Three dimensional thermal finite element simulation of electro-discharge diamond surface grinding

The key to achieve good surface integrity in the workpiece due to Electro-Discharge Diamond Grinding (EDDG) process, which is hybrid of grinding and EDM, is by preventing the excessive temperature and thermal stress generated during the process. EDDG in surface grinding mode called Electro-Discharge Diamond Surface Grinding (EDDSG), used for finishing operation, is a complex machining process where several disciplines of science and engineering are involved in its theory. The complexity of the process includes the random occurrence of spark during EDM process and nonlinear behavior of workpiece material includes temperature dependent thermal properties. The present work involves the development of a simulation model to simulate the complex EDDSG process which consists of simulation of each constituent process namely EDM and surface grinding for temperature and thermal stress distribution. In order to simulate the realistic complex conditions, the three dimensional FEM is used in the process of development of the model accounting the random occurrence of the spark during EDM. The effect of different dielectric fluid, duty factor and energy partition during EDM on the temperature distribution and MRR study related to EDM contribution are reported. It is observed that the spark contributes primarily to the temperature. The predicted results can be used to determine the surface integrity of the machined surface.     

End mill design and machining via cutting simulation

This paper describes a design process for an end mill. A solid model of the designed cutter is constructed together with the computation of the cutter’s geometry, wheel geometry, and wheel positioning data for fabricating end mills with the required cutter geometry. The main idea of the process is to use the cutting simulation method to obtain the machined shape of an end mill by using Boolean operations between a given grinding wheel and a cylindrical workpiece (raw stock). The major design parameters of a cutter, such as rake angle and inner radius, can be verified by interrogating the section profile of its solid model. This study investigates the relationship between various dimensional parameters and proposes an iterative approach to obtain the required geometry of a grinding wheel and cutter location (CL) data for machining an end mill that satisfies the design parameters. This research was implemented using a commercial computer aided design (CAD) system with API function programming and is currently used by a commercial tool maker in Korea. It can eliminate the need to produce a physical prototype during the design stage and can be used in virtual cutting tests and analyses.     

Mathematical modelling and finite element simulation of smart tubular composites

This paper presents a mathematical modelling and numerical simulation method for three-dimensional smart tubular 1(0)-3 composites based on a representative composite volume (RCV) approach. For the problems we consider, numerical results show that the maximum mechanical displacement varies linearly with the applied electrical potential and grows nonlinearly with increasing the RCV height. Further, we observe that decreasing the distance between the inner and outer radii results in increasing the maximum displacement. This refers to composites with large Young’s modulus of the polymer phase, whereas for “soft” polymers (i.e. for Young’s modulus of the polymers of order less than GPa) no particular ‘rule’ is evident, in which case the Poisson’s ratio is the most important parameter.     

Feature based object decomposition for finite element meshing

Performing a finite element analysis requires overlaying an object with a mesh of varying density based on the expected stress levels within the part. Attempts have been made in the past to automat the finite element meshing procedure. The method presented here is intelligent in the sense that it examines the complete part for potential stress gradients and decomposes the part into hexahedral regions according to the geometry gradients in the part. High geometry gradients are regions of high curvature, especially edges. The algorithm segregates high gradient features into isolation volumes. It then continues to decompose each isolation volume dependent on the particular geometry contained in the feature. The result is a set of hexahedral bricks suitable for passing to an automatic meshing routine.     

Genetic algorithms in mesh optimization for visualization and finite element models

This paper investigates the use of a genetic algorithm (GA) to perform the large-scale triangular mesh optimization process. This optimization process consists of a combination of mesh reduction and mesh smoothing that will not only improve the speed for the computation of a 3D graphical or finite element model, but also improve the quality of its mesh. The GA is developed and implemented to replace the original mesh with a re-triangulation process. The GA features optimized initial population, constrained crossover operator, constrained mutation operator and multi-objective fitness evaluation function. While retaining features is important to both visualization models and finite element models, this algorithm also optimizes the shape of the triangular elements, improves the smoothness of the mesh and performs mesh reduction based on the needs of the user.     

