Journal articles: 'ABAQUS UEL'

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Ye, Nan, Chao Su, and Yang Yang. "PSBFEM-Abaqus: Development of User Element Subroutine (UEL) for Polygonal Scaled Boundary Finite Element Method in Abaqus." Mathematical Problems in Engineering 2021 (September 15, 2021): 1–22. http://dx.doi.org/10.1155/2021/6628837.

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The polygonal scaled boundary finite element method (PSBFEM) is a novel method integrating the standard scaled boundary finite element method (SBFEM) and the polygonal mesh technique. This work discusses developing a PSBFEM framework within the commercial finite element software Abaqus. The PSBFEM is implemented by the User Element Subroutine (UEL) feature of the software. The details on the main procedures to interact with Abaqus, defining the UEL element, and solving the stiffness matrix by the eigenvalue decomposition are present. Moreover, we also develop the preprocessing module and the postprocessing module using the Python script to generate meshes automatically and visualize results. Several benchmark problems from two-dimensional linear elastostatics are solved to validate the proposed implementation. The results show that PSBFEM-UEL has significantly better than FEM convergence and accuracy rate with mesh refinement. The implementation of PSBFEM-UEL can conveniently use arbitrary polygon elements by the polygon/quadtree discretizations in the Abaqus. The developed UEL and the associated input files can be downloaded from https://github.com/hhupde/PSBFEM-Abaqus.

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Khalili, Ashkan, Ratneshwar Jha, and Dulip Samaratunga. "The Wavelet Spectral Finite Element-based user-defined element in Abaqus for wave propagation in one-dimensional composite structures." SIMULATION 93, no. 5 (January 23, 2017): 397–408. http://dx.doi.org/10.1177/0037549716687377.

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A Wavelet Spectral Finite Element (WSFE)-based user-defined element (UEL) is formulated and implemented in Abaqus (commercial finite element software) for wave propagation analysis in one-dimensional composite structures. The WSFE method is based on the first-order shear deformation theory to yield accurate and computationally efficient results for high-frequency wave motion. The frequency domain formulation of the WSFE leads to complex-valued parameters, which are decoupled into real and imaginary parts and presented to Abaqus as real values. The final solution is obtained by forming a complex value using the real number solutions given by Abaqus. Four numerical examples are presented in this article, namely an undamaged beam, a beam with impact damage, a beam with a delamination, and a truss structure. A multi-point constraint subroutine, defining the connectivity between nodes, is developed for modeling the delamination in a beam. Wave motions predicted by the UEL correlate very well with Abaqus simulations. The developed UEL largely retains the computational efficiency of the WSFE method and extends its ability to model complex features.

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Cui, X., X. Han, S. Y. Duan, and G. R. Liu. "An ABAQUS Implementation of the Cell-Based Smoothed Finite Element Method (CS-FEM)." International Journal of Computational Methods 17, no. 02 (October 24, 2019): 1850127. http://dx.doi.org/10.1142/s021987621850127x.

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The smoothed finite element method (S-FEM) has been developed recent years and is increasingly used for stress analysis for engineering design of structures, due to its high computational accuracy and outstanding robustness in against mesh distortion. However, there is currently no commercial S-FEM software package available for convenient engineering applications. This paper aims to integrate S-FEM into the [Formula: see text] software, because it is most widely used in engineering analyses and well integrated in computer aided engineering (CAE). From a family of S-FEM models, the cell-based finite element method (CS-FEM) is chosen to be implemented in ABAQUS, because a smoothing cell in the CS-FEM involves only one element, and hence the implementation can be achieved via the use of the user-defined element library (UEL). Since only nodal displacement results can be extracted when UEL subroutine is used in ABAQUS, a post-processing program is also developed to compute nodal strains/stresses and strain energy results that are useful in structure analysis and CAE. Our CS-FEM UEL is validated using four numerical examples under plane stress conditions. Compared with standard ABAQUS, the CS-FEM in ABAQUS improves the solution accuracy remarkably, and we have also confirmed the robustness of CS-FEM against heavily distorted meshes.

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Lim, Hyean-Ho, Ho-Young Kim, and Hyun-Gyu Kim. "Development of an Abaqus User Element (UEL) Subroutine for Trimmed Hexahedral Elements." Transactions of the Korean Society of Mechanical Engineers - A 45, no. 4 (April 30, 2021): 329–38. http://dx.doi.org/10.3795/ksme-a.2021.45.4.329.

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Chen, Jianyong, Hailong Wang, Pengfei Yu, and Shengping Shen. "A Finite Element Implementation of a Fully Coupled Mechanical–Chemical Theory." International Journal of Applied Mechanics 09, no. 03 (April 2017): 1750040. http://dx.doi.org/10.1142/s1758825117500405.

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A finite element implementation with UEL user-defined element (UEL) subroutines in ABAQUS for fully coupled mechanical–chemical processes, which accounts for deformation, mass diffusion, and chemical reactions based on irreversible thermodynamics, is presented. The finite element formulations are deduced from the Gibbs function variational principle. To demonstrate the robustness of the numerical implementation, one- and two-dimensional numerical simulations with different boundary conditions are conducted. The results present the validity and capability of the UEL subroutines and the coupled theory, and show the interaction among deformation, mass diffusion and chemical reaction. This work provides a valuable tool to the researchers for the study of coupled problems.

