• 한국기계가공학회지
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• 제17권3호
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• pp.109-119
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• 2018

The purpose of this study is to evaluate the structural safety of the front-end loader for the 90 kW class of agricultural tractors in impact test conditions. Deformation and stress on the loader under the impact test conditions are analyzed using the commercial finite element analysis software ANSYS. In previous research dealing with the initial design of the loader, the maximum stress occurred in the mount and exceeded the yield strength of the material. In this paper, an improved design of the mount of the loader was proposed to reduce the stress concentration in the initial design. The safety of the improved design was verified by performing rigid-body dynamics analysis, transient structural analysis, and static structural analysis under three impact test conditions: a drop and catch test, a corner pull test, a corner push test. It was found that the local stress concentration in the mount that appeared in the initial design was greatly reduced in the improved design, and that the maximum stresses occurred in the three impact test conditions are smaller than the yield strength. It is expected that the design improvement of the mount proposed in this study and the method of analysis may be effectively used to enhance structural safety in the development of new model front loaders in the future.

• 대한기계학회논문집A
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• 제26권5호
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• pp.932-938
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• 2002

In structural applications, brittle materials such as soda-lime glasses and ceramics are usually subjected to multiaxial stress state. Brittle materials with cracks or damage by foreign object impacts are apt to fracture abruptly from cracks, because of their properities of very high strength and low fracture toughness. But in most cases, the residual strength of structural members with damage has been tested under uniaxial stress condition such as the 4-point bend test. Depending upon the crack pattern developed, the strength under multiaxial stress state might be different from the one under uniaxial. A comparative study was carried out to investigate the influence of stress state on the residual strength evaluation. In comparable tests, the residual strength under biaxial stress state by the ball-on-ring test was greater than that under the uniaxial one by the 4-point bend test, when a small size indendation crack was introduced. In the case that crack having an angle of 90deg. to the applied stress direction, the ratio of biaxial to uniaxial flexure strength was about 1.12. The residual strength was different from crack angles to loading direction when it was evaluated by the 4-point bend test. The ratio of residual strength of 45deg. crack to 90deg. one was about 1.20. In the case of specimen cracked by a spherical impact, it was shown that an overall decrease in flexure strength with increasing impact velocity, and the critical impact velocity for formation of a radial and/or cone crack was about 30m/s. In those cases that relatively large cracks were developed as compared with the case of indented cracks, the ratio of residual strength under biaxial stress state to one uniaxial became small.

• 한국안전학회지
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• 제32권5호
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• pp.69-75
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• 2017

Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

• 한국강구조학회 논문집
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• 제24권6호
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• pp.711-723
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• 2012

플랜지와 웨브에 서로 강도가 다른 이종강재를 사용한 CFT 합성구조의 거동특성을 파악하기 위하여, 플랜지는 건축용 800MPa급 강재인 HSA800, 웨브에는 일반강도 강재인 SM490 강재를 사용하여 실험연구를 수행하였다. 주요실험 변수는 강관의 강도 조합, 충전된 콘크리트의 강도, 콘크리트 충전효과이다. 이종강재간의 용접접합부는 낮은강도 강재에 적합한 용접부를 사용하여 접합부 성능을 검증하였다. 실험체의 거동특성을 평가하기 위해 편심압축 실험을 수행하였으며, 현행 설계기준들에 따른 예측결과와 비교하였다. 플랜지에 고강도 강재를 적용함에 따라 단면의 축강도 및 휨모멘트강도가 증가하였으며, 부재 강도를 충분히 발현한 이후 용접부에서 파괴가 일어났다. 실험결과 현행 설계기준을 적용하여 합성단면의 축력-모멘트 상관관계 및 유효휨강성을 안전측으로 예측 가능하였다.

• 한국정밀공학회지
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• 제33권4호
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• pp.317-324
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• 2016

Stress tests were conducted in the carbody of the railroad car to check the structural strength of the body of the railroad car. The objective of this study was to evaluate safety of the carbody of a railroad car under the maximal strength. The carbody of rolling stock is a principal structure that supports major equipment of the underframe and the freight. Therefore, the strength evaluation of this structure is important. This study was carried out to analyze the structure of carbody and evaluate safety under maximum vertical load, compressive load, and torsional load. Accordingly, stress tests were conducted on the carbody to measure the stress on each of their parts. Before the load test, a structural-analysis program was used for the stress distribution analysis of the body structure.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.140-146
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• 2005

This study presents the development of a round recliner using the finite element method. That reduces the number of test repeating times and gives an information about stiffness. A simulation model of round recliner mounting seat module and tooth strength simulation are established using a PAM-CRASH and ABAQUS. With the optimization of gear profile, structural strength design of round recliner was achieved. The round recliner seat module simulation, structure strength simulation and a crash safety are requested by FMVSS test. Solution of round recliner optimum variable study and design problem are searched for round recliner stress, deformation and application. Also an examination of safety is made.

