scholarly journals Experimental Study and Damage Model Study of Rock Salt Subjected to Cyclic Loading and Cyclic Creep

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Baoyun Zhao ◽  
Tianzhu Huang ◽  
Liu Dongyan ◽  
Dongsheng Liu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Energy Dissipation ◽  
Cyclic Loading ◽  
Rock Salt ◽  
Damage Evolution ◽  
Damage Model ◽  
Cyclic Creep ◽  
Cycle Life ◽  
Stress Strain ◽  
Three Stages

Due to the gas injection and production of underground salt caves during the operational phase, rock salt is often subjected to a combined stress of cyclic pressure and constant pressure. In order to investigate the damage evolution of rock salt under different combined stresses, the uniaxial cyclic loading test and cyclic creep test were carried out. The stress-strain curves, energy characteristics, energy dissipation, and damage of rock salt in the two experiments were analyzed and compared. The test results show that the stress-strain curves of the two tests presented three stages of “sparse”-“dense”-“sparse.” As the maximum stress increases, the stage of “dense” will decrease and the rock salt cycle life will decrease. The relationship between cycle life and Δσ (difference between maximum and minimum stress in the tests) is an exponential function under cyclic loading and a linear relationship under cyclic creep. Based on the experimental data, the energy dissipation of rock salt is analyzed. The damage variables were defined from the perspective of energy dissipation, and the damage evolution of rock salt under two tests was obtained. There are three corresponding stages of energy dissipation and damage: initial, constant speed, and acceleration. The damage model is obtained by inverse functioning the s function, and then the correction coefficient is added to the model to obtain the modified damage model. The modified damage model is compared with the experimental data. The results show that the model can accurately describe the three stages of rock salt damage. The significance of parameters in the modifying damage model is also discussed.

scholarly journals A Strain Rate-Dependent Damage Evolution Model for Concrete Based on Experimental Results

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Bin Xu ◽  
Xiaoyan Lei ◽  
P. Wang ◽  
Hui Song
Keyword(s):  
Strain Rate ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Model ◽  
Evolution Model ◽  
Experimental Results ◽  
Strain Rates ◽  
Compression Tests ◽  
Stress Strain ◽  
Actual Damage

There are various definitions of damage variables from the existing damage models. The calculated damage value by the current methods still could not well correspond to the actual damage value. Therefore, it is necessary to establish a damage evolution model corresponding to the actual damage evolution. In this paper, a strain rate-sensitive isotropic damage model for plain concrete is proposed to describe its nonlinear behavior. Cyclic uniaxial compression tests were conducted on concrete samples at three strain rates of 10−3s−1, 10−4s−1, and 10−5s−1, respectively, and ultrasonic wave measurements were made at specified strain values during the loading progress. A damage variable was defined using the secant and initial moduli, and concrete damage evolution was then studied using the experimental results of the cyclic uniaxial compression tests conducted at the different strain rates. A viscoelastic stress-strain relationship, which considered the proposed damage evolution model, was presented according to the principles of irreversible thermodynamics. The model results agreed well with the experiment and indicated that the proposed damage evolution model can accurately characterize the development of macroscopic mechanical weakening of concrete. A damage-coupled viscoelastic constitutive relationship of concrete was recommended. It was concluded that the model could not only characterize the stress-strain response of materials under one-dimensional compressive load but also truly reflect the degradation law of the macromechanical properties of materials. The proposed damage model will advance the understanding of the failure process of concrete materials.

scholarly journals STRESS-STRAIN STATE IN EMBEDMENT OF REINFORCEMENT IN CASE OF REPEATED LOADINGS

Vestnik MGSU ◽  
2016 ◽  
pp. 28-38
Author(s):  
Ilshat Talgatovich Mirsayapov
Keyword(s):  
Cyclic Loading ◽  
Strain State ◽  
Endurance Limit ◽  
Cyclic Creep ◽  
Inclined Crack ◽  
Stress Strain ◽  
Adhesion Mechanism ◽  
Plastic Deformations ◽  
Stress Strain State ◽  
Mechanical Phenomena

The author offer transforming the diagram of ideal elastic-plastic deformations for the description of the stress-strain state of embedment of reinforcement behind a critical inclined crack at repeatedly repeating loadings. The endurance limit of the adhesion between concrete and reinforcement and its corresponding displacements in case of repeated loadings are accepted as the main indicators. This adhesion law is the most appropriate for the description of physical and mechanical phenomena in the contact zone in case of cyclic loading, because it simply and reliably describes the adhesion mechanism and the nature of the deformation, and greatly simplifies the endurance calculations compared to the standard adhesion law. On the basis of this diagram the author obtained the equations for the description of the distribution of pressures and displacements after cyclic loading with account for the development of deformations of cyclic creep of the concrete under the studs of reinforcement.

Damage evolution of rock salt under cyclic loading in unixial tests

2013 ◽  
Vol 9 (1) ◽  
pp. 153-160 ◽  
Author(s):  
Jianfeng Liu ◽  
Heping Xie ◽  
Zhengmeng Hou ◽  
Chunhe Yang ◽  
Liang Chen
Keyword(s):  
Cyclic Loading ◽  
Rock Salt ◽  
Damage Evolution

Deformation and damage evolution of rock salt under multilevel cyclic loading with constant stress intervals

2021 ◽  
pp. 108191
Author(s):  
Kai Zhao ◽  
Hongling Ma ◽  
Yinping Li ◽  
Peng Li ◽  
Zhikai Dong ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Rock Salt ◽  
Damage Evolution ◽  
Constant Stress

scholarly journals Visualization of the damage evolution for Ti–3Al–2Mo–2Zr alloy during a uniaxial tensile process using a microvoids proliferation damage model

