• 한국산학기술학회논문지
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• 제16권8호
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• pp.5051-5059
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• 2015

농업용 트랙터 프론트 로더의 낙하정지시험, 코너당김시험, 코너충돌시험의 세 가지 충격시험 조건에 대하여 강체동해석, 과도구조해석, 정적구조해석 등을 수행하여 각 부품의 응력분포를 구하고 안전성을 평가하였다. 낙하정지시험은 프론트 로더를 최대높이에서 시작하여 세 단계로 나누어 낙하시킨 후 정지시켜서 충격을 가하는 경우를 해석하였다. 코너당김시험은 체인으로 버켓 밑면의 모서리를 지면에 구속한 상태에서 프론트 로더를 갑자기 상승시키는 경우를 해석하였다. 코너충돌시험은 주행 중에 버켓의 모서리가 충격장애물과 충돌하는 경우를 해석하였다. 세 가지 충격시험 조건에 대한 해석 결과, 모두 마운트의 사각관 모서리와 마운트의 양쪽 꺾임 위치에서 국부적 응력집중이 발생하였다. 이러한 결과를 바탕으로 새로운 프론트 로더의 설계 및 수정 시 파단에 관한 안전성을 개선하는데 도움이 될 것으로 기대된다.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1894-1903
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• 2003

It is necessary to have a dummy that describes the anthropometry of a victim with accuracy. This study presents three scaled side impact dummies constructed for the use of MADYMO. They represent five, fifty and ninety-five percentile Korean males ranged from the age of 25 through 39. Thirty-five anthropometric data were used to scale input files required for MADYSCALE. Geometries, inertia, joints and other parameters for dummies were scaled based on the configurations of EuroSID-1. This study proposes the lateral impact response requirements for head, thorax and pelvis of Korean side impact dummies. A lateral drop impact test was conducted for the head at the height of 200 mm. Lateral pendulum impact tests were also carried out for thorax and pelvis at three specific impact velocities. All these test results were obtained from simulation based on MADYMO. All the procedures of the three tests followed the requirement of ISO/TR 9790.

• 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.

• 대한조선학회논문집
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• 제57권4호
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• pp.182-190
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• 2020

This study reports a series of drop impact tests performed to generate denting damages on stiffened plates and their residual ultimate strength tests under axial compression. The models were fabricated of general structural steel, and each model has six longitudinal stiffeners and two transverse frames. Among six fabricated models, four were damaged, and two were left intact for reference. To investigate the effects of collision velocity and impact location on the extent of damage, the drop height and the impact location were changed in each impact test. After performing the collision tests, the ultimate axial compression tests were conducted to investigate the residual strengths of the damaged stiffened plates. Finite element analyses were also carried out using a commercial package Abaqus/Explicit. The material properties obtained from a quasi-static tensile tests were used, and the strain-rate sensitivity was considered. After importing the collision simulation results, the ultimate strength calculations were carried out and their results were compared with the test data for the validation of the finite element analysis method.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.106-109
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• 2000

Impact tester was build up to evaluate the characterization of CFRP laminate plates under the low velocity impact. The tests were conducted on several laminates of different ply orientation A system was budded for the impact strength of CFRP laminates in consideration of stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen having four interfaces is higher than that of orthotropic laminates with two interfaces. Also the damage area was measured with ultrasonic C-scanner on some samples. In the specimens the relationship was linear between damaged area and absorbed energy to some degree. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.

• 한국해양공학회지
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• 제31권1호
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• pp.22-27
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• 2017

This paper presents the results of an experimental study on the wedge slamming impact problem, including the fluid-structure interaction. A free drop test was performed to estimate the hydroelasticity. Three wedges were fabricated of 5 mm thick steel plate. The deadrise angles were $15^{\circ}$, $20^{\circ}$, and $25^{\circ}$. Plate thicknesses of 2 mm and 3 mm were used to determine the effect of the structural rigidity. The drop heights were 25 cm, 50 cm, 75 cm, and 100 cm. The pressure on a rigid part of the wedge and strain of the elastic plate were measured at four different locations. The pressure was compared using the Wagner theory and generalized Wagner theory.