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Zhou, Hong Liang. "Implementation of Crack Problem of Functionally Graded Materials with ABAQUS^TM." Advanced Materials Research 284-286 (July 2011): 297–300. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.297.

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An implementation method of the virtual crack closure technique (VCCT) for fracture problems of non-homogeneous materials such as functionally graded materials (FGMs) with commercial finite element software ABAQUSTMis introduced in this paper. In order to avoid the complex post proceeding to extract fracture parameters, the interface crack element based on the VCCT is developed. The heterogeneity of FGMs is characterized though user subroutine UMAT and the interface crack element is implemented by user subroutine UEL. Several examples are analyzed to demonstrate the accuracy of the present method.

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Lazhar, Derradji, Maalem Toufik, Merzouki Tarek, and Messai Abderraouf. "Solid strain based finite element implemented in ABAQUS for static and dynamic plate analysis." Engineering Solid Mechanics 9, no. 4 (2021): 449–60. http://dx.doi.org/10.5267/j.esm.2021.5.001.

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An existing robust three dimensional finite element based on the strain approach is presented. This element is implemented, for the first time in the commercial computer code ABAQUS, by using the subroutine (UEL), for the static and dynamic analysis of isotropic plates, whatever thin or thick. It is Baptised SBH8 (Strain Based Hexahedral with 8 nodes) and has the advantage to overcome the problems involved in numerical locking, when the thickness of the plate tends towards the smallest values. The implementation is justified by the capacities broader than offers this code, especially, in the free frequencies computation. The results obtained by the present element are better than those given by elements used by ABAQUS code and the other elements found in the literature, having the same number of nodes.

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Kumbhar, Pramod Y., A. Francis, N. Swaminathan, R. K. Annabattula, and S. Natarajan. "Development of User Element Routine (UEL) for Cell-Based Smoothed Finite Element Method (CSFEM) in Abaqus." International Journal of Computational Methods 17, no. 02 (October 24, 2019): 1850128. http://dx.doi.org/10.1142/s0219876218501281.

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In this paper, we discuss the implementation of a cell-based smoothed finite element method (CSFEM) within the commercial finite element software Abaqus. The salient feature of the CSFEM is that it does not require an explicit form of the derivative of the shape functions and there is no need for isoparametric mapping. This implementation is accomplished by employing the user element subroutine (UEL) feature in Abaqus. The details on the input data format together with the proposed user element subroutine, which forms the core of the finite element analysis are given. A few benchmark problems from linear elastostatics in both two and three dimensions are solved to validate the proposed implementation. The developed UELs and the associated input files can be downloaded from https://github.com/nsundar/SFEM_in_Abaqus .

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Zhang, Quanwu, Zhiguo Shi, Jiazeng Shan, and Weixing Shi. "Secondary Development and Application of Bio-Inspired Isolation System." Sustainability 11, no. 1 (January 8, 2019): 278. http://dx.doi.org/10.3390/su11010278.

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Near-fault pulse motions will cause excessive and much larger base displacement in traditional isolated structures than common earthquake motions. The new isolation system inspired by the “sacrificial bonds and hidden length” biomechanics of an abalone shell can control the base displacement efficiently and reach almost the same vibration isolation efficiency as a semi-active control system. The current research is confined to the lumped mass model and cannot uncover the exact performance of isolators and structures in practical applications. A user subroutine is developed based on the interface of UEL in Abaqus. Subsequent verification has been done in both the lumped mass model and 3D complex model with Abaqus, Matlab/Simulink, and SAP2000. It can be revealed from the comparative results that the calculation accuracy of the secondary developed user subroutine can meet the demand of design and research.

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Bhowmick, Sauradeep, and Gui-Rong Liu. "Three Dimensional CS-FEM Phase-Field Modeling Technique for Brittle Fracture in Elastic Solids." Applied Sciences 8, no. 12 (December 4, 2018): 2488. http://dx.doi.org/10.3390/app8122488.

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The cell based smoothed finite element method (CS-FEM) was integrated with the phase-field technique to model brittle fracture in 3D elastic solids. The CS-FEM was used to model the mechanics behavior and the phase-field method was used for diffuse fracture modeling technique where the damage in a system was quantified by a scalar variable. The integrated CS-FEM phase-field approach provides an efficient technique to model complex crack topologies in three dimensions. The detailed formulation of our combined method is provided. It was implemented in the commercial software ABAQUS using its user-element (UEL) and user-material (UMAT) subroutines. The coupled system of equations were solved in a staggered fashion using the in-built non-linear Newton–Raphson solver in ABAQUS. Eight node hexahedral (H8) elements with eight smoothing domains were coded in CS-FEM. Several representative numerical examples are presented to demonstrate the capability of the method. We also discuss some of its limitations.

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Alfano, Marco, Franco Furgiuele, A. Leonardi, Carmine Maletta, and Glaucio H. Paulino. "Cohesive Zone Modeling of Mode I Fracture in Adhesive Bonded Joints." Key Engineering Materials 348-349 (September 2007): 13–16. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.13.

