• 한국소음진동공학회논문집
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• 제13권11호
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• pp.882-889
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• 2003

This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using the flexible multibody dynamic analysis and the finite element one. This method is executed in 3 steps. In the 1st step, time dependent quantities such as dynamic loads, modal coordinates and gross body motion of the flexible body are calculated through a flexible multibody dynamic analysis. And frequency response functions of those time dependent quantities are computed through Fourier transforms. In the 2nd step, acoustic pressure coefficients are obtained through structure-acoustic coupling analyses by the finite element method. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2960-2967
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• 2021

In this work, a new hardening model is proposed for the depth-dependent hardness of ion-irradiated polycrystals with obvious grain size effect. Dominant hardening mechanisms are addressed in the model, including the contribution of dislocations, irradiation-induced defects and grain boundaries. Two versions of the hardening model are compared, including the linear and square superposition models. A succinct parameter calibration method is modified to parametrize the models based on experimentally obtained hardness vs. indentation depth curves. It is noticed that both models can well characterize the experimental data of unirradiated polycrystals; whereas, the square superposition model performs better for ion-irradiated materials, therefore, the square superposition model is recommended. In addition, the new model separates the grain size effect from the dislocation hardening contribution, which makes the physical meaning of fitted parameters more rational when compared with existing hardness analysis models.

• 한국기계가공학회지
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• 제19권3호
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• pp.36-41
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• 2020

Mechanical systems installed in transport devices, such as vehicles, airplanes, and ships, are mostly subject to translational accelerations at the joints during operations. This base acceleration excitation has a large influence on the performance of the system, therefore, its response must be well analyzed. However, the existing methods for dynamic analysis of structures have some limitations in use. This study presents a new numerical method using relative acceleration to solve these limitations. If the governing equation of motion is linear and the mass matrix, the damping matrix, and the stiffness matrix are constant over time in the finite element analysis, the proposed method can be applied to the transient behavior analysis and the harmonic response analysis of the structure. Because it is not necessary to introduce a virtual mass and the rigid body motions are removed from the analysis, it is possible to use not only the direct integration method in the time domain but also the mode superposition method to obtain the dynamic responses. This paper demonstrates with three examples how the present method is suitable for the dynamic analysis of a structure with multi-degree of freedom.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.361.1-361
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• 2002

Coupling adjacent steel frame using elastic dampers fer control of response to low and moderate dynamic event is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristic, mainly modal damping ratio and modal frequency, of damper linked linear adjacent steel frame for fractical use. Dynamic response of steel frame linked by hydraulic-excitation method. (omitted)

• 콘크리트학회지
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• 제11권1호
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• pp.279-288
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• 1999

콘크리트 구조물의 크리프해석은 주로 크리프식의 중첩원리에 기초한 방법에 의해 수행되고 있다. 그러나 크리프식의 중첩을 응력이 증가하거나 일정할 경우에는 비교적 정확한 예측이 가능하지만, 응력이 감소하는 경우에는 상당한 오차를 나타낸다. 이것은 지속하중과 응력감소 과정에서 크리프와 관련된 콘크리트의 성질이 변화되므로 크리프 회복을 크리프 식의 중첩으로 정확하게 모사할수 없기 때문이다. 따라서, 본 연구에서는 감소와 증가를 반복하는 응력 이력을 지니는 콘크리트 구조물의 좀더 정확하고 합리적인 장기거동 해석을 위하여 응력의 감소를 단순히 크리프식의 중첩에 의해 해석한 기존의 방법과는 달리 크리프식과 크리프 회복식으로 표현하여, 소위 2함수 방법(two-function method)를 콘크리트구조물의 해석에 적용하는 방법을 제시하였다. 본 연구의 2함수방법을 콘크리트 구조물의 장기거동 해석을 적용하기 위해, 시간단계 동안 다양한 응력 변화에 대하여 크리프 변형도 증분량을 계산하는 방법을 제시하였다. 본 연구의 해석방법에 의해서 해석된 결과를 기존의 크리프식의 중첩에 의한 결과 및 기존의 실험결과들과 비교 분석한 결과, 기존의 중첩법은 실험결과와 많은 차이를 보이고 있으나 본 연구의 해석방법은 실험결과와 잘 맞고 있음을 보여주고 있다. 따라서, 크리프회복식을 이용하는 본 연구의 해석방법은 기존의 크리프식의 중첩방법이나 기존의 설계기준에 비해 변화하는 응력이력 하에서의 콘크리트 구조물의 크리프거동을 더 정확하게 서술할 수 있는 방법으로서 앞으로 설계기준 작성과 실제 구조물 해석에 효율적인 응용이 기대되고 있다.

