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The paper presents a practical implementation of hybrid simulation using Real Time Finite Element Method (RTFEM). Hybrid simulation is a technique for investigating dynamic material and structural properties of mechanical systems by performing numerical analysis and experiment at the same time. It applies to mechanical systems with elements too difficult or impossible to model numerically. These elements are tested experimentally, while the rest of the system is simulated numerically. Data between the experiment and numerical simulation are exchanged in real time. Authors use Finite Element Method to perform the numerical simulation. The following paper presents the general algorithm for hybrid simulation using RTFEM and possible improvements of the algorithm for computation time reduction developed by the authors. The paper focuses on practical implementation of presented methods, which involves testing of a mountain bicycle frame, where the shock absorber is tested experimentally while the rest of the frame is simulated numerically. [ABSTRACT FROM AUTHOR]

The mathematical modeling of the throughput-pressure behavior of the co-rotating twin screw extrusion process was subject of a variety of publications. Due to limited options within the area of numerical simulations, most of the modeling was based on analytical simplifications and adaptions. For that reason, commonly known models for describing the throughput behavior of co-rotating twin screws are based on the concept of the kinematical inversion principle. Within this concept, in comparison to the real kinematic behavior supposing the screws are rotating with a rotational velocity, the barrel is inducing the drag flow with an approximated translational velocity in the system. Further, the channel geometry is transferred to a rectangular shape with a constant channel height and is set in two-dimensional level for a simplified calculation. However, with regards to the geometrical diversity of the co-rotating systems with varying ratios of outer to inner diameter of the screws, the resulting channel geometry indicates different heights which have a significant influence on the inducing drag flow within the process. The model for the melt throughput-pressure behavior allows a variation of general screw and barrel geometry ratios but neglects the significance of the induced drag flow depending on the varying channel height. For that reason, a new method to measure the influence of the non-inverted drag flow by using 3D FEM simulations are presented in this paper. With the presented data, it is possible to extend the conventional model by considering the varying channel height and the correct induction of the drag flow with different screw ratios. The results indicate a systematical deviation between the analytical model and the data of this study. Overall, the consideration of the varying channel height increase the accuracy of the induced drag flow within the calculation of the throughput-pressure gradient. [ABSTRACT FROM AUTHOR]

Wrinkling is one of the major defects in forming processes of auto-body panels. This paper focuses on application of universal formability technology to analyze and eliminate wrinkling defect. To analyze refinedly and eliminate efficiently, universal formability technology is introduced into finite element environment. This paper presents a procedure of formability simulation analysis for wrinkles appeared on an auto fender model. The analysis results provide the approaches to eliminating wrinkles, which demonstrates the effectiveness of universal formability technology to analyze wrinkling phenomenon. The study also shows the feasibility of universal formability technology introduced into finite element environment. [ABSTRACT FROM AUTHOR]

This paper deals with the computer modelling of tightening of the bolted connection. The analysed bolted connection consisting of the M24 metric thread is used for clamping the flexible yokes that fix the steel segments of the mine yielding support. In mining practise, it is necessary to cause the prescribed pretension in the bolted connection. One of the methods to precisely determine dependency of tightening moment on the pretension in the bolt is the finite element method. The models of the bolt and the nut were created and assembled according to drawings without shape simplification. This work was created on the basis of practical requirements from mining industry and the obtained results will be reflected in the optimization of the bolted connection. [ABSTRACT FROM AUTHOR]

This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline. [ABSTRACT FROM AUTHOR]

Taylor impact test presented in a previous study on a commercial high strength and super hard aluminum alloy 7A04-T6 are numerically evaluated using the finite element code ABAQUS/Explicit. In the present study, the influence of fracture criterion in numerical simulations of the deformation and fracture behavior of Taylor rod has been studied. Included in the paper are a modified version of Johnson-Cook, the Cockcroft-Latham(C-L), the constant fracture strain, the maximum shear stress and the maximum principle stress fracture models. Model constants for each criterion are calibrated from material tests. The modified version of Johnson-Cook fracture criterion with the stress triaxiality cut off idea is found to give good prediction of the Taylor impact fracture behavior. However, this study will also show that the C-L fracture criterion where only one simple material test is required for calibration is found to give reasonable predictions. Unfortunately, the other three criteria are not able to repeat the experimentally obtained fracture behavior. The study indicates that the stress triaxiality cut off idea is necessary to predict the Taylor impact fracture. [ABSTRACT FROM AUTHOR]

This paper presents the preliminary results of our numerical simulations designed and performed to address the high Weissenberg number problem that is the major challenge in the simulation of viscoelastic flows. The mathematical model used to explore this problem is based on Oldroyd type model. A new simple computational test case is proposed and solved to demonstrate the nature of the high Weissenberg number problem. Various finite-volume as well as finite-element methods are introduced to be tested for this test case. Some of our very first results are presented and discussed at the end. [ABSTRACT FROM AUTHOR]

This paper presents the formulation of an axi-symmetric element based on an efficient method called 'Inverse Approach' (I.A.) for the numerical modeling of cold forging process. In contrast to the classical incremental methods, the Inverse Approach exploits the known shape of the final part and executes the calculation from the final part to the initial billet. The assumptions of the proportional loading and the simplified tool actions make the I.A. calculation very fast. The metal's incompressibility is ensured by the penalty method. The comparison with ABAQUS® and FORGE® shows the efficiency and limitations of the I.A. This simplified method will be a good tool for the preliminary preform design. [ABSTRACT FROM AUTHOR]

In cold extrusion of steel tools make direct contact with the metal to be extruded. Those tools are exposed to high contact stresses which, in certain cases, may be limiting factors in applying this technology. The present paper was bound to the influence of punch head design on radial stress at the container wall in the process of cold backward extrusion. Five different punch head geometries were investigated. Radial stress on the container wall was measured by pin load cell technique. Special tooling for the experimental investigation was designed and made. Process has been analyzed also by FE method. 2D models of tools were obtained by UGS NX and for FE analysis Simufact Forming GP software was used. Obtained results (experimental and obtained by FE) were compared and analyzed. Optimal punch head geometry has been suggested. [ABSTRACT FROM AUTHOR]

A heartbeat is the consequence of cardiac tissue deforming in response to tension generated in cardiac fibres. This tension is a result of biochemical reactions that occur as part of cardiac electrophysiology. This coupled electro-mechanical system is usually modelled by coupling a model of tissue deformation with a tissue level model of cardiac electrophysiology such as the bidomain equations [1]. One difficulty with computing a numerical solution of this coupled system is numerical stability [3, 7]. In this paper we describe how numerical stability may be attained by embedding the model of generation of active tension within the tissue deformation model. [ABSTRACT FROM AUTHOR]

Solar thermal power generation systems, including direct steam generation, require isothermal energy storage systems for a saturation temperature range between 190° C and 310° C. One option to fulfill this requirement is the application of phase-change materials to absorb or release energy. In this paper, the basic concept of latent heat storage system is described, and a model of phase-change heat transfer of latent heat storage thermal unit for thermal energy storage system is built. Base on the practical thermo-physical properties of phase-change materials, Quasi-Steady State temperature distribution of phase-change heat transfer is analyzed under low Ste number. Numerical simulation (finite element method) taking account into the sensible heat is adopted and the results prove that the Quasi-Steady State temperature distribution obtained from theoretical is in good agreement with the results of numerical simulation. For a latent heat storage system with low Ste number characteristic, Quasi-Steady State solution can be used as the theoretical calculation foundation for engineering design. [ABSTRACT FROM AUTHOR]