• Structural Engineering and Mechanics
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• 제56권5호
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• pp.767-785
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• 2015

The stochastic finite element method is employed to obtain a stochastic dynamic model of angled beams subjected to impact loads when uncertain material properties are described by random fields. Using the perturbation technique in conjunction with a precise time integration method, a random analysis approach is developed for efficient analysis of random elastic waves. Formulas for the mean, variance and covariance of displacement, strain and stress are introduced. Statistics of displacement and stress waves is analyzed and effects of bend angle and material stochasticity on wave propagation are studied. It is found that the elastic wave correlation in the angled section is the most significant. The mean, variance and covariance of the stress wave amplitude decrease with an increase in bend angle. The standard deviation of the beam material density plays an important role in longitudinal displacement wave covariance.

• 대한기계학회논문집A
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• 제36권2호
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• pp.125-135
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• 2012

잔류응력 생성을 위한 대부분의 숏피닝 유한요소 해석모델은 숏볼이 재료표면에 수직으로 충돌하는 것을 가정한다. 하지만 실제 피닝공정에서 숏볼은 경사각을 갖고 재료표면에 충돌한다. 본 논문 에서는 잔류응력평가를 위한 3차원 경사충돌 유한요소 해석모델을 제안하였다. 다중경사충돌 유한요소 해석모델을 이용하여, 투사각, 충돌패턴, 숏볼수량 등 피닝인자들이 해석해에 미치는 영향을 조사하였다. 아울러 숏볼의 소성변형도 고려하였다. 유한요소해와 XRD 실험해의 비교를 통해 해석모델의 유효성을 검증했다. 본 논문에서 제안된 모델은 다양한 경사각에 대한 다중숏 충돌 유한요소 해석모델의 기초가될 것이다.

• 한국정밀공학회지
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• 제34권2호
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• pp.151-156
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• 2017

Shot peening is widely used to improve the fatigue life and strength of various mechanical parts and an accurate method is important for the prediction of the compressive residual stress caused by this process. A finite element (FE) model with an elliptical multi-shot is suggested for random-angled impacts. Solutions for compressive residual stress using this model and a normal random vertical-impact one with a spherical multi-shot are obtained and compared. The elliptical multi-shot experimental solution is closer to an X-ray diffraction (XRD) than the spherical one. The FE model's peening coverage also almost reaches the experimental one. The effectiveness of the model based on an elliptical shot ball is confirmed by these results and it can be used instead of previous FE models to evaluate the compressive residual stress produced on the surface of metal by shot peening in various industries.

• Steel and Composite Structures
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• 제51권3호
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• pp.325-335
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• 2024

Yielding dampers exhibit varying cyclic behavior based on their geometry. These dampers not only increase the energy dissipation of the structure but also increase the strength and stiffness of the structure. In this study, parametric investigations were carried out to explore the impact of angled U-shape damper (AUSD) dimensions on its cyclic behavior. Initially, the numerical model was calibrated using the experimental specimen. Subsequently, analytical equations were presented to calculate the yield strength and elastic stiffness, which agreed with the experimental results. The outcomes of the parametric studies encompassed ultimate strength, effective stiffness, energy dissipation, and equivalent viscous damper ratio (EVDR). These output parameters were compared with similar dampers. Also, the magnitude of the effect of damper dimensions on the results was investigated. The results of parametric studies showed that the yield strength is independent of the damper width. The length and thickness of the damper have the greatest effect on the elastic stiffness. Reducing length and width resulted in increased energy dissipation, effective stiffness, and ultimate strength. Damper width had a more significant effect on EVDR than its length. On average, every 5 mm increase in damper thickness resulted in a 3.6 times increase in energy dissipation, 3 times the effective stiffness, and 3 times the ultimate strength of the model. Every 15 mm reduction in damper width and length increased energy dissipation by 14% and 24%, respectively.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.11-17
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• 2006

In this paper, crashworthiness of EMU carbody against overhead line structure is numerically evaluated. The material of the EMU carbody is made of stainless steel(SS301L). The material of the overhead line structure(a portal-type) is structure steel (SS400). The EMU carbody is numerically analyzed under collision conditions such as upright side-on impact scenario and angled impact scenario to collide against overhead line structure(a portal-type) at 64.6 kph, respectively.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.52-59
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• 2014

Front impacted SUV vehicle shows that the front parts of side members are collapsed by the bending due to the transverse load exerted at the end of side members. Side member models were impacted with various angles in order to study the crash performance according to the impact angle. Even for the small impact angle of $10^{\circ}$, crash performance seriously deteriorated and the deformations for impact angle $15^{\circ}$ were similar to those from the front body impact analysis. In addition, the angled front impact analysis for the straight member with hat section was carried out and the effects of inner reinforcement shape on crash performance was investigated.

• 한국철도학회논문집
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• 제10권4호
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• pp.381-387
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• 2007

In this paper, crashworthiness of the EMU carbody of Incheon Metro is numerically evaluated against two types of overhead line structures (headspan and portal-type). The material of the EMU carbody is stainless steel (SUS301L), and that of the overhead line structures is the structural steel (SS400). The EMU carbody is analyzed under collision conditions, such as upright side-on impact, side-on roof impact and angled roof impact scenarios, to be collided against the headspan type or the portal type at the speed of 64.4km/h, respectively. It is concluded from the numerical results that the overhead line structures will not do so much harm to the EMU carbody of Incheon Metro for various collisions caused by derailment. Furthermore, the overhead line structure of the portal type is superior to that of the headspan type in the crashworthy point of view.

• 자동차안전학회지
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• 제15권4호
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• pp.48-57
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• 2023

With the advance of autonomous vehicle technology various sitting posture is possible like relax position (inclined seating posture). Parametric study was done with MADYMO, a mutibody dynamics solver, to investigate the effect of sitting posture in different frontal crash modes, full frontal, 40% offset, and angled rigid barrier crash as well as various impact speeds. Hybrid III 50th male and 5th female dummies were used to figure out the difference induced by occupant weight and dimension. Restraint system parameters complying to current safety protocols like NCAP are studied if they still work effectively in relax position which is feasible with autonomous vehicles.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.55-62
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• 1996

The dynamic photoelastic technique has been utilized to investigate the possibility of relieving the large local singular stresses which are induce in the corner of a right angled indenter. The indenter compresses a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effect of geometric changes to the indenter in terms of the diameter (d) and the location (ℓ) of the notch on the relieving of the dynamic contact stresses are investigated. A multi-spark-high speed camera with twelve sparks was used to take dynamic photographs. The contact singular stresses were found to be released by introducing the relief notch along the indenter. The optimal location and geometry of the relief notch need further experimental investigation.

• Transactions on Control, Automation and Systems Engineering
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• 제4권4호
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• pp.341-346
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• 2002

When a construction company builds a high structure. many piles should be driven into the ground by a hammer whose weight is 7,000 kg in order to make the ground under the structure safe and strong. So. it is essential to determine whether a pile is penetrated into the ground enough to support the weight of the structure since ground characteristics at different locations are different each other. This paper proposes a visual measurement system for pile rebound and penetration movement including vibration using a high-speed line-scan camera and a specially designed mark to recognize two-dimensional motion parameters of the mark using only a line-scan camera. A mark stacking white and black right-angled triangles is used for the measurement, and movement information for vertical distance, horizontal distance and rotational angle is determined simultaneously. Especially- by adopting a line-scan CCD camera whose line rate is 20 ㎑. the measurement performance of dynamic characteristics of the pile at impact instant is improved dramatically.