• 대한조선학회지
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• 제13권1호
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• pp.17-23
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• 1976

Some methods of analysis of rectangular plates under distributed load of various intensity with interior supports are presented herein. Analysis of many structures such as bottom, side shell, and deck plate of ship hull and flat slab, with or without internal supports, Floor systems of bridges, included crthotropic bridges is a problem of plate with elastic supports or continuous edges. When the four edges of rectangular plate is simply supported, the double Fourier series solution developed by Navier can represent an exact result of this problem. If two opposite edges are simply supported, Levy's method is available to give an "exact" solution. When the loading condition and supporting condition of a plate does not fall into these cases, no simple analytic method seems to be feasible. Analysis of a simply supported rectangular plate under irregularly distributed loads of various intensity with internal supports is carried out by applying Navier solution well as the "Principle of Superposition." Finite difference technique is used to solve plates under irregularly distributed loads of various intensity with internal supports and with various boundary conditions. When finite difference technique is applied to the Lagrange's plate bending equation, any of fourth order derivative term in this equation produces at least five pivotal points leading to some troubles when the resulting linear algebraic equations are to be solved. This problem was solved by reducing the order of the derivatives to two: the fourth order partial differential equation with one dependent variable, namely deflection, is changed to an equivalent pair of second order partial differential equations with two dependent variables. Finite difference technique is then applied to transform these equations to a set of simultaneous linear algebraic equations. Principle of Superposition is then applied to handle the problems caused by concentrated loads and interior supports. This method can be used for the cases of plates under irregularly distributed loads of various intensity with arbitrary conditions such as elastic supports, or continuous edges with or without interior supports, and this method can also be solve the influence values of deflection, moment and etc. at arbitrary position of plates under the live load.

• 한국항해학회지
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• 제25권4호
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• pp.407-415
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• 2001

In the present study, irregular disturbances to ship dynamics is proposed, where irregular disturbances implying irregular wave and the fluctuating component of wind for the evaluation of automatic steering system of ship in following seas. Prediction method based on the principle of linear superposition. Irregular wave disturbances in following seas is calculated by frequency variation method. The mathematical model of each element of an automatic steering system is derived, which takes account of a few non-linear mechanisms. PD(Proportional-Derivative) controller and low-pass filter with a weather adjustment are adopted to modelling the characteristics of an autopilot. Performance index is introduced from the viewpoint of energy saving, which derived from the concept of energy loss on ship propulsion. Finally, the present methods are applied to two typical types of ship ; an ore carrier and a fishing boat. The various effects of control constants of autopilot on propulsive energy loss are investigated

• Journal of Power Electronics
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• 제17권6호
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• pp.1480-1489
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• 2017

In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.211-229
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• 2004

The main purpose of this paper is the numerical analysis of the non-linear seismic response of a RC building mock-up. The mock-up is subjected to different synthetic horizontal seismic excitations. The numerical approach is based on a 3D-model involving multilayered shell elements. These elements are composed of several single-layer membranes with various eccentricities. Bending effects are included through these eccentricities. Basic equations are first written for a single membrane element with its own eccentricity and then generalised to the multilayered shell element by superposition. The multilayered shell is considered as a classical shell element : all information about non-linear constitutive relations are investigated at the local scale of each layer, whereas balance and kinematics are checked afterwards at global scale. The non-linear dynamic response of the building is computed with Newmark algorithm. The numerical dynamic results (blind simulations) are considered in the linear and non linear cases and compared with experimental results from shaking table tests. Multilayered shell elements are found to be a promising tool for predictive computations of RC structures behaviour under 3D seismic loadings. This study was part of the CAMUS International Benchmark.

• 한국강구조학회 논문집
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• 제12권2호통권45호
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• pp.151-165
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• 2000

교량에 통행하는 차량의 대형화와 통행교통량의 급격한 증가로 인하여 교량부재에서 피로손상이 많이 보고되고 있다. 교량부재의 피로손상을 방지하고, 안전을 유지하기 위해서 합리적인 피로조사를 실시하여야 한다. 교량의 피로설계에서는 차량 1대만 재하 시키는 방법을 채택하고 있으나, 실제 교량의 상부에 차량이 1대만 통과하는 일은 거의 없다. 통상 교량의 상부에는 복수의 차량이 동시에 재하되므로 합리적인 피로설계를 위해서는 동시재하의 영향을 고려하여야 한다. 본 논문에서는 도로교를 통행하는 차륜하중에 대해 선형중첩법과 교통류의 몬테카를로 시뮬레이션에 의한 변동응력해석을 실시하고, 피로 손상도를 구함으로써 통행차량의 차축하중에 대한 동시재하의 영향에 대해 연구하였다.