scholarly journals A Nonlinear Fractional Viscoelastic-Plastic Creep Model of Asphalt Mixture

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1278
Author(s):  
Yongjun Zhang ◽  
Xiu Liu ◽  
Boyuan Yin ◽  
Wenbo Luo
Keyword(s):  
Permanent Deformation ◽  
High Stress ◽  
Asphalt Mixture ◽  
Creep Model ◽  
Creep Process ◽  
Creep Tests ◽  
Model Predictions ◽  
Stress Levels ◽  
Plastic Creep ◽  
Good Agreement

The mechanical behavior of asphalt mixture under high stresses presents nonlinear viscoelasticity and permanent deformation. In this paper, a nonlinear fractional viscoelastic plastic (NFVEP) creep model for asphalt mixture is proposed based on the Nishihara model, with a Koeller spring-pot replacing the Newton dashpot. The NFVEP model considers the instantaneous elasticity, viscoelasticity with damage and time-hardening viscoplasticity with damage concurrently, and the viscoelastic response is modeled by fractional derivative viscoelasticity. To verify the model, uniaxial compressive creep tests under various stresses ranging from 0.4 MPa to 0.8 MPa were carried out at room temperature. The NFVEP model predictions are in good agreement with the experiments. The comparison with the modified Nishihara model and the Burgers model reveals the advantages of the NFVEP model. The results show that the NFVEP model, with the same set of parameters, can not only describe the primary and steady-state creep stages of asphalt mixture under low stress levels but also the whole creep process, including the tertiary creep stage, of asphalt mixture under high stress levels.

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 Viscoelastic Damage Characteristics of Asphalt Mixtures Using Fractional Rheology

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5892
Author(s):  
Qipeng Zhang ◽  
Xingyu Gu ◽  
Zilu Yu ◽  
Jia Liang ◽  
Qiao Dong
Keyword(s):  
Damage Evolution ◽  
High Stress ◽  
Creep Damage ◽  
Asphalt Mixtures ◽  
Creep Process ◽  
Model Parameters ◽  
Creep Tests ◽  
Steady Stage ◽  
Stress Levels ◽  
Different Temperatures

The mechanical behavior of asphalt mixtures at high stress levels are characterized by non-linear viscoelasticity and damage evolution. A nonlinear damage constitutive model considering the existence of creep hardening and creep damage mechanisms in the entire creep process is proposed in this study by adopting the fractional rheology theory to characterize the three-stage creep process of mixtures. A series of uniaxial compressive creep tests under various stresses were conducted at different temperatures to verify the model. The results indicated that the model predictions were in good agreement with the creep tests. The relationship between the model parameters and applied stresses was established, and the stress range in which the mixture exhibited only creep consolidation was obtained. The damage to the asphalt mixture was initiated in the steady stage; however, it developed in the tertiary stage. A two-parameter Weibull distribution function was used to describe the evolution between the damage values and damage strains at different stress levels and temperatures. The correlation coefficients were greater than 0.99 at different temperatures, indicating that a unified damage evolution model could be established. Thus, the parameters of the unified model were related to material properties and temperature, independent of the stress levels applied to the mixtures.

scholarly journals Effects of Aggregate Mesostructure on Permanent Deformation of Asphalt Mixture Using Three-Dimensional Discrete Element Modeling

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3601 ◽  
Author(s):  
Deyu Zhang ◽  
Linhao Gu ◽  
Junqing Zhu
Keyword(s):  
Surface Texture ◽  
Deformation Behavior ◽  
Negative Impact ◽  
Permanent Deformation ◽  
Asphalt Mixture ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Discrete Element ◽  
Asphalt Mixtures ◽  
Creep Tests

This paper investigated the effects of aggregate mesostructures on permanent deformation behavior of an asphalt mixture using the three-dimensional (3D) discrete element method (DEM). A 3D discrete element (DE) model of an asphalt mixture composed of coarse aggregates, asphalt mastic, and air voids was developed. Mesomechanical models representing the interactions among the components of asphalt mixture were assigned. Based on the mesomechanical modeling, the uniaxial static load creep tests were simulated using the prepared models, and effects of aggregate angularity, orientation, surface texture, and distribution on the permanent deformation behavior of the asphalt mixtures were analyzed. It was proven that good aggregate angularity had a positive effect on the permanent deformation performance of the asphalt mixtures, especially when approximate cubic aggregates were used. Aggregate packing was more stable when the aggregate orientations tended to be horizontal, which improved the permanent deformation performance of the asphalt mixture. The influence of orientations of 4.75 mm size aggregates on the permanent deformation behavior of the asphalt mixture was significant. Use of aggregates with good surface texture benefitted the permanent deformation performance of the asphalt mixture. Additionally, the non-uniform distribution of aggregates had a negative impact on the permanent deformation performance of the asphalt mixtures, especially when aggregates were distributed non-uniformly in the vertical direction.