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This paper deals with the application of Cohesive Zone Model (CZM) concepts to study mode I fracture in adhesive bonded joints. In particular, an intrinsic piece-wise linear cohesive surface relation is used in order to model fracture in a pre-cracked bonded Double Cantilever Beam (DCB) specimen. Finite element implementation of the CZM is accomplished by means of the user element (UEL) feature available in the FE commercial code ABAQUS. The sensitivity of the cohesive zone parameters (i.e. fracture strength and critical energy release rate) in predicting the overall mechanical response is first examined; subsequently, cohesive parameters are tuned comparing numerical simulations of the load-displacement curve with experimental results retrieved from literature.

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El Fakkoussi, S., H. Moustabchir, A. Elkhalfi, and C. I. Pruncu. "Application of the Extended Isogeometric Analysis (X-IGA) to Evaluate a Pipeline Structure Containing an External Crack." Journal of Engineering 2018 (October 17, 2018): 1–10. http://dx.doi.org/10.1155/2018/4125765.

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This work proposes a novel strategy for a two-dimensional problem that includes the approach of extended isogeometric analysis (X-IGA) in order to detect the behavior of a crack in pipeline structures. The nonrational B-Spline uniform function (NURBS) was used for the approximation of the solution fields (displacements) taking into account its geometry constrains. The modeling of the X-IGA was implemented under Abaqus/Standard software via subroutine (UEL) where the Stress Intensity Factor (KI) was extracted. The results permit detecting with accuracy the fracture toughness of a pipeline structure containing an external crack that can be submitted to critical pressures. To validate the performances of the novel strategy a careful comparison with existing literature and analytical and numerical computation methods was performed.

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Aslan, Ozgur, and Emin Bayraktar. "Analytical Solutions of Model Problems for Large-Deformation Micromorphic Approach to Gradient Plasticity." Applied Sciences 11, no. 5 (March 7, 2021): 2361. http://dx.doi.org/10.3390/app11052361.

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The objective of this work is to present analytical solutions for several 2D model problems to demonstrate the unique plastic fields generated by the implementation of micromorphic approach for gradient plasticity. The approach is presented for finite deformations and several macroscopic and nonstandard microscopic boundary conditions are applied to a gliding plate to illustrate the capability to predict the size effects and inhomogeneous plastic fields promoted by the gradient terms. The constitutive behavior of the material undergoing plastic deformation is analyzed for softening, hardening and perfect plastic response and corresponding solutions are provided. The analytical solutions are also shown to match with the numerical results obtained by implementing a user element subroutine (UEL) to the commercial finite element software Abaqus/Standard.

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Kozák, Vladislav, and Zdeněk Chlup. "Microindentation Test Modelling in the Silicon Nitride Ceramics by Application of the Cohesive Zone Approach." Key Engineering Materials 627 (September 2014): 329–32. http://dx.doi.org/10.4028/www.scientific.net/kem.627.329.

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Silicon nitride based ceramics have received considerable attention during the last decades due to their very good room and high-temperature properties. Ceramics such as silicon nitride (Si3N4) are acknowledged as first choice for modern bearing applications. The influence of grain bridging on the strength and toughness was found. The prediction of crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated from amount damage models. Using cohesive models the behaviour of materials is realized by two types of elements. The former is the element for classical continuum and the latter is the connecting cohesive element. Within the standard finite element package Abaqus the new finite element has been developed; it is written via the UEL procedure. The shape of the traction separation law for experimental materials is estimated from macroscopic tests,J–Rcurve is predicted and stability of the bridging law is tested. The shape of the bridging law is verified using the microindentation test, where the maximum crack length not exceeded 150 μm. The scope of the bridging effect is verified using the standard XFEM elements implemented in Abaqus.

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Yang, Z. J., F. Yao, and Y. J. Huang. "Development of ABAQUS UEL/VUEL subroutines for scaled boundary finite element method for general static and dynamic stress analyses." Engineering Analysis with Boundary Elements 114 (May 2020): 58–73. http://dx.doi.org/10.1016/j.enganabound.2020.02.004.

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Cui, X., and Y. H. Qie. "Using Axisymmetric Smoothed Finite Element Method (S-FEM) to Analyze Pressure Piping with Defect in ABAQUS." International Journal of Computational Methods 17, no. 08 (September 26, 2019): 1930001. http://dx.doi.org/10.1142/s0219876219300010.

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Pressure piping is the most productive way for large-volume compressed natural gas (CNG) transportation. In pipeline constructions, the thickness at the point where two pipes join together is often not consistent due to the mismatch in dimensions, and thus stress concentrations can often occur at the pipe joints, causing safety concerns. Therefore, it is important to accurately analyze the key influencing factors of dimensional mismatch defects, providing a theoretical basis for the preliminary design and post-repair of pipelines. This work uses the smoothed finite element method (S-FEM) that has been proven accurate in stress analysis compared with the traditional FEM. Since geometry and load of the pressure piping are axisymmetric, a novel axisymmetric S-FEM element is first developed, coded and integrated in ABAQUS using the User-defined Element Library (UEL). Intensive studies are then carried out to examine the effects of different levels of mismatch in the thicknesses of two joined pipes and the effects of the radius of the transitional fillet used to bridge the mismatches. It is found that the maximum hoop stress reduces as the radius of the transitional fillet increases. For the thinner section of the pipe, the maximum hoop stress is only affected by the thickness mismatch.

