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.
Multiaxial stress rupture behaviour and stress-state sensitivity of creep damage distribution in Durehete 1055 and 2.25Cr1Mo steel
Abstract Creep rupture tests on uniaxial and double notched bar specimens have been performed at 550 °C to understand the multiaxial stress rupture behaviour in two different materials Durehete 1055 and 2.25Cr1Mo steel. The criterion for governing multiaxial rupture stress for the materials was established and compared from the relationship between the representative stress and the skeletal point stresses. Different multiaxial stress rupture criterion were produced. Semi-quantitative metallurgical evaluation of creep damage on the representative tested specimens has been carried out to investigate the stress-state sensitivity of creep damage distribution in two different materials. The steady state stress distribution from finite element solutions was correlated with the semi-quantitative damage map of the test specimens. The different governing multiaxial stress criterion between 2.25Cr1Mo steel and Durehete 1055 steel resulted in the significant difference in creep damage distribution across the notch throat of the materials.
The effect of carbon on 2.25 Cr-1 Mo steel: (II). Creep—rupture properties☆
Abstract The creep-rupture properties of normalized-and-tempered 2.25 Cr-1 Mo steel with 0.009, 0.030, 0.120, and 0.135 wt % C were determined at 454, 510, and 565°C; the results show an effect of carbon that depends on temperature. At all three temperatures, the 0.120 and 0.135 wt % C steels have similar strengths, and at 565°C are considerably stronger than the 0.009 and 0.030 wt % C steels, which also have similar strengths. At 454 and 510°C, however, the properties for the 0.030 wt % C steel are superior to those of the 0.009 wt % C steel and approach those for the 0.120 and 0.135 wt % C steels. These observations can be explained in terms of the type of carbide precipitation reactions that occur in 2.25 Cr-1 Mo steel.