scholarly journals Nonlinear Creep Damage Constitutive Model of Concrete Based on Fractional Calculus Theory

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1505 ◽  
Author(s):  
Cong Zhang ◽  
Zhende Zhu ◽  
Shu Zhu ◽  
Zhilei He ◽  
Duan Zhu ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Fractional Calculus ◽  
Constitutive Model ◽  
Fractional Order ◽  
Creep Damage ◽  
Creep Process ◽  
Structural Development ◽  
Nonlinear Creep ◽  
Concrete Creep ◽  
Damage Constitutive Model

Concrete creep has become one of the major problems that threatens concrete structural development and construction. However, a reasonable and accurate calculation model for numerical analysis is the key to control and solve the creep deformation of concrete. To better describe the concrete nonlinear creep damage evolution rule, the visco-elasticity Plasticity Rheological Theory, Riemann Liouville Theory and Combined Model Theory are quoted, and the Able dashpot is used to reconstruct fractional-order soft-body composite elements to propose the expression of the stress-strain relationship of the elastomer, visco-elasticity plasticity body, and Viscoplasticity body, considering the evolution of the concrete compression damage process. A nonlinear creep damage constitutive model of concrete, based on fractional calculus theory, is conducted, and the parameters of the specific calculation method of the model are given. The influence of stress level σ, fractional order n and material parameter α on the concrete creep process is determined by a sensitivity analysis of the model parameters. The creep process and deformation amount of concrete in practical engineering can be effectively controlled by the results of the proposed sensitivity analysis. The research results can be used to provide guidance and reference for the safe construction of concrete engineering in actual practice.

scholarly journals Investigation of Nonlinear Creep Behaviour of Millettia Laurentii Wood Through Zener Fractional Rheological model

2021 ◽  
Author(s):  
Atchounga Kuida Prisca ◽  
Njankouo Jacques Michel ◽  
Foadieng Emmanuel ◽  
Talla Pierre Kisito
Keyword(s):  
Sensitivity Analysis ◽  
Rheological Model ◽  
Creep Behaviour ◽  
Research Work ◽  
Creep Process ◽  
Model Parameters ◽  
Structural Development ◽  
Nonlinear Creep ◽  
Deformation Amount ◽  
Creep Constitutive Model

Abstract Nowadays one of the principal difficulties that wood structural development and construction have to face is wood creep. Nevertheless, the secret to master and solve the creep deformation of wood relies on a sensible and exact rheological model for numerical analysis. In this research work our goal is to study the nonlinear creep behaviour of the Cameroonian wood species Millettia Laurentii known as Wengé wood through fractional calculus approach. So, we have conducted a nonlinear creep constitutive model of Millettia Laurentii wood, that is the Zener fractional rheological model, and the parameters of this model have been determined. We have studied the influence of stress level σ and fractional order n on the Millettia Laurentii wood creep process by a sensitivity analysis of the model parameters. The outcomes of this sensitivity analysis are of paramount importance because they can be used in reality to inspect the creep process and deformation amount of Millettia Laurentii wood in practical engineering. Moreover, guidance for the secure construction of Millettia Laurentii wood engineering can be given by the means of the findings of this research.

Nonlinear creep damage constitutive model for soft rocks

2016 ◽  
Vol 21 (1) ◽  
pp. 73-96 ◽  
Author(s):  
H. Z. Liu ◽  
H. Q. Xie ◽  
J. D. He ◽  
M. L. Xiao ◽  
L. Zhuo
Keyword(s):  
Constitutive Model ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Soft Rocks ◽  
Damage Constitutive Model

A nonlinear creep damage model for salt rock

2018 ◽  
Vol 28 (5) ◽  
pp. 758-771 ◽  
Author(s):  
Fei Wu ◽  
Jie Chen ◽  
Quanle Zou
Keyword(s):  
Test Data ◽  
Damage Model ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Salt Rock ◽  
Creep Tests ◽  
Nonlinear Constitutive Equation ◽  
Damage Constitutive Model ◽  
Creep Damage Model ◽  
Actual Stress

