Conventional FE Models Research Articles

An efficient method for nonlinear characteristic analysis of fixed contact surface and interface in bolted joint and its application

This paper proposes a modelling method for nonlinear characteristic analysis of bolted joint considering the combined effect of contact surface and the interface interaction. First, the discontinuous contact region of the bolted structure is regarded as a flat continuous medium based on the hypothesis of equivalent virtual material. Second, two user-defined elements are respectively developed to simulate the contact surface and flexible interface. Then, a typical example of bolted structure is simulated using the proposed method. The comparison of the simulation results and the measurements indicates that the method is valid for the nonlinear characteristic analysis of the joint. Moreover, the method also presents advantage in computational efficiency according to the comparison with the conventional FE model. Hence, the proposed method provides a feasible solution for bolted problem in practical engineering applications, such as the precision instrument design, ultra-precision position control and multi-body dynamics simulation of complex mechanical system.

An effective and efficient numerical method for thermal management in 3D stacked integrated circuits

Three dimensional (3D) integration technology has emerged as a promising solution to improve the performance of microelectronic devices. However, the complex structures and the consequent increase in power density exacerbate the challenge of thermal management in the device with multiple chips. Thus, an effective thermal analysis method is crucial for the reliability of 3D IC device. In this paper, a fast and accurate equivalent approach based on finite element analysis (FEA) was proposed for estimating the equivalent thermal conductivity of 3D IC device, and the proposed numerical model was validated by 3D FEA method. In addition, the estimated equivalent thermal conductivity was employed in thermal analysis of real 3D IC device, whose efficiency significantly outperformed the conventional detailed FE model with comparable accuracy. Furthermore, the effect of the structure and material related parameters on steady-state temperature profiles in 3D stacked packages has been systematically analyzed, including the diameter and pitch of TSVs, the thickness of SiO2, the heat source setting as well as underfill materials, which provides useful insights for thermal management in 3D IC industry.

A proposal of conventional fe-model for layered braided composite tube

A proposal of conventional fe-model for layered braided composite tube

Application of the wave finite element method to reinforced concrete structures with damage

Vibration based methods are commonly deployed to detect structural damage using sensors placed remotely from potential damage sites. Whilst many such techniques are modal based there are advantages to adopting a wave approach, in which case it is essential to characterise wave propagation in the structure. The Wave Finite Element method (WFE) is an efficient approach to predicting the response of a composite waveguide using a conventional FE model of a just a short segment. The method has previously been applied to different structures such as laminated plates, thinwalled structures and fluid-filled pipes. In this paper, the WFE method is applied to a steel reinforced concrete beam. Dispersion curves and wave mode shapes are first presented from free wave solutions, and these are found to be insensitive to loss of thickness in a single reinforcing bar. A reinforced beam with localised damage is then considered by coupling an FE model of a short damaged segment into the WFE model of the undamaged beam. The fundamental bending, torsion and axial waves are unaffected by the damage but some higher order waves of the cross section are significantly reflected close to their cut-on frequencies. The potential of this approach for detecting corrosion and delamination in reinforced concrete beams will be investigated in future work.

Sensitivity analysis of phase transformation model based on solution of diffusion equation

Presented work is focused on modelling of the phase transformation during laminar cooling after hot rolling of dual phase steel strips. Conventional FE model describing heat transfer was used in the macroscale. The model based on the solution of the diffusion equation with moving boundary was selected to predict properties of the steel based on phase transformations which occur in microscale. Preliminary observations indicated that results depend on various parameters of the model, such as: diffusion coefficient, boundary velocity factor and cooling rate. Therefore, sensitivity analysis of the model with respect to these parameters was performed in order to enhance the predictive capabilities of the model and to simplify further solution.

A robust model for determining the mesh stiffness of cylindrical gears

A model for determining mesh stiffness of cylindrical gears is proposed using a combination of finite element method (FEM) and local contact analysis of elastic bodies. The deformation at each contact point is separated into a linear global term and a nonlinear local contact term. The global compliances are obtained using an even mesh technique and substructure method of a three-dimensional finite element analysis to make the deformation of a global term insensitive to the twist of gear structure under different gear basic parameters, while the local contact deformations are derived through an analytical line-contact formula deduced from the Hertzian contact theory. The time-varying mesh stiffness and load distribution can be well predicted in this model. It is proved that the mesh stiffness calculated from the proposed method is in close agreement with that from published formulae, but with less time consumption and improved steadiness compared with conventional FE models using contact elements. The sensitivities of total mesh force, gear basic parameters and body parameters on mesh stiffness are investigated and discussed.

