scholarly journals Simulating the Formation of Blasting-Excavation-Induced Zonal Integration in Deep Tunnels with an Elastoplastic Damage Model

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Qiang Gao ◽  
Chuanxiao Liu ◽  
Jian Zhang ◽  
Guangtan Cheng
Keyword(s):  
Coupling Effect ◽  
Damage Model ◽  
Morphological Characteristics ◽  
Numerical Approach ◽  
Surrounding Rock ◽  
Strain Gradient Theory ◽  
Zonal Disintegration ◽  
Gradient Theory ◽  
Blasting Excavation ◽  
Elastoplastic Damage

More deep tunneling projects will be constructed due to the increasing demand of underground energy and resource. The zonal disintegration phenomena are frequently encountered with the surrounding rock of deep tunnels. To explain the mechanisms underlying the formation of zonal disintegration, an elastoplastic damage model and failure criterion are proposed in this study based on the strain gradient theory and the damage property of rock mass. A coupling calculation subroutine is thereafter developed by the ABAQUS code. The dynamic formation and development regularity of zonal disintegration in the deep tunnel are simulated by this subroutine. The radial displacement, radial stress, and tangential stress show the oscillated variation of peaks and troughs alternately. The coupling effect of the blasting load and the initial geostress transient unloading leads to the variation of alternation oscillation in the surrounding rock stress field, which is an important reason for the zonal disintegration of the surrounding rock. The morphological characteristics of fractured zones and nonfractured zones obtained from numerical simulations are in good agreement with the results from the in situ observations, which confirm the correctness and feasibility of the damage and numerical approach. The method proposed in the current study can be utilized to provide a basis for the prediction and supporting design of fractured modes.

scholarly journals Study of a Microbistable Piezoelectric Energy Harvesting

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Li Hua Chen ◽  
Shou Jie Cui ◽  
Shuo Yang ◽  
Wei Zhang
Keyword(s):  
Energy Harvesting ◽  
Coupling Effect ◽  
Resonance Region ◽  
Strain Gradient Theory ◽  
Gradient Theory ◽  
Energy Capture ◽  
Piezoelectric Energy ◽  
Four Corners ◽  
Voltage Frequency ◽  
The Ideal

A microbistable piezoelectric energy harvester has been developed. The harvester was based on a center-fixed and quadrilateral-free microbistable plate with mass blocks placed at the four corners. Considering the thermoelectromechanical coupling effect, a nonlinear oscillation differential equation was established by Hamilton’s principle. Strain gradient theory was applied to consider the size effect, and von Karman theory was used to consider the large deformation effect. The influences of the laying position and area of the piezoelectric layer on the efficiency of energy capture were investigated. The voltage-frequency response of the nonlinear system was investigated, and the snap-through behavior of the bistable plate results in energy harvesting achieving the ideal broaden frequency range before the resonance region.

scholarly journals Research on the escape mechanism and influencing factors of harmful gas induced by blasting excavation in deep rock tunnel

2021 ◽  
Author(s):  
Yi Luo ◽  
Hangli Gong ◽  
Dengxing Qu ◽  
Xinping Li ◽  
Shaohua Hu ◽  
...  
Keyword(s):  
Coupling Effect ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Water Soluble ◽  
Damage Effect ◽  
Escape Mechanism ◽  
Blasting Excavation ◽  
Deep Rock ◽  
Explosion Load