2021 ◽  
Vol 40 (1) ◽  
pp. 310-324
Author(s):  
Ying Tong ◽  
Jiang Zhao ◽  
Guo-zheng Quan
Keyword(s):  
Plastic Deformation ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Damage Model ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Stress Strain ◽  
Gtn Damage Model

Abstract Understanding the damage evolution of alloys during a plastic deformation process is significant to the structural design of components and accident prevention. In order to visualize the damage evolution in the plastic deformation of Ti–3Al–2Mo–2Zr alloy, a series of uniaxial tensile experiments for this alloy were carried out under the strain rates of 0.1–10 s−1 at room temperature, and the stress–strain curves were achieved. On the other hand, the finite element (FE) models of these uniaxial tensile processes were established. A microvoids proliferation model, Gurson–Tvergaard–Needleman (GTN) damage model, was implanted into the uniaxial tensile models, and the simulated stress–strain curves corresponding to different GTN parameter combinations were obtained. Based on the simulated and experimental stress–strain curves, the GTN parameters of this alloy were solved by response surface methodology (RSM). The solved GTN parameters suggest that higher strain rate can enhance the proliferation and coalescence of microvoids. Furthermore, the uniaxial tensile tests over different strain rates were simulated using the solved GTN parameters. Then, the damage processes were visualized and evaluated. The result shows that the degradation speed of this alloy is slow at the initial stage of the tensile deformation and then accelerates once the voids volume fraction reaches a critical value.

Modeling the hysteretic responses of RC shear walls under cyclic loading by an energy-based plastic-damage model for concrete

2019 ◽  
Vol 29 (1) ◽  
pp. 184-200
Author(s):  
Shen Zhang ◽  
Ming Cheng ◽  
Jie Wang ◽  
Jian-Ying Wu
Keyword(s):  
Cyclic Loading ◽  
Software Package ◽  
Damage Evolution ◽  
Failure Modes ◽  
Damage Model ◽  
Shear Walls ◽  
Benchmark Tests ◽  
Plastic Damage ◽  
Commercial Software Package ◽  
Evolution Laws

This paper addresses application of an energy-based plastic-damage model for concrete to the modeling of hysteretic responses of reinforced concrete (RC) shear walls. Both damage evolution and plastic flows are accounted for within the framework of thermodynamics, resulting in consistent energy-based damage evolution laws. The model is implemented in the commercial software package ABAQUS via the user-defined material subroutine and applied to two representative benchmark tests of RC shear walls under cyclic loading. It is shown that with the steel reinforcement properly accounted for, the energy-based plastic-damage model can capture realistically the failure modes, load capacities, and overall load–deformation responses of RC shear walls.

scholarly journals A Research on Fatigue Damage Constitutive Equation of Asphalt Mixture

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yazhen Sun ◽  
Chenze Fang ◽  
Dong Fan ◽  
Jinchang Wang ◽  
Xuezhong Yuan
Keyword(s):  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Loading Rate ◽  
Damage Model ◽  
Asphalt Mixture ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Three Point Bending ◽  
Three Stages

The laboratory investigations of fatigue damage constitutive equation of asphalt mixture were carried out by three-point bending fatigue tests. The three-point bending fatigue tests were performed at three levels of stress-strength ratio (SSR), temperature, and loading rate. The coupled multifactor (stress-strength ratio, temperature, and loading rate) fatigue life equation was established, which can well predict the fatigue life of the asphalt mixture. Both a damage model and a damage evolution equation have been established based on the E-N curve, which indicate that fatigue damage evolution is nonlinear and consists of three stages. The sensitivity analysis of damage model parameters indicates that each parameter has different effects on the three stages of damage evolution. Based on the researches above, the fatigue damage constitutive equations were finally built based on the σ-ε curves, which consist of two parts: the damage accumulation stage and the fatigue failure stage. The elasticity-power hardening model was used to describe the constitutive relation of damage accumulation stage. The elasticity-power hardening model and the Sidoroff damage model were used to describe the constitutive relation of damage failure stage. The constitutive equations can well characterize the fatigue damage performance of the asphalt mixtures under cyclic loading.

scholarly journals A Modified Phase-Field Damage Model for Metal Plasticity at Finite Strains: Numerical Development and Experimental Validation

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Jelena Živković ◽  
Vladimir Dunić ◽  
Vladimir Milovanović ◽  
Ana Pavlović ◽  
Miroslav Živković
Keyword(s):  
Phase Field ◽  
Damage Evolution ◽  
Deformation Gradient ◽  
Damage Model ◽  
Steel Structures ◽  
Plasticity Model ◽  
Metal Plasticity ◽  
Damage And Fracture ◽  
Von Mises ◽  
Von Mises Plasticity

Steel structures are designed to operate in an elastic domain, but sometimes plastic strains induce damage and fracture. Besides experimental investigation, a phase-field damage model (PFDM) emerged as a cutting-edge simulation technique for predicting damage evolution. In this paper, a von Mises metal plasticity model is modified and a coupling with PFDM is improved to simulate ductile behavior of metallic materials with or without constant stress plateau after yielding occurs. The proposed improvements are: (1) new coupling variable activated after the critical equivalent plastic strain is reached; (2) two-stage yield function consisting of perfect plasticity and extended Simo-type hardening functions. The uniaxial tension tests are conducted for verification purposes and identifying the material parameters. The staggered iterative scheme, multiplicative decomposition of the deformation gradient, and logarithmic natural strain measure are employed for the implementation into finite element method (FEM) software. The coupling is verified by the ‘one element’ example. The excellent qualitative and quantitative overlapping of the force-displacement response of experimental and simulation results is recorded. The practical significances of the proposed PFDM are a better insight into the simulation of damage evolution in steel structures, and an easy extension of existing the von Mises plasticity model coupled to damage phase-field.

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