• 대한기계학회논문집A
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• 제32권11호
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• pp.930-936
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• 2008

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

• 동력기계공학회지
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• 제10권4호
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• pp.25-30
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• 2006

This paper represents the numerical analysis in unsteady state on the variation of diameter and environmental velocity of carbon heating source. In general heating system, the oil and sheath heater is widely used, but these systems have many problems. So, the heating source with carbon ingredient has been researched in many country about manufacture, thermal and electrical properties. In this research, the carbon heating source was studied through numerical analysis on several conditions of unsteady state, heat generation, diameter and environmental velocity. The temperature distributions at steady state are appeared as a non-proportional linear pattern with variations of environmental velocity due to the Nesselt number with convective heat flux is proportioned to 0.805 of Reynolds number. As the radius is increasing, the temperature distributions is appeared the minus tilt because of the environmental condition is cooling by constant temperature. So, the correlation equation between temperature at steady state and environmental velocity was obtained.

• Advances in Computational Design
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• 제9권1호
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• pp.39-52
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• 2024

If the governing differential equation arising from engineering problems is treated as an analytic, continuous and derivable function, it can be expanded by one point as a series of finite numbers. For the function to be zero for each value of its domain, the coefficients of each term of the same power must be zero. This results in a recursive relationship which, after applying the natural conditions or the boundary conditions, makes it possible to obtain the values of the derivatives of the function with acceptable accuracy. The elastoplastic analysis of an inhomogeneous thick sphere of metallic materials with linear variation of the modulus of elasticity, yield stress and Poisson's ratio as a function of radius subjected to internal pressure is presented. The Beltrami-Michell equation is established by combining equilibrium, compatibility and constitutive equations. Assuming axisymmetric conditions, the spherical coordinate parameters can be used as principal stress axes. Since there is no analytical solution, the natural boundary conditions are applied and the governing equations are solved using a proposed new method. The maximum effective stress of the von Mises yield criterion occurs at the inner surface; therefore, the negative sign of the linear yield stress gradation parameter should be considered to calculate the optimal yield pressure. The numerical examples are performed and the plots of the numerical results are presented. The validation of the numerical results is observed by modeling the elastoplastic heterogeneous thick sphere as a pressurized multilayer composite reservoir in Abaqus software. The subroutine USDFLD was additionally written to model the continuous gradation of the material.

• 한국해양공학회지
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• 제11권4호
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• pp.249-261
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• 1997

A basic study on the lifting lug design has performed through the rational and systematic process. In order to evaluate the proper design-load distribution around lug eye investigation of contact force between lifting lug and shackle pin is performed using non-linear parametric analysis idealized by gap element models. Gap element modeling and nonlinear analysis procedures are illustrated and discussed based on MSC/NASTRAN. Some analysis and design guides are suggested through the consideration of several important effects such as stress distribution pattern, circumferential contact force distribution along the lug eye face, loading share rate between lug main plate and doubler, effect of loading direction, relation between applied force and deflection and size effect of shackle pin radius. Additionally optimum design studies are performed and general trends according to the variation of design parameters are suggested.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.953-958
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• 2007

To assess the derailment safety of the Samaeul Train, We developed a fleet analysis model and carried out sensitivity analysis of the variables related to derailment factors with ADAMS/Rail computing analysis method. Depending on the variation of the running speed in curve section, derailment coefficient and wheel load reduction rate are high at right side wheels in slow running speed section and low at left side wheel in high running speed. According to decreasing the radius of curve, derailment coefficient and wheel load decreasing rate are increased. Derailment coefficient is proportional to transition curve length and wheel load decreasing rate is constant. Cant value rising causes wheel load deduction rate rising.

• 물과 미래
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• 제23권4호
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• pp.435-444
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• 1990

만곡수로에서의 곡률반경에 대한 하폭비 변화에 따른 흐름특성을 단순화된 수치모형을 이용하여 분석하였다. 각 운동량 방정식과 힘의 평형원리로부터 각가 2차 흐름속도와 횡방향하상경사를 계산하였다. 깊이 방향으로 적분된 연속방정식과 흐름방향의 운동방정식을 양적 유한차분법으로부터 그 해를 구하였다. 곡률반경에 대한 하폭의 비를(Rc/B) 2.7, 5.4 및 8.1로 변화시키면 수치실험을 실행하여, 그 결과로부터 2차 흐름속도, 흐름방향유속, 최대유속의 이동경로, 편의각 및 질량이동유속에 관한 특성을 분석하였다.

• 한국철도학회논문집
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• 제10권5호
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• pp.492-498
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• 2007

곡선통과 새마을호 열차의 주행안전성을 평가하기 위하여 다물체동력학 해석모델이 사용된다. 이 모델과 ADAMS/Rail 사용하여 탈선계수와 관련된 변수의 변화에 따른 민감도해석이 수행된다. 저속에서 우측차륜의 탈선계수와 윤중감소율이 좌측차륜보다 높으나, 고속의 경우는 좌측차륜이 우측차륜보다 높다. 곡선반경의 감소에 따라 탈선계수와 윤중감소율이 감소된다. 완화곡선의 길이가 증가하면 탈선계수는 증가하나 윤중감소율은 변화가 없다. 캔트가 증가하면 탈선계수와 윤중감소율이 증가한다.

• Geomechanics and Engineering
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• 제24권5호
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• pp.479-490
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• 2021

Pre-drainage of groundwater in the roof aquifer by boreholes is the main method for prevention of roof water disaster, and the drop in the water level during the drainage leads to the variation of the local stress in the overlying strata. Based on a multitude of boreholes for groundwater drainage from aquifer above the 1303 mining face of Longyun Coal Mine, theoretical analysis and numerical simulation are used to investigate the local stress variation in the process of borehole drainage. The results show that due to the drop in the water level of the roof aquifer during the drainage, the stress around the borehole gradually evolved. From the center of the borehole to the outside, a stress-relaxed zone, a stress-elevated zone, and a stress-recovered zone are sequentially formed. Along with the expansion of drainage influence, the stress peak in the stress-elevated zone also moves to the outside. When the radius of influence develops to the maximum, the stress peak position no longer moves outward. When the coal mining face advances to the drainage influence range, the abutment pressure in front of the mining face is superimposed with the high local stress around the borehole, which increases the risk of stress concentration. The present study provides a reference for the stress concentration caused by borehole drainage, which can be potentially utilized in the optimal arrangement of drainage boreholes in underground mining.

• 소성∙가공
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• 제8권5호
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• pp.507-519
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• 1999

An approach using the energy method has veen proposed for the analysis of cone spinning having the complicated deformation modes mixed by shear and normal deformation. In the proposed method, the corresponding solution is found through optimization of the total energy dissipation with respect to the parameters assumed by the velocity field defined as the variation of the length in longitudinal direction. The sheet blank is divided into three layers to consider the bending effect and the energy dissipated by shear deformation is superposed to the energy consumption due to normal deformation related with the shrinking deformation is superposed to the energy consumption due to normal deformation related with the shrinking deformation of axi-symmetric sheet element for the evaluation of total deformation energy. In order to check the validity of the proposed method, the complex spinning for making the conical cup is analyzed and the computed results are compared with the experimental results. In comparison of the computed results with existing experimental results,, the good agreement is obtained for the variation of outer radius and the distribution of thickness, and it has thus been shown that the present approach is applicable to the analysis of complex spinning.

• Smart Structures and Systems
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• 제24권4호
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• pp.435-446
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• 2019

The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.