Application of a Composite Model in the Analysis of Creep Deformation at Low and Intermediate Temperatures
The creep behaviors of TA2 and R60702 at low and intermediate temperature were presented and discussed in this paper. Experimental results indicated that an apparent threshold stress exhibited in the creep deformation of R60702. Meanwhile, the primary creep phase was found as the main pattern in the room temperature creep behavior of TA2. Compared with exponential law, the power law has been proved to be a proper constitutive model in the description of primary creep phase. It also showed that θ projection method had its significant advantage in the evaluation of accelerated creep stage. Thus, a composite model which combined power law with θ projection method was applied in the creep curves evaluation at low and intermediate temperature. Based on the multiaxial creep deformation results, the model was modified and discussed. A linear relationship existed between composite model parameters and applied load. Finally, the creep life could be accurately predicted and the composite model method is suitable for application in low and intermediate temperature creep life analysis.
Comparative Analysis of Creep Behavior Prediction of Heat Resistant Steel Based on Theta Projection and Composite Model
The difference of the creep curves of P92 steel was comparatively analyzed by theta projection method and composite model.The results show that both the creep-time curves of P92 steel with two methods have a higher accuracy.However,when describing the creep rate-time curves,the theta projection method exhibits big error,while,the composite model can show more accurate results;When extrapolating creep rate,the theta projection method has large deflection,while,the composite model can predict more near the actual trend.When extrapolating creep rupture life based on creep curves,the results show that the fracture strain between 5% and 50% has little effect on the life prediction.The values of endurance life extrapolated by the two models are approximately the same.
The development of a multiaxial stress rupture criterion for bolting steels using new and service aged materials
Abstract Creep rupture tests on uniaxial and notched bar specimens of a variety of geometries have been performed at 550°C, in order to understand the creep rupture behaviour of new and ex-service Durehete 1055 under multiaxial stress states. Existing finite element solutions for skeletal point steady state stresses in the notched bars were used to identify a representative rupture stress. A criterion for governing multiaxial rupture stress was established using the creep rupture data obtained. A good correlation between representative stresses evaluated using the Cane representative stress model and uniaxial stresses was produced. In all cases notch strengthening was observed.