Study on very long-term creep tests and nonlinear creep-damage constitutive model of salt rock

2021 ◽  
Vol 146 ◽  
pp. 104873
Author(s):  
Cheng Lyu ◽  
Jianfeng Liu ◽  
Yi Ren ◽  
Chao Liang ◽  
Yilin Liao
Keyword(s):  
Constitutive Model ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Salt Rock ◽  
Creep Tests ◽  
Damage Constitutive Model ◽  
Term Creep

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.

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.

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.

Creep Behavior of Building Silicone Sealant under Long-Term External Loading and its Time-Stress Equivalence

2014 ◽  
Vol 633 ◽  
pp. 451-454
Author(s):  
Xiao Gen Liu ◽  
Yi Wang Bao ◽  
Xiu Fang Wang
Keyword(s):  
Creep Curve ◽  
Creep Behavior ◽  
External Loading ◽  
Nonlinear Creep ◽  
Creep Tests ◽  
Time Stress ◽  
Silicone Sealant ◽  
Term Creep ◽  
Term Performance

The main mechanics behavior character of building silicone sealant is its time dependence£¬which lies in the existence of the interior timepiece or the characteristic time. The creep behaviors were fundamental to evaluating the long-term performance of the building silicone sealant under long-term external loading. A series of creep tests of building silicone sealant were conducted in the laboratory under different combinations of external loads, the characteristics of the creep curve were obtained. In this work, the creep behaviors of building silicone sealant were also investigated under various temperatures at invariable stress. The test measurements show that the creep behavior of building silicone sealant are nonlinear, Nonlinear creep behavior is analyzed by means of the equivalence principle of time-stress, the main creep curve under reference stress was obtained by fitting with the viscoelastic rheological model. So the long-term creep behavior of the building silicone sealant under lower stress can be predicted by short-term creep behavior under higher stress.

An Improved Continuum Damage Constitutive Model for Creep Deformation of Cast 20Cr32Ni1Nb Steel

2017 ◽  
Author(s):  
Xiaofeng Guo ◽  
Jianming Gong ◽  
Luyang Geng
Keyword(s):  
Constitutive Model ◽  
Creep Damage ◽  
Aging Treatment ◽  
Continuum Damage ◽  
Variable Theory ◽  
Centrifugally Cast ◽  
Proposed Model ◽  
Damage Constitutive Model ◽  
Life Predictions

An improved continuum damage constitutive model is presented to describe the creep behavior of centrifugally cast 20Cr32Ni1Nb stainless steel. In order to determine the internal softening mechanisms of the steel, microstructural observations of damage in 20Cr32Ni1Nb steel are made using the long-term iso-thermal aging treatment. Based on the physics of microstructural processes, a two state variable theory which represents two damage mechanisms related to particle coarsening and microcrack is employed to account for tertiary creep. The kinetic equation which describes the coarsening of the precipitates with time is coupled with Liu-Murakami creep damage constitutive model. Good agreement between predicted and experimental data proves the validity of the proposed model. Compared with the failure times predicted by power law based models, such as Kachanov-Robotnov and Liu-Murakami model, life predictions based on the proposed model are found to be more reasonable over a wide stress range. Additionally, the proposed model is also applied to analyze the accumulation and development of damage in 20Cr32Ni1Nb manifold components.

Study on long-term uniaxial compression creep mechanical behavior of rocksalt-mudstone combined body

2021 ◽  
pp. 105678952110354
Author(s):  
Cheng Lyu ◽  
Jianfeng Liu ◽  
Yi Ren ◽  
Chao Liang ◽  
Qiangxing Zhang
Keyword(s):  
Mechanical Behavior ◽  
Constitutive Models ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Creep Experiment ◽  
Rock Creep ◽  
Accelerated Creep ◽  
Term Creep ◽  
Bedded Rocks

Rocksalt and mudstone are usually under common stress in salt storage caverns, resulting in different mechanical properties from pure rocksalt and mudstone. To accurately obtain the creep mechanical characteristics of rocksalt-mudstone combined body, we have made three different combinations. The long-term creep experiment of bedded rocks can more closely reflect the long-term mechanical behavior of surrounding rock of salt storage caverns. The experimental results indicated that the long-term creep curve of the combined body includes initial and steady creep stages, and even includes accelerated creep stage. The strain of mudstone layer in the combined body was lower than that of rocksalt because of the higher strength. With the increase of the height ratio of mudstone, the creep strain of the combined body and each rock layer decreased, but the creep rate increased. A new nonlinear creep-damage constitutive model was proposed, which can well describe the creep evolution characteristics of the experiment. Compared with the fitting curves of classical Burgers and Nishihara creep constitutive models, it is revealed that the proposed model is most consistent with the experimental data. The duration of the long-term creep experiment under lower stress has a highly significant effect on the accuracy of predicting rock creep results. This research will contribute to a deeper understanding of the long-term creep characteristics of bedded rocks in salt storage caverns.

scholarly journals A 3D Creep Model considering Disturbance Damage and Creep Damage and Its Application in Tunnel Engineering

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Geng-Feng Wang ◽  
Fan Sun ◽  
Xiao-Hui Xiong ◽  
Lei He ◽  
Ke-Hong Zhang
Keyword(s):  
Space Dimension ◽  
Creep Damage ◽  
Wave Theory ◽  
Creep Model ◽  
Time Dimension ◽  
Creep Tests ◽  
Railway Tunnel ◽  
Damage Theory ◽  
Term Creep

Based on the Kachanov damage theory and elastic wave theory, considering the long-term creep damage from time dimension and instantaneous disturbance damage from space dimension, we presented a 3D damage creep model and converted it to difference expressions in order to write into the finite difference software FLAC3D. Then, according to the results of creep tests, we conducted parameter inversion of our damage creep model with the help of the particle swarm optimization (PSO) method. Finally, the damage creep model was applied in a railway tunnel project in Yunnan to simulate the tunnel deformation. Compared with the Burgers model and the model considering only creep damage, our model which considers both creep damage and disturbance damage yielded more reasonable results.

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