Papers by Keyword: Elasto-Plastic

Abstract: This study is mainly based on five sets of mold cone angle and friction coefficient of micro-tube tube end necking forming analysis, and the tool cone angle of 60° experimental verification is carried out to analyze the titanium alloy (Grade 1) micro-tube for different mold cone angle and the different friction coefficient caused by the difference between the shrinkage forming. In this paper, Prandtl-Reuss's plastic flow rule, combined with finite element deformation theory and updated Lagrangian formulation (ULF) concept, establish an incremental elasto-plastic finite element analysis program for simulating the miniature tube end necking. The forming process also uses the generalized r_min algorithm to deal with elasto-plastic state and contact problems. From the simulation data of necking process, deformation history, punch load and punch stroke, stress and strain distribution is obtained. The analysis results show that by increasing the mold cone angle and friction coefficient, the thickness tends to be thicker in the certain area.

Abstract: In this work, 2-D/3-D forming problems (extrusion and deep drawing) are numerically simulated by extended finite element method (XFEM). The updated Lagrangian formulation is used to model the large deformation. The von-Mises yield criterion is used to model the elasto-plastic behavior assuming isotropic hardening. Penalty approach is employed to impose the contact constraints and non–penetration condition at the material interfaces. The level set approach is used for locating the material interfaces. The numerical simulations of two forming problems are presented using developed nonlinear XFEM code.

Abstract: This paper develops a three dimensional elastic fracture analysis method, PDS-FEM (Particle Discretization Scheme Finite Element Method), to its elasto-plastic version. The Newton-Raphson iteration method is adopted for solving material nonlinearity, and the conjugate gradient method is applied to solve the linear equations of FEM. In order to apply the fracture analysis method to the engineering scale analysis, CPU based parallel computing technology is applied, and the computation speed is highly advanced. In this trial test, a simple stress based failure criterion is employed for the failure analysis of a cantilever steel beam. The numerical results without fracture match well with the commercial FEM software, ANSYS’s, which verifies the accuracy of the developed platform.

Abstract: This study is focused on the influences of micro stretching process, miniaturized of micro square hole-flange to stainless steel (SUS304) material, and different thicknesses (0.2, 0.1, 0.05mm) of plate. By undergoing finite element program analysis of material parameter corrected by scale factor, we can discover the differences of different thicknesses of plate during micro stretching forming process. The finite element method in this paper is combined with the plastic flow rule of Dynaform and LS-DYNA solver, finite element deformed theory, and updated Lagrangian formulation to simulate the process of micro square hole-flange. The point of this research is by simulating and analyzing all datum of micro stretching forming process, relation between punch load and stroke, distribution of thickness, distribution of stress and strain, the maximum diameter of flange’s hole and the maximum height of flange. Design three pairs of micro square hole-flange tool undergoing micro stretching experience through SUS304 plate. Compare the experience to the results of the simulation to test the reliability of this analyzing program. Through finite element analysis and the results of the experience, we can discover that the minimum of the thickness, the biggest stress and major strain centralize areas where blank and punch corner meet.

Abstract: Ultrasonic assisted turning (UAT) is a novel manufacturing technology, where high frequency vibrations are imposed on the movement of a cutting tool. A 2D FE transient simulation is developed in DEFORM, where ultrasonic vibrations of frequency 20 kHz and amplitude of 20 μm are provided to the cutting tool in the direction of cutting velocity. The prediction of residual stress distribution is carried out using elasto-plastic finite element simulations. Experimental analysis is carried out in measuring the strain at the cutting tool during CT and UAT along with the chip mechanism and chip microstructure study to validate the residual stress distribution. The ultrasonic vibrations yield a considerable improvement in compressive residual stresses which ultimately benefits in improving fatigue life of titanium alloys.

Abstract: To develop a generalized numerical model by the elasto-plastic formulation coupling with dynamic finite element method for the shot peening process of metal alloys is the main goal of this paper. The analysis code is based on the finite deformation theory; the optimum numerical technique and the relevant parameters of forming process. In this study, the simulations of single and multi shot forming process were performed. The effects of impact velocity and strain rate, size of workpiece, and the residual stress were observed and discussed in details. After comparing with the corresponding papers, the universal model for metal shot peening analyses will be developed completely. The most significant advantage of this paper is the development of the precise analysis technology to suit for the future necessity of the manufacturing processes. The suggested models and techniques are helpful in solving of impact problems or metal forming processes.

Abstract: 2D elasto-plastic finite element method was adopted to analyze the forced state of the surrounding rock and the tunnel lining in every step of the construction project for Fulongping double-decked tunnel. In the analysis,Mohr-Coulombs yield criterion was employed incoporating associated flow law to account for the elasto-plastic characteristics of materials. The tangent stiffness method was adopted to solve the equation of equilibrium, and the stresses which exceeded yielded point were adjusted.

Abstract: UHMWPE/LDPE thermoplastic composites present obvious plastic deformation in the off-axis direction, especially in the transverse direction. In this paper, the elastoplastic property of UHMWPE/LDPE composites in transverse tensile direction was studied. Mises yield potential plastic model was used as the plastic model, together with a power hardening law to analyze the plastic behavior of UHMWPE/LDPE composite in transverse direction. Abaqus software and subroutine UMAT were used to simulate the tensile property of UHMWPE/LDPE composites, and the simulation results are accordance with the experiment results very well.

Abstract: Structure and anisotropy are two fundamental aspects of natural clays. They cant be ignored because of their significant influences on soils strength and stress-strain behavior, etc. Therefore, anisotropic tensor and structural parameters are introduced in Modified Cam Clay Model which is only suitable for isotropic remolded clays, and evolution laws of them are given in this paper. Thus, an elasto-plastic constitutive model considering the influences of natural soil structure and anisotropy is established. Most parameters involved in this model have explicit physical meaning and are easily determined through geotechnical tests, which makes this model more flexible, practical and applicable to practical engineering.

Abstract: Simulations of Single Point Incremental Forming generally require a very high computation time because the tool path is long and small elements are required everywhere on the sheet. In this paper, a remeshing method based on refinement and coarsening strategies is used with abaqus/explicit to reduce the computational time. The simulation of a semi-spherical cup with a fine mesh is considered as a reference simulation. The remeshing method allows reducing the number of elements and therefore the CPU time during the simulations. A good prediction is observed with the remeshing method.