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Zouari, Wajdi, M. Elhadrouz, and T. Ben Zineb. "Development of a Ferroelectric Shell Finite Element." Advances in Science and Technology 56 (September 2008): 57–63. http://dx.doi.org/10.4028/www.scientific.net/ast.56.57.

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Ferroelectricity is the non-linear behaviour exhibited by piezoelectric ceramics, especially in the application of high electric field. Actually, the demand for numerical tools taking into account this non linear phenomenon is increasing to reliably design applications using piezoelectric ceramics. In this context, a shell finite element based on the Reissner/Mindlin's theory and integrating a bi-dimensional macroscopic constitutive law for domain switching effects (ferroelectricity) is developed. This element is implemented into the finite element code ABAQUS using the subroutine UEL (User ELement). The thermodynamical framework of the law is based on two scalar valued functions: the Helmoltz free energy and an electric switching function. One internal variable (the remanent polarization) is introduced and a non linear switching effect hardening is considered. An implicit integration of the constitutive equations based on the return-mapping algorithm is developed.

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Zhou, Li Ming, Guang Wei Meng, Xiao Lin Li, and Feng Li. "Analysis of Dynamic Fracture Parameters in Functionally Graded Material Plates with Cracks by Graded Finite Element Method and Virtual Crack Closure Technique." Advances in Materials Science and Engineering 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/8085107.

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Based on the finite element software ABAQUS and graded element method, we developed a dummy node fracture element, wrote the user subroutines UMAT and UEL, and solved the energy release rate component of functionally graded material (FGM) plates with cracks. An interface element tailored for the virtual crack closure technique (VCCT) was applied. Fixed cracks and moving cracks under dynamic loads were simulated. The results were compared to other VCCT-based analyses. With the implementation of a crack speed function within the element, it can be easily expanded to the cases of varying crack velocities, without convergence difficulty for all cases. Neither singular element nor collapsed element was required. Therefore, due to its simplicity, the VCCT interface element is a potential tool for engineers to conduct dynamic fracture analysis in conjunction with commercial finite element analysis codes.

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Qin, Shenghuan, Zaiyin Xiong, Yingsong Ma, and Keshi Zhang. "Low Cycle Fatigue Life Evaluation of Notched Specimens Considering Strain Gradient." Materials 13, no. 4 (February 23, 2020): 1001. http://dx.doi.org/10.3390/ma13041001.

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An improved model based on the Chaboche constitutive model is proposed for cyclic plastic behavior of metal and low cycle fatigue of notched specimens under cyclic loading, considering the effect of strain gradient on nonlinear kinematic hardening and hysteresis behavior. The new model is imported into the user material subroutine (UMAT) of the finite element computing software ABAQUS, and the strain gradient parameters required for model calculation are obtained by calling the user element subroutine (UEL). The effectiveness of the new model is tested by the torsion test of thin copper wire. Furthermore, the calibration method of strain gradient influence parameters of constitutive model is discussed by taking the notch specimen of Q235 steel as an example. The hysteresis behavior, strain distribution and fatigue failure of notched specimens under cyclic loading were simulated and analyzed with the new model. The results prove the rationality of the new model.

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Fang, Eugene, Xiaodong Cui, and Jim Lua. "A continuum damage and discrete crack-based approach for fatigue response and residual strength prediction of notched laminated composites." Journal of Composite Materials 51, no. 15 (June 2017): 2203–25. http://dx.doi.org/10.1177/0021998317705975.

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This paper presents a combined continuum damage and discrete crack (CDDC) modelling approach for fatigue damage characterization and post-fatigue residual strength prediction of laminated composite components with a hole. In order to capture both the fatigue cycle-driven material degradation and discrete damage-induced stress concentration and redistribution, an overlapped element approach is developed based on a combined user-defined material (UMAT) and user-defined element (UEL). An Abaqus element coupled with UMAT for fatigue damage characterization is used to detect the location of failure initiation, while the discrete crack network-based (DCN) UEL is applied to insert a crack without remeshing. The intensified stress field induced by the newly inserted matrix crack is used for the evaluation of failure initiation and stiffness degradation. The UMAT for the fatigue analysis has incorporated the stress-cycle ( S-N) curves for the damage evolution characterization associated with matrix and fiber based on the tested S-N curves for plies at their different orientations. A continuum damage mechanics (CDM) approach is used for the fatigue-driven delamination initiation and propagation by insertion of a finite thickness interface layer at each ply interface. Both the blind and recalibrated predictions are performed for specimens of three different layups under the Air Force Tech Scout 1 program. The predicted fatigue failure progression and the stiffness against cycle curves are compared with the test data provided by the Air Force Research Lab (AFRL). In addition, post-fatigue residual strength predictions are performed for these notched specimens under tension and compression.

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Bing, Lin. "Analysis of Hydrogen Diffusion in Notched High-Strength Steel Wires." Key Engineering Materials 340-341 (June 2007): 1339–44. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.1339.

