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学者姓名：雷钧
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Abstract ：
Lots of experiments observe the size-dependent phenomena of concrete mechanical behaviors. In this paper, the micropolar theory is adopted to describe the size effects by introducing two size-related parameters into their constitutive equations, named coupling number N and characteristic length l. A micropolar damage model is built for size-dependent concrete fracture problems utilizing the bond-based peridynamic (PD) idea. That is, the material damage and fracture behaviors are determined by the local damage factors of the PD bonds. Then, the tensile strength of a concrete specimen is numerically estimated by the PD differential operator (PDDO) method. The influences of the size parameters N and l on the tensile strength are studied. By comparing with the transformed Bazant size-effect law and the fitting error analysis, the reasonable values of N and l are determined for a certain reinforced concrete composite. Finally, by using the determined micropolar damage model, the crack propagation paths in concrete members are numerically simulated.
Keyword ：
Micropolar theory Micropolar theory Size effect Size effect Concrete Concrete Damage Damage Peridynamic differential operator Peridynamic differential operator
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| GB/T 7714 | Lei, Jun , Lu, Yong , Sun, Yue et al. A micropolar damage model for size-dependent concrete fracture problems and crack propagation simulated by PDDO method [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2024 , 167 . |
| MLA | Lei, Jun et al. "A micropolar damage model for size-dependent concrete fracture problems and crack propagation simulated by PDDO method" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 167 (2024) . |
| APA | Lei, Jun , Lu, Yong , Sun, Yue , Jiang, Songwei . A micropolar damage model for size-dependent concrete fracture problems and crack propagation simulated by PDDO method . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2024 , 167 . |
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Abstract ：
In this article, the elastodynamic problems are investigated within the framework of a consistent couple-stress theory (CCST). The basic equations for the CCST elastodynamic problems are derived at first. These dynamic formulas are then analyzed in the frequency domain by the Fourier transform. The frequency-domain fundamental solutions to the transformed elastodynamic problems are subsequently derived for the two-dimensional (2D) plane-strain state. Based on the fundamental solutions and the elastodynamic reciprocal theorem, the frequency-domain boundary integral equations (BIEs) are established. Then, the BIEs are numerically solved by a collocation method in conjunction with analytical and numerical treatments of the arising singular integrals. To obtain the time-domain dynamic responses, an exponential window method (EWM) is adopted to transform the frequency-domain results to the time-domain solutions. By using the developed boundary element method (BEM), several typical couple-stress elastodynamic problems are numerically investigated and the size-effects are studied by using different values of the length-scale parameter in the CCST. Good agreements between the results obtained by the developed BEM for a tiny length-scale parameter and the corresponding classical BEM results or analytical solutions are achieved, which validates the high accuracy of the present BEM.
Keyword ：
boundary element method boundary element method elastodynamic problems elastodynamic problems frequency-domain fundamental solutions frequency-domain fundamental solutions consistent couple-stress theory consistent couple-stress theory size-effects size-effects boundary integral equations boundary integral equations
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| GB/T 7714 | Lei, Jun , Shao, Caixia , Zhang, Chuanzeng . Frequency-domain fundamental solutions and boundary element method for consistent couple stress elastodynamic problems [J]. | INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING , 2023 , 124 (22) : 4992-5019 . |
| MLA | Lei, Jun et al. "Frequency-domain fundamental solutions and boundary element method for consistent couple stress elastodynamic problems" . | INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 124 . 22 (2023) : 4992-5019 . |
| APA | Lei, Jun , Shao, Caixia , Zhang, Chuanzeng . Frequency-domain fundamental solutions and boundary element method for consistent couple stress elastodynamic problems . | INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING , 2023 , 124 (22) , 4992-5019 . |
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Abstract ：
In this paper, the general equations of plane strain problems are first summarized for three typical couple stress theories. Based on the constitutive relations, the general traction boundary integral equations (TBIEs) are then derived from the displacement BIEs (DBIEs) along with the explicit high-order fundamental solutions for the plane couple-stress problems. Then, the boundary element method (BEM) codes based on the DBIEs (DBEM) and TBIEs (TBEM) discretized by the collocation scheme are developed separately. Some typical elastic couple-stress problems are numerically studied. For crack problems, the displacement extrapolation formulas are derived for computing the stress and couple-stress intensity factors. Good agreements are observed between the results obtained by the DBEM and the TBEM. The high accuracy of the present BEM results is verified by comparing them with the analytical results.
