An improved unsteady creep model based on the time dependent mechanical parameters

2020 ◽  
pp. 1-11 ◽  
Author(s):  
Wenbo Liu ◽  
Shuguang Zhang
Keyword(s):  
Time Dependent ◽  
Creep Model ◽  
Mechanical Parameters ◽  
Model Based ◽  
Unsteady Creep

scholarly journals Nonlinear Viscoelastic–Plastic Creep Model Based on Coal Multistage Creep Tests and Experimental Validation

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3468 ◽  
Author(s):  
Junxiang Zhang ◽  
Bo Li ◽  
Conghui Zhang ◽  
Peng Li
Keyword(s):  
Creep Behavior ◽  
Physical Property ◽  
Creep Model ◽  
Creep Process ◽  
Creep Tests ◽  
Model Based ◽  
Nonlinear Viscoelastic ◽  
Improved Model ◽  
And Control ◽  
Plastic Creep

The development of fractures, which determine the complexity of coal creep characteristics, is the main physical property of coal relative to other rocks. This study conducted a series of multistage creep tests to investigate the creep behavior of coal under different stress levels. A negative elastic modulus and a non-Newtonian component were introduced into the classical Nishihara model based on the theoretical analysis of the experimental results to propose a nonlinear viscoelastic–plastic creep model for describing the non-decay creep behavior of coal. The validity of the model was verified by experimental data. The results show that this improved model can preferably exhibit decelerating, steady state, and accelerating creep behavior during the non-decay creep process. The fitting accuracy of the improved model was significantly higher than that of the classical Nishihara model. Given that acceleration creep is a critical stage in predicting the instability and failure of coal, its successful description using this improved model is crucial for the prevention and control of coal dynamic disasters.

scholarly journals New Maxwell Creep Model Based on Fractional and Elastic-Plastic Elements

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Hao Tang ◽  
Dongpo Wang ◽  
Zhao Duan
Keyword(s):  
Rock Salt ◽  
Damage Mechanics ◽  
Rheological Behaviour ◽  
Creep Model ◽  
Creep Data ◽  
Creep Equation ◽  
New Model ◽  
Elastic Plastic ◽  
Simulation Performance ◽  
Model Based

Creep models are mainly used to describe the rheological behaviour of geotechnical materials. An important research focus for studying creep in geotechnical materials is the development of a model with few parameters and good simulation performance. Hence, in this study, by replacing the Newtonian dashpot and spring in the classical Maxwell model with fractional and elastic-plastic elements, a new Maxwell creep model based on fractional derivatives and continuum damage mechanics was developed. One- and three-dimensional (1D/3D) creep equations of the new Maxwell creep model were derived. The 1D creep equation of the new model was used to fit existing creep data of rock salt, and the 3D creep equation was used to fit the creep data of remolded loess. The model curves matched the creep data very well, showing considerably higher accuracy than other models. Furthermore, a sensitivity study was carried out, showing the effects of the fractional derivative order β and exponent α on the creep strain of rock salt. This new model is simple with few parameters and can effectively simulate the complete creep behaviour of geotechnical materials.

Comparison of the Isochronous Method and a Time-Explicit Model for Creep Analysis

2008 ◽  
Author(s):  
William Koves ◽  
Mingxin Zhao
Keyword(s):  
Elevated Temperature ◽  
Large Scale ◽  
Time Dependent ◽  
Creep Model ◽  
Full Time ◽  
Pure Bending ◽  
Stress Strain ◽  
Creep Analysis ◽  
Generalized Time ◽  
Strain Method

The design of components or structures at elevated temperature is complex. The use of rigorous time dependent material models may not be practical for many large scale industrial problems. The use of simplified methods permits the creep analysis of components that would be impractical by rigorous time dependent models. The Isochronous Stress-Strain method is an approach that has been used extensively for the creep evaluation of elevated temperature components. The method has been used for the analysis of problems containing both primary and secondary stresses. The method has also been used to evaluate creep buckling problems. Although the method has been accepted as an alternative to a full time dependent creep analysis, the limitations and accuracy of the method have not been investigated systematically and are not fully understood. This study compares the isochronous stress-strain method with a generalized time-explicit creep model for materials in high temperature applications. Analytical solutions are developed for three basic loading configurations, including uniaxial tension, pure bending, and torsion in either load or displacement controlled conditions. Deformations, stresses, and creep strains are compared between the two different methods.

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