Abaqus Implementation Research Articles

Bio-based connections and hybrid planar truss: A parallel genetic algorithm approach for model updating

Bolted steel to laminated bio-based material connections experience significant performance challenges due to the nonlinear response and high stress concentrations at their joints. This paper introduces an innovative 3D plasticity-fracture continuum Finite Element (FE) model that significantly advances the simulation of such truss joints by integrating Hill's yielding criteria with an element removal methodology for fracture simulation. This novel approach captures both plastic and fracture behaviors simultaneously, a capability not sufficiently addressed in existing models. We detail the theoretical framework for these models, including the derivation of constitutive equations and the algorithms necessary for their implementation in ABAQUS. Additionally, it is provided a low-fidelity modeling of truss joints, offering a comprehensive analysis of connector elements, joint models, and parametric modeling via Python scripting. The model's efficacy is demonstrated through identification of connection and of hybrid planar trusses under cyclic loading, which validates the practical applicability of the method. To optimize computational efficiency, we developed a Parallel Genetic Algorithm (PGA) that integrates seamlessly with ABAQUS and Python to facilitate parameter calibration. This integration not only enhances the model's accuracy but also reduces computational load, making it feasible for complex engineering applications. Our findings illustrate a significant improvement in modeling accuracy and efficiency, establishing a robust methodology for analyzing truss joints in bio-based construction materials.

On the implementation in Abaqus of the global–local iterative coupling and acceleration techniques

This paper presents results and convergence study of the Global–Local Iterative Coupling through the implementation in the commercial software Abaqus making use of the co-simulation engine. A hierarchical modeling and simulation approach is often required to alleviate modeling burdens. Particular focus has been devoted here on convergence acceleration and performance optimization. Two applications in statics with nonlinear material behavior and geometrically nonlinear formulation are considered here: first a holed curved plate under traction with elastic–plastic material, then a pre-stressed bolted joint connecting two plates between each other and subjected to traction load. Three different convergence acceleration techniques are compared in terms of convergence performance and accuracy. An inexact solver strategy is proposed to improve computing time performance. The results show promising results for the coupling technology and constitute a step forward in the availability of non-intrusive multi-scale modeling capabilities for complex structures and assemblies.

Abaqus implementation of a large family of finite viscoelasticity models

In this paper, we introduce an Abaqus UMAT subroutine for a family of constitutive models for the viscoelastic response of isotropic elastomers of any compressibility – including fully incompressible elastomers – undergoing finite deformations. The models can be chosen to account for a wide range of non-Gaussian elasticities, as well as for a wide range of nonlinear viscosities. From a mathematical point of view, the structure of the models is such that the viscous dissipation is characterized by an internal variable Cv, subject to the physically-based constraint detCv=1, that is solution of a nonlinear first-order ODE in time. This ODE is solved by means of an explicit Runge–Kutta scheme of high order capable of preserving the constraint detCv=1 identically. The accuracy and convergence of the code is demonstrated numerically by comparison with an exact solution for several of the Abaqus built-in hybrid finite elements, including the simplicial elements C3D4H and C3D10H and the hexahedral elements C3D8H and C3D20H. The last part of this paper is devoted to showcasing the capabilities of the code by deploying it to compute the homogenized response of a bicontinuous rubber blend.

Very High Cycle Fatigue Life Prediction of SLM AlSi10Mg Based on CDM and SVR Models

A novel fatigue evolution model considering the effect of defect size and additive manufacturing building direction based on the theories of continuum damage mechanics and its numerical implementation in ABAQUS is proposed in this paper. First, the constitutive model, fatigue damage evolution model and their parameter calibration methods are presented. Second, using the ABAQUS platform, the proposed model is implemented with user-defined subroutines. After that, based on the proposed model and its numerical implementation, the fatigue life of additively manufactured AlSi10Mg is predicted and its applicability is verified through experimental results. Finally, a support vector regression model is established to predict the fatigue life, and its results are compared to those of the numerical finite element method. The results show that the support vector regression model makes better predictions than the finite element method.