• Earthquakes and Structures
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• 제17권6호
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• pp.567-575
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• 2019

In order to investigate the dynamic impact resistance of steel fiber reinforced full light-weight concretes, we implemented drop weight impact test on a total of 6 reinforced beams with 0, 1 and 2%, steel fiber volume fraction. The purpose of this test was to determine the failure modes of beams under different impact energies. Then, we compared and analyzed the time-history curves of impact force, midspan displacement and reinforcement strain. The obtained results indicated that the deformations of samples and their steel fibers were proportional to impact energy, impact force, and impact time. Within reasonable ranges of parameter values, the effects of impact size and impact time were similar for all volumetric contents of steel fibers, but they significantly affected the crack propagation mechanism and damage characteristics of samples. Increase of the volumetric contents of steel fibers not only effectively reduced the midspan displacement and reinforcement strain of concrete samples, but also inhibited crack initiation and propagation such that cracks were concentrated in the midspan areas of beams and the frequency of cracks at supports was reduced. As a result, the tensile strength and impact resistance of full light-weight concrete beams were significantly improved.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4146-4158
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• 2022

Ultra-high performance concrete (UHPC) has been widely utilized in military and civil protective structures to resist intensive loadings attributed to its excellent properties, e.g., high tensile/compressive strength, high dynamic toughness and impact resistance. At present, aiming to improve the defects of the traditional vertical concrete cask (VCC), i.e., the external storage facility of spent fuel, with normal strength concrete (NSC) shield, e.g., heavy weight and difficult to fabricate/transform, the feasibility of UHPC applied in the shield of VCC is numerically examined considering its high radiation and corrosion resistance. Firstly, the finite element (FE) analyses approach and material model parameters of NSC and UHPC are verified based on the 1/3 scaled VCC tip-over test and drop hammer test on UHPC members, respectively. Then, the refined FE model of prototypical VCC is established and utilized to examine its dynamic behaviors and damage distribution in accidental tip-over and end-drop events, in which the various influential factors, e.g., UHPC shield thickness, concrete ground thickness, and sealing methods of steel container are considered. In conclusion, by quantitatively evaluating the safety of VCC in terms of the shield damage and vibrations, it is found that adopting the 300 mm-thick UHPC shield instead of the conventional 650 mm-thick NSC shield can reduce about 1/3 of the total weight of VCC, i.e., about 50 t, and 37% floor space, as well as guarantee the structural integrity of VCC during the accidental drop simultaneously. Besides, based on the parametric analyses, the thickness of concrete ground in the VCC storage site is recommended as less than 500 mm, and the welded connection is recommended for the sealing method of steel containers.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.111-116
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• 2018

본 논문은 시스템 에어컨 실외기 포장품의 낙하충격해석 및 시험검증을 수행한 내용을 다룬다. 포장은 낙하충격으로 부터 제품을 보호할 수 있도록 충격에너지를 흡수할 수 있는 완충재질과 이를 제품에 고정하기 위한 부재로 구성되는데 작은 부피로 충분한 완충성능을 발휘하는 포장 설계를 위해서는 충격 시 제품에 가해지는 충격가속도 등을 정확히 평가하는 것이 필수적이다. 본 논문에서는 외연적 시간적분을 활용하는 유한요소해석 기법을 활용하여 실외기 포장품의 낙하충격해석을 수행하였다. 정확한 해석을 위한 해석모델 구축, 재료 시험을 통한 데이터 획득 및 재료 모델의 선정, 신뢰성 있는 해석 데이터 확보를 위한 계측 센서의 모델링 등이 수행되었으며 이렇게 구해진 해석데이터와 시험으로 구해진 가속도 및 변형률 시간이력을 비교하였다. 해석모델에 반영된 감쇄계수 등의 오차로 인하여 대체로 해석결과가 시험 결과에 비해 충격 가속도 및 변형률을 크게 예측하고 있으나 전체적인 데이터의 경향과 낙하 방향의 충격가속도는 정확하게 계산되었다. 이에 본 연구에 사용된 모델 및 해석기법을 에어컨 실외기 포장 설계에 활용할 수 있음을 확인하였다.

• 화약ㆍ발파
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• 제29권1호
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• pp.41-47
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• 2011

발파에 의한 암반손상영역을 평가하고 암반 파쇄도를 제어하기 위해서는 장약실 내 발생하는 폭발압력에 관한 정보는 중요하다. 이를 위하여 본 연구에서는 철, 알루미늄, 아크릴 재질의 센서에 대한 낙추 충격 시험으로부터 동적 변형률 신호를 측정하여 센서의 동적 응답 특성을 분석하였다. 철재 센서의 경우 충격하중에 가장 적은 변형률 출력 값을 보였으며 센서길이에 대한 출력 값의 변화는 적게 나타났다. 철제 센서를 뇌관의 충격하중 측정에 적용하였다.