were performed to explore the working behavior and the lifespans after repeated relaxing-retightening The results show that an exponential relationship exists between the equivalent failure energy and the cycle number before failure, and the predicted lifespan is related to both the pretightening load and the initial extension.