A consistent formulation for yarn re-orientation in shear and off-axis loading of woven composites RVEs

The mechanical response of woven composites under off-axis tensile loading is strongly affected by the damage mechanism in the yarn-yarn and yarn-matrix interfaces. Due to damage in these interfaces, the yarns will be able to rotate and reorient. For plain weave and satin weaving schemes, the yarns will reorient towards the loading direction in off-axis tensile loading, resulting an increase in the apparent stiffness. The material model used to simulate the reinforcing yarns needs to handle this property as the material axes corresponding to the fiber direction should be updated during loading to reach realistic results. The key ingredient of a material model required to achieve this is a fiber frame stress rate description (Badel et al., 2008), which will be compared with a hyperelastic model (Bonet and Burton, 1998). The definition of the fiber frame is reformulated to properly conform to woven composites and the implementation of the model is extended for an implicit solver. Simulations are performed in ABAQUS/Standard with models implemented in UMAT routines. The results are compared with the standard ABAQUS implementation and are shown to retrieve a realistic stiffness evolution induced by fiber reorientations.

A Vehicle–Bridge Interaction Element: Implementation in ABAQUS and Verification

Vibration analysis of bridges induced by train loads is a crucial aspect of railway design, particularly considering the complexity of vehicle components such as bogie-suspension systems. Consequently, railway engineers have endeavored to improve the computational efficiency and applicability of train models using the finite-element method. This paper introduces a toolbox implemented in ABAQUS through a user-defined element (UEL) subroutine, which incorporates the vehicle–bridge interaction (VBI) element theory. This toolbox effectively handles diverse vehicle–bridge interaction systems. In the proposed theory, the wheel-track contact force is derived based on the bridge response, eliminating the need for an iterative process and significantly reducing computational workload compared to classical physics-based analysis. The presented approach is validated through a moving sprung mass model and a moving rigid bar model. Furthermore, a case study is conducted on a three-dimensional finite-element model of a high-speed railway bridge in China, based on a design sketch, to showcase the capabilities of the developed scheme. The study demonstrates the practical application of the proposed methodology in analyzing vehicle–bridge structures with high complexity.

A dynamic large-deformation particle finite element method for geotechnical applications based on Abaqus

In this paper, the application of Abaqus-based particle finite element method (PFEM) is extended from static to dynamic large deformation. The PFEM is based on periodic mesh regeneration with Delaunay triangulation to avoid mesh distortion. Additional mesh smoothing and boundary node smoothing techniques are incorporated to improve the mesh quality and solution accuracy. The field variables are mapped from the old to the new mesh using the closest point projection method to minimize the mapping error. The procedures of the proposed Abaqus-based dynamic PFEM (Abaqus-DPFEM) analysis and its implementation in Abaqus are detailed. The accuracy and robustness of the proposed approach are examined via four illustrative numerical examples. The numerical results show a satisfactory agreement with published results and further confirm the applicability of the Abaqus-DPFEM to solving dynamic large-deformation problems in geotechnical engineering.

Computation of energy evolution during the dynamic fracture of elastomers using the finite viscoelastic model: Its implementation in Abaqus

Cracks propagating in elastomers consume the strain energy available in the body through viscoelastic effects and the creation of new fracture surfaces. Determining the energy consumed by the dissipative and the fracture processes explicitly helps understand the fracture mechanisms better and if they are rate-dependent. In literature, crack propagation experiments are usually performed on thin sheets of elastomers. The displacement fields in the body as the crack propagates through it during the experiments can be accessed using the Digital Image Correlation (DIC) technique. These displacement fields can then be used as boundary conditions in finite element analysis to compute the energy evolution in the body. Using an appropriate material model to describe the bulk material, the strain energy and the viscoelastic dissipation can be computed, thereby allowing to study the energy evolution in the body as the crack passes through.In the current study, the behavior of the elastomer material through which the crack passes has been described by the finite viscoelastic (FV) model. In such models, the viscoelastic effects are described by using some internal variables, whose evolution is prescribed through certain constitutive equations. This article first discusses the implementation of the FV model for plane stress conditions and applies it to study the dynamic fracture of elastomer membranes. The crack propagation through an elastomer is simulated by imposing the displacement fields extracted from the experiments along the crack faces onto the finite element model (thereby implicitly imposing the crack speed). The energy evolution in the body is studied to compute the energy release rate and the dissipation in the body as a consequence of viscoelastic effects. A significant portion of the energy has been observed to be consumed as the viscoelastic dissipation in the bulk material as the crack propagated.

