• Composites Research
• /
• v.13 no.6
• /
• pp.23-29
• /
• 2000

The internal residual stresses within the multilayered structure with sharp interface induced by the difference in thermal expansion coefficient between the materials of adjacent layers often provide the source of failure such as delamination of interfaces etc. Recent development of the multilayered structure with functionally graded interface would be the solution to prevent this kind of failure. However a systematic thermo-mechanical analysis is needed for the customized structural design of multilayered structure. In this study, theoretical model for the thermo-mechanical analysis is developed for multilayered structures of the $Al-SiC_p$ functionally graded composite for electronic packaging. The evolution of curvature and internal stresses in response to temperature variations is presented for the different combinations of geometry. The resultant analytical solutions are used for the optimal design of the multilayered structures with functionally graded interface as well as with sharp interface.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.114-114
• /
• 2009

최근 국내외에서 자동차 연비와 성능 향상을 위하여 고부가가치 자동변속기의 개발이 적극적으로 추진되고 있다. 특히, 유럽(ZF)과 일본(JATCO, AISIN)을 비롯한 변속기 부품의 기술선진국에서는 전자빔 용접을 적용한 고부가가치 자동변속기 제품이 개발되어 다양한 고급차 모델에 적용되고 있으며 2010년까지 8속 자동변속기를 출시할 예정으로 개발을 추진하고 있다. 이러한 자동변속기를 개발하기 위하여 부품의 성형 및 가공정밀도 관리가 중요하며, 최종 조립되는 부품의 전처리(연질화처리, 탈지, 이물질 제거등)와 용접시 용접변형을 최소화하기 위한 공정조건의 엄격한 관리가 요구되고 있다. 변속기 부품으로 사용되는 소재는 성형성 확보를 위한 연질재(SPCC)와 강도를 확보하기 위한 고강도강(SAPH400, SPFH590)으로 서로 다른 두께의 재질이 조립되어 최종단계에서 용접공정에 의해 제작되고 있다. 특히, 연질재는 복잡한 형상으로 성형한 다음, 가공을 거쳐 경화를 위한 연질화처리가 요구되기 때문에 건전한 용접을 하기 위해서는 용접면에 접한 연질화 처리부는 연질화 처리재가 잔존하지 않도록 완전한 제거할 필요가 있다. 만약 전처리 공정에서 충분한 세척과 가공품의 정도관리가 확보되지 않으면 전자빔 용접시 고온에서 이물질 증발과 잔류, 스패터 발생등에 의한 용접부 결함발생이나 용접변형으로 인하여 제품불량이 발생하게 된다. 따라서 본 연구에서는 최종 조립공정인 용접작업시 발생되는 결함을 방지하고 이 두께 및 이종소재의 전자빔 용접비드 형상(비드 폭, 용입깊이)을 최적화 함으로서 용접부 변형을 최소화하고 충분한 강도를 확보하고자 전자빔 용접전류와 속도에 따른 비드형상을 비교검토 하고자 하였다. 그리고 실차적용시 신뢰성을 확보하기 위하여 전자빔 용접한 자동차 변속기 부품의 비틀림 시험을 실시하였으며 전자빔 용접 전, 후의 변형량을 측정하여 변속기 부품으로서의 적용성을 검증하고자 하였다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.6
• /
• pp.719-730
• /
• 2007

This study presents a thin-walled space frame element based on the classical Timoshenko beam theory. The element is derived according to the assumed strain field in order to resolve the shear-locking phenomenon. The shape function is developed in accordance with the strain field which is assumed to be constant at a 2-noded straight frame element. In this study, the geometrically nonlinear analysis applies the Corotational procedure in order to evaluate unbalanced loads. The bowing effect is also considered faithfully. Two numerical examples are given; monosymmetric curved and nonsymmetric straight cantilever. When these example structures behave lateral-torsional bucking, the critical loads are obtained by this study and ABAQUS shell elements. Also, the post-buckling behavior is examined. The results give good agreement between this study and ABAQUS shell.

• Journal of the Korea Convergence Society
• /
• v.12 no.2
• /
• pp.173-177
• /
• 2021

In this study, the torsional rigidity and durability of the stabilizer models with the hollow axis of light and large sized cars were compared and investigated each other. Model 1 was applied with the moment more than three times as much as model 2, but the maximum deformation of model 1 was seen to be about 2.6 times larger than that of model 2. Commonly, models 1 and 2 are seen to get the most stress at the neck of stabilizer bar link. Also, the maximum stress of model 1 was about 2.9 times larger than that of model 2. Model 1 at large car showed more than 20 times more deformed energy than model 2 at small car. Overall, it could be examined that the deformation energy of the bracket part on the side where the moment fixing the stabilizer bar was applied was greater than that of the stabilizer. It is thought that the analysis results in this study can be helped at the design of its convergent research as a durable component of the stabilizer at a light or large sized car.

