Papers by Keyword: Aging Parameter

Abstract: To study the aging degree, aging rate of recycled SBS modified asphalt at different aging time and the difference between the recycled one and the new one, aging nonlinear differential equations of recycled SBS modified asphalt and new SBS modified asphalt are established, aging parameters have been calculated by determining the technical indexes of the recycled SBS modified asphalt and the new one. In addition, aging properties of recycled SBS modified asphalt have been analyzed according to the aging parameters and aging equation. The results show that: the nolinear equation can depict the aging properties of both the recycled SBS modified asphalt and the new one; moreover, during the early period of aging, Various performance of recycled SBS modified asphalt decay more rapidly than new one except ductility, while after aging for a long time, various performance tends to be the same.

Abstract: X20CrMoV12 1 steels were exposed at three different high temperatures and various durations. Aging parameter, LMP _s, was used to describe long-term thermal history. Creep rupture, hardness and tensile tests for aged X20CrMoV12 1 steels were carried out. Yield strength was slightly decreased and hardness was rapidly decreased afterLMP _s reached 20.6. Creep strength of aged X20CrMoV12 1 steel decreased rapidly after the LMP_s reached 20.6. It was shown that the creep strength decreased due to the coarsening of acicular type M₂₃C₆ at subgrain boundaries and the agglomeration of M₂₃C₆ at prior austenite grain boundaries. After LMP_s reached 20.6, the assumed linear regression line of stress and Larson-Miller parameter,LMP_f, also moved toward a lower LMP_f region as aging parameter increased. The dependency of creep rupture life on the microstructural degradation could be represented by C_LMPs, which is LMP_f at stress of 1 kg/mm². It was found that the creep rupture life of X20CrMoV12 1 steel could be predicted by considering the material degradation during and prior to creep test.