• 제어로봇시스템학회논문지
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• 제11권2호
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• pp.117-121
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• 2005

This paper presents a 3D last design system utilizing an uniform foot pressure FFD method. The proposed uniform foot pressure FFD(UFPFFD) is operated on the rule of foot pressure unbalance analysis and FFD. The deformation factor of the UFPFFD is constructed on the FFD lattice with the foot pressure unbalance analysis on the measured 3D foot bottom shape. In addition, the control points of FFD lattice are decided on the anatomical point and the foot pressure distribution. The 3D last design result obtained from the proposed UFPFFD is saved as a 3D dxf data format. The experimental results demonstrate that the proposed last design guarantees the balanced foot pressure distribution against on the conventional last design method.

• Journal of Computing Science and Engineering
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• 제11권3호
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• pp.79-91
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• 2017

In this paper, the abdominal-deformation measurement scheme is conducted on a shape-flexible mannequin using the DIC technique in a stereo-vision system. Firstly, during the integer-pixel displacement search, a novel fractal dimension based on an adaptive-ellipse subset area is developed to track an integer pixel between the reference and deformed images. Secondly, at the subpixel registration, a new mutual-learning adaptive particle swarm optimization (MLADPSO) algorithm is employed to locate the subpixel precisely. Dynamic adjustments of the particle flight velocities that are according to the deformation extent of each interest point are utilized for enhancing the accuracy of the subpixel registration. A test is performed on the abdominal-deformation measurement of the shape-flexible mannequin. The experiment results indicate that under the guarantee of its measurement accuracy without the cause of any loss, the time-consumption of the proposed scheme is significantly more efficient than that of the conventional method, particularly in the case of a large number of interest points.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1549-1559
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• 2022

As an accident tolerant fuel (ATF) concept, oxide dispersion strengthened Zircaloy-4 (ODS Zry-4) cladding has been developed to enhance the mechanical properties of cladding using laser processing technology. In this study, a simulation technique was established to investigate the mechanical properties and effects of Y₂O₃ particles for the ODS Zry-4. A 3D representative volume element (RVE) model was developed considering the parameters of the size, shape, distribution and volume fraction (VF) of the Y₂O₃ particles. From the 3D RVE model, the Young's modulus, coefficient of thermal expansion (CTE) and creep strain rate of the ODS Zry-4 were effectively calculated. It was observed that the VF of Y₂O₃ particles had a significant effect on the aforementioned mechanical properties. In addition, the predicted properties of ODS Zry-4 were applied to a simulation model to investigate cladding deformation under a transient condition. The ODS Zry-4 cladding showed better performance, such as a delay in large deformation compared to Zry-4 cladding, which was also found experimentally. Accordingly, it is expected that the simulation approach developed here can be efficiently employed to predict more properties and to provide useful information with which to improve ODS Zry-4.

• 한국컴퓨터그래픽스학회논문지
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• 제18권2호
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• pp.55-62
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• 2012

본 논문에서는 GPU의 정점 셰이더에서 각 정점별 질량-스프링 모의 실험을 수행하여, 매우 빠른 속도로 피부의 2차 변형을 표현하는 새로운 방법을 제안한다. 3차원 캐릭터의 각 피부 정점에 대해, 길이가 0인 스프링으로 가상 정점을 연결하고, 캐릭터 동작에 따라서 피부 정점의 위치 및 속도가 변화하면, 질량-스프링 모의 실험을 통해 렌더링 될 가상 정점의 위치를 GPU의 정점 셰이더를 사용하여 병렬적으로 계산한다. 본 논문에서 제시하는 방법을 통해 피부의 재질 특성을 반영하는 2차 변형을 매우 빠르게 표현할 수 있으며, 각 피부 정점에 제안한 방법을 동적으로 적용하면 전통적인 2차원 애니메이션에서 관찰되는 수축-팽창(squash-and-stretch), 추종(follow-through)과 같은 효과도 매우 빠른 연산시간에 효과적으로 표현할 수 있다. 따라서 본 논문의 결과는 게임과 같은 실시간 응용분야에서 가상 캐릭터의 피부 변형을 표현하는데 효과적으로 사용될 수 있다.