AN EXTENDED SUBSTRUCTURING TECHNIQUE FOR EFFICIENT EVALUATION OF NONLINEAR LOAD-BEARING STRUCTURES IN THE CONCEPTUAL DESIGN STAGE

The research presented in this paper has extended the substructuring technique into the nonlinear domain in order to apply the finite element analysis (FEA) method to complex nonlinear structural design problems in the conceptual design stage. As conventional FE models based on substructures allow only linear analysis, it was necessary in this research to introduce a new algorithm capable of linearizing nonlinear structural problems with sufficient accuracy in order to enable evaluation of engineering design concepts in a more objective and rigorous manner in the early stages of design. The developed method was implemented within a commercial FE solver, and validated using a select number of case studies. The results obtained for the two sample solutions indicate that the new method has achieved an improvement in accuracy of 90% and 98% respectively compared to the conventional FE-based approach applied to the same class of design problems.

Comparative Evaluation of Engineering Design Concepts Based on Non-Linear Substructuring Analysis

The paper presents a novel approach to comparative evaluation of engineering design concepts that exhibit non-linear structural behaviour under load. The developed method has extended the substructures technique in order to apply the Finite Element Analysis (FEA) method to complex non-linear structural problems in the conceptual design phase. As conventional FE models based on substructures allow only linear analysis, it was necessary in this research to introduce a new algorithm capable of linearizing non-linear structural problems with sufficient accuracy in order to enable comparative evaluation of design concepts relative to each other under the given constraints and loading conditions. A comparative study with respect to model size, efficiency, accuracy and confidence was performed to validate the developed method. Obtained results indicate significant improvement over more traditional approaches to applying FEA in the conceptual design phase. The improvements achieved using the developed method compared to the traditional FE based approach are superior by a factor of 2.7 in efficiency and by a factor of 4.5 in confidence while not sacrificing the optimality of the solutions.

Springback Prediction of the TRIP Sheet Steel Stamping

An enhanced elastic-plastic constitutive equation taking into account strain induced transformation is developed. The variation of the Young’s modulus with the martensitic transformation during stamping process is also introduced to improve the accuracy of springback simulation for TRIP steel. The accuracy of the proposed method is verified by comparing with the conventional FE model and experimental results. The enhanced material model is testified to be efficient in accurate prediction on springback for TRIP steels, which will put forward the application of TRIP steel sheet in auto body manufacturing.

Amultilayered Solid Element used to Model Composite Delamination

This paper focuses on the latest development of a solid hexahedron element for composite delamination analysis. The 8-node solid is derived from a 20-node hexahedron. It is transformed into two physical independent 4-node shell elements according to the propagation of delamination process within the element. This transformation is driven by a transfer and damage laws that are defined by calibrating the element with a FE modeling for a double cantilever beam (DCB) test. According to the position of the crack in the element, one parameter defines the degradation of the transverse properties at the Gauss point as well as the transfer of the volume element towards the bi-plate formulation. A sensitivity study of the element is presented. A global-local finite element approach coupled with the traditional virtual crack closure technique (VCCT) method allows to calculate the energy release rates and to control the propagation of cracking in the element. This method is validated by comparison between conventional FE models and experimental tests [DCB, and end load split (ELS)]. Experimental asymmetric double cantilever beam (ADCB) test is carried out and modelled using the developed element. The numerical simulation properly correlates with the experimental results.

An Adaptive Efg-Fe Coupling Method for the Numerical Simulation of Extrusion Processes

An adaptive EFG-FE coupling method is proposed and developed for the numerical simulation of lateral extrusion and forward-backward extrusion. Initially, the simulation has been implemented by using a conventional FE model. During the deforming process, mesh quality is checked at every incremental step. Distorted elements are automatically converted to EFG nodes, whereas, the less distorted elements are reserved. A new algorithm to generate EFG nodes and interface elements is presented. This method is capable of dealing with large deformation and has higher computational efficiency than using an EFG method wholly. Numerical results demonstrate that the adaptive EFG-FE coupling method has reasonable accuracy and is effective for local bulk metal forming such as extrusion processes.

Use of a 3D compartment model for simplified full ship FE model. Part II: validation of the simplified FE model

This is Part II in a series of papers. Part I (J Mar Sci Technol 13:154–163) deals with an approach employed to construct a simplified FE model using a 3D compartment model available from the beginning of the ship design process. This paper begins by describing the limitations of an analytical approach based on shear warping beam theory for assessing torsional strength. Next, the structural parts of a container ship that have a negligible effect on hull girder bending strength and torsional strength are determined. This is verified by removing these parts from a conventional FE model and comparing the results obtained using this modified model with those yielded by the original model. The fore end part, the aft end part and the deck house are examined. Since these parts have complicated structures and relevant drawings for them are issued later than cargo structure drawings, modeling them exactly can result in a delay in the completion of the full ship FE model. This paper also verifies the validity of the simplified FE model built by applying the method proposed in Part I and comparing the results obtained with it with those given by a conventional full ship FE model. The stresses on hatch coaming top, the maximum diagonal elongations of the hatch coaming, and the maximum hatch corner movements are evaluated to check the validity of the simplified model.

