• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.286-287
• /
• 2008

The determination of roll speeds in continuous rolling system is an important factor along with the design of roll profile and roll gap. The tensile force on the workpiece induces reduced cross section area and the compressive force induces wrinkles. To determine the optimal roll speeds of current rough rolling system for wire rod, FE analysis was performed. We could predict the workpiece shape and the stress level more precisely by considering the elasto-plastic behavior of workpiece. Also the efficient analysis methodology is presented to reduce the calculation time by combining the ALE and lagrangian method.

• Structural Engineering and Mechanics
• /
• v.3 no.4
• /
• pp.325-340
• /
• 1995

The iterative procedure to use the nonconforming elements in elasto-plastic problems is established and applied to the variable node transition solid element developed for the automated three-dimensional local mesh refinement. Through numerical tests, the validity and performance of the element are examined. As the nonlinear iterative procedure presented in this paper is accomplished for the general three-dimensional case, it can also be easily applied to the two-dimensional elements such as membranes, plates and shells.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.746-752
• /
• 2001

Design sensitivity analysis for nonlinear structural problems has been emerged in the last decade as a glowing area of engineering research. As a result, theoretical formulations and computational algorithms have already developed for design sensitivity of nonlinear structural problems. There is not enough research for practical nonlinear problems using multi-element, due to difficulties of implementation into FEA. Therefore, nonlinear response analysis for stiffened shell which consists of Mindlin plate and Timoshenko beam, was considered. Specially, it presents the backward-Euler method which is adopted to describe an exact yield state in the stress computation procedure. Then, design sensitivity analysis of nonlinear structures, particularly elasto-perfectly-plastic structure, is developed using direct differentiation method. The accuracy of the developed sensitivity analysis was compared with the central finite difference method. Finally, on the basis of above results, design improvement for stiffened shell is suggested.

• Journal of Korean Port Research
• /
• v.14 no.3
• /
• pp.331-340
• /
• 2000

For the rational and economic design of the structural elements of ships which is built using welding, the ultimate strength analyses of the plates having initial imperfections, such as welding residual stresses and strains, are needful. The welding deformation usually relied on approximative equations or based on expert's experience. But in this paper, for the thermal elasto-plastic analysis of plates, the finite element analysis was performed, based on initial strain method. In formulating the incremental analysis, unbalanced force terns were included. In the plastic domain during the incremental process, the 2nd order terns stress increment and yield stress increment were considered, so that time increment could be controlled for a more stable solution. The ultimate strength analysis program of the plates having initial imperfections was made. The ultimate strength analysis was carried out based on the results of the welding deformations of this paper. In the ultimate strength analysis the Rayleigh-Ritz method based on the minimum potential theory was used.

• Journal of Welding and Joining
• /
• v.15 no.4
• /
• pp.70-77
• /
• 1997

Welding is one of the most important and popular joining techniques employed in structures. In spite of, weld designs depend on the rules and regulations. Moreover, the study to optimize a shape of welding joint not may be sufficient and systematic on the theoretical and experimental sides. Therefore, in this study, a computer program based on thermal elasto plastic theory is developed for optimizing(minimizing) shape of weld joints. By the results, study is made on the characteristics of the distributions of welding residual stresses and plastic strains, and their production mechanisms. Also, Various kinds of tests are carried out to find out mechanical characteristics due to shape of weld joints. As a result of this optimization(minimization) of weld joints, the productivity and the reliability will be improved.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.2A
• /
• pp.71-77
• /
• 2011

In this paper elasto-plastic dynamic behavior of solid is analyzed by using smoothed particle hydrodynamics (SPH) without tensile instability which caused by a clustering of SPH particles. In solid body computations, the instability may corrupt physical behavior by numerical fragmentation which, in some cases of elastic or brittle solids, is so severe that the dynamics of the system is completely wrong. The instability removed by using an artificial stress which introduces negligible errors in long-wavelength modes. Applications to several test problems show that the artificial stress works effectively. These problems include the collision of rubber cylinders, fracture and crack of plate.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.5
• /
• pp.487-499
• /
• 2009

The postprocessing technology has been advanced diversely to accommodate the tendency of increasingly refined and complicated practices of finite element modeling in pace with enhanced capabilities of computers and improved algorithm of equation solvers. As a result of such progresses in both hardware and software, it became practically meaningful to inspect and analyze the elasto-plastic behavior using the intermediate results from the increasing number of incremental and iterative processes. This paper is concerned about the new methods of postprocessing with computer graphic visualization of elasto-plastic behavior on the basis of the theoretically reorganized analysis results. This paper proposes a new method of rendering the plastic zone, and new approaches of analyzing and interpreting the elasto-plastic behavior using the graphical information visualized in the form of the yield surface and the stress path, or in the form of the Mohr circles and the failure envelope.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.334-339
• /
• 2003

The welding residual stress has on important effect on welding deformation, fatigue fracture, buckling strength, brittle fracture, etc. For the purpose of relaxation of welding residual stress, post welding heat treatment is widely used. In this paper, residual stresses were calculated by two dimensional thermal elasto-plastic analysis using finite element method. Heat transfer analysis are performed by transient analysis. Also structure analysis are carried out by of thermal-mechanical coupled analysis. Numerical analysis are used by ANSYS 5.7.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.3
• /
• pp.49-56
• /
• 2012

Rupture disks are a kind of safety device in high pressure equipment and they are used to control rupture pressure in the solid rocket motor. In this paper, a series of rupture experiments was performed using rupture disks made of AISI 316L and rupture pressure of rupture disks was calculated through various assumptions in relation between elasto-plastic material properties and true stress-strain curve. Experiment and FEA indicated rupture pressure is determined by size of rupture disks. As a result of elasto-plastic analysis, only multi-linear stress-strain curve was able to calculate meaningful estimations. Experimental results also showed rupture location are decided by the size of rupture disks. Experimental and FEA results will be applied to control rupture pressure of disks.

• Computers and Concrete
• /
• v.2 no.2
• /
• pp.97-110
• /
• 2005

Rheological behaviour of fresh concrete is an important factor in controlling concrete quality. It is recognized that the measurement of the slump is not a sufficient test method to adequately characterize the rheology of fresh concrete. To further understand the slump measurement and its relationship to the rheological properties, an elasto-viscoplastic, 2-D axisymmetric finite element (FE) model is developed. The FE model employs the Bingham material model to simulate the flow of a slump test. An experimental program is carried out using the Slump Rate Machine (SLRM_II) to evaluate the finite element simulation results. The simulated slump-versus-time curves are found to be in good agreement with the measured data. A sensitivity study is performed to evaluate the effects of yield stress, plastic viscosity and cone withdrawal rate on the measured flow curve using the FE model. The results demonstrate that the computed yield stress compares well with reported experimental data. The flow behaviour is shown to be influenced by the yield stress, plastic viscosity and the cone withdrawal rate. Further, it is found that the value of the apparent plastic viscosity is different from the true viscosity, with the difference depending on the cone withdrawal rate. It is also confirmed that the value of the final slump is most influenced by the yield stress.