Finite Element Analysis Scheme Research Articles

Impact of partially damaged passive protection on the fire response of bolted steel connections using finite element analysis

This article aims to quantify the impact of a potential failure of passive fire protection on the ultimate response of a top and seat steel connection with double web angles. A numerical, finite element analysis scheme is proposed considering the real, semi-rigid behaviour of the connection, using unilateral contact-friction laws between the interfaces of the beam, the column, and the steel angles. The model has been validated by previous experimental research at ambient temperatures. Scenarios of unprotected connections, undamaged and partially damaged fire protections are numerically tested. A change in the failure mode and a reduction of the strength equal to 28% for standard fire and 35% for hydrocarbon fire arise for the model with the damaged protection. In this case, maximum temperatures locally at the beam reach the ones of the unprotected connection (900 °C), which is more than 800 °C higher than the connection with undamaged protection. Significant temperature increases of more than 288 °C and 406 °C for standard and hydrocarbon fires also arise on the top angle, compared to the model with undamaged fire protection.

Investigations of the failure mode for additive manufactured interlocked interface structure based on X-Ray CT image guided finite element analysis and experimental comparisons

Suture-inspired interlocked interfaces in nature exhibit promising industrial application potentials for advanced mechanical structures, devices and equipment. It is of significant scientific interest for studying the pull-out response and failure mode of interlocked structure as well as internal stress variations during the loading process. In this paper, finite element analysis (FEA) simulation based on X-Ray tomographic images is proposed for understanding the effects of manufacturing defects on the performances of interlocked structures, which are of critical importance for controlling the stress evolution of the interface structure and corresponding failure modes. Firstly, X-ray micro computed tomography (micro-CT) was applied for non-destructive scanning inspection of aluminum alloy additive manufacturing samples, high spatial resolution and calculation efficiency can be realized through tomographic image guided FEA scheme for generating high fidelity simulation results. Afterwards, non-uniform rational B-splines fitting method was employed for optimizing sample boundaries harvested from CT images, which allows smooth conversion from CT pixel images to high precision fitted finite element model. The B-spine fitting model can significantly improve the computational efficiency for finite element simulation without losing calculation reliability and resolution, overcoming the inherent contradictions between efficiency and resolution of the traditional pixel image finite element method. Finally, considering the mechanical contributions and interactions of external and internal porosity defects, the failure modes of the interlocked structures were further analyzed based on the results of finite element analysis.

Comparison between different models of magnetic hysteresis in the solution of the TEAM 32 problem

AbstractThe numerical modeling of magnetic materials in simulators is a difficult task, above all in real devices with specific excitation. The aim of this work is to compare the accuracy of scalar and vector Preisach models in a well know test benchmark: the TEAM 32 problem. The availability of measured data for this benchmark test and the simple geometry allow us to build hysteresis models and to test them in a 2D finite element analysis (FEA) scheme. The specific numerical formulation of each hysteresis model implemented is described, including the technique for the numerical identification of parameters starting from measured data. The comparison among the models is done in terms of accuracy, but also in terms of easy implementation in the FEA scheme and of computational cost.

Optimization design and finite element analysis of welding robot base based on ANSYS Workbench

A welding robot is a standard industrial robot, and its base is the essential component of the robot, which needs to ensure its safety, stability, and reliability. Using Solid Works software, taking a robot base in an automobile workshop as an example, a three-dimensional model of the robot base structure was established. The model was then directly imported into ANSYS Workbench without error. The finite element analysis method was used to carry out static analysis, modal analysis, and harmonious response analysis of the base model. According to the finite element calculation, the equivalent stress and deformation distribution cloud diagram of the robot base structure model is obtained. The structure size is optimized, and the original model is compared with the improved and optimized design scheme for finite element analysis. The solution’s size is reduced, but the dynamic and static performance is also more advantageous, which achieves the expected structural optimization goal. The finite element simulation experiment verified that the welding robot base could be optimized in size to make its strength and working space better meet the design requirements. The simulation experiment analysis results are accurate and the design scheme is feasible.

Mathematical Strategies for Design Optimization of Multiphase Materials

This work addresses various mathematical solution strategies adapted for design optimization of multiphase materials. The goal is to improve the structural performance by optimizing the distribution of multiple phases that constitute the material. Examples include the optimization of multiphase materials and composites with spatially varying fiber paths using a finite element analysis scheme. In the first application, the phase distribution of a two-phase material is optimized to improve the structural performance. A radial basis function (RBF) based machine learning algorithm is utilized to perform a computationally efficient design optimization and it is found to provide equivalent results with the physical model. The second application concentrates on the optimization of spatially varying fiber paths of a composite material. The fiber paths are described by the Non-Uniform Rational Bezier (B)-Spline Surface (NURBS) using a bidirectional control point representation including 25 parameters. The optimum fiber path is obtained for various loading configurations by optimizing the NURBS parameters that control the overall distribution of fibers. Next, a direct sensitivity analysis is conducted to choose the critical set of parameters from the design point to improve the computational time efficiency. The optimized fiber path obtained with the reduced number of NURBS parameters is found to provide similar structural properties compared to the optimized fiber path that is modeled with a full NURBS representation with 25 parameters.