• 소성∙가공
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• 제26권4호
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• pp.234-239
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• 2017

A general approach is proposed for 3-D coupled FE analysis of the deformation of the strip and rolls in flat rolling. FE formulation, schemes for the treatment of contact occurring in a cluster of deforming objects, and the solution strategy are described in detail. The validity of the approach is examined through comparison with observed measurements. The approach is applied to the analysis of deformation in a four-high and six-high mill.

• 소성∙가공
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• 제21권4호
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• pp.252-257
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• 2012

Crystallographic texture evolution during forming processes has a significant effect on the anisotropic flow behavior of crystalline material. In this study, a crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into a three-dimensional finite element method, was used to investigate texture evolution of a face-centered-cubic material - an aluminum alloy. A rate-dependent polycrystalline theory was fully implemented within an in-house program, CAMPform3D. Each integration point in the element was considered to be a polycrystalline aggregate consisting of a large number of grains, and the deformation of each grain in the aggregate was assumed to be the same as the macroscopic deformation of the aggregate. The texture evolution during three different deformation modes - uniaxial tension, uniaxial compression, and plane strain compression - was investigated in terms of pole figures and compared to experimental data available in the literature.

• Smart Structures and Systems
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• 제20권4호
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• pp.509-524
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• 2017

In this article, a free vibration analysis of functionally graded (FG) plates resting on elastic foundations is presented using a quasi-3D hybrid-type higher order shear deformation theory. Undetermined integral terms are employed in the proposed displacement field and modeled based on a hybrid-type (sinusoidal and parabolic) quasi-3D HSDT with five unknowns in which the stretching effect is taken into account. Thus, it can be said that the significant feature of this theory is that it deals with only 5 unknowns as the first order shear deformation theory (FSDT). The elastic foundation parameters are introduced in the present formulation by following the Pasternak (two-parameter) mathematical model. Equations of motion are obtained via the Hamilton's principles and solved using Navier's method. Accuracy of the proposed theory is confirmed by comparing the results of numerical examples with the ones available in literature.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2312-2322
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• 2021

In recent studies, the creep rate of Zircaloy-4, one of the basic property parameters of the nuclear fuel code, has been commonly used with the axial creep model proposed by Rosinger et al. However, in order to calculate the circumferential deformation of the fuel cladding, there is a limitation that a difference occurs depending on the anisotropic coefficients used in deriving the circumferential creep equation by using the axial creep equation. Therefore, in this study, the existing axial creep law and the derived circumferential creep results were analyzed through a circumferential creep test by the internal pressurization method in the isothermal conditions. The circumferential creep deformation was measured through the optical image analysis method, and the results of the experiment were investigated through constructed IDECA (In-situ DEformation Calculation Algorithm based on creep) code. First, preliminary tests were performed in the isotropic β-phase. Subsequently in the anisotropic α-phase, the correlations obtained from a series of circumferential creep tests were compared with the axial creep equation, and optimized anisotropic coefficients were proposed based on the performed circumferential creep results. Finally, the IDECA prediction results using optimized anisotropic coefficients based on creep tests were validated through tube burst tests in transient conditions.

• Journal of electromagnetic engineering and science
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• 제17권4호
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• pp.228-232
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• 2017

The radiation properties and fabrication precautions of a 3D printed, electrically small folded spherical meander wire monopole antenna are investigated. The antenna is self-resonant and shows sufficiently high radiation efficiency at an electrical size ka of 0.4, with the radiation quality factor Q approaching the lower physical bound. In antenna fabrication, the possible structural deformation due to gravity is examined before the antenna frame is 3D-printed. The required conductivity is achieved by multiple manual paintings of a silver paste. The radiation efficiency and pattern show very good agreement with the computed expectations, whereas the resonant frequency deviates by 11.8%. The method to minimize such a fabrication error when using 3D printing technology for wire antennas is discussed.

• 한국기계가공학회지
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• 제17권4호
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• pp.64-69
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• 2018

This paper investigates the compressive deformation behavior of direct metal tooling (DMT), processing titanium alloy (Ti-6Al-4V) parts under high strain loading conditions. Split Hopkinson Pressure Bar (SHPB) experiments were performed to determine the flow stress and the coefficients of the Johnson-Cook model. This model is described as a function of strain, strain rate, and temperature. SHPB experiments were performed to characterize the deformation behavior of specimens made with 3D printers, using Ti-6Al-4V material under high temperature and dynamic loading.