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Fick's laws were used to model the hydrogen diffusion in notched high-strength steel wires loaded in tension under elastic-plastic conditions. The plastic deformation at the notch tip has an effect on the peak distribution of the hydrostatic stress ( h σ ). So, in stress-assisted diffusion analysis, elastic-plastic material behavior should be considered. Coupled diffusion elastic-plastic finite element analysis was implemented in the finite element program ABAQUS using the user element subroutine (UEL) and the coupled temperature-displacement solver routine to solve the variational form of the diffusion equation in order to obtain the hydrogen concentration distribution ahead of the notch tip in high-strength steel wires under plane strain conditions. The analysis results are compared with those obtained from elastic analysis, which shows that, if a critical hydrogen concentration is regarded as a local fracture criterion, the elastic-plastic analysis results can be used to evaluate the hydrogen embrittlement of high-strength steel wires.

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Kozák, Vladislav, Zdeněk Chlup, Petr Padělek, and Ivo Dlouhý. "Prediction of the Traction Separation Law of Ceramics Using Iterative Finite Element Modelling." Solid State Phenomena 258 (December 2016): 186–89. http://dx.doi.org/10.4028/www.scientific.net/ssp.258.186.

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Specific silicon nitride ceramics, the influence of the grain size and orientation on the bridging mechanisms was found. In ceramic matrix composites, crack-bridging mechanisms can provide substantial toughness enhancement coupled with the same and/or increased strength. The prediction of the crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated. From a number of damage concepts the cohesive models seem to be especially attractive for the practical applications. Within the standard finite element package Abaqus a new finite element has been developed; it is written via the UEL (user’s element) procedure. Its shape can be modified according to the experimental data for the set of ceramics and composites. The element seems to be very stable from the numerical point a view. The shape of the traction separation law for four experimental materials is estimated via the iterative procedure based on the FEM modeling and experimentally determined displacement in indentation experiments, J–R curve is predicted and stability of the bridging law is tested.

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Wang, Jichang, Xiaoming Guo, and Nailong Zhang. "Study of the progressive failure of concrete by phase field modeling and experiments." International Journal of Damage Mechanics 30, no. 9 (March 24, 2021): 1377–99. http://dx.doi.org/10.1177/10567895211001410.

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In this research, experiments and numerical simulations are employed to research the failure process of concrete. Fracture experiments on three-point bending (TPB) concrete beams with a prefabricated edge notch at the middle of the beam bottom are performed using a modified rigid testing instrument. The characteristics of the crack and section are analyzed, including the crack tensile opening displacement, crack length and width, and crack faces characteristics. Also, the full curves of the force-crack tensile opening displacement (CMOD) and force-deflection of the TPB beams with the prefabricated edge notch after breakage are obtained. The phase field (PF) damage model is applied to the mixed-mode and mode-I failure processes of concrete structures through the ABAQUS subroutine user defined element (UEL). The crack path and the full curves of force-CMOD and force-deflection obtained by numerical calculations are consistent with the experimental results and the calculated results of other researchers. The influences of the mesh sizes, initial lengths, and notched depths on the TPB beam of concrete are also analyzed.

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Kozák, Vladislav, and Zdeněk Chlup. "Crack Growth Modelling in the Silicon Nitride Ceramics by Application of the Cohesive Zone Approach." Key Engineering Materials 592-593 (November 2013): 193–96. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.193.

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Specific silicon nitride based materials are considered according to certain practical requirements of process, the influence of the grain size and orientation on the bridging mechanisms was found. Crack-bridging mechanisms can provide substantial increases in toughness coupled with the strength in ceramics. The prediction of the crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated and from the amount of damage models the cohesive models seem to be especially attractive for the practical applications. Using cohesive models the behaviour of materials is realized by two types of elements. The former is the element for classical continuum and the latter is the connecting cohesive element. Within the standard finite element package Abaqus a new finite element has been developed; it is written via the UEL (users element) procedure. Its shape can be very easily modified according to the experimental data for the set of ceramics and composites. The new element seems to be very stable from the numerical point a view. The shape of the traction separation law for three experimental materials is estimated from the macroscopic tests, JR curve is predicted and stability of the bridging law is tested.

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Silitonga, Sarmediran, Johan Maljaars, Frans Soetens, and Hubertus H. Snijder. "Numerical Simulation of Fatigue Crack Growth Rate and Crack Retardation due to an Overload Using a Cohesive Zone Model." Advanced Materials Research 891-892 (March 2014): 777–83. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.777.

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In this work, a numerical method is pursued based on a cohesive zone model (CZM). The method is aimed at simulating fatigue crack growth as well as crack growth retardation due to an overload. In this cohesive zone model, the degradation of the material strength is represented by a variation of the cohesive traction with respect to separation of the cohesive surfaces. Simulation of crack propagation under cyclic loads is implemented by introducing a damage mechanism into the cohesive zone. Crack propagation is represented in the process zone (cohesive zone in front of crack-tip) by deterioration of the cohesive strength due to damage development in the cohesive element. Damage accumulation during loading is based on the displacements in the cohesive zone. A finite element model of a compact tension (CT) specimen subjected to a constant amplitude loading with an overload is developed. The cohesive elements are placed in front of the crack-tip along a pre-defined crack path. The simulation is performed in the finite element code Abaqus. The cohesive elements behavior is described using the user element subroutine UEL. The new damage evolution function used in this work provides a good agreement between simulation results and experimental data.