• Composites Research
• /
• v.28 no.4
• /
• pp.204-211
• /
• 2015

This paper presents a theory related to a two-dimensional linear cross-sectional analysis, recovery relationship and a one-dimensional nonlinear beam analysis for composite wing structure with initial twist. Using VABS including a related theory, the design process of the composite rotor blade has been described. Cross-sectional analysis was performed at cutting point including all the details of geometry and material. Stiffness matrix and mass matrix were linked to each section to make 1D beam model. The 3D strain distributions within the structure were recovered based on the global behavior of the 1D beam analysis and visualize numerical results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.435-438
• /
• 2008

High temperature deformation of Ti-6Al-4V alloy with a lamellar colony microstructure was investigated by hot compression and torsion tests. The torsion and compression tests were carried out under a wide range of temperatures and strain rates with true strain up to 2 and 0.7, respectively. The processing maps were generated on the basis of compression and torsion test data and using the principles of dynamic materials modeling (DMM). The shapes of the strain-stress curves in alpha-beta region and processing maps obtained on the two different tests have been compared with a view to evaluate the effect of the microstructure evolution on the flow softening behavior of Ti-6Al-4V alloy with a lamellar colony microstructure.

• Computational Structural Engineering
• /
• v.5 no.3
• /
• pp.19-28
• /
• 1992

이 글에서는 막 구조물의 설계에서 자주 제기되는 형상결정 문제에 대한 접근방법을 제시하고자 하였다. 형상결정 문제는 막 구조물이 휨 강성이 전혀 없거나, 빈약한 재료를 사용하는데 기인하여 제기되고, 막 구조물의 설계에서 불안정영역의 발생을 피하기 위해서는 형상의 기준면에서 곡률과 비틀림의 변화를 최소화해야 하며 이러한 변화를 최소화하기 위해서는 형상이 적용하중의 막력에 의한 평형면에 근접하는 것이 바람직하다. 또한, 초기에 막 구조물에 도입된 초기장력에 오차가 발새하면 막면은 스스로 등장력의 형태로 이동하게 되므로, 초기에 막장력의 분포가 등장력의 상태가 되도록 그 형상을 결정하는 것이 바람직하다. 따라서, 이러한 조건을 만족하는 형상탐색문제는 이러한 종류의 구조물의 설계에서는 매우 중요한 문제가 된다. 그러나 국내에서는 막과 케이블 구조물의 형상해석과 응력-변형해석에 범용적으로 사용될 수 있는 프로그램의 개발이 미약하고 이러한 구조방식에 대한 국내의 인식에 크게 부족한 실정이다. 따라서 이 글이 막과 케이블 구조물의 설계에서 형상탐색해석이 반드시 필요한 이 구조물의 구조적 특성을 이해하는데 조금이라도 도움이 될 수 있기를 기대한다.

• Composites Research
• /
• v.12 no.4
• /
• pp.1-7
• /
• 1999

Fatigue life prediction of matrix dominated composite laminates, which have a nonlinear stress/strain response, was studied analytically and experimentally. A stress function describing the relation of initial fatigue modulus and elastic modulus was used in order to consider the material nonlinearty. New modified fatigue life prediction equation was suggested based on the fatigue modulus and reference modulus concept as a function of applied stress. The prediction was verified by torsional fatigue test using crossply carbon/epoxy laminate tubes. It was shown that the proposed equation has wide applicability and good agreement with experimental data.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.9
• /
• pp.1897-1904
• /
• 2002

Monotonic torsional and pure torsional low cycle fatigue(LCF) test with artificial degradation were performed on duplex stainless steel(CF8M). CF8M is used in pipes and valves in nuclear reactor coolant system. It was aged at 430$^{\circ}C$ for 3600hrs. Through the monotonic and LCF test, it is found that mechanical properties(i.e., yield strength, strain hardening exponent, strength coefficient etc.) increase and fatigue life(N$\sub$f/) decreases with degradation of material. The relationship between shear strain amplitude(${\gamma}$$\sub$a/)and N$\sub$f/ was proposed.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.4 no.4
• /
• pp.48-53
• /
• 2005

This research is materialized the mechanism of a interlocking elevator device to meet with customer's requirement demanding a variety of function. On this suitably theoretical translation and by considering of material significance of the most factor's tension spring and torsion spring, it's compared and reviewed the stress's calculation according that SWC and SWPB applied differently. And also that is approved through actual experiment. Out of a variety of feasible movement. Torque Balance is materialized by combination of tension spring, torsion spring and disk spring. So that application of 3 factors for optimal design is very important factor. In future, this research thesis make sure to play a highly role for application and improvement mechanically in various industry sector out of materializing interlock.