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W Sun - One of the best experts on this subject based on the ideXlab platform.
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determination of material parameters for a unified viscoplasticity Damage model for a p91 power plant steel
International Journal of Mechanical Sciences, 2016Co-Authors: Si Thu Kyaw, J.p. Rouse, W SunAbstract:Societal pressures are mounting on electricity operators to operate traditional fossil-fuel power plants in an efficient and flexible manner in conjunction with renewable power plants. This requires the uses of high frequency start up – shut down load profiles in order to better match market demands. As such, high temperature/pressure components such as steam pipe sections and headers experience fluctuating mechanical and thermal loads. There is therefore an industrial need for the accurate prediction of fatigue and creep Damage in order to estimate remnant component life. In the present work, a continuum Damage model has been coupled with a Chaboche unified viscoplastic constitutive model in order to predict stress-strain behaviour of a P91 martensitic steel (a material used for power plant steam pipes) due to cyclic plasticity and Damage accumulation. The experimental data used here are from the previous work [1]. Cyclic fully reversed strain controlled experiments (±0.4%, ±0.25% and ±0.2% strain ranges) and cyclic test with a dwell period (±0.5% strain ranges) for a P91 martensitic steel under isothermal conditions (600°C) are utilised. The physically relevant material parameters are determined and optimised using experimental results. Although many material parameter identification procedures can be found in the literature [1-6], there are uncertainties in determining the limits for the parameters used in the optimisation procedure. This could result in unrealistic parameters while optimising using experimental data. The issue is addressed here by using additional dwell test to identify the limits for stress relaxation parameters before using Cottrell’s stress partition method to identify the limits for strain hardening parameters. Accumulated stored energy for Damage Initiation Criterion and Damage evolution parameters are also extracted from the experimental results. The estimated failure lifetimes for ±0.4%, ±0.25% and ±0.2% cases are 1600, 4250 and 9500 cycles, respectively, as opposed to 1424, 3522 and 10512 cycles as given by experiments.
Jinyang Zheng - One of the best experts on this subject based on the ideXlab platform.
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failure analysis of carbon fiber epoxy composite cylindrical laminates using explicit finite element method
Composites Part B-engineering, 2014Co-Authors: P F Liu, L J Xing, Jinyang ZhengAbstract:Abstract Based on continuum Damage mechanics, the progressive failure analysis using explicit finite element method is performed to predict the failure properties and burst strengths of aluminum–carbon fiber/epoxy composite cylindrical laminate structures in terms of three composite pressure vessels with different geometry sizes. The failure analysis employs the Hashin Damage Initiation Criterion and the fracture energy-based Damage evolution law for composite layers. The numerical convergence problem is solved by introducing viscous damping effect into finite element equations for strain softening phenomenon. Effects of the calculation time and mesh sizes on the failure properties of composite laminates are explored. In addition, the predicted failure strengths of composite laminates using explicit finite element analysis are also compared with those by experiments and implicit finite element analysis.
P K Kaiser - One of the best experts on this subject based on the ideXlab platform.
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A Procedure for Determining Rock-Type Specific Hoek-Brown Brittle Parameter s
Rock Mechanics and Rock Engineering, 2008Co-Authors: F. T. Suorineni, D. R. Chinnasane, P K KaiserAbstract:The Hoek-Brown failure Criterion constants m and s are equivalent rock friction and cohesion parameters, respectively. On the laboratory scale, m depends on the rock type and texture (grain size), while s = 1 for all rocks. On the field scale, m is a function of rock type, texture, and rock mass quality (geological strength index, GSI), while s is simply a function of rock mass quality. The brittle Hoek-Brown Damage Initiation Criterion ( m -zero Criterion) is a modification to the conventional Hoek-Brown failure Criterion with m = 0 and s = 0.11. The m -zero Damage Initiation Criterion has been shown to better predict depths of failure in excavations in some moderate to massive (GSI ≥ 75) rock masses, but over predicts depths of failure in other rock types. It is now recognized that the Hoek-Brown brittle parameter ( s ) is not the same for all hard, strong, brittle, moderate to massive rock masses, but depends on the rock type. However, there are no guidelines for its determination for specific rock types. This paper presents a semi-empirical procedure for the determination of rock-type specific brittle Hoek-Brown parameter s from the rock texture, mineralogical composition, and microstructure. The paper also differentiates between brittle and tenuous rocks. It is shown that, while the use of the term ‘brittle’ is appropriate for rock mechanical excavation and mode of failure in weak rocks with limited deformability, it is inappropriate for use in explaining the difference in resistance to stress-induced Damage in different rock types, and can cause confusion. The terms ‘tenacity/toughness’ are introduced to describe rock resistance to stress-induced Damage in excavation performance assessment, and a rock tenacity/toughness rating system is presented.
