• 재활복지공학회논문지
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• 제5권1호
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• pp.59-64
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• 2011

인공 중이 (IMEHD, implantable middle ear hearing device)용 플로팅 매스 트랜스듀서는 제작 과정상에서 발생하는 구조적 오차 및 제작 결합시의 문제점들로 인해 설계 시 의도와 다른 진동 특성을 가질 수 있게 되고, 이렇게 제작된 진동 트랜스듀서는 향후 실제 환자에게 이식되었을 때의 진동체 진동 성능을 예측하기 어려운 문제점이 있다. 본 연구에서는 제작된 플로팅 매스형 트랜스듀서에 대해 설계값과의 비교 평가 및 향후 컴퓨터 모델화된 청각 중이 집중 소자 모델에 적용이 가능하도록 기 제작된 진동체의 집중 소자 모델 파라미터들을 추정할 수 있는 방법을 제안하였으며, 제안된 방법을 LabVIEW 기반의 그래픽 유저 인터페이스 소프트웨어로 구현하였다. 제안된 방법은 실제 제작된 플로팅 매스형 진동체의 진동 변위 및 위상 데이터를 이용하여 해당 진동체의 집중 모델 파라미터들을 순차적 이차 프로그래밍 (SQP, sequential quadratic programming) 방법으로 추정하는 방식이다. 구현된 방법을 이용하여 측정 데이터에 가해지는 잡음의 양에 따른 플로팅 매스형 진동 트랜스듀서의 집중 모델 파라미터 추정 시의 발생 오차 변화를 컴퓨터 시뮬레이션을 통해 조사하여 본 방법의 파라미터 추정 정확도를 확인하였다. 또한, 실제로 제작한 인공중이용 진동 트랜스듀서에 대해 측정된 진동 변위 및 위상 데이터를 이용하여 진동체의 집중 모델 파라미터들을 추정하였으며, 기존 설계값들과 비교를 통해 제안된 방법의 유용성을 평가하였다.

• 대한기계학회논문집A
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• 제25권3호
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• pp.495-501
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• 2001

In this paper, a new technique which models the joints characteristics through reduction of DOFs of structures with joints using component mode synthesis (CMS) method is proposed. Bolt joints are modeled by mass-spring systems. Also generalized mass and stiffness matrices for this models are introduced. Because bolt joints have influence on eigenvalues of structures, exact eigenvalues from modal test are used. The results show that the behaviors of structures with bolt joints depend to a large extent on the translational DOFs and not on rotational DOFs of mass and stiffness matrices of bolts. Furthermore it is confirmed that lumped mass-spring systems as models of bolt joints are effective models considering the facts that joint characteristics converged to constant values in some iterations and eignevalues from proposed method are in good agreement with ones from modal test.

• Coupled systems mechanics
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• 제7권3호
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• pp.321-331
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• 2018

When a cantilever beam with a lumped mass at its free end undergoes free transverse vibration, internal axial forces are produced in the beam. Such internal axial forces have an effect on free transverse vibration of the beam. This effect is studied in this paper. The equations of motion for the beam in terms of the generalized coordinates including the effect are derived. The method for determining free transverse vibration of the beam including the effect is presented. In numerical simulations, the results of free transverse vibration of the free end of the beam including and not including the effect are obtained. Based on comparison between the results obtained, the conclusions concerning the effect are given.

• 대한조선학회논문집
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• 제40권1호
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• pp.36-46
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• 2003

To investigate the affection of lumped mass and spring on the vibration power flow of cross-stiffened plate experiencing bending vibration, structural intensity analysis is done using the modal analysis based on assumed mode method. The numerical analysis is carried out varying the mass and spring constant and their attached positions. The results show that both the spring and the mass may cause to large variation of not only vibratory displacement but also vibratory power flow patterns in case of little change of natural frequencies, and the attachments near to excitation location can effectively reduce the magnitude of maximum structural intensity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.349-354
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• 1992

In this paper, a modal analysis is applied for a hung Euler-Bernoulli beam with a lumped mass. We first derive the equations of motion using the Hamilton's principle. Then regarding the tension of beam as constant, we characterize the eigenfrequencies and the feature of eigenfunctions. The approximation employed here is corresponding that the lumped mass is sufficiently large than that of beam. Finally we compare the eigenfrequencies derived here with those obtained based on the Southwell's method.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권3호
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• pp.243-259
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• 2016