• 대한임베디드공학회논문지
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• 제6권5호
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• pp.273-280
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• 2011

In this paper, we describe the structural reinforcement approach of the throwing-type firefighter assistance robot which can be thrown into a fire site to monitor inside the place and search trapped people while ensuring a firefighter's safety. The reinforcement design is focused on high strength with low weight for the robot. The in-depth structural analysis of the platform is carried out to track down the weakest part, especially with the 1.8m height of drop test. The analysis is verified by comparing with the 1.8m height of the drop test of the throwing-type firefighter assistance robot. The optimal approach for improving the strength of the weakest part aims at topological equivalent and equivalently stress distributed shape.

• 한국항공우주학회지
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• 제33권12호
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• pp.39-47
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• 2005

본 연구에서는 고속 충격환경을 경험하는 플라스틱 구조 소재에 대한 인장속도별 물성 평가 시험 및 구조건전성 평가에 음향방출 기법을 적용하였다. 인장속도별 물성 평가시험을 통하여 플라스틱 소재 구조물의 건전성 평가에 유용한 음향방출 신호 특성 인자들을 획득하였다. 인장속도에 따른 인장강도는 저속 인장속도 구간에서는 속도가 증가함에 따라 강도가 증가하는 특성을 보여주었으나 일정 속도 영역 이상의 고속 인장시험에서는 인장속도 증가와 무관하게 일정한 강도 값을 나타내었다. 정적 압축 구조시험에서는 음향방출 기법을 적용함으로써 플라스틱 쉘 구조물의 균열발생 시점 및 위치 등을 정확히 평가할 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권4호
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• pp.11-22
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• 2023

본 연구에서는 원심성형 기법을 이용하여 구조용 콘크리트 각형보를 개발하였으며, 단면의 휨 강성을 확보하기 위하여 단면의 중 공률은 10 % 이하로 하며 이를 위하여 기존의 빈배합상태의 콘크리트가 아닌 고슬럼프(150~200 mm)의 물성을 가지며 설계강도가 100 MPa 이상인 콘크리트 배합비를 개발하여 적용하고, 원심성형 각형보를 제작하기 위한 특수거푸집을 제작하여 원심성형 각형보를 생산하였다. 생산된 원심성형 각형보는 원심성형 부재의 표준 휨 및 전단 시험기준에 따라 성능시험을 수행하였다. 4개의 시험체에 대한 정적재하시험 결과는 설계기준에서 제시하고 있는 단면의 공칭휨강도, 공칭전단강도 이상으로 나타나 초고강도 원심성형 각형보의 구조적인 신뢰성이 입증되었다.

• 콘크리트학회논문집
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• 제23권5호
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• pp.637-645
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• 2011

압축강도 50 MPa이 넘는 고강도 콘크리트가 화재에 취약하다는 것은 널리 알려진 사실이다. 그러나 화재 피해를 입은 고강도 콘크리트 구조 부재의 구조 성능 저감 정도를 정확하게 파악하기 위해서는 단순히 열역학적 거동만으로 파악하는 것이 아니라, 구조 거동에 대한 연구가 필요하다. 따라서 이 연구에서는 비재하 상태에서 고온에 일정시간 노출시킨 고강도 콘크리트 단주를 대상으로 하중 재하 실험을 수행하였다. 실험 변수로는 콘크리트 압축강도, 가열시간, 그리고 폴리프로필렌 섬유 혼입을 통한 폭렬 저감 공법 사용 유무가 있었으며, 실험의 결과로는 콘크리트 강도 및 가열 시간이 증가할수록 구조 성능은 저감되는 것으로 나타났다. 특히 폴리프로필렌 섬유를 혼입하여 폭렬이 저감 된 경우에도 구조 성능에는 변화가 없거나 오히려 감소하는 것으로 나타났다. 이 연구를 통하여 알아낸 바를 토대로 보다 안전하고 경제적인 내화 설계를 할 수 있으며, 또한 화재로 인한 고강도 콘크리트 구조물의 구조성능 저감 정도를 예측하는데 유용하게 활용될 수 있을 것이라고 사료된다.