Keyword ：
Boundary integral equations Boundary integral equations Boundary element method Boundary element method Plane strain Plane strain Couple stress theory Couple stress theory Crack analysis Crack analysis
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| GB/T 7714 | Lei, Jun , Wei, Xun , Ding, Pengsheng et al. General displacement and traction BEM for plane couple-stress problems [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2022 , 140 : 59-69 . |
| MLA | Lei, Jun et al. "General displacement and traction BEM for plane couple-stress problems" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 140 (2022) : 59-69 . |
| APA | Lei, Jun , Wei, Xun , Ding, Pengsheng , Zhang, Chuanzeng . General displacement and traction BEM for plane couple-stress problems . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2022 , 140 , 59-69 . |
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Abstract ：
In this paper, the boundary element method (BEM) based on the elasticity theory is developed for fracture analysis of cracked thin structures with the relative thickness-to-length ratio in the micro- or nano-scales. A special crack-tip element technique is employed for the direct and accurate calculation of stress intensity factors (SIFs). The nearly singular integrals, which are crucial in applying the BEM for thin-structural problems, are calculated accurately by using a nonlinear coordinate transformation method. The present BEM procedure requires no remeshing procedure regardless of the thickness of thin structure. Promising SIFs results with only a small number of boundary elements can be achieved with the relative thickness of the thin film is as small as 10(-9), which is sufficient for modeling most of the thin bodies as used in, for example, smart materials and micro/nano-electro-mechanical systems. (C) 2021 Published by Elsevier B.V.
Keyword ：
Boundary element method Boundary element method Crack analysis Crack analysis Nearly singular integrals Nearly singular integrals Thin-walled structures Thin-walled structures Stress intensity factors Stress intensity factors
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| GB/T 7714 | Gu, Yan , Lei, Jun . Fracture mechanics analysis of two-dimensional cracked thin structures (from micro- to nano-scales) by an efficient boundary element analysis [J]. | RESULTS IN APPLIED MATHEMATICS , 2021 , 11 . |
| MLA | Gu, Yan et al. "Fracture mechanics analysis of two-dimensional cracked thin structures (from micro- to nano-scales) by an efficient boundary element analysis" . | RESULTS IN APPLIED MATHEMATICS 11 (2021) . |
| APA | Gu, Yan , Lei, Jun . Fracture mechanics analysis of two-dimensional cracked thin structures (from micro- to nano-scales) by an efficient boundary element analysis . | RESULTS IN APPLIED MATHEMATICS , 2021 , 11 . |
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Abstract ：
A novel space-time generalized finite difference method based on the direct space-time discretization technique is developed for solving dynamic coupled thermoelasticity problems. By considering the time scale as an additional space dimension, the spatial and temporal domains are simultaneously discretized. In our numerical implementation, the velocity is introduced as an additional unknown field quantity for dealing with the inertia item appearing in elastodynamic equations. Some dynamic coupled thermoelasticity problems in homogeneous or heterogeneous plates under different loading cases are numerically analyzed by this method. The accuracy of the present method is verified by comparison with analytical solutions or other numerical results.
Keyword ：
Space-time discretization Space-time discretization Meshless method Meshless method Heterogeneous Heterogeneous GFDM GFDM Dynamic coupled thermoelasticity Dynamic coupled thermoelasticity
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| GB/T 7714 | Lei, Jun , Wei, Xun , Wang, Qin et al. A novel space-time generalized FDM for dynamic coupled thermoelasticity problems in heterogeneous plates [J]. | ARCHIVE OF APPLIED MECHANICS , 2021 , 92 (1) : 287-307 . |
| MLA | Lei, Jun et al. "A novel space-time generalized FDM for dynamic coupled thermoelasticity problems in heterogeneous plates" . | ARCHIVE OF APPLIED MECHANICS 92 . 1 (2021) : 287-307 . |
| APA | Lei, Jun , Wei, Xun , Wang, Qin , Gu, Yan , Fan, Chia-Ming . A novel space-time generalized FDM for dynamic coupled thermoelasticity problems in heterogeneous plates . | ARCHIVE OF APPLIED MECHANICS , 2021 , 92 (1) , 287-307 . |
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Abstract ：
Based on a consistent couple stress elasticity theory, a two-dimensional (2D) boundary element method (BEM) is developed to solve the boundary value problems in the couple stress elastic materials. The displacement boundary integral equations (BIEs) are applied to compute the mechanical quantities on the boundary. The integral representations for the generalized strains and stresses at internal points are also presented together with the explicit expressions for the high-order fundamental solutions. The collocation method is adopted for the spatial discretization of the BIEs. Some special numerical and semi-analytical techniques are provided for the evaluation of weakly and strongly singular integrals. The sinh transformation is used to deal with the nearly singular integrals for near-boundary internal points or boundary nodes in thin structures. An error-controlled integration scheme is adopted for computing the non-singular integrals to improve the accuracy. Three repre-sentative 2D boundary value problems in the consistent couple stress elasticity theory are studied by the developed BEM. The correctness and accuracy of the present BEM results are verified by comparison with the corresponding analytical results. Then, multiple flat elliptical holes in a plate are numerically studied to show the interaction effects on the stress concentration.