An overview of implicit and explicit phase field models for quasi-static failure processes, implementation and computational efficiency

Phase field models have become a promising tool in modelling failure processes for various engineering applications. However, their computational inefficiency has posed challenges for a wider application which is desired in engineering. While most papers present implicit phase field models, only a few studies devoted to explicit phase field models have been reported in recent years and most papers report their high computational efficiency compared to implicit phase field models. The purpose of this contribution is to present an overview of the implicit and explicit phase field models for quasi-static failure processes, detailing about their theories and implementation in the commercial software ABAQUS. The provided ABAQUS implementation programs can serve as a numerical tool for modelling engineering problems. Several numerical examples are then presented and a comparison of their computational efficiency is subsequently provided. Moreover, a mass/viscosity scaling scheme for the explicit phase field model and a non-iteration scheme for the implicit phase field model are introduced both improve their efficiency. The comparison results clearly reveal that the computational efficiency can be improved significant by using the explicit phase field model, and more attention should be paid to it.

Seismic analysis of post-tensioned concrete gravity dams using scaled boundary finite elements implemented as ABAQUS UEL

This paper presents an efficient numerical framework for the seismic analysis of post-tensioned concrete gravity dams, which automatically inserts anchors into the structure. The proposed approach is implemented in the commercial finite element software ABAQUS by introducing a polygonal user element (UEL) derived by the scaled boundary finite element method (SBFEM). By inserting nodes in the polygonal structural mesh along the anchor layouts, duplicating the inserted nodes representing anchors, and generating cohesive elements on the node pairs, post-tensioned anchors are naturally embedded into the structure, and the bond–slip interactions are considered. Furthermore, an unbounded UEL derived by the SBFEM is implemented to simulate the unbounded foundation in the dam–reservoir–foundation interaction systems. The unbounded UEL only requires a small truncation area around the region of interest to rigorously capture the dynamic properties of the infinite foundation in terms of a displacement unit-impulse response. This ABAQUS implementation allows the use of built-in capabilities of ABAQUS for nonlinear dynamic analysis, including contact modeling and cohesive fracture. Weak structural interfaces existing in a concrete gravity dam (dam–foundation interface and construction joints) are modeled by a cohesive–frictional contact scheme. In the end, sophisticated numerical models dams featuring post-tensioned gravity dams with weak interfaces and anchors can be generated in a fully automatic manner, requiring no special treatments for mesh generation such as partitioning. The accuracy of the proposed technique is verified through a numerical example of the Manly dam strengthened by a vertical anchor. The efficiency of this approach is demonstrated through a dam with three construction joints anchored by multiple inclined anchors. The input files of the numerical examples are available from the authors upon request.

A biophysically guided constitutive law of the musculotendon-complex: modelling and numerical implementation in Abaqus

Background and Objective: Many biomedical, clinical, and industrial applications may benefit from musculoskeletal simulations. Three-dimensional macroscopic muscle models (3D models) can more accurately represent muscle architecture than their 1D (line-segment) counterparts. Nevertheless, 3D models remain underutilised in academic, clinical, and commercial environments. Among the reasons for this is a lack of modelling and simulation standardisation, verification, and validation. Here, we strive towards a solution by providing an open-access, characterised, constitutive relation (CR) for 3D musculotendon models. Methods: The musculotendon complex is modelled following the state-of-the-art active stress approach and is treated as hyperelastic, transversely isotropic, and nearly incompressible. Furthermore, force-length and -velocity relationships are incorporated, and muscle activation is derived from motor-unit information. The CR was implemented within the commercial finite-element software package Abaqus as a user-subroutine. A masticatory system model with left and right masseters was used to demonstrate active and passive movement. Results: The CR was characterised by various experimental data sets and was able to capture a wide variety of passive and active behaviours. Furthermore, the masticatory simulations revealed that joint movement was sensitive to the muscle’s in-fibre passive response. Conclusions: This user-material provides a “plug and play” template for 3D neuro-musculoskeletal finite element modelling. We hope that this reduces modelling effort, fosters exchange, and contributes to the standardisation of such models.