Abstract The escape of toxic and harmful gases is a common disaster effect in tunnel engineering. Frequent drilling and blasting excavation disturbances under high in-situ stress environment will inevitably lead to cumulative damage effect on surrounding rock, which will increase the permeability coefficient of surrounding rock, increase the risk of toxic and harmful gas escape, and seriously endanger construction safety. In this paper, based on real-time monitoring data of harmful gases during blasting and excavation of Yuelongmen Tunnel on Chengdu-Lanzhou Railway, this study summarized laws and distribution characteristics of harmful gas escape intensified by the blasting excavation, and the effectiveness of shotcreting and grouting for water blocking to inhibit gas escape is verified. Then, taking water-containing and gas-containing voids as carriers, considering the influence of different in-situ stress, explosion load and void parameters (including void pressure, void diameter and distance between void and tunnel), to carry out research on the escape mechanism of water-soluble (H 2 S) and insoluble (CH 4 ) toxic and harmful gases under the coupling effect of stress-seepage-damage. The relationship between the amount of harmful gas escaped and the damage degree of the surrounding rock of the tunnel is analyzed, and the functional relationship between it and the in-situ stress, explosion load and cave parameters is established. The results further demonstrate that the amount of escaped harmful gases, such as methane and H 2 S is closely related to lithology of surrounding rock, occurrence conditions of the deep rock mass, development degree of structural fractures and void parameters. The damage of surrounding rock caused by dynamic disturbance during blasting excavation is the main reason of aggravating harmful gas escape. The research results can provide a theoretical reference for preventing harmful gas from escaping in the similar engineering construction.

Numerical Study of CFRP-Bonded Pressure Pipes Subject to Impact Load

2014 ◽  
Vol 602-605 ◽  
pp. 432-437 ◽  
Author(s):  
Yang Zhao ◽  
Zhen Yu Wang ◽  
Zhi Guo He
Keyword(s):  
Internal Pressure ◽  
Dynamic Behavior ◽  
Impact Load ◽  
Coupling Effect ◽  
Numerical Study ◽  
Damage Model ◽  
Numerical Approach ◽  
Pressure Pipes ◽  
History Of ◽  
Insight Into

A numerical approach is carried out to investigate the dynamic behavior of the CFRP strengthened pressure pipes subjected to impact load. In the FE analyses, Johnson-cook model is used to simulate metal subjected to large plastic strains and high strain rates, the fluid and pipe interaction is modeled by the surface-based fluid cavity to include the coupling effect between the deformation of the pipe and the internal pressure. Besides, the Hashin damage model is used to predict the damage of CFRP. The objectives of the numerical simulations are to capture the measured forming and crash history of the CFRP strengthened pressure pipes and gain an insight into the dynamic behavior of CFRP strengthened pressure pipes subject to impact load. The effects of internal pressure and the thickness of the CFRP are investigated, providing a detailed understanding of parameter sensitivity.

On size-dependent bending behaviors of shape memory alloy microbeams via nonlocal strain gradient theory

2021 ◽  
pp. 1045389X2098699
Author(s):  
Bo Zhou ◽  
Zetian Kang ◽  
Xiao Ma ◽  
Shifeng Xue
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Functionally Graded ◽  
Strain Gradient Theory ◽  
Gradient Theory ◽  
Size Dependent ◽  
Material Length Scale Parameter ◽  
Material Length Scale ◽  
Material Length ◽  
Nonlocal Strain Gradient

This paper focuses on the size-dependent behaviors of functionally graded shape memory alloy (FG-SMA) microbeams based on the Bernoulli-Euler beam theory. It is taken into consideration that material properties, such as austenitic elastic modulus, martensitic elastic modulus and critical transformation stresses vary continuously along the longitudinal direction. According to the simplified linear shape memory alloy (SMA) constitutive equations and nonlocal strain gradient theory, the mechanical model was established via the principle of virtual work. Employing the Galerkin method, the governing differential equations were numerically solved. The functionally graded effect, nonlocal effect and size effect of the mechanical behaviors of the FG-SMA microbeam were numerically simulated and discussed. Results indicate that the mechanical behaviors of FG-SMA microbeams are distinctly size-dependent only when the ratio of material length scale parameter to the microbeam height is small enough. Both the increments of material nonlocal parameter and ratio of material length-scale parameter to the microbeam height all make the FG-SMA microbeam become softer. However, the stiffness increases with the increment of FG parameter. The FG parameter plays an important role in controlling the transverse deformation of the FG-SMA microbeam. This work can provide a theoretical basis for the design and application of FG-SMA microstructures.

