• Transactions of Materials Processing
• /
• v.31 no.4
• /
• pp.200-206
• /
• 2022

The finite element analysis is one of the representative methods for predicting the materials behavior for experiments that are difficult to perform empirically. Constitutive equations are essential for reducing computation time and sharing data because they enable finite element analysis simulations through simple formulae. However, it is difficult to derive accurate flow curves for all materials as most constitutive equations are not formulated based on their physical meaning. Also, even if the constitutive equation is a good representation of the flow curve to the experimental results, some fundamental issues remain unresolved, such as the effect of mesh size on the calculation results. In this study, a new constitutive equation was proposed to predict various materials by modifying the combined Swift-Voce model, and the calculation results with various mesh sizes were compared to better simulate the experimental results.

• Journal of the Korean Society of Industry Convergence
• /
• v.7 no.4
• /
• pp.355-361
• /
• 2004

The finite element method were used to determine the stress intensity factor of cracked plate. The stress method, displacement method and J Integral are most popular finte element method. ANSYS proposed another a kind of displacement method. In this paper, it was examined that the accuracy and utility of the ANSYS method could believable to determine the stress intensity factors of centered inclined crack. Generally, inclined crack has two portion of stress intensity factors, tensile mode F1 and shear mode F2. For the purpose of increasing the accuracy of stress intensity factors, examined the effect of the numbers of nodes and elements, crack tip element size and number of partition of the crack tip vicinity. It was found that the method proposed by ANSYS is useful and has high accuracy. Accuracy of calculated stress intensity factors was increased by increase of the number of nodes and elements, and at the small size of crack tip elements can get more highly accuracy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.3 no.2
• /
• pp.97-102
• /
• 1991

Finite element method has been developed recently for the solution of the convection-diffusion problems. Finite element method has several advantages over finite difference method, but its requirement of the larger memory size of the computer has prevented from wide application. In the present study, line-by-line technique has been implemented to finite element method to overcome this disadvantage. Two dimensional laminar natural convection in square cavity was chosen as an example in this study. The numerical result shows good agreement with bench mark solution and the size of the coefficient marix has been reduced drastically.

• Transactions of Materials Processing
• /
• v.15 no.8 s.89
• /
• pp.544-549
• /
• 2006

In this work, we have employed the strain gradient plasticity theory to investigate the effect of material size on the deformation behavior in metal forming process. Flow stress is expressed in terms of strain, strain gradient (spatial derivative of strain) and intrinsic material length. The least square method coupled with strain gradient plasticity was used to calculate the components of strain gradient at each element of material. For demonstrating the size effect, the proposed approach has been applied to plane compression process and micro rolling process. Results show when the characteristic length of the material comes to the intrinsic material length, the effect of strain gradient is noteworthy. For the microcompression, the additional work hardening at higher strain gradient regions results in uniform distribution of strain. In the case of micro-rolling, the strain gradient is remarkable at the exit section where the actual reduction of the rolling finishes and subsequently strong work hardening take places at the section. This results in a considerable increase in rolling force. Rolling force with the strain gradient plasticity considered in analysis increases by 20% compared to that with conventional plasticity theory.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.8
• /
• pp.25-32
• /
• 2021

Washboarding is a crucial problem occurring on unpaved roads. This phenomenon involves the formation of ripples on the surface of the unpaved road and causes a critical problem to vehicles and riders. The phenomenon is affected by several parameters, but we focused on the velocity and the size of the rotating body. In the precedent research, we observed that a critical velocity existed for the occurrence of the phenomenon, and the phenomenon's grade was related to the velocity. Therefore, this study, using a discrete element method, aimed to analyze the relation between the velocity and the size of the rotating body for the occurrence of the phenomenon and perform a fast Fourier transform (FFT) analysis to determine the correlation between the phenomenon and the period. The study observed that the critical velocity could vary from the velocity and the size of the rotating body, and there was a certain range of frequency for the occurrence of the Washboarding phenomenon.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.05a
• /
• pp.209-212
• /
• 2001

It is known that the mim forming processes show somewhat different phenomena compared with the conventional metal forming processes, namely, the size effect, enhanced friction effect and etc. Such typical phenomena, however, are not predicted by the conventional finite element analysis, which has been an efficient numerical tool to predict the metal forming processes. It is due to the fact that the constitutive relations used does not describe the microstructural characteristics of the materials. In the present investigation, the finite element formulation using the rate-dependent rigid plastic crystal plasticity model of the face-centered cubic materials is conducted to predict the micro mechanical behaviors during the mim forming processes. The finite element analysis, however, provides mesh-dependent solutions for the intragranular deformations. Therefore, the couple stress energy is additionally introduced into the variational principle and formulated within the framework of the rigid plastic finite element method to obtain mesh-independent solutions. Micro deformations of single crystal and bicrystal with various orientations are calculated to show the potential of the developed formulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.9A
• /
• pp.1419-1424
• /
• 1999

In order to implement morphological filters on image processing systems, the size of structuring element must be small due to the architectural constraints of the systems, which requires the decomposition of structuring element into small elements for the filters with large structuring elements. In this paper, an algorithm for decomposition of structuring element with no restriction on the shape and size is developed which enables sub-optimal implementation of any morphological filter on 3X3 pipeline machine. The given structuring element is first decomposed into the union of elements using sequential search procedure, then each element is further decomposed optimally into 3X3 elements, resulting in final sub-optimal 3$\times$3 hybrid decomposition. The proposed algorithm is applied to some structuring elements and the results close to the optimum are obtained.

• Structural Engineering and Mechanics
• /
• v.69 no.3
• /
• pp.243-255
• /
• 2019

Utilization of fiber beam-column element has gained considerable attention in recent years due mainly to its ability to model distributed plasticity over the length of the element through a number of integration points. However, the relatively high sensitivity of the method to modeling parameters as well as material behavior models can pose a significant challenge. Residual drift is one of the seismic demands which is highly sensitive to modeling parameters and material behavior models. Permanent deformations play a prominent role in the post-earthquake evaluation of serviceability of bridges affected by a near-fault ground shaking. In this research, the influence of distributed plasticity modeling parameters using both force-based and displacement-based fiber elements in the prediction of internal forces obtained from the nonlinear static analysis is studied. Having chosen suitable type and size of elements and number of integration points, the authors take the next step by investigating the influence of material behavioral model employed for the prediction of permanent deformations in the nonlinear dynamic analysis. The result shows that the choice of element type and size, number of integration points, modification of cyclic concrete behavior model and reloading strain of concrete significantly influence the fidelity of fiber element method for the prediction of permanent deformations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.08a
• /
• pp.320-326
• /
• 1999

In the present investigation, recrystallization occurring during hot rolling of thick steel plate was predicted. The thermo-mechanical history of a material point was traced by the finite element method and the recrystallization was predicted by the Sellars equations. The investigation was performed for 4 different cases; two different pass schedules in conventional rolling and two different pass schedules in controller rolling. Variations of temperature, strain, strain rate and grain size were compared with each other. It was found out that the difference of grain size through thickness was more distinctive in the cases of controller rolling.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.837-842
• /
• 1994

The boundary element method was used for studying singularities of an interface crack with contact zones. Because the contact zone size was extremely small in a tention field, a large number of Gaussian points were is used for numerical integration of the Kernels. In order to estimate the contact zone size, iteration method was used. The interface crack tips with contact zones showed no oscillatory behavior and J-integral values across the interface were conserved.