• Transactions of Materials Processing
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• v.4 no.4
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• pp.365-374
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• 1995

Numerical simulation of blade forming is carried out as stretch forming by an elasto-plastic finite element method. The method adopts a Lagrangian formulation, which incorporates large deformation and rotation, with a penalty method to treat the contact boundary condition. Numerical integration is done with a directional reduced integration scheme to avoid shear locking. The numerical results demonstrates various final shapes of blades which depend on the variation of the stretching force. The strain distributions in deformed blades are also obtained with the variation of the stretching force.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.186-197
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• 2019

Purpose: This study intends to develop a nonlinear cyclic plasticity damage model in the framework of finite element formulation, which is capable of taking large deformation effects into account, in order to accurately predict the hysteretic behavior of stainless steel structures. Method: The new cyclic constitutive equations that utilize the combined isotropic-kinematic hardening rule for plastic deformation is incorporated into the damage mechanic model in conjunction with the large strain formulation. The damage growth law is based on the experimental observations that the evolution of microvoids yields nonlinear damage accumulation with plastic deformation. The damage model parameters and the procedure for their identification are presented. Results and Conclusion: The proposed nonlinear damage model has been verified by simulating uniaxial strain-controlled monotonic and cyclic loading tests, and successfully applied to a thin-walled stainless steel pipe subjected to constant and alternating strain-controlled cyclic loadings.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.153-158
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• 1999

In the design and analysis of soil nailed slope, interaction between soil and nail is one of important problems. In the present analysis approaches for the interactions have developed a elastic analysis approach or a plastic analysis approach. However these approaches are not able to estimate the general interaction between soil and nail. In this study the general interaction between soil and nail using the strain wedge model is proposed. Also results of comparison between the proposed method and full scale test results by Gassler(1976) and large scale experimental results at Oxford University are shown in good agreements.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.76-79
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• 2009

The current understanding for phase/grain boundary sliding and low-temperature/high-strain rate superplasticity of two-phase titanium alloys is summarized. The quantitative analysis on boundary sliding revealed increased sliding resistance on the order of $\alpha/\beta\;\ll\;\alpha/\alpha\;\approx\;\beta/\beta$ boundary, hence, led to the conclusion that approximately 50% alpha(or beta) volume fraction and/or grain refinement is beneficial for obtaining large superplastic elongation at low temperature and/or high strain rate. To predict the temperature for 50% alpha volume in various alpha/beta Ti, artificial neural network was applied. Finally, much enhanced superplasticity was achieved through grain refinement utilizing dynamic globularization.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1718-1722
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• 2008

This study explores the influence of volume fraction of nanocrystals of Cu-Zr amorphous alloys on shear band formation. As the number of crystals with very tiny size increases, the strain localization, i.e. shear band, decreases without large drop of flow stress. The DPRs also depict no sudden drop and relatively high values. The strain state during the deformation represents a few shear bands at low volume fraction while there are no distinguishable shear bands at high volume fraction of nanocrystals.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.76-84
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• 1999

The residual stress generated when the steel plates were produced, did not influence on the out-of-plane deformation and residual stress generated by welding. When the initial deflection shape was a concave(Type I), the out-of-plane deformation became the same shape as that of the initial deflection and its magnitude became small. When the initial deflection made a winding in the welding direction(Type III), the out-of-plane deformation became large in the plate width. The initial deflection shape did not influence on residual stress and plastic strain produced by welding.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.111-114
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• 2004

Using the embedded optical fiber sensor of totally-reflected extrinsic Fabry-Perot interferometer(TR-EFPI), longitudinal strains(Ex) of the core and skin layers in glass fiber reinforced plastic(GFRP) cross-ply composite laminates have been measured. Transmission optical microscopy was employed to study the damage formation around the TR-EFPI sensor. It was observed that values of ex in the interior of the skin layer and the core layer measured by embedded TR-EFPI sensor was significantly higher than that of the specimen surface measured by strain gauges. The experimental results agreed well with those from finite element analysis on the basis of uniform stress model. Large strains in the core layer led to the occurrence of transverse cracks which drastically reduced the strain at failure of optical fiber sensor embedded in the core layer.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.77-86
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• 1997

The advanced development in many fields of engineering and science has caused much interests and demands for crashworthiness and non-linear dynamic transient analysis of structure response. Crash and impact problems have a dominant characteristic of large deformation with material plasticity for short time scales. The structural material shows strain rate-dependent behaviors in those cases. Conventional rate-independent constitutive equations used in the general purposed finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate-dependent constitutive equation for elastic-plastic material is developed. The plastic stretch rate is modeled based on slip model with dislocation velocity and its density so that there is neither yielding condition, nor loading conditions. Non-linear hardening rule is also introduced for finite strain. Material constants of present constitutive equation are determined by experimental data of mild steel, and the constitutive equation is applied to uniaxile tension loading.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.215-228
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• 2002

In a companion paper. (Oh, 2002), the constitutive model, called GUX model, was implemented as a user subroutine in ABAQUS code, where the GUX model could describe the behavior of overall strain range. An accuracy analysis verified that the implicit stress integration maintained the accuracy of solutions successfully. Since the GUX model is an anistropic hardening elasto-plastic constitutive model based on total stress concept, geotechnical problems under fully drained or undrained condition can be analyzed after acquisition of stress-strain relationships from drained or undrained triaxial tests. This study includes the analyses of the stability of embankments on soft clays and weathered soils and the example of axially loaded soil-pile system. In the large deformation analyses, geometric nonlinearity was considered and the result of analyses with GUX model was compared with that of Mises model for the overall strain range behavior.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.354-360
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• 2001

By applying Eshelby's theory on the'transformation' and' inhomogeneity'problems of an ellipsoidal inclusion, a microscopic stress-strain is formulated for a composite material consisting of a matrix and a large number of aligned ellipsoidal inclusions. Some of the composites of practical interest, such as unidirectionally fiber- reinforced, Particle dispersion strengthened and layered composites can be treated by changing the axial ratios of the ellipsoidal inclusion. The macroscopic stress-strain relation obtained is applicable to elastic and elasto-plastic deformation of the composite in uniform loading.