Papers by Keyword: Elasto-Plastic

Abstract: In order to model the elasto-plastic behavior of steel-concrete beams in high-rise buildings correctly and conveniently, plastic hinge method is used. Based on experimental and theoretical research on composite beams, the trilinear moment-curvature skeleton curve of steel-concrete composite beams is amended by numerical simulation and theoretical analysis. And the 4 poly-line moment-curvature skeleton curve model is suggested for elasto-plastic analysis of steel-concrete composite beams. The elastic-plastic model is then used for real composite beams under monotonic load experimental analysis to verify its precision. The suggested model can lay a foundation for the dynamic analysis under strong earthquake for the globe steel-concrete composite structures.

Abstract: Analysis of the expansion of cylindrical and spherical cavities in soil and rock provides a versatile and accurate geomechanics approach for study of important problems in geotechnical engineering. As the method getting more important, the analysis of non-circular shape cavity is becoming significance. The paper has investigated the cavity wall shape varying characteristic and elasto-plastic distribution of stress of elliptic shape cavity under internal uniform pressure during the expansion period through ABAQUS FEM numerical. It pointed that the elliptic cavity wall will tend to circle shape as the internal uniform pressure increasing. It also gain that the elasto-plastic distribution around the elliptic cavity is bigger than spherical cavity’s and smaller than spherical cavity’s when material and pressure are same . The stress characters and the cavity wall transfiguration result is useful for estimate non-circular shape cavity expansion.

Abstract: The strength and deformation behaviors of unsaturated soil can be approximately described by elasto-plastic constitutive model that was proved by abundance academic and test researches. The Barcelona elastic-plastic model is an excellent model that can simulate the strength and deformation of unsaturated soil. But their calculated result of shear strength is low. So an improved Barcelona model is settled by using drop-shaped shear yield surface and hardening theory of dual stress. The results show that the improved model can more accurately predict the strength and deformation behaviors of unsaturated soil under suction-controlled triaxial compression stress states.

Abstract: Driven by the wide range of new material properties offered by multi-material 3D printing, there is emerging need to create predictive material models for these materials. A data driven process for estimating nonlinear material model is presented in this paper. In contrast with classical methods which derive the engineering stress-strain relationship assuming constant cross-section area and fixed length of a specimen, the proposed approach takes full advantage of 3D geometry of the specimen to estimate the material models. Give a hypothetical material model, virtual tensile tests are performed using Finite Element Analysis (FEA) method, and the parameters of the material model are estimated by minimizing the discrepancies of the virtual responses and the experimental results. The detailed material models, numerical algorithms as well as the optimization approaches are presented and finally preliminary results are offered.

Abstract: The NST 37-2 steel represents about 75% volume of Nigerian-produced steel which is yet to be fully characterized for its fatigue behavior. Thus, its suitability for many applications is questionable. This paper presents a framework based on the theory of elasto-plasticity in order to make appropriate recommendations in this regard. Experimentally, tensile tests were carried out on test specimens to establish the baseline material properties of the steel in annealed, as-rolled, normalized and hardened/tempered conditions. Fatigue tests were then conducted at 60% Su; 70% Su and 80% Su of the test material and fractographic examinations on the test specimens were subsequently carried out. The frequency harmonic fatigue analysis was implemented in the ANSYS software environment for the numerical study. The elastic-plastic material property was described by the von Mises yield criterion, the flow rule of Prandtl-Reuss, and the kinematic hardening rule of Prager. The numerical results indicate with respect to rate-dependence fatigue behavior that the annealed test specimen is most resilient under cyclic deformation as compared with the normalized, hardened/tempered and as-rolled specimens respectively. The experimental and numerical results were found to be in close agreement and based on the general performance, the steel material is recommended for use in low cycle, quasi-static fatigue applications.

Abstract: Only a limited number of experimental and analysis reports exist concerning bolted flange connections under bending loading. In order to investigate the complex nonlinear phenomena, three dimensional elasto-plastic finite element analyses are performed. In those analyses, frictional contact model with small sliding option is applied between contacting pair surfaces of all connecting elements. Bolt pretension force is introduced in the initial step of analysis. From this study, the following results are obtainted:1) proposed finite element analysis method can be applicable to estimate complex nonlinear behavior of bolted flange type connections; 2) There is a sharp change in bending stiffness during loading, and lateral slip between two jointed flanges cause the bolt to carry shear load. The design of bolted joints should consider the interaction among cylinders, flanges and bolts.

Abstract: A thermo-mechanical coupling model for the rough surface is established. The model considers friction contact between a rigid flat plane and a rough surface based on 3D fractal theory and allows the analysis of the effects of elastic-plastic deformation of rough body and the interplay among asperities. The contact pressure distribution for the static state beneath different loading mode and for the dynamic state in the presence of the frictional heat flux is found. The results show the fluctuation of the average contact pressure during the process of loading is related to the velocity of loading. The synthetical function of multiple factors such as the thermal deformation, the rising temperature, the interaction between asperities makes the complicated relationships among the maximum temperature, the maximum contact pressure and the real contact area.

Abstract: A special elasto-plastic dynamic finite element code named RingForm has been developed to analyze cold ring rolling process. Central difference method was introduced to solve the dynamic explicit finite element equations. Strain state was estimated by the value of yield function of the last and the present time step. To reduce the accumulative error caused by elasto-plastic constitutive relations, the radial return algorithm was employed. In comparison with the experimental results, the cold ring rolling process of a ring with rectangular section has been simulated to verify the accuracy and stability of the system solver.

Abstract: This paper is concerned with the geometrical similarity of heat conduction-elastioplastic structural problems. When the dimensions of a structure are geometrically scaled down/up, the similarity relations for both isolated heat conduction and elastoplastic structural problems are derived. For cases of thermo-structural coupled, it is concluded that heat conduction-static elastoplastic problems can be geometrically similarly scaled down/up and a set of similarity relations are drawn accordingly. As examples, a full-, half- and quarter-scale unilaterally-tensioned plate and internally-pressured cylindrical shell irradiated by a laser pulse are numerically analysed and the numerical results have confirmed this conclusion. However, heat conduction-dynamic elastoplastic problems are found not to comply compatibly with the geometrically similar scaling.

Abstract: This study aims to clarify the process conditions of the UO-tube of a sheet metal of steel. It provides a model that predicts not only the correct punch load for drawing, but also the precise final shape of products after unloading, based on the tensile properties of the material and the geometry of the tools used. An elasto-plastic incremental finite-element computer code, based on an updated Lagrangian formulation, was developed to simulate the UO-tube process of sheet metal; the results are compared with corresponding experimental results. Special care was taken to formulate accurate boundary conditions of penetration, separation and alternation of the sliding-sticking state of friction, as the contact conditions between the tools and the sheet varied throughout the entire processes of U-bending and successive O-bending. Calculated sheet geometries and forming force agree well with experimental data. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The extended r-minimum technique was used to deal with the elasto-plastic state and contact problems at the tool-metal interface. A series of simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history, the distribution of stress and the distribution of strain during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. The simulation demonstrates clearly the efficiency of the code to simulate various bending processes that proceed under complicated deformation- and contact-history.