Keyword ：
Multiple holes Multiple holes Couple stress theory Couple stress theory Stress concentration Stress concentration Size-dependence Size-dependence Boundary element method Boundary element method Static problems Static problems
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| GB/T 7714 | Lei, Jun , Ding, Pengsheng , Zhang, Chuanzeng . Boundary element analysis of static plane problems in size-dependent consistent couple stress elasticity [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2021 , 132 : 399-415 . |
| MLA | Lei, Jun et al. "Boundary element analysis of static plane problems in size-dependent consistent couple stress elasticity" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 132 (2021) : 399-415 . |
| APA | Lei, Jun , Ding, Pengsheng , Zhang, Chuanzeng . Boundary element analysis of static plane problems in size-dependent consistent couple stress elasticity . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2021 , 132 , 399-415 . |
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Abstract ：
In this paper, a novel space-time generalized finite difference method (GFDM) is proposed for solving transient heat conduction problems by integrating a direct space-time discretization technique into the meshless GFDM. The spatial and temporal dimensions are simultaneously discretized by randomly distributed nodes in the coupled space-time continuum. Transient heat conduction in homogenous and heterogeneous materials are analyzed by this novel meshless space-time GFDM. Examples involving multidimensional spatiotemporal domains and various complex boundary conditions are studied and discussed. The high accuracy and efficiency of this new algorithm are verified by comparing with analytical and other numerical results.
Keyword ：
Heterogeneous Heterogeneous Transient heat conduction Transient heat conduction GFDM GFDM Space-time discretization Space-time discretization
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| GB/T 7714 | Lei, Jun , Wang, Qin , Liu, Xia et al. A novel space-time generalized FDM for transient heat conduction problems [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2020 , 119 : 1-12 . |
| MLA | Lei, Jun et al. "A novel space-time generalized FDM for transient heat conduction problems" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 119 (2020) : 1-12 . |
| APA | Lei, Jun , Wang, Qin , Liu, Xia , Gu, Yan , Fan, Chia-Ming . A novel space-time generalized FDM for transient heat conduction problems . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2020 , 119 , 1-12 . |
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Abstract ：
This paper documents the first attempt to apply the generalized finite difference method (GFDM), a recently developed meshless method, for the numerical solution of problems with cracks in general anisotropic materials. To solve the resulting second-order elliptic partial differential equations with mixed boundary conditions, the explicit formulae for the partial derivatives of unknown functions in the equations are derived by using the Taylor series expansions combining with the moving-least squares approximation in this meshless GFD method. To deal with the strong discontinuous crack-faces, some special treatments are applied to modify this GFDM. The node distributions are locally refined in the vicinity of the crack-tips. By dividing the crack domain into two parts, the sub-domain method is also used for comparing with the single-domain method. The direct displacement extrapolation method, the path-independent J-integral and the interaction integral methods are, respectively, used to compute the stress intensity factors and compared. Finally, some classical crack examples are presented to show the effectiveness and accuracy of the proposed meshless method for crack problems.
