A Unified Continuum Damage Mechanics Model for Predicting the Stress Relaxation Behavior of High-Temperature Bolting

Abstract

Two stress relaxation constitutive models have been developed to predict the stress relaxation behavior for high-temperature bolting according to continuum damage mechanics, Kachanov–Robatnov (K–R), and Othman–Hayhurst (O–H) creep constitutive equations as well as stress relaxation strain equations. To validate the effectiveness of constitutive equations, the predicted results were compared with the experimental data of uniaxial isothermal stress relaxation tests using 1Cr10NiMoW2VNbN steel. The results show that the results obtained by the stress relaxation constitutive model based on the K–R creep equation overestimates the stress relaxation behavior, while the model deduced by the O–H creep equation is more in agreement with the experimental data. Moreover, the stress relaxation damage predicted increases with the increment of initial stress significantly. These indicate that the new models can predict the stress relaxation behavior of high-temperature bolting well.

Prediction of stress relaxation from creep data in terms of average creep rate

“…Moreover, the stress relaxation results predicted under different initial stresses are nearly the same after a long hold time. 14,21 This is of great interest for engineering application because the maintenance cycle of current high-temperature equipments in power plant is 30,000 h and may even be extended to 50,000 h. 22 Accordingly, the above two kinds of creep-to-stress relaxation conversion models have high accuracy to predict the stress relaxation behavior after a long-term operation. It is worth noting that the initial stress has little effect on evaluating the long-term stress relaxation behavior based on both two CDM equations and ACR equations, which is convenient for engineering design because one can predict the stress relaxation behavior easily using any initial stress.…”

Compressive ratcheting and creep of non-asbestos fibre composite considering temperature effect

“…Especially, the creep deformation will accelerate the leakage failure of sealing systems at relatively elevated temperature. [27][28][29] Accordingly, it is necessary to study the ratcheting effect of composite materials under repeated compression taking into consideration of various important influence factors.…”

Ratcheting effect of reinforced graphite sheet with stainless steel insert (RGSWSSI) under cyclic compression at elevated temperature

“…Lee et al developed a gasket‐integrated carbon/silicone elastomer composite bipolar plate to enhance the sealing reliability of proton exchange membrane fuel cell system. Under high‐temperature condition, creep and stress relaxation of gaskets and bolts have significant effect on the sealing joints . However, according to the best knowledge of authors, investigations on accumulated compressive deformation features of RGSWSSI are still very few, especially at elevated temperature.…”