scholarly journals Evaluation of Permanent Deformation of Unmodified and Rubber-Reinforced SMA Asphalt Mixtures Using Dynamic Creep Test

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Herda Yati Katman ◽  
Mohd Rasdan Ibrahim ◽  
Mohamed Rehan Karim ◽  
Nuha Salim Mashaan ◽  
Suhana Koting
Keyword(s):  
Creep Test ◽  
Creep Behaviour ◽  
Permanent Deformation ◽  
High Stress ◽  
Crumb Rubber ◽  
Asphalt Mixtures ◽  
Creep Model ◽  
Deformation Parameters ◽  
Dynamic Creep ◽  
C 50

This paper presents the evaluation of permanent deformation of rubber-reinforced SMA asphalt mixtures by using dynamic creep test. The effect of trans-polyoctenamer as a cross-linking agent in permanent deformation of rubberized mixtures was also evaluated. Dynamic creep test was conducted at different stress levels (200 kPa, 400 kPa) and temperatures (40°C, 50°C). Permanent deformation parameters such as dynamic creep curve, ultimate strain, and creep strain slope (CSS) were used to analyse the results. Finally, the creep behaviour of the specimens was estimated by the Zhou three-stage creep model. The results show that crumb rubber and trans-polyoctenamer significantly affected the parameters especially at high stress and temperatures. Consistent findings were observed for all permanent deformation parameters. Moreover, based on Zhou model, it was concluded that resistance to permanent deformation was improved by application of crumb rubber and trans-polyoctenamer.

scholarly journals An Analysis of Creep Phenomena in the Power Boiler Superheaters

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 892
Author(s):  
Piotr Duda ◽  
Łukasz Felkowski ◽  
Andrzej Duda
Keyword(s):  
Operating Temperature ◽  
Steam Superheater ◽  
Creep Model ◽  
Creep Process ◽  
Safe Operation ◽  
Creep Tests ◽  
Fem Model ◽  
European Standards ◽  
Power Boiler

Higher temperatures of the power boiler superheater operation may lead to high strains caused by the creep phenomenon. This paper presents a determination of the maximum allowable operating temperature limited by the creep phenomenon for steam superheater SH3. The calculations are carried out first on the basis of applicable European standards. Then, calculations are performed based on conducted creep tests, a proposed creep model, and a finite element method (FEM) model. A detailed creep phenomenon analysis based on the conducted creep tests shows that stresses that determine the creep process are mainly caused by pressure. Normal stresses resulting from bending are mainly the effect of thermal expansion. These stresses undergo significant relaxation because of creep. The creep phenomenon analysis explains the equations of the European standards. The presented calculations enable estimation of a safe value of the operating temperature which is constant over time. The estimated time of safe operation does not take account of temperature spikes. For this reason, pressure elements working at high temperatures must be inspected regularly to assess their wear state.

An Improved Mechanism-Based Creep Constitutive Model Using Stress-Dependent Creep Ductility

2016 ◽  
Author(s):  
Yu Zhou ◽  
Chen Xuedong ◽  
Zhichao Fan ◽  
Han Yichun
Keyword(s):  
Damage Mechanics ◽  
Constitutive Models ◽  
Continuum Damage Mechanics ◽  
Creep Process ◽  
Ferritic Steels ◽  
Creep Tests ◽  
Creep Ductility ◽  
Wide Range ◽  
Stress Levels ◽  
Stress Dependent

Creep ductility which is assumed to be constant at a given temperature in many creep constitutive models, actually varies with temperature, stress level and creep strain rate, etc. In this paper, the relationship between creep ductility and stress levels of ferritic steels has been briefly discussed from the perspective of failure mechanisms. It can be generally divided into three regimes, including the upper shelf, lower shelf and the transition regime. The four-parameter logistic model has been adopted to quantitatively describe the stress-dependent creep ductility. Furthermore, a modified mechanism-based continuum damage mechanics (CDM) model for ferrtic steels has been proposed using the stress-dependent creep ductility model. Uniaxial creep tests of 2.25Cr1Mo0.25V steel at three stress levels have been carried out and the experimental data points realistically reflecting the creep behavior have been carefully selected to fit the improved CDM model using genetic algorithm (GA). It is shown that the improved model has the capability to characterize the whole creep process of ferritic steels and the stress-dependent creep ductility over a wide range of applied stress.

