scholarly journals Rock damage evolution model of pulsating fracturing based on energy evolution theory

2020 ◽  
Vol 8 (4) ◽  
pp. 1050-1067 ◽  
Author(s):  
Yuwei Li ◽  
Yudong Zhao ◽  
Jizhou Tang ◽  
Liyuan Zhang ◽  
Yuyang Zhou ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Evolution Model ◽  
Rock Damage ◽  
Evolution Theory ◽  
Energy Evolution

scholarly journals Investigation of Microcrack Propagation and Energy Evolution in Brittle Rocks Based on the Voronoi Model

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2108
Author(s):  
Guanlin Liu ◽  
Youliang Chen ◽  
Xi Du ◽  
Peng Xiao ◽  
Shaoming Liao ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Damage Evolution ◽  
Rock Sample ◽  
Rock Fracture ◽  
Damage Threshold ◽  
Crack Development ◽  
Energy Evolution ◽  
Shear Cracks ◽  
Compression Tests ◽  
Microcrack Propagation

The cracking of rock mass under compression is the main factor causing structural failure. Therefore, it is very crucial to establish a rock damage evolution model to investigate the crack development process and reveal the failure and instability mechanism of rock under load. In this study, four different strength types of rock samples from hard to weak were selected, and the Voronoi method was used to perform and analyze uniaxial compression tests and the fracture process. The change characteristics of the number, angle, and length of cracks in the process of rock failure and instability were obtained. Three laws of crack development, damage evolution, and energy evolution were analyzed. The main conclusions are as follows. (1) The rock’s initial damage is mainly caused by tensile cracks, and the rapid growth of shear cracks after exceeding the damage threshold indicates that the rock is about to be a failure. The development of micro-cracks is mainly concentrated on the diagonal of the rock sample and gradually expands to the middle along the two ends of the diagonal. (2) The identification point of failure precursor information in Acoustic Emission (AE) can effectively provide a safety warning for the development of rock fracture. (3) The uniaxial compression damage constitutive equation of the rock sample with the crack length as the parameter is established, which can better reflect the damage evolution characteristics of the rock sample. (4) Tensile crack requires low energy consumption and energy dispersion is not concentrated. The damage is not apparent. Shear cracks are concentrated and consume a large amount of energy, resulting in strong damage and making it easy to form macro-cracks.

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.

Partitioned Cyclic Fatigue Damage Evolution Model for PB-Free Solder Materials

2007 ◽  
Author(s):  
Leila J. Ladani ◽  
A. Dasgupta
Keyword(s):  
Fatigue Damage ◽  
Creep Deformation ◽  
Damage Evolution ◽  
Evolution Model ◽  
Micro Scale ◽  
Elastic Plastic ◽  
Constitutive Properties ◽  
Free Solder ◽  
Cyclic Damage ◽  
Creep Deformations

This study presents an approach to predict the degree of material degradation and the resulting changes in constitutive properties during cyclic loading in viscoplastic materials in micro-scale applications. The objective in the modeling approach is to address the initiation and growth of distributed micro-damage, in the form of micro-cracks and micro-voids, as a result of cyclic, plastic and creep deformations of material. This study extends an existing micromechanics-based approach, developed for unified viscoplastic models [Wen, et al, 2001], which uses dislocation mechanics to predict damage due to distributed micro-scale fatigue crack initiation [Mura and Nakasone, 1990]. In the present study, the approach is extended to a partitioned viscoplastic framework, because the micro-scale mechanisms of deformation and damage are different for plastic and creep deformation. In this approach, the model constants for estimating cyclic damage evolution are allowed to be different for creep and plastic deformations. A partitioned viscoplastic constitutive model is coupled with an energy partitioning (E-P) damage model [Oyan and Dasgupta, 1992] to assess fatigue damage evolution due to cyclic elastic, plastic and creep deformations. Wen’s damage evolution model is extended to include damage evolution due to both plastic and creep deformations. The resulting progressive degradation of elastic, plastic and creep constitutive properties are continuously assessed and updated. The approach is implemented on a viscoplastic Pb-free solder. Dominant deformation modes in this material are dislocation slip for plasticity and diffusion-assisted dislocation climb/glide for creep. The material’s behavior shows a good correlation with the proposed damage evolution model. Damage evolution constants for plastic and creep deformation were obtained for this Pb-free solder from load drop data collected from the mechanical cycling experiments at different temperatures. The amount of cyclic damage is evaluated and compared with experiment.

A new ductile damage evolution model

1993 ◽  
Vol 60 (4) ◽  
pp. R73-R76
Author(s):  
S. Chandrakanth ◽  
P. C. Pandey
Keyword(s):  
Damage Evolution ◽  
Evolution Model ◽  
Ductile Damage

New damage evolution model of rock material

2020 ◽  
Vol 86 ◽  
pp. 207-224 ◽  
Author(s):  
Wei Gao ◽  
Xin Chen ◽  
Chengjie Hu ◽  
Cong Zhou ◽  
Shuang Cui
Keyword(s):  
Damage Evolution ◽  
Rock Material ◽  
Evolution Model

scholarly journals Evaluation Approach of Rock Brittleness Index for Fracturing Acidizing Based on Energy Evolution Theory and Damage Constitutive Relation

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Shaobo Jin ◽  
Xin Wang ◽  
Zhen Wang ◽  
Shaoyuan Mo ◽  
Fengshou Zhang ◽  
...  
Keyword(s):  
Constitutive Relation ◽  
Ph Value ◽  
Acid Corrosion ◽  
Strain Curve ◽  
Brittleness Index ◽  
Evaluation Methodology ◽  
Evolution Theory ◽  
Energy Evolution ◽  
Soaking Time ◽  
The Impact

Abstract Acidizing, as an essential approach for well stimulation of sandstone or carbonate reservoirs, greatly affects the brittleness of the rock mass. Therefore, it is of great significance to develop a scientific brittleness evaluation methodology for the acid-corroded rock. In this paper, firstly, a damage constitutive model considering the compression hardening process of the acid-corroded sandstone under uniaxial loading is established and verified. Then, the evolution formulae of the relevant mechanical and fitting parameters are derived, and the stress-strain curve of the sandstone subjected to acid corrosion with soaking time is predicted. Finally, a theoretical model for evaluating the brittleness index (BI) of the acid-corroded sandstone based on energy evolution theory and damage constitutive relation is proposed. Based on this model, the BI of the sandstone subjected to acid corrosion is calculated and analyzed, and the BI of the acid-corroded sandstone with the soaking time is predicted. Results show that the BI of the sandstone is negatively correlated with the soaking time, and the rate of descent of the BI decreases with the increment of the soaking time. In addition, the decline degree of the BI has a negative correlation with the pH value. On the other hand, the temperature (25°C, 50°C, and 75°C) has greater weakening effects on the BI compared with the impact of the pressure (5 MPa, 10 MPa, and 15 MPa). Besides, days 50 and 120 are two turning points where the decreasing rates of the BI change from rapid to slow and slow to almost constant, respectively. Furthermore, a coefficient (θ) is proposed to quantify the effect of the acid corrosion, and some suggestions are provided for the application of the acidizing treatment.

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