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Lin, J. P., J. F. Wang, and R. Q. Xu. "Cohesive Zone Model Based Numerical Analysis of Steel-Concrete Composite Structure Push-Out Tests." Mathematical Problems in Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/175483.

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Push-out tests were widely used to determine the shear bearing capacity and shear stiffness of shear connectors in steel-concrete composite structures. The finite element method was one efficient alternative to push-out testing. This paper focused on a simulation analysis of the interface between concrete slabs and steel girder flanges as well as the interface of the shear connectors and the surrounding concrete. A cohesive zone model was used to simulate the tangential sliding and normal separation of the interfaces. Then, a zero-thickness cohesive element was implemented via the user-defined element subroutine UEL in the software ABAQUS, and a multiple broken line mode was used to define the constitutive relations of the cohesive zone. A three-dimensional numerical analysis model was established for push-out testing to analyze the load-displacement curves of the push-out test process, interface relative displacement, and interface stress distribution. This method was found to accurately calculate the shear capacity and shear stiffness of shear connectors. The numerical results showed that the multiple broken lines mode cohesive zone model could describe the nonlinear mechanical behavior of the interface between steel and concrete and that a discontinuous deformation numerical simulation could be implemented.

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Zuo, Di, Stéphane Avril, Haitian Yang, S. Jamaleddin Mousavi, Klaus Hackl, and Yiqian He. "Three-dimensional numerical simulation of soft-tissue wound healing using constrained-mixture anisotropic hyperelasticity and gradient-enhanced damage mechanics." Journal of The Royal Society Interface 17, no. 162 (January 2020): 20190708. http://dx.doi.org/10.1098/rsif.2019.0708.

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Healing of soft biological tissues is the process of self-recovery or self-repair after injury or damage to the extracellular matrix (ECM). In this work, we assume that healing is a stress-driven process, which works at recovering a homeostatic stress metric in the tissue by replacing the damaged ECM with a new undamaged one. For that, a gradient-enhanced continuum healing model is developed for three-dimensional anisotropic tissues using the modified anisotropic Holzapfel–Gasser–Ogden constitutive model. An adaptive stress-driven approach is proposed for the deposition of new collagen fibres during healing with orientations assigned depending on the principal stress direction. The intrinsic length scales of soft tissues are considered through the gradient-enhanced term, and growth and remodelling are simulated by a constrained-mixture model with temporal homogenization. The proposed model is implemented in the finite-element package Abaqus by means of a user subroutine UEL. Three numerical examples have been achieved to illustrate the performance of the proposed model in simulating the healing process with various damage situations, converging towards stress homeostasis. The orientations of newly deposited collagen fibres and the sensitivity to intrinsic length scales are studied through these examples, showing that both have a significant impact on temporal evolutions of the stress distribution and on the size of the damage region. Applications of the approach to carry out in silico experiments of wound healing are promising and show good agreement with existing experiment results.

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Dean, Aamir, Pavan Kumar, Ammar Babiker, Martin Brod, Salih Elhadi Mohamed Ahmed, Jose Reinoso, and Elsadig Mahdi. "Phase-Field Modeling of Damage and Fracture in Laminated Unidirectional Fiber Reinforced Polymers." FES Journal of Engineering Sciences 9, no. 2 (February 22, 2021): 110–16. http://dx.doi.org/10.52981/fjes.v9i2.687.

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The damage and fracture behavior of Fiber Reinforced Polymers (FRPs) is quite complex and is different than the failure behavior of the traditionally employed metals. There are various types of failure mechanisms that can develop during the service life of composite structures. Each of these mechanisms can initiate and propagate independently. However, in practice, they act synergistically and appear simultaneously. The difficulties that engineers face to understand and predict how these different failure mechanisms result in a structural failure enforce them to use high design safety factors and also increases the number of certification tests needed. Considering that the experimental investigations of composites can be limited, very expensive, and time-consuming, in this contribution the newly developed multi Phase-Field (PF) fracture model [1] is employed to numerically study the failure in different Unidirectional Fiber Reinforced Polymers (UFRPs) laminates, namely, fracture in single-edge notched laminated specimens, matrix cracking in cross-ply laminates, and delamination migration in multi-layered UFRPs. The formulation of the PF model incorporates two independent PF variables and length scales to differentiate between fiber and inter-fiber (matrix-dominated) failure mechanisms. The physically motivated failure criterion of Puck is integrated into the model to control the activation and evolution of the PF parameters. The corresponding governing equations in terms of variational formulation is implemented into the Finite Element (FE) code ABAQUS utilizing the user-defined subroutines UMAT and UEL.

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29

Onishi, Yuki. "A Concept of Cell-Based Smoothed Finite Element Method Using 10-Node Tetrahedral Elements (CS-FEM-T10) for Large Deformation Problems of Nearly Incompressible Solids." International Journal of Computational Methods 17, no. 02 (October 24, 2019): 1845009. http://dx.doi.org/10.1142/s0219876218450093.