Modélisation du comportement du milieu granulaire en fonction de l'écrasement des grains

1998 ◽  
Vol 35 (3) ◽  
pp. 517-523
Author(s):  
Afif Rahma
Keyword(s):  
Mechanical Properties ◽  
Computer Simulations ◽  
Numerical Solutions ◽  
High Stress ◽  
Physical And Mechanical Properties ◽  
Plastic Work ◽  
Constitutive Law ◽  
Grain Crushing ◽  
Stress Levels ◽  
Good Agreement

The influence of grain crushing under high stress levels is introduced in the elasto-plastic constitutive law (Hujeux's model) using additional variables that change with the physical and mechanical properties of the grains. These variables are defined as functions of the amount of dissipated plastic work, which is proposed as a parameter for describing the material yield. The results of computer simulations along oedometric and triaxial paths indicate a very good agreement between the experimental curves and the numerical solutions. The proposed modifications are therefore validated.Key words: correlation, grain crushing, constitutive law, modelization, plastic work.[Journal translation]

scholarly journals A Creep Model of Asphalt Mixture Based on Variable Order Fractional Derivative

2020 ◽  
Vol 10 (11) ◽  
pp. 3862
Author(s):  
Wenbo Luo ◽  
Bo Li ◽  
Yongjun Zhang ◽  
Boyuan Yin ◽  
Jingling Dai
Keyword(s):  
Mechanical Properties ◽  
Stress Level ◽  
Asphalt Mixture ◽  
Primary Creep ◽  
Creep Model ◽  
Creep Process ◽  
Variable Order ◽  
Time Varying ◽  
Steady Creep ◽  
Creep Stage

In order to quantitatively describe the time-varying mechanical properties of asphalt mixture during creep process, a nonlinear viscoelastoplastic creep model was proposed, by using variable-order fractional calculus. The differential order of the variable-order fractional element of the model is no longer constant, but a variable that changes with time, which reflects the changes of the mechanical properties of the material during the creep process. Whereas the tertiary creep phase is modeled by the viscoplastic element with time-varying viscosity, which is attributed to damage evolution. The uniaxial creep compression tests of AC-13C asphalt mixture under different stress levels (0.7 MPa, 0.9 MPa, 1.1 MPa, 1.3 MPa, 1.5 MPa, 1.7 MPa) were carried out with MTS-809 testing machine at 25 °C, and the test results were analyzed by the model using Levenberg–Marquardt optimization algorithm. It is shown that creep damage occurs when the applied stress exceeds a certain critical value, and the damage incubation time depends on the applied stress level. The higher stress decreases the damage incubation time. The model is in good agreement with the experimental results, and is applicable to describe the entire creep process, which consists of primary, steady and tertiary stages. Moreover, the variation of the model parameter can describe the change of viscoelastic properties of the material during the creep process. The differential order of the variable-order fractional element is constant during the primary creep stage, indicating that the creep behavior of the asphalt mixture is linear viscoelastic in small strain range. For the same stress level, the fractional order of the steady creep stage is greater than that of the primary creep stage, and it increases with the increasing stress level, which shows that the viscous behavior in the steady creep is more remarkable than that in the primary creep, and the higher the stress level, the more prominent the viscous performance exhibits.

scholarly journals Uniaxial Tensile Creep Behavior of Epoxy-Based Polymer Using Molecular Simulation

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 261
Author(s):  
Xueliang Li ◽  
Xiaoyu Zhang ◽  
Jianzhong Chen ◽  
Li Huang ◽  
Yong Lv
Keyword(s):  
Epoxy Resin ◽  
Free Volume ◽  
Stress Level ◽  
Creep Behavior ◽  
High Stress ◽  
Dynamics Simulation ◽  
Tensile Creep ◽  
Creep Process ◽  
Uniaxial Tensile ◽  
Stress Levels

Based on the all-atomic molecular dynamics simulation method, the tensile creep behavior of epoxy-based polymer was discussed. The physical and mechanical properties of the model were characterized, such as glass transition temperature and yield strength. The simulation results are very close to the previous simulation and experimental results, and the correctness of the model is verified. On this basis, the tensile creep behavior and free volume evolution of polymer epoxy resin at different temperatures and stress levels were studied. The model fully predicted the three classical stages of epoxy resin creep (the primary, secondary and tertiary) and the dependent behavior of epoxy resin creep on temperature and stress level at the molecular level, and the creep rate increases with the increase of temperature and stress level. It was found that with the progress of the creep process, the proportion of free volume increases gradually under high stress levels, indicating that the effect of creep behavior on the structure of epoxy resin is that the interaction between atoms becomes weaker and weaker by increasing the distance between atoms, which finally induces creep failure in the material.

Sign in / Sign up

Export Citation Format

Share Document