Comparison of finite element and pendulum models for simulation of sloshing

The pendulum model is a cost effective tool for the simulation of sloshing. However, the accuracy and applicability of the model has not been well established. In this article, we compare the simulation results obtained from the pendulum model and a more complicated finite element model for sloshing of liquids in tanker trucks. In the pendulum model, we assume that the liquid in the tanker is a point mass oscillating like a frictionless pendulum subjected to an external acceleration. In the finite element model, we solve the full Navier-Stokes equations written for two fluids to obtain the location and motion of the free surface. Stabilized finite element formulations are used in these complex 3D simulations. These finite element formulations are implemented in parallel using the message-passing interface libraries. The numerical example includes the simulation of sloshing in tanker trucks during turning.     

Feature-preserving adaptive mesh generation for molecular shape modeling and simulation

We describe a chain of algorithms for molecular surface and volumetric mesh generation. We take as inputs the centers and radii of all atoms of a molecule and the toolchain outputs both triangular and tetrahedral meshes that can be used for molecular shape modeling and simulation. Experiments on a number of molecules are demonstrated, showing that our methods possess several desirable properties: feature-preservation, local adaptivity, high quality, and smoothness (for surface meshes). We also demonstrate an example of molecular simulation using the finite element method and the meshes generated by our method. The approaches presented and their implementations are also applicable to other types of inputs such as 3D scalar volumes and triangular surface meshes with low quality, and hence can be used for generation/improvement of meshes in a broad range of applications.     

Experimental study and simulation of a hydraulic engine mount with fully coupled fluid-structure interaction finite element analysis model

Non-linear properties of a generic hydraulic engine mount (HEM) are identified and characterized by experiment and simulation approaches. The experimental methods for obtaining static and dynamic performances of the HEM are presented. The characteristics of two configurations of the take-apart HEMs (one is with an inertia track and a free decoupler and the other one is only with an inertia track) and their rubber springs are studied. The relations between static stiffness of an HEM and its rubber springs in three orthogonal directions are investigated. The influences of preload, excitation amplitudes and frequencies on the dynamic stiffness of an HEM are verified. The effects of the free decoupler on dynamic characteristics of the HEM are studied by comparisons of the test results of the two HEMs. The dynamic fluid pressure and the temperature in the upper chamber of an HEM are measured under different excitation conditions. A fully coupled fluid-structure interaction (FSI) and finite element analysis (FEA) model for simulation of HEMs is developed in this paper, which can be used to simulate the static and dynamic performances of the HEMs with only stress versus strain relations of the rubber materials, the fluid physical parameters and the HEMs sizes. The simulated results of one HEM with the proposed model are given, and the results match well with the measured data, or in coincidence with the working mechanisms of HEMs.     

Three dimensional finite element modeling of thermomechanical frictional contact between finite deformation bodies using R-minimum strategy

An algorithm for analyzing the transient thermal coupling with the frictional contact between the multiple elastic–plastic bodies in finite deformation is presented using the R-minimum strategy. An arbitrarily shaped contact element strategy, named as node-to-point contact element strategy, is proposed to handle the thermomechanical frictional contact between finite deformation bodies. Assuming the material properties to be temperature dependent, the constitutive equations for both the thermomechanical frictional contact and the thermal-elastic–plastic materials are deduced respectively and applied in our finite element code. Finally, two examples are presented to show the efficiency and usefulness of this algorithm.     

Distributed finite element computations using object-oriented techniques

An object-oriented parallel finite element framework has been developed to facilitate rapid prototyping of a wide variety of parallel finite element computations. Parallel computing and object-oriented technologies are integrated to achieve efficiency in both computation and software development. The paper presents various reusable and extensible components that constitute the parallel finite element architecture.     