Si Thu Kyaw - One of the best experts on this subject based on the ideXlab platform.
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determination of material parameters for a unified viscoplasticity Damage model for a p91 power plant steel
International Journal of Mechanical Sciences, 2016Co-Authors: Si Thu Kyaw, J.p. Rouse, W SunAbstract:Societal pressures are mounting on electricity operators to operate traditional fossil-fuel power plants in an efficient and flexible manner in conjunction with renewable power plants. This requires the uses of high frequency start up – shut down load profiles in order to better match market demands. As such, high temperature/pressure components such as steam pipe sections and headers experience fluctuating mechanical and thermal loads. There is therefore an industrial need for the accurate prediction of fatigue and creep Damage in order to estimate remnant component life. In the present work, a continuum Damage model has been coupled with a Chaboche unified viscoplastic constitutive model in order to predict stress-strain behaviour of a P91 martensitic steel (a material used for power plant steam pipes) due to cyclic plasticity and Damage accumulation. The experimental data used here are from the previous work [1]. Cyclic fully reversed strain controlled experiments (±0.4%, ±0.25% and ±0.2% strain ranges) and cyclic test with a dwell period (±0.5% strain ranges) for a P91 martensitic steel under isothermal conditions (600°C) are utilised. The physically relevant material parameters are determined and optimised using experimental results. Although many material parameter identification procedures can be found in the literature [1-6], there are uncertainties in determining the limits for the parameters used in the optimisation procedure. This could result in unrealistic parameters while optimising using experimental data. The issue is addressed here by using additional dwell test to identify the limits for stress relaxation parameters before using Cottrell’s stress partition method to identify the limits for strain hardening parameters. Accumulated stored energy for Damage Initiation Criterion and Damage evolution parameters are also extracted from the experimental results. The estimated failure lifetimes for ±0.4%, ±0.25% and ±0.2% cases are 1600, 4250 and 9500 cycles, respectively, as opposed to 1424, 3522 and 10512 cycles as given by experiments.
Yanan Chai - One of the best experts on this subject based on the ideXlab platform.
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A delamination failure Criterion considering the effects of through-thickness compression on the interlaminar shear failure of composite laminates
Composite Structures, 2020Co-Authors: Xiangming Chen, Xiasheng Sun, Puhui Chen, Yanan ChaiAbstract:Abstract Through-thickness compressive stress of composite laminates can inhibit the interlaminar shear failure which has been proved by experiments. However, common delamination Damage Initiation Criterion cannot well describe this mechanism. For this issue, in this article, based on the insight of the failure mechanism, an interlaminar failure function is constructed at first. Then, a delamination failure Criterion considering the effect of through-thickness compression on interlaminar shear failure is established based on logical deductions from a polynomial expansion of the failure function. In the Criterion, a constant coefficient with physical meaning is used to describe the effect of through-thickness compression on the interlaminar shear failure, and the estimation method of the coefficient is also given in this study. Here, this failure Criterion can be considered as a general form to describe the delamination between laminae, by defining different coefficient, it can be converted to other criteria such as the conventional secondary stress failure Criterion or the Christensen failure Criterion. Finally, by comparing the numerical calculation and experimental results, the delamination failure Criterion proposed in this study exhibited a good prediction ability for the interlaminar Damage under different loading conditions.