In the creep tests, stress is no longer a constant and increases gradually under the influence of damage occurring during accelerating creep, which is a slow-loading process rather than a conventional creep. With the accumulation of the damage over time, the actual stress increases greatly. The increased actual stress not only generates loading strain but also causes the steady creep rate to rise. This coupling possibly explains why salt rock presents nonlinear accelerating characteristics at the accelerating creep stage. In this work, the constraint of the present creep concept was overcome by assuming that the acceleration creep phase is a coupling process of loading and creeping. Furthermore, we demonstrate that the total strain in this phase is equal to the sum of loading strain and creeping strain. A new nonlinear constitutive equation for creep was then derived, and the mechanisms underlying the nonlinear accelerating characteristics emerging at the stage of accelerating creep are further explained. A step-loading experiment on salt rock was performed for a period of six months. The characteristics of accelerating creep appeared in the last step of loading. This new nonlinear creep damage constitutive model was used to fit and analyze the test data. Obtained results show that this model fits well to these test data and also favorably represents the nonlinear characteristics of accelerating creep, thus supporting the model’s validity.

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.

Sensitivity Analysis of the Networks with Fractional Order Reactance

2013 ◽  
Vol 860-863 ◽  
pp. 2309-2314
Author(s):  
Gui Shu Liang ◽  
Xing Hua Zheng ◽  
Long Ma ◽  
Hua Ying Dong
Keyword(s):  
Sensitivity Analysis ◽  
Fractional Calculus ◽  
Fractional Order ◽  
Network Theory ◽  
Network Models ◽  
Element Model ◽  
Network Sensitivity

Fractional calculus theory has gained more and more applications in numerous fields. In many cases, using fractional reactance element model can describe the properties of objects more accurately and simply. This paper studies the sensitivity of networks with fractional order reactance, puts forward the adjoint network sensitivity formulas and the incremental network models of fractional order capacitor and inductor, which will further develop the adjoint network and Incremental network theory. The simulation verification is also given.

Constitutive model of concrete creep damage considering the deterioration of creep parameters

2021 ◽  
Vol 308 ◽  
pp. 125047
Author(s):  
Wenbo Liu ◽  
Hui Zhou ◽  
Shuguang Zhang ◽  
Shuai Jiang
Keyword(s):  
Constitutive Model ◽  
Creep Damage ◽  
Concrete Creep

scholarly journals Features and Constitutive Model of Gypsum’s Uniaxial Creep Damage considering Acidization

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Wei Chen ◽  
Wen Wan ◽  
Senlin Xie ◽  
Wenlong Kuang ◽  
Wenqing Peng ◽  
...  
Keyword(s):  
Hydrochloric Acid ◽  
Constitutive Model ◽  
Stress Level ◽  
Failure Modes ◽  
Failure Time ◽  
Acid Corrosion ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Creep Tests ◽  
Acidic Groundwater

Acidic fluids cause rock erosion and further endanger the safety of rock engineering, especially the corrosion of pillars by acidic or weakly acidic groundwater. In this paper, the rock samples in the gypsum mining area were taken as the research object. Uniaxial compression creep tests were carried out under neutral water, pH=6 and pH=5 hydrochloric acid solutions, respectively. Meanwhile, the specimens before and after saturation were observed by an electron microscope scanner. The results show that (1) the gypsum specimens with pH=5 hydrochloric acid were damaged at the first stress level, while that with pH=6 and pH=7 were destroyed at the second stress level. The failure modes of the three groups were basically the same, with cleavage and end damage of different degrees. The difference is that the failure time of the former is earlier than that of the latter, which indicates that the stronger acidity causes greater corrosion on the creep of the samples. (2) From the perspective of microstructure, the samples saturated in the neutral aqueous solution and dry state are compact and complete in structure, and the whole is relatively homogeneous. However, after saturating in the acid solution, the samples significantly increased dense pores with large size and loose structure. Due to the rapid increase, the surfaces of the samples are almost like “holes”. (3) A new nonlinear creep constitutive model was established by connecting Burgers model with nonlinear viscoplastic body (NVPB) model in series, which can well describe the creep characteristics of gypsum rocks under acid corrosion.

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