The Richards equation for water movement in unsaturated soil is highly nonlinear partial differential equations which are not solvable analytically unless unrealistic and oversimplifying assumptions are made regarding the attributes, dynamics, and properties of the physical systems. Therefore, conventionally, numerical solutions are the only feasible procedures to model flow in partially saturated porous media. The standard Finite element numerical technique is usually coupled with an Euler time discretizations scheme. Except for the fully explicit forward method, any other Euler time-marching algorithm generates nonlinear algebraic equations which should be solved using iterative procedures such as Newton and Picard iterations. In this study, lumped mass and distributed mass in the frame of Picard and Newton iterative techniques were evaluated to determine the most efficient method to solve the Richards equation with finite element model. The accuracy and computational efficiency of the scheme and of the Picard and Newton models are assessed for three test problems simulating one-dimensional flow processes in unsaturated porous media. Results demonstrated that, the conventional mass distributed finite element method suffers from numerical oscillations at the wetting front, especially for very dry initial conditions. Even though small mesh sizes are applied for all the test problems, it is shown that the traditional mass-distributed scheme can still generate an incorrect response due to the highly nonlinear properties of water flow in unsaturated soil and cause numerical oscillation. On the other hand, non oscillatory solutions are obtained and non-physics solutions for these problems are evaded by using the mass-lumped finite element method.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.313-321
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• 2012

Vibration analysis of a thin-walled structure can be performed with a consistent mass matrix determined by the shape functions of all degrees of freedom (d.o.f.) used for construction of conventional stiffness matrix, or with a lumped mass matrix. In similar way stability of a structure can be analysed with consistent geometric stiffness matrix or geometric stiffness matrix with lumped buckling load, related only to the rotational d.o.f. Recently, the simplified mass matrix is constructed employing shape functions of in-plane displacements for plate deflection. In this paper the same approach is used for construction of simplified geometric stiffness matrix. Beam element, and triangular and rectangular plate element are considered. Application of the new geometric stiffness is illustrated in the case of simply supported beam and square plate. The same problems are solved with consistent and lumped geometric stiffness matrix, and the obtained results are compared with the analytical solution. Also, a combination of simplified and lumped geometric stiffness matrix is analysed in order to increase accuracy of stability analysis.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.108-115
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• 2002

This paper suggests a new analysis algorithm for the time historical response of three dimensional rectilinear structure which is frequently found in a pipe line system of plant by the combination of the transfer stiffness coefficient method(TSCM) and the Newmark method. The present analysis algorithm for a time historical response can improve the computational accuracy and time remarkably owing to advantages of the TSCM in comparison with transfer matrix method(TMM). The structural system is modeled as a lumped mass system in this method. The analysis algorithm was formulated far the three dimensional rectilinear structure. We confirmed the validity of the present algorithm by comparing the numerical computation results of TSCM with those of TMM.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.637-642
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• 2000

This paper suggests new analysis algorithm for tile dynamic response of three dimensional structure which is frequently found in pipe line system of plant by the combination of the transfer stiffness coefficient method(TSCM) and Newmark method. Presented analysis algorithm for dynamic response can improve the computational accuracy remarkably owing to advantages of tile TSCM in comparison of transfer matrix method(TMM). Analysis system was modeled as a lumped mass system in this mettled. The analysis algorithm for dynamic response was formulated for the three dimensional structure. The validity of the this method is demonstrated through the results of numerical experiment for simple computational model by the TSCM and TMM.

• 한국해양공학회지
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• 제32권6호
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• pp.466-473
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• 2018

This paper presents an estimation method for the static configuration of a steel lazy wave riser (SLWR) using the dynamic relaxation method applied to estimate the configuration of structures with strong geometric non-linearity. The lumped mass model is introduced to reflect the flexible structural characteristics of the riser. In the lumped mass model, the tensions, shear forces, buoyancy, self-weights, and seabed reaction forces at nodal points are considered in order to find the static configuration of the SLWR. The dynamic relaxation method using a viscous damping formulation is applied to the static configuration analysis. Fictitious masses are defined at nodal points using the sum of the largest direct stiffness values of nodal points to ensure the numerical stability. Various case studies were performed according to the bending stiffness and size of the buoyancy module using the dynamic relaxation method. OrcaFlex was employed to validate the accuracy of the developed numerical method.