Recommendations for tool-handle material choice based on finite element analysis

Huge areas of work are still done manually and require the usages of different powered and non-powered hand tools. In order to increase the user performance, satisfaction, and lower the risk of acute and cumulative trauma disorders, several researchers have investigated the sizes and shapes of tool-handles. However, only a few authors have investigated tool-handles' materials for further optimising them. Therefore, as presented in this paper, we have utilised a finite-element method for simulating human fingertip whilst grasping tool-handles. We modelled and simulated steel and ethylene propylene diene monomer (EPDM) rubber as homogeneous tool-handle materials and two composites consisting of EPDM rubber and EPDM foam, and also EPDM rubber and PU foam. The simulated finger force was set to obtain characteristic contact pressures of 20 kPa, 40 kPa, 80 kPa, and 100 kPa. Numerical tests have shown that EPDM rubber lowers the contact pressure just slightly. On the other hand, both composites showed significant reduction in contact pressure that could lower the risks of acute and cumulative trauma disorders which are pressure-dependent. Based on the results, it is also evident that a composite containing PU foam with a more evident and flat plateau deformed less at lower strain rates and deformed more when the plateau was reached, in comparison to the composite with EPDM foam. It was shown that hyper-elastic foam materials, which take into account the non-linear behaviour of fingertip soft tissue, can lower the contact pressure whilst maintaining low deformation rate of the tool-handle material for maintaining sufficient rate of stability of the hand tool in the hands. Lower contact pressure also lowers the risk of acute and cumulative trauma disorders, and increases comfort whilst maintaining performance.     

An object-oriented blackboard based approach for automated finite element modeling and analysis of multichip modules

This paper addresses the application of the blackboard system architecture and object-oriented data abstraction techniques to the domain of finite element modeling and analysis. Specifically, a hierarchical object-oriented database was used to represent the physical system at different levels of abstraction including the user-defined physical system level, a computer-generated, simplified physical model level, and the finite element model level. Object link relationships within a given abstraction level and across different abstraction levels resulted in seamless bidirectional information exchange. The blackboard system architecture employed provided a framework for distributed cooperative problem solving, for the application of simplifying domain-specific modeling assumptions, and for integrating the various software modules that are involved in the entire finite element modeling and analysis process. These methodologies were implemented in a prototype computational tool calledIMCMA theIntelligentMultichipModuleAnalyzer. An example illustrates howIMCMA automates finite element thermal analysis of small integrated circuit features in multichip modules through a two-step finite element submodeling process.     

Optimization of finite element codes

A general algorithm for constructing finite element matrices within a multiple input, multiple data stream (MIMD) vector-processing environment is presented. Efficiency of the vectorized code is determined by the number of elements which differs from the more intuitive algorithms based on the number of quadrature points or shape functions. Performance is evaluated analytically and then verified by timings obtained by a series of experimental runs on a Cray Y-MP. A speedup factor of 25 is observed.     

Evaluation of distributed finite element algorithms on a workstation network

This paper discusses the design, implementation and evaluation of linear finite element programs that distribute their computations over a network of workstations. We consider five different algorithms based on direct, iterative and hybrid equation solvers, each of which partitions and maps the model domain across conventional network hardware. A software architecture based on the client-server model distributes the computations and, at the language level, Berkeley sockets enable communication between processes. We evaluate and describe the performance of these algorithms in terms of execution time and speed-up, and we conclude that distributed solvers, particularly those based on substructuring and static condensation, can be effective even on high-latency communication networks.     

Accurate finite element modeling of acoustic waves

In the paper we suggest an accurate finite element approach for the modeling of acoustic waves under a suddenly applied load. We consider the standard linear elements and the linear elements with reduced dispersion for the space discretization as well as the explicit central-difference method for time integration. The analytical study of the numerical dispersion shows that the most accurate results can be obtained with the time increments close to the stability limit. However, even in this case and the use of the linear elements with reduced dispersion, mesh refinement leads to divergent numerical results for acoustic waves under a suddenly applied load. This is explained by large spurious high-frequency oscillations. For the quantification and the suppression of spurious oscillations, we have modified and applied a two-stage time-integration technique that includes the stage of basic computations and the filtering stage. This technique allows accurate convergent results at mesh refinement as well as significantly reduces the numerical anisotropy of solutions. We should mention that the approach suggested is very general and can be equally applied to any loading as well as for any space-discretization technique and any explicit or implicit time-integration method.     