Keyword ：
Crack problems Crack problems Anisotropic Anisotropic Meshless method Meshless method Generalized finite difference method Generalized finite difference method Stress intensity factors Stress intensity factors
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| GB/T 7714 | Lei, Jun , Xu, Yanjie , Gu, Yan et al. The generalized finite difference method for in-plane crack problems [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2019 , 98 : 147-156 . |
| MLA | Lei, Jun et al. "The generalized finite difference method for in-plane crack problems" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 98 (2019) : 147-156 . |
| APA | Lei, Jun , Xu, Yanjie , Gu, Yan , Fan, Chia-Ming . The generalized finite difference method for in-plane crack problems . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2019 , 98 , 147-156 . |
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Abstract ：
In this paper, the fatigue crack problems in piezoelectric materials under cyclic mechanical loading or alternating electric field were analyzed by a single-domain boundary element method. To determine the direction of the crack propagation, the fracture criteria of maximum of hoop mechanical strain energy release rate was used. Meanwhile, for evaluating the remaining life of the cracked piezoelectric specimens, the Paris-type laws based on different fracture parameters were employed and compared. All the involved fracture parameters were computed by the interaction integral method. Numerical examples were considered and analyzed for cyclic mechanical and electrical loadings, respectively. The comparisons showed the efficiency of the present BEM program in analyzing fatigue cracks and the choice of the effective fracture parameter in Paris' law for life prediction.
Keyword ：
Single-domain BEM Single-domain BEM Fatigue crack Fatigue crack Piezoelectric Piezoelectric Paris' law Paris' law Hoop mechanical energy release rate Hoop mechanical energy release rate
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| GB/T 7714 | Lei, Jun , Chen, Yuling , Tinh Quoc Bui et al. Fatigue crack analysis in piezoelectric specimens by a single-domain BEM [J]. | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2019 , 104 : 71-79 . |
| MLA | Lei, Jun et al. "Fatigue crack analysis in piezoelectric specimens by a single-domain BEM" . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 104 (2019) : 71-79 . |
| APA | Lei, Jun , Chen, Yuling , Tinh Quoc Bui , Zhang, Chuanzeng . Fatigue crack analysis in piezoelectric specimens by a single-domain BEM . | ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS , 2019 , 104 , 71-79 . |
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Abstract ：
Based on the concept of the hoop field intensity factors of an initial crack prior to any kink, an apparent hoop mechanical (strain) energy release rate (MERR) is defined to approximate the MERR of a piezoelectric crack with an infinitesimal kink at any arbitrary angle. The validity and the efficiency of the simplified approximation are examined by numerical examples using the boundary element method (BEM). The generalized crack-opening-displacements or displacement jumps are computed by the traction boundary integral equations (BIEs). By using the displacement extrapolation method, the crack-tip field intensity factors of any arbitrarily kinked crack in linear piezoelectric materials are obtained and the BEM results are validated by comparing them with the available reference analytical results. Then, the differences between the conventional field intensity factors and MERR of an infinitesimally kinked crack and the hoop field intensity factors and hoop MERR of the main crack prior to any kink are numerically analyzed. Finally, the crack propagation in an infinite linear piezoelectric material is numerically simulated. The paths of the crack growth are predicted by adopting four different fracture criteria, namely, the maximum hoop stress intensity factor (SIF) and MERR fracture criteria for the main crack-tip before the next propagation, and the maximum K-1 and MERR fracture criteria for the kinked tip of the main crack with an infinitesimal branch at an arbitrary kinking angle evaluated by using a trial crack extension technique. The comparisons among these results show that the present simplified approximation can efficiently provide a sufficient accuracy for numerical simulation of crack growth in linear piezoelectric materials. (C) 2017 Elsevier Ltd. All rights reserved.
Keyword ：
Piezoelectric materials Piezoelectric materials Mechanical energy release rate Mechanical energy release rate Fracture criteria Fracture criteria Traction BIEs Traction BIEs Crack problems Crack problems
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| GB/T 7714 | Lei, Jun , Zhang, Chuanzeng . A simplified evaluation of the mechanical energy release rate of kinked cracks in piezoelectric materials using the boundary element method [J]. | ENGINEERING FRACTURE MECHANICS , 2018 , 188 : 36-57 . |
| MLA | Lei, Jun et al. "A simplified evaluation of the mechanical energy release rate of kinked cracks in piezoelectric materials using the boundary element method" . | ENGINEERING FRACTURE MECHANICS 188 (2018) : 36-57 . |
| APA | Lei, Jun , Zhang, Chuanzeng . A simplified evaluation of the mechanical energy release rate of kinked cracks in piezoelectric materials using the boundary element method . | ENGINEERING FRACTURE MECHANICS , 2018 , 188 , 36-57 . |
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