Numerical and experimental investigation of a complete contact problem by comparing with an asymptotic analysis

The stress and displacement fields of a complete contact problem are investigated using a finite element analysis (FEA) and a Moiré experiment, respectively. Asymptotic analysis of an adhered contact condition is preceded for comparison. Aluminum and copper alloys are used as the contact materials, from which specimens of different contact angles are fabricated. The FEA scheme is validated through comparison with the displacement distributions that are measured in the Moiré experiment. In turn, the generalized stress intensity factors are calculated using the validated FE models. These factors are used to evaluate the dimensional stress distributions in the asymptotic analysis, which are then compared with the FEA results. Excellent agreement in stress components is found between the asymptotic and FE methodologies. The relative error of the stress components σ rr and σ θθ between the methodologies was less than 3.8% within the range from the contact edge to 1 mm, and it increased gradually as the distance from the contact edge increased. In addition, a slight discrepancy is found in the contact of an elastically dissimilar case.

On the Compressibility of Arterial Tissue.

Arterial tissue is commonly assumed to be incompressible. While this assumption is convenient for both experimentalists and theorists, the compressibility of arterial tissue has not been rigorously investigated. In the current study we present an experimental-computational methodology to determine the compressibility of aortic tissue and we demonstrate that specimens excised from an ovine descending aorta are significantly compressible. Specimens are stretched in the radial direction in order to fully characterise the mechanical behaviour of the tissue ground matrix. Additionally biaxial testing is performed to fully characterise the anisotropic contribution of reinforcing fibres. Due to the complexity of the experimental tests, which entail non-uniform finite deformation of a non-linear anisotropic material, it is necessary to implement an inverse finite element analysis scheme to characterise the mechanical behaviour of the arterial tissue. Results reveal that ovine aortic tissue is highly compressible; an effective Poisson's ratio of 0.44 is determined for the ground matrix component of the tissue. It is also demonstrated that correct characterisation of material compressibility has important implications for the calibration of anisotropic fibre properties using biaxial tests. Finally it is demonstrated that correct treatment of material compressibility has significant implications for the accurate prediction of the stress state in an artery under in vivo type loading.

Adaptive meshing for finite element analysis of heterogeneous materials

Adaptive meshing of 2D planar regions, curved surfaces as well as 3D volumes has been extensively studied in Finite Element Analysis (FEA) in the past few decades. Despite the maturity of these adaptive meshing approaches, most of the existing schemes assume the domain or sub-domain of interest is homogeneous. In the context of FEA of heterogeneous objects, traditional adaptive mesh generation strategies become inadequate as they fail to take into account the material heterogeneities. This paper is motivated to tackle such problems and propose an adaptive mesh generation scheme for FEA of versatile heterogeneous materials. The proposed approach takes full advantages of the material heterogeneity information, and the mesh density is formulated with a specific function of the material variations. Dual triangulation of centroidal Voronoi tessellation is then constructed and necessary mesh subdivision is applied with respect to a predefined material threshold. Experiments show that the proposed approach distributes the material composition variation over mesh elements as equally as possible and thus minimizes the number of elements in terms of the given material threshold. FEA results show that the proposed method can significantly decrease the mesh complexities as well as computational resources in FEA of heterogeneous objects and compared with existing approaches, significant mesh reduction can be achieved without sacrifice in FEA qualities.

Iterative substructure method employing concept of inherent strain for large-scale welding problems

When structures such as ships, automobiles, and bridges are assembled by welding, distortion and residual stress are produced as unavoidable consequence of local shrinkage due to welding. The dimensional error deteriorates the performance of the structures and becomes an obstacle to achieve smooth manufacturing if the error exceeds the tolerable limit. On the other hand, residual stress plays an important role in crack initiation and fatigue life. Thus, it is necessary to predict the welding distortion and stress beforehand, so that effective measure and control can be taken. Since the welding is a highly nonlinear problem, it is difficult to predict the distortion quantitatively. For accurate prediction, finite element analysis (FEA) can be a powerful tool. In this research, an enhanced FEA scheme namely i-ISM is developed based on the inherent strain concept and iterative substructure method (ISM). Its capability of solving large-scale practical problems is demonstrated through typical models.

