• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.422-428
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• 2005

In this paper, the contact force between two colliding bodies is modeled by using Hertz's force-displacement law and nonlinear damping function. In order to verify the appropriateness of the proposed contact force model, the drop type impact test is carried out for different impact velocities and different materials of the impacting body, such as rubber, plastic and steel. In the drop type impact experiment, six photo interrupters in series close to the collision location are installed to measure the velocity before impact more accurately. The characteristics of contact force model are investigated through experiments. The parameters of the contact force model are estimated using the optimization technique. Finally the estimated parameters are used to predict the impact force between two colliding bodies in opening action of the magnetic contactor, a kind of switch mechanism for switching electric circuits.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1878-1886
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• 2021

For industrial package (IP)-type transport containers for radioactive materials, a free drop test should be conducted under regulatory conditions. Owing to various uncertainties observed during the drop test, errors in drop angles inevitably occur. In IP-type metal transport containers in which the container directly impacts onto a rigid target without any shock absorbing materials, the error in the drop angle due to a slight misalignment makes a significant difference from the ideal drop. In particular, in a vertical drop, the error in the drop angle causes a strong secondary impact. In this paper, a numerical method is proposed to estimate the error in the drop angle occurring during the test. To determine this error, an optimization method accompanying a computational drop analysis is proposed, and a surrogate model is introduced to ensure calculation efficiency. Effectiveness of the proposed method is validated by performing the verification and comparison between the test and the analysis applied with the drop angle error.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 추계 학술대회 논문집
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• pp.339-347
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• 2005

IP-2형 운반용기는 정상운반조건의 낙하시험을 거친 후에 방사성내용물의 유실 또는 분산이 없고 외부표면에서의 방사선량률이 $20\%$ 이상 증가할 수 있는 차폐능력의 상실이 없어야 한다. 차폐체의 두께가 큰 경우에는, 볼트체결방식을 사용하면 IP형 운반용기로 많이 사용되고 있는 ISO 컨테이너에서의 문을 사용하는 경우보다 방사성내용물의 유실 또는 분산이 일어나지 않을 것이다. 본 연구에서는 볼트체결방식의 IP-2형 운반용기에 대한 낙하시험을 실시하기 전에, 낙하방향에 따른 볼트인장력과 볼트체결력을 시험으로 평가하는 방법을 알아보기 위하여 예비시험모델을 제작하여 시험 및 평가하였다. 바닥과 뚜껑방향의 수직낙하, 수평낙하, 4방향의 경사낙하 등 총 7가지 낙하방향으로 자유낙하를 실시하였다. 낙하충격에 의한 볼트인장력은 힘센서를 이용하여 측정하였고, 볼트체결력은 낙하시험 전의 체결토르크에서 낙하충격 이후의 풀림토르크의 변화를 이용하여 알아보았다.

• 정보저장시스템학회논문집
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• 제9권2호
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• pp.56-61
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• 2013

The recent increased use of mobile phone has resulted in a technical focusing on reliability issues related to drop performance. Since mobile phone may be dropped several times during their use, it is required to survive common drop accidents. The plastic injection parts such as base stopper and carrier in the encoder type actuator can be broken easily in the actual reliability test of 1.5m free drop. So, we analyzed the shock resistance characteristics of auto focus actuator with variables in the material properties using finite element method. By applying the new resin materials, we can decrease the breakage of plastic injection parts and improve the reliability of mobile phone.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.250-254
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• 2011

Main role of landing gear is to absorb the energy which is generated by aircraft lanidng and ground maneuvering. Generally, in order to absorb the impact energy during landing, oleo-pneumatic type shock absorber is used for aircraft landing gear. Oleo-pneumatic type shock absorber has a good energy absorbing efficiency and is light in weight because its structure is relatively simple. For the landing gear development, it is necessary to conduct drop test in order to verify shock absorbing performance. In the drop test, first, gas spring curve verification tests are conducted. Then, limit and reserve energy absorption drop tests are performed based on the STANAG 4671. The drop tests results with performance analysis results are presented.

