An Improved Continuum Damage Constitutive Model for Creep Deformation of Cast 20Cr32Ni1Nb Steel

2017 ◽  
Author(s):  
Xiaofeng Guo ◽  
Jianming Gong ◽  
Luyang Geng
Keyword(s):  
Constitutive Model ◽  
Creep Damage ◽  
Aging Treatment ◽  
Continuum Damage ◽  
Variable Theory ◽  
Centrifugally Cast ◽  
Proposed Model ◽  
Damage Constitutive Model ◽  
Life Predictions

An improved continuum damage constitutive model is presented to describe the creep behavior of centrifugally cast 20Cr32Ni1Nb stainless steel. In order to determine the internal softening mechanisms of the steel, microstructural observations of damage in 20Cr32Ni1Nb steel are made using the long-term iso-thermal aging treatment. Based on the physics of microstructural processes, a two state variable theory which represents two damage mechanisms related to particle coarsening and microcrack is employed to account for tertiary creep. The kinetic equation which describes the coarsening of the precipitates with time is coupled with Liu-Murakami creep damage constitutive model. Good agreement between predicted and experimental data proves the validity of the proposed model. Compared with the failure times predicted by power law based models, such as Kachanov-Robotnov and Liu-Murakami model, life predictions based on the proposed model are found to be more reasonable over a wide stress range. Additionally, the proposed model is also applied to analyze the accumulation and development of damage in 20Cr32Ni1Nb manifold components.

A Creep-Damage Constitutive Model for Sandstone

2012 ◽  
Vol 170-173 ◽  
pp. 289-294 ◽  
Author(s):  
Wei Wang ◽  
Jun Lv ◽  
Hai Cheng Wang
Keyword(s):  
Constitutive Model ◽  
Creep Test ◽  
Creep Damage ◽  
Creep Model ◽  
Whole Process ◽  
Proposed Model ◽  
Accelerated Creep ◽  
Damage Constitutive Model ◽  
Triaxial Creep ◽  
Triaxial Creep Test

Based on the results obtained by the triaxial creep test, a creep-damage constitutive model for sandstone is presented by using the damage theory and by introducing the concept of “the whole process of damage” into Burgers creep model. The parameters of the model are determined by fitting the creep test data. The result shows that the proposed model can not only describe efficiently the variation of decay and steady creep under relatively low stress condition, but also give a satisfied representation of damage behavior in accelerated creep stage.

Application of a Creep Damage Constitutive Model for the Rotor of a 1000 MW Ultra-Supercritical Steam Turbine

2015 ◽  
Author(s):  
Jishen Jiang ◽  
Weizhe Wang ◽  
Nailong Zhao ◽  
Peng Wang ◽  
Yingzheng Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Steam Turbine ◽  
Axial Stress ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Creep Analysis ◽  
Wide Range ◽  
Damage Constitutive Model ◽  
Creep Constitutive Model ◽  
Basic Features

A damage-based creep constitutive model for a wide stress range is applied to the creep analysis of a 1000 MW ultra-supercritical steam turbine, the inlet steam of which reaches 600°C and 35 MPa. In this model, the effect of complex multi-axial stress and the nonlinear evolution of damage are considered. To this end, the model was implemented into the commercial software ABAQUS using a user-defined material subroutine code. The temperature dependent material constants were identified from the experimental data of advanced heat resistant steels using curve fitting approaches. A comparison of the simulated and the measured results showed that they reached an acceptable agreement. The results of the creep analysis illustrated that the proposed approach explains the basic features of stress redistribution and the damage evolution in the steam turbine rotor over a wide range of stresses and temperatures.

A statistical damage constitutive model considering whole joint shear deformation

2020 ◽  
Vol 29 (6) ◽  
pp. 988-1008 ◽  
Author(s):  
Shijie Xie ◽  
Hang Lin ◽  
Yixian Wang ◽  
Yifan Chen ◽  
Wei Xiong ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Damage Evolution ◽  
Shear Stiffness ◽  
Rock Joints ◽  
Residual Phase ◽  
Proposed Model ◽  
Damage Constitutive Model ◽  
Damage Theory ◽  
Joint Shear ◽  
Statistical Damage

The whole shear deformation of rock joints significantly affects the long-term behavior and safety of engineering projects. In this paper, a new damage constitutive model related to the Weibull distribution and statistical damage theory is proposed. This model considers the shear stiffness degradation, post-peak softening, and residual phase of rock joints in the whole shearing process. Main works include the three following aspects: First, the phase of initial damage is determined on the assumption that the joint shear failure is regarded as a result of damage evolution, according to the typical joint shear curve and the three-parameter Weibull distribution. Then, a statistical damage evolution model for the whole joint shearing process is introduced to make this model be capable of describing the residual phase of rock joints. Finally, a statistical constitutive model for the whole joint shearing process is proposed by statistical damage theory, and the calculated results of the models are compared to the experimental results. The results indicate that the proposed model shows a good agreement with the experimental examples, and the proposed model can distinctly reflect the effects of residual stress, peak stress, and shear stiffness. In addition, the model parameters can be mathematically confirmed and have distinct physical meanings.

Study on Non-Local Damage Constitutive Model of Concrete under Freeze-Thaw Action

2010 ◽  
Vol 452-453 ◽  
pp. 133-136 ◽  
Author(s):  
Zong Min Liu ◽  
Ji Ze Mao ◽  
Hai Yan Song
Keyword(s):  
Constitutive Model ◽  
Internal State ◽  
Constitutive Relations ◽  
Irreversible Thermodynamics ◽  
Local Damage ◽  
Variable Theory ◽  
Freeze Thaw ◽  
Adjacent Point ◽  
Damage Constitutive Model ◽  
Non Local

Concrete is multi-phase composites. Due to the inhomogeneity of mechanical properties and complexity of physical properties, constitutive relations of concrete are more complicated. Starting from irreversible thermodynamics theory, internal state variable theory and nonlocal field theory, non-local damage constitutive model of concrete under freeze-thaw action is established in this paper. In the model, non-local influence functions are discussed which are used to describe interplay of damage between adjacent point.

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