Multistring analysis of wellhead movement and uncemented casing strength in offshore oil and gas wells

This paper presents a theoretical method and a finite element method to describe wellhead movement and uncemented casing strength in offshore oil and gas wells. Parameters considered in the theoretical method include operating load during drilling and completion and the temperature field, pressure field and the end effect of pressure during gas production. The finite element method for multistring analysis is developed to simulate random contact between casings. The relevant finite element analysis scheme is also presented according to the actual procedures of drilling, completion and gas production. Finally, field cases are presented and analyzed using the proposed methods. These are four offshore wells in the South China Sea. The calculated wellhead growths during gas production are compared with measured values. The results show that the wellhead subsides during drilling and completion and grows up during gas production. The theoretical and finite element solutions for wellhead growth are in good agreement with measured values and the deviations of calculation are within 10%. The maximum von Mises stress on the uncemented intermediate casing occurs during the running of the oil tube. The maximum von Mises stress on the uncemented production casing, calculated with the theoretical method occurs at removing the blow-out-preventer (BOP) while that calculated with the finite element method occurs at gas production. Finite element solutions for von Mises stress are recommended and the uncemented casings of four wells satisfy strength requirements.

The Research of Finite Element Modeling and Contacts for Connecting Bolts of Wind Turbine

Combined with characteristics of wind turbine bolt connection structure, with the connection of pitch bearing inner ring and the blade root as the research object, through the finite element analysis software Ansys, establish various connection model, using the multiple point coupling constraint and nonlinear contact for finite element analysis , research on bolt truss element types, connections of each component and the establishment of contact, then obtain and analysis affects of finite element calculation with different element types of bolt truss ,contact relationship ,compared with theoretical results, put forward feasible finite element analysis scheme of wind turbine bolt connection, and provide basis for the structure design and intensity analysis.

Two-scale analysis of a filament-wound cylindrical structure and application of periodic boundary conditions

A two-scale numerical approach to predict the effective in-plane properties of helical filament-wound thin-walled cylindrical tubes is provided. A meso-scale repeated unit cell (RUC) model for a filament-wound tube is established according to the manufacturing process, in which cross-overs, undulations and overlaps of fibre bundles are described using a bottom-up solid modelling technique. An approach to implement the general periodic boundary conditions in a finite element analysis scheme is also presented. As an application example, the effective in-plane elastic constants of glass fibre/epoxy filament-wound tubes are predicted and the influences of the number of the winding circuits and the shape of the fibre bundles are analyzed and discussed. In addition, the stress/strain distribution in the RUC is obtained which provides the essential information on the stress/strain concentration due to fibre cross-over/undulation/overlap. This then indicates the location where damage will initiate.

Numerical and Experimental Approach for Rectangular Cup of Li-Ion Battery Container with Extreme Aspect Ratio

The main goal of this study was to develop the technique of process design and manufacturing for a rectangular deep drawn cup with very narrow width by using finite element analysis scheme and a series of experiments. The manufacturing process of this rectangular cup required several intermediate steps to generate the final shape. The multi-stage deep drawing process was applied to finite element analysis, and a continuous progressive press was employed in a series of experiments. Final specifications of the rectangular deep drawn cup were length of 33.70mm, height of 48.30mm and width of 3.46mm, respectively. In this study, finite element analysis for this drawing process was carried out from the first to the seventh stage, and a series of practical experiment was performed. These simulated results of the rectangular cup were compared with the prototypes of the experiments in view of the deformed shape in each mid-part. The results of finite element analysis showed good agreement with those from the experiments.

A scheme for finite element analysis of mode I and mixed mode stable crack growth and a case study with AISI 4340 steel

A new scheme for elastic–plastic finite element analysis has been proposed for the study of stable crack growth (SCG) from initiation to instability in both mode I and mixed modes (I and II). The scheme is based on node-release technique and helps to determine the variation of fracture load with crack extension without requiring much computer storage and time. The scheme permits predictions of load variation with load line displacement (LLD), maximum fracture load, crack tip current plastic zone and crack edge profile. In the analysis the condition for crack extension at every stage of the SCG is considered to be governed by CTOA/COD reaching a critical value. The scheme of analysis is different from the ones proposed by earlier investigators. The whole SCG is analysed in a few stages using the ANSYS software and a single discretization. Element arrangement in the discretization is decided from the very beginning; it has a capability of accommodating changes in boundary conditions arising out of crack extension in the later stages. Each stage is analysed afresh ignoring state of stress–strain reached at a material point at the end of the previous stage. Case studies on both mode I and mixed mode presented considering AISI 4340 steel, which is widely used in nuclear power industry, indicate that the SCG through it can be characterized in terms of a single COD or CTOA. Predictions for the initiation and maximum fracture loads in both the cases compare very closely with the experimental data reported. The results presented also include the value of critical COD/CTOA (0.035 mm/0.0875 rad) characterizing the SCG through the steel and show that the initiation load is not significantly affected by crack tip radius up to 0.05 mm.