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A new concept of smoothed finite element method (S-FEM) using 10-node tetrahedral (T10) elements, CS-FEM-T10, is proposed. CS-FEM-T10 is a kind of cell-based S-FEM (CS-FEM) and thus it smooths the strain only within each T10 element. Unlike the other types of S-FEMs [node-based S-FEM (NS-FEM), edge-based S-FEM (ES-FEM), and face-based S-FEM (FS-FEM)], CS-FEM can be implemented in general finite element (FE) codes as a piece of the element library. Therefore, CS-FEM-T10 is also compatible with general FE codes as a T10 element. A concrete example of CS-FEM-T10 named SelectiveCS-FEM-T10 is introduced for large deformation problems of nearly incompressible solids. SelectiveCS-FEM-T10 subdivides each T10 element into 12 four-node tetrahedral (T4) subelements with an additional dummy node at the element center. Two types of strain smoothing are conducted for the deviatoric and hydrostatic stress evaluations and the selective reduced integration (SRI) technique is utilized for the stress integration. As a result, SelectiveCS-FEM-T10 avoids the shear/volumetric locking, pressure checkerboarding, and reaction force oscillation in nearly incompressible solids. In addition, SelectiveCS-FEM-T10 has a relatively long-lasting property in large deformation problems. A few examples of large deformation analyses of a hyperelastic material confirm the good accuracy and robustness of SelectiveCS-FEM-T10. Moreover, an implementation of SelectiveCS-FEM-T10 in the FE code ABAQUS as a user-defined element (UEL) is conducted and its capability is discussed.

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30

Mantelli, Sincero. "Quia scarabaeus uel cantharus uermis est stercoris. Una glossa erasmiana nel Commentario ad Abacuc di Gerolamo." Augustinianum 50, no. 2 (2010): 443–51. http://dx.doi.org/10.5840/agstm201050216.

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In the main editions of the Commentary by Jerome on the prophet Habakkuk one can read a gloss (« quia scarabaeus uel cantharus uermis est stercoris ») which cannot be found in the manuscript that is usually consulted. The codices show different readings which in most cases quote a corrupt text. Considering that the above-mentioned note does not appear in the pre-Erasmian editions one can draw the conclusion that Erasmus himself corrected the text, adding the meaningful note. To confirm what has been said one can add other corrections, perhaps less significant but which nevertheless can be equally attributed to the hand of the Rotterdam Humanist.

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31

Chen, Jianyong, Hailong Wang, K. M. Liew, and Shengping Shen. "A Fully Coupled Chemomechanical Formulation With Chemical Reaction Implemented by Finite Element Method." Journal of Applied Mechanics 86, no. 4 (January 30, 2019). http://dx.doi.org/10.1115/1.4042431.

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Based on the irreversible thermodynamics, a fully coupled chemomechanical model, i.e., the reaction–diffusion–stress model, is proposed and implemented numerically into the finite element method (FEM) with user-defined element (UEL) subroutines in abaqus. Compositional stress and growth stress are induced by the diffusion and chemical reactions in the solid, and in turn, both the diffusion and chemical reactions are stress-dependent. By providing specialization of the chemical reaction and free energy function, the specialized constitutive equations are introduced, which are highly coupled and nonlinear. The FE formulations are derived from the standard Galerkin approach and implemented via UEL subroutines in abaqus. Several illustrative numerical simulation examples are shown. The results demonstrate the validity and capability of the UEL subroutines, and show the interactions among mechanical deformation, diffusion, and chemical reaction.

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32

Ahmed, Bilal, George Z. Voyiadjis, and Taehyo Park. "Local and non-local damage model with extended stress decomposition for concrete." International Journal of Damage Mechanics, February 25, 2021, 105678952199872. http://dx.doi.org/10.1177/1056789521998728.

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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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You, Shengyu, Jinyuan Tang, and Yuqin Wen. "Three-Dimensional Elastoplastic Contact Analysis of Rough Surface Considering a Micro-Scale Effect." Journal of Tribology 144, no. 1 (April 22, 2021). http://dx.doi.org/10.1115/1.4050737.

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Abstract The micro-surface asperity scale of grinding metal parts is within several microns. When two grinding surfaces are in contact, the unevenness of the plastic deformation of the asperities at the micro-scale leads to greater plastic hardening strength of the material. The results of the nano-indentation experiment conducted in this paper confirmed this phenomenon. Based on conventional mechanism-based strain gradient (CMSG) plasticity theory, the micro-scale plastic constitutive equation of materials is given and then is verified by the nano-indentation experiment. Finite element software abaqus and the user-defined element (UEL) subroutine are used to build three-dimensional rough surface elastoplastic contact models. By calculating the grinding rough surface contact in the macro-scale constitutive model based on J2 theory and in the CMSG plasticity constitutive model, the influence law of plastic micro-scale effect on contact performance is obtained.

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34

Hu, Xiaofei, Peng Zhang, and Weian Yao. "Phase field modelling of microscopic failure in composite laminates." Journal of Composite Materials, December 13, 2020, 002199832097679. http://dx.doi.org/10.1177/0021998320976794.

