• Structural Engineering and Mechanics
• /
• v.22 no.1
• /
• pp.17-32
• /
• 2006

The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.4
• /
• pp.362-370
• /
• 2008

In this paper, we propose a 2D-FE model in single impact with combined physical factors to obtain a unique residual stress by shot peening. Applied physical parameters consist of elastic-plastic deformation of shot ball, material damping coefficients, strain rate, dynamic friction coefficients. As a kinematical parameter, there is impact velocity. Single impact FE model consists of 2D axisymmetric elements. The FE model with combined factors showed converged and unique distributions of surface stress, maximum compressive residual stress and deformation depth. Further, in contrast to the FE models with rigid shot and elastic deformable shot, FE model with plastic deformable shot produces residual stresses very close to experimental solutions by X-ray diffraction. We therefore validated the 2D FE model with combined peening factors and plastic deformable shot. This FE model will be a base of the 3D FE model for residual stresses by multi-impact shot peening.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.5 no.4
• /
• pp.19-30
• /
• 2002

The stability of slope using root-pile like to the reinforcements is affected by the interaction behavior mechanism of soil-reinforcements. Through the studying on the interaction in joint of its, therefore, the control roles can be find out in installed slope. In study, the stress level ratio based on the insert angle of installed reinforcements in soil used to numerical analysis, which was results from the duty direct shear test in Lab. The maximum shear strain variation on the reinforcements was observed at insert angle, which was approximately similar to the calculated angle based on the equation proposed by the Jewell. The elasto-plastic joint model on the contact area of soil-reinforcements was presumed, the reinforced soil assumed non-linear elastic model and the reinforcements supposed elastic model, respectively. The finite element analysis of assumed models was performed. The shear strain variation of non-reinforced state obtained by the FEM analysis including elasto-plastic joint elements were shown the rationality of general limit equilibrium analysis for the slope failure mode on driving zone and resistance zone, which based on the stress level step according to failure ratio. Through the variation of shear strain for the variation of inserting angle of reinforcements, the different mechanism on the bending and the shear resistance of reinforcements was shown fair possibility.

• International Journal of Korean Welding Society
• /
• v.3 no.1
• /
• pp.51-56
• /
• 2003

It is important to evaluate the fracture initiation behaviors of steel structure. It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of notch radius, which can elevate plastic constraint due to heterogeneous plastic straining on critical condition to initiate ductile crack using two-parameters. Hense, the crack initiation testing were conducted under static loading using round bar specimens with circumferential notch. To evaluate the stress/strain state in the specimens was used thermal elastic-plastic FE-analysis. The result showed that equivalent plastic strain to initiate ductile crack expressed as a function of stress triaxiality obtained from the homogeneous specimens with circumferential notched under static loading. And it was evaluated that by using this two-parameters criterion, the critical crack initiation of homogeneous specimens under static loading.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.603-608
• /
• 2008

It is well known that the topology optimization for plastic problem is not easy since the iterative analyses to evaluate the objective and cost function with respect to the design variation are very time-consuming. The finite element limit analysis is an efficient tool which is possible to predict collapse modes and sequential collapse loads of a structure considering not only large deformation but also plastic material behavior with moderate computing cost. In this paper, the optimum topology of a structure considering large and plastic deformation is obtained using the finite element limit analysis. To verify the constructed optimization code, topology optimizations of some typical problems are performed and the optimal topologies by elastic design and plastic design are compared.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.7
• /
• pp.759-768
• /
• 2012

This paper proposes a method to determine the elastic follow-up factors for the $C(t)$-integral under secondary stress. The rate of creep crack growth for transient creep is correlated with the $C(t)$-integral. Elastic follow-up behavior, which occurs in structures under secondary loading, prevents a relaxation of stress during transient creep. Thus, both the values of $C(t)$ and creep crack growth increase as increasing elastic follow-up. An estimation solution for $C(t)$ was proposed by Ainsworth and Dean based on the reference stress method. To predict the value of $C(t)$ using this solution, an independent method to determine the elastic follow-up factors for cracked bodies is needed. This paper proposed that the elastic follow-up factors for $C(t)$ can be determined by elastic-plastic analyses using the plastic-creep analogy. Finite element analyses were performed to verify this method.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.57-58
• /
• 2008

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.465-467
• /
• 2004

Finite element analysis of welding processes, which entail phase evolution, heat transfer and deformation, is considered in this paper. Attention focuses on numerical implementation of the thermo-elastic-plastic constitutive equation proposed by Leblond et al in consideration of the transformation plasticity. Based upon the multiplicative decomposition of deformation gradient, hyperelastic formulation is employed for efficient numerical integration, and the algorithmic consistent moduli for elastic-plastic deformations including transformation plasticity are obtained in the closed form. The convergence behavior of the present implementation is demonstrated via a couple of numerical examples. Several locking phenomena removed by Solid-shell element.

• Structural Monitoring and Maintenance
• /
• v.5 no.2
• /
• pp.173-187
• /
• 2018

Performance evaluation of RC frame building by nonlinear static pushover analysis that accounts for elastic and post elastic behavior is becoming very popular as a valid decision making tool in seismic hazard resistant designs. Available literature suggests great amount of interest has shown by researchers in suggesting refinements to geometric and material modelling to bridge the gap between analytical predictions and observed performances. Notwithstanding the attempts gaps still exists. Sequence of plastic hinge formation which has great influence on pushover analysis results is an area less investigated. This paper attempts to highlight the importance of hinge sequence considerations to make analysis results more meaningful. Variation in analysis results due to different hinge sequences have been quantified, compared and bounds on analysis results have been presented.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1154-1158
• /
• 2003

Finite element analysis of welding processes, which entail phase evolution, heat transfer and deformations, is considered in this paper. Attention focuses on numerical implementation of the thermo-elastic-plastic constitutive equation proposed by Leblond in consideration of the transformation plasticity. Based upon the multiplicative decomposition of deformation gradient, hyperelastic formulation is employed for efficient numerical integration, and the algorithmic consistent moduli for elastic-plastic deformations including transformation plasticity are obtained in the closed form. The convergence behavior of the present implementation is demonstrated via a couple of numerical examples.