• 대한기계학회논문집
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• 제18권2호
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• pp.359-371
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• 1994

A drop weight type impact test system is designed and set up to experimentally investigate impact responses of composite laminates subjected to the low-velocity impact. Using the test system, the impact velocity and the rebound velocity of the impactor as well as the impact force history are measured. An error of the measured data due to a difference in measuring position of the sensor is corrected and, for the estimation of real contact force history, a method of correcting an error due to friction forces is developed. Experimental methods to fix the boundary edgy of laminate specimens in impact testing are investigated and the impact tests on the specimens fixed by those methods are performed. Impact force histories and dynamic strains measured from the tests are compared with numerical results from the finite element analysis using the contact law. Consequently, the nonlinear numerical results considering the large deflection effects are agreed with the experimental results better than the linear ones.

• 한국소음진동공학회논문집
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• 제20권7호
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• pp.658-664
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• 2010

A control element drive mechanism(CEDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod containing a neutron absorbing material within a reactor core to control the reactivity of the core. The ball-screw type CEDM for the integral reactor has a spring-damper system to reduce the impact force due to the scram of the CEDM. This paper describes the experimental results to obtain the drop and damping characteristics of the CEDM. The drop tests are performed by using a drop test rig and a facility. A drop time and a displacement after an impact are measured using a LVDT. The influences of the rod weight, the drop height and the flow area of hydraulic damper on the drop and damping behavior are also estimated on the basis of test results. The drop time of the control element is within 4.5s to meet the design requirement, and the maximum displacement is measured as 15.6 mm. It is also found that the damping system using a spring-hydraulic damper plays a good damper role in the CEDM.

• 대한기계학회논문집A
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• 제22권1호
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• pp.52-63
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• 1998

The impact programmer for impact test was designed and the impact analysis was conducted. The effects of the material and geometric parameters on the impact force and pulse shape were investigated. The impact characteristics were examined by experimental and finite element method. The impact test was conducted with free drop impact tester. The ABAQUS/Explicit 5.5 version was used for finite element analysis. The geometric parameters of the conical and dome type impact programmer were analyzed. The polyurethane impact programmers were fabricated and tested. The effects of the hardness and thickness of the impact programmer were studied. The peak acceleration and time duration of impact programmer have close correlation with the hardness, impact energy and thickness of the impactor. The experiment was good agreement with analytical predictions. The impact pulse shape generated with polyurethane impact programmer was half sine shape. The maximum impact force was proportional to impact energy. The impact acceleration was decreased with thickness of impact programmer. The maximum impact time duration level was about 2 msec.

• 대한기계학회논문집A
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• 제21권3호
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• pp.457-469
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• 1997

A nuclear spent fuel shipping cask is required by IAEA and domestic regulations to withstand a 9m free drop condition. In this paper, the structural analysis under the 9m side drop condition was performed to understand the dynamic impact behavior and to evaluate the safety of the cask for 7 PWR nuclear spent fuel assemblies. The analysis result was compared with the measured value of the 9m side drop test for the 1/3 scaled-down model and the accuracy of the 3D analysis was confirmed. Analysis in accordance with the diameter of impact limiters for the proto-type cask were performed. Through the analysis, the impact behaviors due to the side drop and the effects dependent on the diameter of impact limiters were grasped. Maximum stress intensities on each part of the cask were respectively calculated by using the stress evaluation program and the structural safety of the cask was finally evaluated in accordance with the regulations.

• 한국수소및신에너지학회논문집
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• 제32권3호
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• pp.172-179
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• 2021

The drop impact analysis was carried out on Type 4 pressure containers, and the degree of damage to the falling environment was predicted and determined using smoothed particle hydrodynamics (SPH) techniques. The purpose of the design and the optimization process of the winding pattern of the pressure vessel of the composite material is to verify the safety of the container in actual use. Finally, an interpretation process that can be implemented in accordance with domestic test standards can be established to reduce the cost of testing and containers through pre-test interpretation. The research on the fall analysis of pressure vessels of composite materials was conducted using Abaqus, and optimization was conducted using ISIGHT. As a result, the safety of composite pressure vessels in the falling environment was verified.