Papers by Keyword: Finite Element Model (FEM)

Abstract: Thermal management materials frequently have multi-phase composite character with complex architecture of the constituents. As a result, design rules are needed which can be used in selection of the phases and optimizing their volume fractions. The study shows that such are provided by finite element modeling of these composites. This is demonstrated for a diamond-SiC-Si-(Al) composites, which have been optimized in terms of the volume fraction of SiC, contact area between the components and presence of open porosity.

Abstract: Three-dimensional finite element (FE) methods are used to predict the Young’s modulus of two types of 2D woven carbon/carbon composites. Tensile tests are performed to validate the predictions. The results indicate that a novel image-based route in generating FE meshes gave strong agreement with experimental data, while a comparative unit cell FE model of the structure was found to be poorer. The differences between the image-based and unit cell methodologies were the consideration of the finer architectures of the composites and their porosity. The image-based approach highlighted true porosity in the structure due to meshes forming directly from X-ray tomographic data. However, the finer fibre architectures of the composites were compromised because of limitations in the pixel resolutions employed during the initial scanning process. In comparison, the unit cell models were based solely on idealisations of the composite microstructure, in which porosity was neglected.

Abstract: An experimental investigation was undertaken into the seismic performance of a precast prestressed concrete frame system. A total of three beam-to-column connection models were designed, built, and tested to failure to evaluate their strength and ductility properties under cyclic loading. The comparative study showed that the hysteretic loops were full and the joints had better energy dissipation capacity. It was concluded that satisfactory seismic performance could be expected from this frame system if the slip of the U-shaped reinforcing steel bar was controlled well on the zone of joint. Then the finite element method (FEM) was used to analyze the specimen and the calculation results were in good agreement with those of the test.

Abstract: A computational model, in which the effects of high temperature on steel and concrete’s properties and the composite action and interfacial properties between steel tube and concrete core were considered, was developed using ABAQUS program. Based on a damage model of concrete at ambient condition and tested stress versus strain curves of fire-damaged concrete, a new damage model of concrete after exposure to high temperatures was developed to consider the influence of high temperatures on the damage of concrete. By introducing the damage model of fire-damaged concrete, the reasonable equivalent stress-strain relations of confined concrete and a modified steel tube-concrete interface model into the ABAQUS FE model, the mechanical behaviors of the fire-damaged CFT columns and connections were simulated precisely and verified by some relative test results.

Abstract: External bonding of fiber reinforced polymer (FRP) composites has become a popular technique for strengthening reinforced concrete (RC) structures all over the world. So far, very little information is available on the fire performance of FRP-strengthened concrete members. The analysis presented here aims to develop a nonlinear finite element (FE) model of FRP-strengthened RC beams exposed to fire. The analysis consists of two portions: the initial portion is the calculation of the transient temperature distribution and the second portion is the structural response analysis due to the effect of thermal and mechanical load. The proposed numerical analysis is validated against proving fire tests. The results indicate that the predicted temperatures and deformations are shown to agree to the tests satisfactorily.

Abstract: The plywood material is widely used in civil engineering and furniture industry as cheap, strong, and lightweight material. The progressive failure of the plywood is difficult to be modeled and predicted because of the complexity of its structure and the interaction between different modes of orthogonal damages and interlayer failure. The microstructure of the wood determines the failure of the plies. A micromechanical material model of wooden veneers is developed, which is based on a representative volume cell (RVC) taken from the tubular microstructure of the wood and represented as a truss structure with longitudinal, transverse, and diagonal bar finite elements. The damage variables prescribed for each type of the bars determine the progressive degradation of the material stiffness. The 2-D damage material model of wooden veneers is utilized as user-defined material in continuum shell elements of ABAQUS™ finite element code. The parameters of the model are determined to simulate the behavior of single veneers in tension tests in different directions of loading. Together with cohesive elements representing the interface between the plies, the suggested model can be used to simulate and analyze the progressive failure and damage interaction in the plywood. The simulations could give us better understanding of the complex failure of the plywood, the succession of the damage development and reveal the weakest link in the material. The analysis can be used for optimization of the plywood layup.

Abstract: ECAP (Equal Channel Angular Pressing) is a very interesting method for modifying microstructure in producing UFG (Ultra Fine Grained) materials. It consists of pressing test samples through a die containing two channels, equal in cross section and intersecting at an angle Φ. As a result of pressing, the sample theoretically deforms by simple shear and retains the same cross sectional area to repeat the pressing for several cycles. 2-D and 3-D FEM simulations of both one and four ECAP passes of two modified aluminium alloys were performed in order to investigate the deformation state of processed workpiece and, moreover, the effect of the different alloy related Strain Hardening Rate (SHR), die geometry (in terms of variation of channel outer angle) and friction on deformation distribution and magnitude. FEM results showed a lower equivalent plastic strain on the outer side of both cross and longitudinal sections of the billets after one and four passes. Microhardness tests performed on the same sections of ECAP processed billets supported these findings. Moreover, FEM analysis indicated that an higher SHR means a greater strain inhomogeneity on cross section of the processed billet. The same effect was observed by increasing the channel outer angle by computing friction.

Abstract: Tool wear during high speed machining process plays an important role in machining cost and efficiency. The purpose of this study is to examine the impact of tribological properties of coatings on cutting performance. Finite element methods (FEM) were used to model the effect of coated and uncoated cutting tools (K10) on the machinability of the aluminum alloy 7050T7451. Uncoated, Single coated, such as TiC, TiN and Al2O3 and multi-coated tool were studied. All finite element models were assumed to be plane strain. To achieve constitutive model of Al7050T7451 under conditions of machining that high strain rate, high strain and high temperature occur, high speed impact experiment and material drawing experiment were done. Comparison of FEM results shows that the highest temperatures in tools, the temperature change rates of different tools from surface to its bulk material, and the temperatures in chips are changed greatly. It also shows that the cutting temperature of coated tool is lower than uncoated tools, but cutting forces change very little. All these results show that coatings can be used to reduce adhesion between a tool and a workpiece material. The wear resistance of coated tool can be improved effectively and tool life is increased correspondingly.

Abstract: Quality control is very important in the manufacturing process of cold tube-bending, but most of enterprises can only verify tube quality by the tube bending machine. Based on the platform of commercial software, an integrated system on CAD/CAPP/CAE for bending tube in power plants boiler is developed. The system is carried on re-development under the VC++ language environment, and data is transferred in Pro/E, Ansys and designing module through a reasonable data structure and interface. So we can share data and realize flexibility and standardization of the processing. The application result indicated that the integrated system can offer a whole set of solution from building a CAD model, forecasting tube bending quality and structure optimization by CAE methods to programming CAPP processes.

Abstract: In the process of the ultrasonic machining, the machining efficiency is affected directly by material removal rate. In the paper, the material structure deformation under abrasive impacting is simulated by the LS-DYNA3D software, and the stresses occurring are analyzed numerically. In addition, the effects of some machining parameters on the amount of the material removal are investigated by the experiments.