Calculating bandgaps of nonlinear mechanical metamaterials

Bandgaps are intrinsic physical properties of periodic structures, for example, mechanical metamaterials or phononic crystals, which indicate attenuation of wave propagation within a specific frequency range. Bandgap calculation of mechanical metamaterials is realized via discretizing a representative voluame element (RVE) and imposing complex-valued Bloch wave boundary conditions. It is highly desirable to implement Bloch wave analysis in real-valued commercial finite element software. We present and detail an ABAQUS and Python implementation of Bloch wave analysis. Two-dimensional (2D) soft as well three-dimensional (3D) hard mechanical metamaterials are chosen as numerical examples. Material and geometric nonlinearities are tackled properly and the effects of pre-strains are explored. Our numerical results are validated either by similar results reported in the literature or by our experimental measurement. The presented numerical strategy would aid the design, analysis and utilization of mechanical metamaterials for dynamic applications. The codes and data of the paper could be downloaded from https://github.com/XJTU-Zhou-group/Calculating-band-gaps-of-nonlinear-mechanical-metamaterials .

Implementation of arbitrary polyhedral elements for automatic dynamic analyses of three-dimensional structures

The transition from the geometry to the mesh can be rather difficult, manual and time-consuming, especially for the large scale complex structures. The procedure of mesh generation needs massive human intervention making the automatic engineering analyses of structures from CAD geometry models hardly possible. This paper focuses on implementing a polyhedron element with arbitrary convex topology based on the Scaled Boundary Finite Element Method (SBFEM) in ABAQUS on the strength of the interface of UEL (the subroutine to define a general user-defined element) for automatic dynamic analyses of three-dimensional structures. This implementation empowers ABAQUS to analyze any model with arbitrary polyhedron elements. When the geometry of a structure is obtained from CAD, the dynamic analyses can be launched seamlessly and automatically. Cases of a cantilever subjected to a dynamic harmonic excitation with the traditional hexahedron element and this polyhedron element are compared to verify the accuracy of the UEL. Taking a practical example of the Soil-Structure Interaction analysis of a Nuclear Power Plant, the applicability and performance of this implementation are tested. The results of the two examples confirm that this polyhedron element based on SBFEM can be more accurate using much less degrees of freedom and its implementation in ABAQUS is robust and compatible.

A Biophysically Guided Constitutive Law of the Musculotendon-Complex: Modelling and Numerical Implementation in Abaqus

A Biophysically Guided Constitutive Law of the Musculotendon-Complex: Modelling and Numerical Implementation in Abaqus

Fracture Analysis of Clamped Tapered Beam Specimen under Static Loading by Regularized Extended Finite Element Method in Abaqus Implementation

Fracture Analysis of Clamped Tapered Beam Specimen under Static Loading by Regularized Extended Finite Element Method in Abaqus Implementation

A simple and robust Abaqus implementation of the phase field fracture method

The phase field fracture method is attracting significant interest. Phase field approaches have enabled predicting - on arbitrary geometries and dimensions - complex fracture phenomena such as crack branching, coalescence, deflection and nucleation. In this work, we present a simple and robust implementation of the phase field fracture method in the commercial finite element package Abaqus. The implementation exploits the analogy between the phase field evolution law and the heat transfer equation, enabling the use of Abaqus’ in-built features and circumventing the need for defining user elements. The framework is general, and is shown to accommodate different solution schemes (staggered and monolithic), as well as various constitutive choices for preventing damage under compression. The robustness and applicability of the numerical framework presented is demonstrated by addressing several 2D and 3D boundary value problems of particular interest. Focus is on the solution of paradigmatic case studies that are known to be particularly demanding from a convergence perspective. The results reveal that our phase field fracture implementation can be readily combined with other advanced computational features, such as contact, and deliver robust and precise solutions. The code developed can be downloaded from www.empaneda.com/codes.