Accuracy-Controlled Combined Adaption- Optimization Scheme for Finite-Element Analysis of 3-D Microwave Devices

Greater reliability and large computational savings can be achieved by linking the adaptive iteration of a computational analysis with the outer, optimization iteration, so that at each optimization step, the analysis performed is as accurate as it needs to be, and no more. Earlier work in this area involving scattering parameter calculation of 2-D waveguide structures is extended to 3-D with certain modifications. A more robust error estimator is used, as well as a different direct optimization strategy that better exploits the ready availability of gradient information. Results for two rectangular waveguide components, a transformer and an E-plane U-bend, confirm the efficiency of the method

Finite element modeling of non-orthogonal loosely woven fabrics in advanced occupant restraint systems

The behavior of loosely woven fabrics differs significantly from other types of woven fabrics. Its unique characteristics have been successfully utilized for the correct operation of some recently developed occupant protection devices for the automotive and heavy machine and truck industry. However, this behavior cannot be efficiently modeled using the currently available material models within a finite element analysis scheme. Therefore, the aim of this work is to present the basics of a formulation of a material model for the analysis of loosely woven fabrics and its implementation in a general-purpose explicit finite element code. To assess the performance of the model, results from the simulation are presented and compared to real test data.

Finite element analysis of dynamic response of wrinkling membranes

A new iterative scheme for finite element analysis of wrinkling membranes, originally devised for static analysis, is extended for analyzing dynamic response of wrinkling membranes. The scheme is found to be successfully implemented with an explicit total Lagrangian finite element code based upon the central difference method. The finite element implementation of the scheme is straightforward, and only minor modifications are needed for existing membrane finite element codes. In light of application for contact-impact, discussed are a couple of existing contact algorithms which are well suited for treating contact-impact of wrinkling membranes with rigid bodies. The validity of the scheme is demonstrated via a numerical simulation of an inflating automotive airbag, made of orthotropic membranes, under impulse pressure loading.

A UNIFIED THERMODYNAMIC CONSTITUTIVE MODEL FOR SMA AND FINITE ELEMENT ANALYSIS OF ACTIVE METAL MATRIX COMPOSITES

SUMMARY A unified thermodynamic constitutive model for Shape Memory Alloy (SMA) materials, based on the thermodynamic framework proposed by Boyd and Lagoudas,1is presented in this paper. The specific selections for the form of Gibbs free energy associated with the martensitic volume fraction are identified for several earlier constitutive models for SMA. The thermal energy released or absorbed during the forward or reverse transformation predicted by the different models is compared with the experimental data from calorimetric measurements. The unified constitutive model is then implemented in a finite element analysis scheme using a return mapping integration technique for the incremental formulation of the model. Finally, the constitutive model is utilized to analyse the thermomechanical response of an active metal matrix composite with embedded SMA fibres. Both tetragonal and hexagonal periodic arrangements of SMA fibres are considered in the calculation and the results are compared.

A unified thermodynamic constitutive model for SMA and finite element analysis of active metal matrix composites

SUMMARY A unified thermodynamic constitutive model for Shape Memory Alloy (SMA) materials, based on the thermodynamic framework proposed by Boyd and Lagoudas,1is presented in this paper. The specific selections for the form of Gibbs free energy associated with the martensitic volume fraction are identified for several earlier constitutive models for SMA. The thermal energy released or absorbed during the forward or reverse transformation predicted by the different models is compared with the experimental data from calorimetric measurements. The unified constitutive model is then implemented in a finite element analysis scheme using a return mapping integration technique for the incremental formulation of the model. Finally, the constitutive model is utilized to analyse the thermomechanical response of an active metal matrix composite with embedded SMA fibres. Both tetragonal and hexagonal periodic arrangements of SMA fibres are considered in the calculation and the results are compared.

Rigid-Plastic Explicit Finite Element Formulation for Two-Dimensional Analysis of Sheet Metal Forming Processes

The explicit scheme for finite element analysis of sheet metal forming problems has been widely used for providing practical solutions since it improves the convergency problem, memory size and computational time especially for the case of complicated geometry and large element number. The explicit schemes in general use are based on the elastic-plastic modeling of material requiring large computataion time. In the present work, a basic formulation for rigid-plastic explicit finite element analysis of plain strain sheet metal forming problems has been proposed. The effect of some basic parameters involved in the dynamic analysis has been studied in detail. Thus, the effective ranges of parameters have been proposed for numerical simultion by the rigid-plastic explicit finite element method. A direct trial-and-error method is introduced to treat contact and friction. In computation, sheet material is assumed to possess normal anisotropy and rigid-plastic workhardening characteristics. In order to show the validity and effectiveness of the proposed explicit scheme, computations are carried out for cylindrical punch stretching and the computational results are compared with those by the implicit scheme as well as with a commercial code. The proposed rigid-plastic exlicit finite element method can be used as a robust and efficient computational method for analysis of sheet metal forming.