统一二次曲线拱坝有限元建模系统设计与实现

为评价拱坝安全,运用设计模式原理,开发统一二次曲线拱坝有限元自动化建模与图形显示系统.拱坝三维模型与有限元网格均采用参数化方法自动生成.将工厂模式、策略模式和外观模式等设计模式应用到系统开发中,并针对通用有限元软件开发提出2种新的设计模式:几何-网格分离模式、嵌入单元.通过设计模式的应用使系统的可复用性、可维护性和可扩...     

Development of a methodology for a simplified finite element model and optimum design

As computer power is increased, refined finite element models are employed for structural analysis and design. However, it is still difficult and expensive to make and use refined finite element models in the design stage. The refined models usually cause problems in the preliminary design where the design is frequently changed. Therefore, the development of a simplified finite element model is desirable for use in the preliminary design stage. This paper describes the methodology for the simplified model and its optimum design. A Goal programming algorithm is used for system identification to make the simplified model. The developed methodology consists of three phases such as simplification, design, and inverse process. The simplified finite element model is used for the design change and the changed design is recovered onto the original design. The presented methodology is verified through a few examples.     

Intelligent finite element mesh generation

A knowledge-based and automatic finite element mesh generator (INTELMESH) for two-dimensional linear elasticity problems is presented. Unlike other approaches, the proposed technique incorporates the information about the object geometry as well as the boundary and loading conditions to generate an a priori finite element mesh which is more refined around the critical regions of the problem domain. INTELMESH uses a blackboard architecture expert system and the new concept of substracting to locate the critical regions in the domain and to assign priority and mesh size to them. This involves the decomposition of the original structure into substructures (or primitives) for which an initial and approximate analysis can be performed by using analytical solutions and heuristics. It then uses the concept of wave propagation to generate graded nodes in the whole domain with proper density distribution. INTELMESH is fully automatic and allows the user to define the problem domain with minimum amount of input such as object geometry and boundary and loading conditions. Once nodes have been generated for the entire domain, they are automatically connected to form well-shaped triangular elements ensuring the Delaunay property. Several examples are presented and discussed. When incorporated into and compared with the traditional approach to the adaptive finite element analysis, it is expected that the proposed approach, which starts the process with near optimal initial meshes, will be more accurate and efficient.     

Web-based post-processing visualization system for finite element analysis

In this paper, we propose and implement a website of post-processing system for finite element analysis (WebDFEA). Finite element analysis is a computer-aided engineering tool and is popular for static/dynamic structure analysis. It includes three processing systems where post-processing system is to graphically demonstrate the analysis result of a structure model analyzed by finite element method. WebDFEA performs as a website. It is cross-platform because it can auto-detect a client computer platform and auto-download proper OpenGL API for drawing computer graphics. It can draw precise graphics on webpage which can be free controlled by the mouse as a manner in professional software. A database server is involved to store finite element model data and its analysis result. The graphic user interface (GUI) of WebDFEA is a flexible GUI comprising three parts: the switch buttons designed by HTML, the display board and the color bar both developed in Java. The three components are independent and cooperative with each other. They can be recombined without running errors for different purposes. A ship hull section with half a hatch is chosen as the study case to test WebDFEA website. Its finite element model comprises 11,442 triangle elements (shapes). The timeframe starting when WebDFEA is connected to the end when the model is demonstrated is acceptable.     

Object oriented implementation of distributed finite element analysis in .NET

The paper describes a detailed study into the object-oriented implementation of distributed finite element analysis on desktop computers using the .NET framework. The software design aspects are described in some detail for both direct and iterative solution algorithms. The use of interfaces played an important role in the software design. This, together with the .NET framework, enabled remote objects to be implemented in a relatively seamless fashion. The solution routines were “blind” to whether the objects were local or remote. Numerical tests were carried out and reasonable speed-up was achieved, particularly for direct solution methods. It is concluded that .NET provides a viable framework for implementing distributed computing on networks of personal computers.