A Unified Abaqus Implementation of the Phase Field Fracture Method Using Only a User Material Subroutine.

We present a simple and robust implementation of the phase field fracture method in Abaqus. Unlike previous works, only a user material (UMAT) subroutine is used. This is achieved by exploiting the analogy between the phase field balance equation and heat transfer, which avoids the need for a user element mesh and enables taking advantage of Abaqus’ in-built features. A unified theoretical framework and its implementation are presented, suitable for any arbitrary choice of crack density function and fracture driving force. Specifically, the framework is exemplified with the so-called AT1, AT2 and phase field-cohesive zone models (PF-CZM). Both staggered and monolithic solution schemes are handled. We demonstrate the potential and robustness of this new implementation by addressing several paradigmatic 2D and 3D boundary value problems. The numerical examples show how the current implementation can be used to reproduce numerical and experimental results from the literature, and efficiently capture advanced features such as complex crack trajectories, crack nucleation from arbitrary sites and contact problems. The code developed is made freely available.

An open-source ABAQUS implementation of the scaled boundary finite element method to study interfacial problems using polyhedral meshes

The scaled boundary finite element method (SBFEM) is capable of generating polyhedral elements with an arbitrary number of surfaces. This salient feature significantly alleviates the meshing burden being a bottleneck in the analysis pipeline in the standard finite element method (FEM). In this paper, we implement polyhedral elements based on the SBFEM into the commercial finite element software ABAQUS. To this end, user elements are provided through the user subroutine UEL. Detailed explanations regarding the data structures and implementational aspects of the procedures are given. The focus of the current implementation is on interfacial problems and therefore, element-based surfaces are created on polyhedral user elements to establish interactions. This is achieved by an overlay of standard finite elements with negligible stiffness, provided in the ABAQUS element library, with polyhedral user elements. By means of several numerical examples, the advantages of polyhedral elements regarding the treatment of non-matching interfaces and automatic mesh generation are clearly demonstrated. Thus, the performance of ABAQUS for problems involving interfaces is augmented based on the availability of polyhedral meshes. Due to the implementation of polyhedral user elements, ABAQUS can directly handle complex geometries given in the form of digital images or stereolithography (STL) files. In order to facilitate the use of the proposed approach, the code of the UEL is published open-source and can be downloaded from https://github.com/ShukaiYa/SBFEM-UEL.

A robust multisurface return-mapping algorithm and its implementation in Abaqus

The simulation of complex material failure processes requires a precise differentiation of the involved failure mechanisms like fracture or plasticity. This is commonly achieved by using a so-called multisurface failure criterion, where each failure surface is related to a certain failure mechanism. In the case of plasticity, failure surfaces define the elastic domain of the material and any stress state outside of this domain is considered non-admissible and must be returned to the boundary of the elastic domain. So-called return-mapping algorithms are often used and well-studied methods for finding such valid stress states. However, their implementation in numerical simulation tools is often not robust and efficient enough for complex problems that involve sophisticated multisurface definitions. In this work, we present a multisurface return-mapping algorithm and its implementation in the finite element software Abaqus. We found that with additional and enhanced iterative solver methods, the classic Newton-Raphson-based implementation of the algorithm can be improved in order to find solutions to otherwise not returnable stress states. The added computational burden is minimal, as more stress states can be returned without reducing the size of the load increments. The paper focuses on the implementation aspects of such problems and offers the reader a thorough guide and the source code for an Abaqus implementation. We applied the algorithm to simulate the highly orthotropic behavior of wood, allowing us to predict plastic failure of various wooden structures and components.

ABAQUS Implementation to Analyze the Stress Intensity Factor for Laminated Composite Plate

The objective of this work is Abaqus implementation to analyze the effect of fibre orientation angle on stress intensity factor for Single Edge Notched (SEN) 3D laminate composite plate under tensile loading by various cases. The Abaqus software is used to analyze the various problems through the extended finite element method (XFEM). The effects of various fibre orientation angles on Sress Intensity Factor (SIF), Von Misses stress and displacement are also investigated. The presented work would be useful for enhancing the use of Abaqus software to analyze the composite structure with crack and other discontinuities under various conditions.