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The previous study of the authors on a phase field method for modelling progressive failure in multi-phase materials is further extended in this study to capture microscopic failure processes in composite laminates. The auxiliary phase field model for the regularization of material interface is re-formulated. In the computational model, a small part of the model is built from microscopic length scale to explicitly consider the microstructure of the material while the other area is built from macroscopic length scale to improve the efficiency. Cohesive elements are employed to link the two mesh parts with different length scales and also to capture the intralaminar failure. The existing ABAQUS subroutine “UEL” has been rewritten for the present study due to the introduction of cohesive elements and a BFGS solver is used to improve the iteration stability. The thickness effect of a thin ply made laminate is considered and the crack suppression effect is investigated.

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Peng, Fan, Wei Huang, Y. E. Ma, Z. Q. Zhang, and Yao Zhang. "Phase Field Modeling of Brittle Fracture Based on the Cell-Based Smooth FEM by Considering Spectral Decomposition." International Journal of Computational Methods, September 19, 2020, 2050016. http://dx.doi.org/10.1142/s0219876220500164.

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The spectral decomposition of the strain tensor is an essential technique to deal with the fracture problems via phase field method, and some incorrect results may be obtained without it. A novel phase field model for brittle fracture is developed based on cell-based smooth finite element (CS-FEM) and the spectral decomposition is taken into account. In order to describe the nonlinearity behaviors which contain the varied stress and elastic constitutive response caused by spectral decomposition. A second-order stress tensor and a fourth-order constitutive tensor based on decomposition of strain tensor are derived. A fundamental framework of CS-FEM is established to solve the phase field fracture problems, implemented by user-defined element (UEL) subroutine of ABAQUS software. The proposed model is validated by a typical Mode II crack, and the results show that the derived tensors are effective. Phase field parameter, CS-FEM parameter and mesh inhomogeneity are investigated to provide some useful suggestion for further development. Some classical numerical examples are solved by using the present model. The studies demonstrate that the proposed method can successfully overcome mesh distortion; the number of smooth cell does not show influences on the accuracy. Moreover, some results show that this method has the advantage over the standard FEM in convergence and computing efficiency.

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36

Wang, Jichang, and Xiaoming Guo. "The meso-failure mechanism of lightweight concrete simulated by the phase field method." Engineering Computations ahead-of-print, ahead-of-print (June 11, 2021). http://dx.doi.org/10.1108/ec-10-2020-0564.

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PurposeA mesoscopic phase field (PF) model is proposed to simulate the meso-failure process of lightweight concrete.Design/methodology/approachThe PF damage model is applied to the meso-failure process of lightweight concrete through the ABAQUS subroutine user-defined element (UEL). And the improved staggered iteration scheme with a one-pass procedure is used to alternately solve the coupling equations.FindingsThese examples clearly show that the crack initiation of the lightweight concrete specimens mainly occurs in the ceramsite aggregates with weak strength, especially in the larger aggregates. The crack propagation paths of the specimens with the same volume fraction of light aggregates are completely different, but the crack propagation paths all pass through the ceramsite aggregates near the cracks. The results also showed that with the increase in the volume fractions of the aggregates, the slope and the peak loads of the force-deflection (F-d) curves gradually decrease, the load-bearing capacity of the lightweight concrete specimens decreases, and crack branching and coalescence are less likely during crack propagation.Originality/valueThe mesostructures with a mortar matrix, aggregates and an interfacial transition zone (ITZ) are generated by an automatic generation and placement program, thus incorporating the typical three-phase characteristics of lightweight concrete into the PF model.

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37

Zhang, Shen, Baiqing Zhang, and Ming Cheng. "DEVELOPMENT AND APPLICATION OF ISOLATION BEARING ELEMENT CONSIDERING BI-DIRECATIONAL COUPLED INTERACTION." Proceedings of International Structural Engineering and Construction 7, no. 2 (November 2020). http://dx.doi.org/10.14455/isec.2020.7(2).str-14.

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Base isolation technology, which introduces isolated bearings between the top of foundation and upper structure, is regarded as an effective method to reduce seismic energy absorbed by the upper structure. Lead rubber bearing (LRB), that is, a representative seismic isolation device, has been widely used in isolated structural systems. An isolation bearing element for simulating the behavior of LRB was developed with the user element subroutine (UEL) feature of ABAQUS, which was further introduced into seismic analysis of the base-isolated structure with LRB. The Bouc-Wen bi-directional coupled restoring force model was adopted in the developed element to describe the nonlinear hysteric characteristics for LRB in the lateral direction. Meanwhile, the strength differences of LRB in the vertical direction were also included in the element. The accuracy of the isolation bearing element was verified by close agreement between numerically predicted hysteresis curves and experimental counterparts. Moreover, the nonlinear earthquake responses of a four-story reinforced concrete structure isolated by LRB with and without the bi-directional coupled interaction of bearing restoring forces were separately explored, and it was revealed that the bi-directional coupled interaction had considerable effects on the seismic responses of the isolated buildings. Once these coupled interaction effects were not taken into account, the displacement of LRB was underestimated while the bearing capacity would be over-predicted, which had a detrimental effect on the design of isolated buildings.

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Journal articles on the topic 'ABAQUS UEL'

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