• Journal of KSNVE
• /
• v.5 no.3
• /
• pp.337-344
• /
• 1995

A BEM program is developed for the performance analysis of axisymmetric mufflers. In the program the sub-region method is used to deal with singularity or inner boundary. The program is applied to typical axisymmjetric mufflers such as simple expansion, extended tube, perforated tube and absorptive expansion sufflers. The transmission losses of the mufflers are calculated by the program and compared with experiments. It is found that the prediction is in a good agreement with measurement, except for the absorptive muffler with parallel lining.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.1
• /
• pp.89-96
• /
• 1995

The application of the 4-pole parameter method with 1 - D theory is acceptable for intake system analysis. However, the limitaion appears during the analysis of complicated intake system since this method is developed based on the plane wave thoery. For the intake system analysis, the usage of BEM(Boundary Element Method) is introduced describing its disadvantage. To combine benefits of both method. a hybrid method is introduced. This hybrid method consists of the 4-pole parameter with I-D theory and BEM. The developed method is applied to an automobile intake system analysis to obtain the transmission loss.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.4
• /
• pp.127-133
• /
• 2008

As the application of the MEMS parts increases, the structural safety of MEMS appears importantly. A lot of MEMS parts are made by a multi-grain silicon wafer, which is an orthotropic material. Moreover directions of the materials on each grain are distributed randomly. The stress analysis for the multi-grain is important factor in order to apply the MEMS parts to industrial applications. The finite element method (FEM) is commonly used by a stress analysis method but the boundary element method (BEM) is known as the result of the BEM is more accurate than that of the FEM since the fundamental solution are used. In this study, we derived the boundary integration equation for the orthotropic material by applying fundamental solutions with complex variables. The multi-region analysis procedure for the BEM and the multi-grain generation procedure by a random process technique are developed in order to apply the analysis of the multi-grain orthotropic material. The discontinuous element is used in order to remove the comer problem in the BEM. The results of the present method are compared with those of the finite element method in order to verify the present procedure.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2006.06a
• /
• pp.197-198
• /
• 2006

선저탑재식 음향변환자는 돌출형에 한에 유체항력 및 유체유기소음을 감소시키기 위해 유선형 housing을 장착하고 있다. housing의 형상 및 재질에 따른 흡수손실(absorption loss)은 필연적으로 발생하게 되며, 정밀한 음향설계를 위해서는 이론해석 및 실험검증이 필수적이다. 본 연구는 해석기법으로는 BEM기법을 사용하였고, 실험검증은 음향수조에서 음원준위 측정법을 사용하여 수행하였으며, 해석 및 실험에서 유사한 결과를 도출하였다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.2
• /
• pp.121-131
• /
• 2011

An object oriented programming(OOP) framework is presented to solve plane elastostatic contact problems by means of the boundary element method(BEM). Unified modeling language(UML) is chosen to describe the structure of the program without loss of generality, even though all implemented codes are written with C++. The implementation is based on computational abstractions of both mathematical and physical concepts associated with contact mechanics involving geometrical nonlinearities and the corner node problems for multi-valued traction. The overall class organization for contact analysis is discussed in detail. Numerical examples are also presented to verify the accuracy of the developed BEM program.

• Journal of the Society of Naval Architects of Korea
• /
• v.35 no.4
• /
• pp.38-45
• /
• 1998

It is a tedious and excessive time consuming process to model the local area of crack tip part of structures in calculation of stress intensity factors by FEM. So, in this paper, the hybrid method of FEM and BEM approach was formulated to overcome this type of problems. The multi-domained BEM was adopted to simplify the modelling process of complex geometry and singularity characteristics of crack tip part and the ordinary FEM modelling was used in the rest part. The example calculations shows very good results compared with analytic solutions and other numerical method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.113-117
• /
• 1996

구조물의 진동에 의해 소음이 방사되는 현상은 기계에서 소음의 발생원으로 볼 수 있기 때문에 기게류의 소음을 예측하거나 저감방안을 제시하기 위해서는 구조물의 동특성과 방사특성을 이해하고 있어야 한다. 특히, 엔진블럭, 펀치프레스, 배의 갑판구조물등과 같은 대다수의 소음 발생기계는 평판의 형상을 가진 구조물로서 기계적인 충격 등에 의해 그 표면에서 소음이 발생되므로 강성을 증가시키고, 소음저감을 목적으로 빔과 같은 보강재를 통해 보강되어 있다. 그런데, 해석적인 방법으로는 평판이나 원판 또는 구와 같은 단순한 형태의 특정구조물에 대해서만 그 결과를 얻을 수 있으므로 이와 같은 불연속 평판구조물의 진동 및 방사특성은 평판에 대한 순수 이론으로는 해석이 곤란하여 따라서 본 연구에서는 수치해석적인 방법을 통해 이를 해결하고자 하였다. 수치해석적인 방법으로는 유한요소법(FEM)과 경계요소법(BEM), 및 통계적 에너지 해석기법(SEA)등이 있으며 구조물의 진동-소음연성문제의 경우에 있어서는, 진동해석을 FEM과 SEA으로, 공기 중에서의 방사현상은 BEM으로 예측하고 있다. 본 연구에서는 재질이 균일한 얇은 2차원 평판구조와 보강평판에 대해서 진동특성은 유한요소해석 프로그램을 사용하여 해석하였으며 이때의 진동특성값을 입력데이터로 사용하여 경계요소해석 프로그램으로 방사효율 등을 예측하였다. 또한 이 과정에서 2차원 평판구조의 모우드 밀도와 가진점 모빌리티의 실수값이 가지는 평균치의 물리적 특성을 분석하였으며, 추후 실험을 통해 이를 검증코자 한다.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.730-735
• /
• 2007

This study is a comparison of the results of the orthropic material analysis at cantilever beam model using boundary element(BEM) method and finite element method(FEM). The program with the orthotropic material analysis was developed and applied to the examples in order to evaluate the accuracy of the programs. The examples shows that the results of the BEM is a good agreement with the ABAQUS results.

• 유체기계공업학회:학술대회논문집
• /
• 1999.12a
• /
• pp.208-217
• /
• 1999

The present work describes the prediction method for the unsteady flow field and the acoustic pressure field of a ducted axial fan. The prediction method is comprised of time-marching free-wake method, acoustic analogy, and the Helmholtz-Kirchhoff BEM. The predicted sound signal of a rotor is similar to the experiment one. We assume that the rotor rotates with a constant angular velocity and the flow field around the rotor is incompressible and inviscid. Then, a time-marching free-wake method is used to model the fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The newly developed Helmholtz-Kirchhoff BEM for thin body is used to calculate the sound field of the ducted fan. The ducted fan with 6 blades is analysed and the sound field around the duct is calculated.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.04a
• /
• pp.69-73
• /
• 1992

일반적으로 사출성형법은 유동, 보압, 냉각과정등 크게 3단계로 나눌 수 있는 데 유동해석에 관한 수치해석은 Tadmor 등이 FAN(Flow Analysis Network) 방법을 도입하면서 실제 적용에 활발히 쓰이고있다. 그리고보압은 후충전 과정으로써 충전이 끝난후 수축된 부분을 보상하기 위해서 수행되는 단계이다. 본 연구에서는 실제 사출금형 제작 시 결정해야 될 냉각 채널의 위치, 크기, 수동에 대한 설계기준을 얻을 수 있는 냉각해석 프로그램을 개발하였다. 이를 위하여경계 요소법(Boundary Element Method)을 이용하였으며 일반적인 냉각 채널 즉, Annual, Baffle 및 Bubber등 에 대한 해석이 가능하도록 하였다.