• 한국전산구조공학회논문집
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• 제21권1호
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• pp.43-50
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• 2008

본 연구에서는 볼트의 변형을 고려한 강재 조립 합성보의 휨거동에 대한 해석기법 및 결과가 제시되었다. 볼트의 변형, 합성효과 및 접촉면의 마찰이 합성보의 휨거동에 끼치는 영향을 파악하였다. 볼트의 변형이 합성보의 휨거동에 끼치는 영향을 고려하기 위하여, 구조해석 프로그램인 ABAQUS의 Nonlinear Spring요소를 사용하였으며 볼트의 변형을 고려하지 않은 결과와 비교하였다. 유한요소 모델에 의해서 처짐, 휨응력, 전단응력이 계산되었으며 이런 결과는 완전 비합성보, 부분 합성보 및 완전 합성보의 해석 값과 비교되었다. 해석결과 합성보의 거동은 강재의 마찰보다 볼트의 갯수로 표현되는 합성률에 크게 영향을 받았다. 특히 합성률이 50%이상이 되면 볼트의 변형을 고려한 합성보의 휨거동은 완전합성보와 유사하게 나타났다.

• 소성∙가공
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• 제15권7호
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• pp.524-528
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• 2006

Although equal channel angular pressing (ECAP), imposing large plastic shear strain deformation by moving a workpiece through two intersecting channels, is a promising severe plastic deformation method for grain refinement of metallic materials, its batch type characteristic makes ECAP inefficient for multiple-passing. Rotary-die ECAP (RDECAP) proposed by Nishida et al. can achieve high productivity by using continuous processing without taking out the samples from the channel. However, plastic deformation behavior during RD-ECAP has not been investigated. In this study, material plastic flow and strain hardening behavior of the workpiece during RD-ECAP was investigated using the finite element method. It was found that plastic deformation becomes inhomogeneous with the number of passes due to an end effect, which was not found seriously in ECAP. Especially, decreasing corner gap with increasing the number of passes was observed and explained by the strain hardening effect.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.59-62
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• 2006

Mg alloys have drawn a huge attention in the field of transportation and consumer electronics industries since it is the lightest alloy which could be industrially applicable. Most Mg alloy components have been fabricated by casting method. However, there have been a lot of research activities on the wrought alloys and their plastic forming process recently. The deformation behavior of an AZ31 Mg alloy at the elevated temperature was examined firstly to find out the optimum plastic forming range in terms of temperature and strain rate. During high temperature deformation, AZ31 alloy is usually undergone the dynamic recrystallization which influence the deformation behavior in turn. In the present study, the effect of deformation on dynamic recrystallization of an AZ31 alloy was investigated to clarify the relation between the deformation and recrystallization. In an AZ31 alloy system, the dynamic recrystallization was found to occur continuously. Recrystallized grain size was dependent on the stress level.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1751-1758
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• 2001

Among severe plastic deformation processes, ECAP has drawn much attention due to its advantages including ultra-fine grain size material production. In this paper, ECAP process with pure -Zirconium is investigated due to its applicability to nuclear reactors. The finite element method is employed to investigate the deformation behavior of materials during ECAP process. In particular, effects of process parameters such as die deformation and channel angles on the material behaviors have been investigated. Experimental studies have also been performed to verify the numerical results.

• 한국주조공학회지
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• 제22권1호
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• pp.11-16
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• 2002

Hot deformation behavior of GCD-50 cast iron has been investigated by employing the compressive test. Phenomenological deformation behaviors, which were modeled based on the dynamic materials model and the kinetic model, have been correlated with the microstructural change taken place during compression. Microstructural investigation revealed that the adiabatic shear band caused by the locallized deformation was taken place in low temperature and high strain rate. On the other hand, the wavy and curved grain boundaries, which repersent the occurrence of dynamic microstructure change such as dynamic recovery and dynamic recrystallization, were observed in high temperature and low strain rate. Deformation model based on hyperbolic sine law has also been suggested.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.143-145
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• 2007

The correlation between crystallization and deformation behavior in the supercooled liquid region (SLR) of a $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ bulk metallic glass (BMG) alloy is investigated by compression tests, differential scanning calorimetry (DSC), electron energy loss spectrometry (EELS) and high resolution transmission electron microscopy (HRTEM). In the SLR, This BMG alloy was strongly depended on the deformation temperature and the alloy exhibits important change in deformation behavior after a given time which is directly connected to the development of crystallization. Compressive stress impeded decomposition and consequently retarded forming of nano-crystal, which led to enlarge the homogeneous deformation region of the BMG alloy in SLR during compression test.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.123-126
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• 2007

Deformation behavior of $Zr_{55}Cu_{30}Al_{10}Ni_5$ (at. %) bulk metallic glass (BMG) fabricated by suction casting method has been investigated at elevated temperatures in this study. The BMG was first verified to have an amorphous structure thru X-ray diffraction (XRD) and differential scanning calorimetry (DSC). A series of compression tests has consequently been performed in supercooled liquid temperature region to investigate the high temperature deformation behavior. A transition from Newtonian to non-Newtonian flow appeared to take place depending upon both the strain rate and test temperature. A processing map based on a dynamic materials model has been constructed to estimate a feasible forming condition for this BMG alloy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.172-175
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• 2003

Thermomechanical behavior of Al-Mg-Si alloys have been studied to investigate the effect of microstructural features such as pre-existing substructure and distribution of particles on the deformation characteristics. The controlled compression tests have been carried out to get the basic information on how the alloy responds to temperature, strain amount and strain rate. Then hot forging of Al-Mg-Si alloys has been carried out and analyzed by the comparison with the compression tests. Microstructural features after forging have been discussed in terms of the thermomechanical response of Al-Mg-Si alloys. As already well mentioned, we have found that the deformation of Al-Mg-Si at the elevated temperature brought the recovered structure on most conditions. In a certain time, however, abnormally large grains have been found as a result of deformation assisted grain growth, which means that hot forging of Al-Mg-Si alloys could lead to a undesirable microstructural variation and the consequent mechanical properties such as fatigue strength.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1051-1060
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• 2010

In this study, the pressuremeter test (PMT) and the standard penetration test (SPT) were performed on the lateral pile loading tests site to evaluate the coefficient of subgrade reaction, which is used for load-deformation behavior analysis of laterally loaded piles by elastic subgrade reaction method. As a result, widely used empirical formulas of the coefficient of subgrade reaction by N values of SPT is evaluated conservatively lateral behavior of piles. While the method of directly used PMT results and evaluation method of the coefficient of subgrade reaction considering deformation moduli of soil and a pile diameter that is able to estimate very similar to actual load-deformation behavior of laterally loaded piles in deformation range of 0.5%-1.0% of a pile diameter.

• 소성∙가공
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• 제13권1호
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• pp.27-32
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• 2004

Thermomechanical behavior of Al-Mg-Si alloys was studied to investigate the effect of microstructural features such as pre-existing substructure and distribution of particles on the deformation characteristics. The controlled compression tests were carried out to get the information on how the alloy responds to temperature, strain amount and strain rate. Then hot forging of Al-Mg-Si alloys carried out and analyzed by the comparison with the compression tests. Microstructural features after forging were discussed in terms of the thermomechanical response of Al-Mg-Si alloys. As already well mentioned, we found that the deformation of Al-Mg-Si at the elevated temperature brought the recovered structure on most conditions. In a certain time, however, abnormally large grains were found as a result of deformation assisted grain growth, which means that hot forging of Al-Mg-Si alloys could lead to a undesirable microstructural variation and the consequent mechanical properties such as fatigue strength.