scholarly journals Development of Elastoplastic-Damage Model of AlFeSi Phase for Aluminum Alloy 6061

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 954
Author(s):  
Hailong Wang ◽  
Wenping Deng ◽  
Tao Zhang ◽  
Jianhua Yao ◽  
Sujuan Wang
Keyword(s):  
Aluminum Alloy ◽  
Constitutive Model ◽  
Material Properties ◽  
Damage Model ◽  
Scratch Test ◽  
Aluminum Alloy 6061 ◽  
Ultra Precision ◽  
Simulation Results ◽  
Alloy 6061 ◽  
Elastoplastic Damage

Material properties affect the surface finishing in ultra-precision diamond cutting (UPDC), especially for aluminum alloy 6061 (Al6061) in which the cutting-induced temperature rise generates different types of precipitates on the machined surface. The precipitates generation not only changes the material properties but also induces imperfections on the generated surface, therefore increasing surface roughness for Al6061 in UPDC. To investigate precipitate effect so as to make a more precise control for the surface quality of the diamond turned Al6061, it is necessary to confirm the compositions and material properties of the precipitates. Previous studies have indicated that the major precipitate that induces scratch marks on the diamond turned Al6061 is an AlFeSi phase with the composition of Al86.1Fe8.3Si5.6. Therefore, in this paper, to study the material properties of the AlFeSi phase and its influences on ultra-precision machining of Al6061, an elastoplastic-damage model is proposed to build an elastoplastic constitutive model and a damage failure constitutive model of Al86.1Fe8.3Si5.6. By integrating finite element (FE) simulation and JMatPro, an efficient method is proposed to confirm the physical and thermophysical properties, temperature-phase transition characteristics, as well as the stress–strain curves of Al86.1Fe8.3Si5.6. Based on the developed elastoplastic-damage parameters of Al86.1Fe8.3Si5.6, FE simulations of the scratch test for Al86.1Fe8.3Si5.6 are conducted to verify the developed elastoplastic-damage model. Al86.1Fe8.3Si5.6 is prepared and scratch test experiments are carried out to compare with the simulation results, which indicated that, the simulation results agree well with those from scratch tests and the deviation of the scratch force in X-axis direction is less than 6.5%.

Local and non-local damage model with extended stress decomposition for concrete

2021 ◽  
pp. 105678952199872
Author(s):  
Bilal Ahmed ◽  
George Z Voyiadjis ◽  
Taehyo Park
Keyword(s):  
Shear Stress ◽  
Degrees Of Freedom ◽  
Biaxial Loading ◽  
Damage Model ◽  
Local Model ◽  
Uniaxial Tensile ◽  
Gradient Theory ◽  
Principal Stresses ◽  
Stress Decomposition ◽  
Non Local

In this work, a new damage model for concrete is proposed with an extension of the stress decomposition (limited to biaxial cases), to capture shear damage due to the opposite signed principal stresses. To extract the pure shear stress, the assumption is made that one component of the shear stress is a minimum absolute of the two principal stresses. The opposite signed principal stresses are decomposed into shear stress and uniaxial tensile/compressive stress. A local model is implemented in Abaqus UMAT and it is further extended to a non-local model by utilization of the gradient theory. The concept of three length scales (tension, compression, and shear) is kept the same as the recently proposed nonlocal damage model by the authors. The nonlocal model is implemented in the Abaqus UEL-UMAT subroutine with an eight-node quadrilateral user-defined element, having five degrees of freedom at corner nodes (displacement in X/Y direction and tensile/compressive and shear nonlocal equivalent strain) and two degrees of freedom at internal nodes. Some examples of a local model including uniaxial and biaxial loading are addressed. Also, five examples of mixed crack mode and mode-I cracking are presented to comprehensively show the performance of this model.

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