The Application of Digital Image Correlation for Measuring Residual Stress by Incremental Hole Drilling

The measurement of residual stress using the incremental hole drilling is well established, but the main limitations with the conventional strain gauge approach are the requirements for surface preparation, the need for accurate alignment and drilling, the restricted range of hole geometries commensurate with the specific gauge designs, and the limited range of strain data averaged over the footprint of the strain gauge grid. Recent attempts to extend the method have seen the application of full field optical techniques such as electronic speckle pattern interferometry and holographic interferometry for measuring the strain fields around the hole, but these methods are sensitive to vibration and this limits their practical use to controlled laboratory environments. There are significant potential benefits therefore of using a more robust technique based on Digital Image Correlation (DIC), and work is presented in this study on the development of the method for measuring surface displacements and strain fields generated during incremental hole drilling. Some of the practical issues associated with the technique development, including the optimization of applied patterns, the development of the optical system and integration with current hole drilling equipment are discussed, and although measurements are only presented for a single load case - the equi-biaxial stress state introduced during shot peening - the novel aspect of this work is the integration of DIC measurements with incremental drilling and an application of the Integral Method analysis to measure the variation of residual stress with depth. Validation data comparing results from conventional strain gauge data and FE models is also presented.

The advanced forming process model including the elastic effects of the forming press and tool

This article addresses process, stamping, and manufacturing engineers, as well as tool designers (prototype and series production tools), and press shop planners in the range of metal forming. The paper deals with methods of modelling and simulating the metal forming process and their application in product design, production, and forming process planning. In models usually applied major effects on the forming process are neglected. For instance, the elastic behaviour of presses and die tools is not considered in process and tool planning. Thus, reworking of tools is a consequence of this model oversimplification. The paper illustrates how interactions between forming press, tool and metal forming process can be modelled by enhancing conventional FE models. Several examples demonstrate the information value of the Advanced Forming Process Model (AFPM).

Faster to Sound Parts by Advanced Forming Process Simulation - Advanced Forming Process Model Including the Elastic Effects of the Forming Press and Tool

This article addresses process, stamping, and manufacturing engineers, as well as tool designers (prototype and series production tools), and press shop planners in the range of metal forming. The paper deals with methods of modelling and simulating the metal forming process and their application in product design, production, and forming process planning. In models usually applied major effects on the forming process are neglected. For instance, the elastic behaviour of presses and die tools is not considered in process and tool planning. Thus, reworking of tools is a consequence of this model oversimplification. The paper illustrates how interactions between forming press, die tool and metal forming processes can be modelled by enhancing conventional FE models. Several examples demonstrate the information value of the Advanced Forming Process Model (AFPM).

A modified isoparametric mapping fill method to display color mapping of data

This work presents a reliable and efficient technique for displaying color mapping of data for post-processing of the Hybrid-Trefftz (HT) finite element method (FEM). The isoparametric mapping fill method developed in conventional FE models is generalized to HT FE models. Several steps of the procedure for HT FEM are demonstrated, as well as the aspects to be modified. For illustration purposes, a computer program has been written in VC++ and two 2D examples discretized by HT FEM are provided. The results are found to agree well with the analytical solutions although there are some discrepancies. Finally, conclusions are inferred and extension of this work to the 3D case is discussed.

Inelastic seismic analysis of RC bridge piers including flexure-shear-axial interaction

The effect of shear coupled with axial force variation on the inelastic seismic behaviour of reinforced concrete bridge piers is investigated in this paper. For this purpose, a hysteretic axial-shear interaction model was developed and implemented in a nonlinear finite element analysis program. Thus, flexure-shear-axial interaction is simulated under variable amplitude reversed actions. Comparative studies for shear-dominated reinforced concrete columns indicated that a conventional FE model based on flexure-axial interaction only gave wholly inadequate results and was therefore incapable of predicting the behaviour of such members. Analysis of a reinforced concrete bridge damaged during the Northridge (California 1994) earthquake demonstrated the importance of shear modelling. The contribution of shear deformation to total displacement was considerable, leading to increased ductility demand. Moreover, the effect of shear with axial force variation can significantly affect strength, stiffness and energy dissipation capacity of reinforced concrete members. It is concluded that flexure-shear-axial interaction should be taken into account in assessing the behaviour of reinforced concrete bridge columns, especially in the presence of high vertical ground motion.

A hybrid BEM model

AbstractThe hybrid stress method is very successful for stress concentration problems.1–7 Especially for problems of fracture mechanics, procedures can be found that work efficiently for two‐ and three‐dimensional problems. The rate of convergence with this method, evidently, is higher than that with conventional FE models. The BEM procedure, too, works more efficiently, but shows some essential disadvantages against the FEM, such as that for the direct method no symmetric positive definite matrix can be found and that there occur numerical problems at corners.8,9 This happens also when BEM and FEM are even coupled commonly.10–12. In the following, a hybrid BEM model will be described which combines the advantages of both the FEM and the BEM. It will be shown in this paper that BEM is very successful in formulating finite element functions for the hybrid assumed stress method.