• 한국소음진동공학회논문집
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• 제13권5호
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• pp.327-333
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• 2003

Several tests are performed to evaluate road booming noise. Baseline test delivers the information of road noise characteristics. Coupling effect between structure and acoustics is obtained from the mode shapes and the natural frequencies by the modal test. Equivalent stiffness at joint areas between chassis and car-body system can be determined by the input point inertance test. Noise sensitivity of body mounting point of a chassis part can be obtained from the noise transfer function test with input point inertance test. Operational deflection shape makes us analyze the actual vibration modes of the chassis system under actual leading and find noise sources very easily. Finally, the transfer path analysis is used to Identify noise Paths through the chassis system. The objectives and the procedures of the tests are described in this Paper Also, the guideline for efficient road noise evaluation test can be found.

• Journal of Computational Design and Engineering
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• 제3권3호
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• pp.215-225
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• 2016

In recent years, the automotive industry has known a remarkable development in order to satisfy the customer requirements. In this paper, we will study one of the components of the automotive which is the twist beam. The study is focused on the multicriteria design of the automotive twist beam undergoing linear elastic deformation (Hooke's law). Indeed, for the design of this automotive part, there are some criteria to be considered as the rigidity (stiffness) and the resistance to fatigue. Those two criteria are known to be conflicting, therefore, our aim is to identify the Pareto front of this problem. To do this, we used a Normal Boundary Intersection (NBI) algorithm coupling with a radial basis function (RBF) metamodel in order to reduce the high calculation time needed for solving the multicriteria design problem. Otherwise, we used the free form deformation (FFD) technique for the generation of the 3D shapes of the automotive part studied during the optimization process.

• 한국유체기계학회 논문집
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• 제12권3호
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• pp.26-30
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• 2009

This paper predicts the critical speeds of a 5MW industrial gas turbine by using commercial rotordynamic tool, DYNAMICS 4.3. The gas turbine is operated at 12,975 rpm on squeeze film dampers. The stiffness of the squeeze film dampers are estimated. The critical speeds of the gas turbine rotor are calculated to have a sufficient separation margin (2%) from the 1st bending mode and pass over 2 rigid body modes below 4,000 cpm. This paper discussed the coupling effects on the dynamic response of the gas turbine.

• 소음진동
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• 제7권4호
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• pp.571-578
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• 1997

Recently, many general-purpose packages for fluid-structure interaction problems have been announced. However, they have a lot of limitations to model structures in the fluid-structure interaction problems reasonably. Utilizing general-purpose packages such as MSC/NASTRAN and SYSNOISE, in this paper, a method to slove the radiation scattering problems with some accuracy in the fluid-structure interaction problems was developed. Using a simple model, the results from the presented method here are compared with those from SYSNOISE. The result shows quite a good agreement between the two methods. The problems, which could not be solved by SYSNOISE, were tried to solve with the presented method and results were presented. It was proved that this method could be safely used to solve fluid-structure interaction problems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.813-816
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• 1991

Direct-drive SCARA-type industrial robots are increasingly used in the assembly process of small mechanical parts as well as electronic components, which uses direct-drive (DD) motors instead of reduction gear-type conventional motors for the actuators of manipulator arms. There are many advantages in using DD motors for robots, such as no backlash, low friction, high mechanical stiffness capability for fast and precise arm control, and high repeatability of positioning. However, there exist a number of difficulties which must be overcome to ensure proper construction and operation; increasing effects of load veriation and nonlinear and coupling dynamics, severe vibration caused by resonance of the manipulator components and low mechanical damping, etc. In order to handle these difficulties, lots of efforts have been made such as reduction of the arm inertia and elimination of the resonance, Performance evaluation of a recently developed, domestic DD robot shows that it works excellently compared with conventional robots. It, however, requires proved reliability and price competitiveness against its foreign counterparts.

• Journal of Advanced Marine Engineering and Technology
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• 제22권3호
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• pp.328-336
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• 1998

Marine reduction gears are usually used to increase the propulsion efficiency of propellers for ships powered by medium and small sized high speed diesel engines. Most of shaft systems adopt flexible couplings to absorb the transmitted vibratory torque from the engines to the reduction gears and to prevent the chattering phenomenon of reduction gears. However some elastic couplings show non-linear characteristics due to the variable torque transmitted from the main engines and the change of ambient temperature. In this study dynamic characteristics of flexible couplings sare investigated and their effects upon various vibratory conditions of propulsion systems are clarified. A calculation program of torsional vibration for the propulsion systems are clarified. A calculation program of Results of the program developed are compared with ones of the existing linear method and propulsion systems with the elastic couplings the transfer matrix method is adopted which is found to give satisfied results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1045-1050
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• 2007

Equations of motion of rotating cantilever curved beams are derived based on a dynamic modeling method developed in this paper. The Kane's method is employed to derive the equations of motion. Different from the classical linear modeling method which employs two cylindrical deformation variables, the present modeling method employs a non-cylindrical variable along with a cylindrical variable to describe the elastic deformation. The derived equations (governing the stretching and the bending motions) are coupled but linear. So they can be directly used for the vibration analysis. The coupling effect between the stretching and the bending motions which could not be considered in the conventional modeling method is considered in this modeling method. The natural frequencies of the rotating curved beams versus the rotating speed are calculated for various radii of curvature and hub radius ratios.

• 한국소음진동공학회논문집
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• 제20권6호
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• pp.583-592
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• 2010

Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.

• Coupled systems mechanics
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• 제2권4호
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• pp.349-374
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• 2013

In this work we propose a novel procedure for direct computation of buckling loads for extreme mechanical or thermomechanical conditions. The procedure efficiency is built upon the von Karmann strain measure providing the special format of the tangent stiffness matrix, leading to a general linear eigenvalue problem for critical load multiplier estimates. The proposal is illustrated on a number of validation examples, along with more complex examples of interest for practical applications. The comparison is also made against a more complex computational procedure based upon the finite strain elasticity, as well as against a more refined model using the frame elements. All these results confirm a very satisfying performance of the proposed methodology.

• Structural Engineering and Mechanics
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• 제2권2호
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• pp.211-225
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• 1994

Responses of asymmetrical multistorey buildings to earthquakes are obtained by quasi-static code approach and real time dynamic analysis, using two different structural models. In the first model, all vertical members are assumed to be restrained at the slab levels and hence their end rotations, about horizontal axes, are taken as zero. In the second model this restriction is removed and the rotation is assumed to be proportional to the lateral stiffness of the member. A simple microcomputer based procedure is used in the analyses, by both models. Numerical examples are presented where results obtained from both the models are given. Effects of modelling on the response of three buildings, each with a different type and degree of asymmetry, are studied. Results for deflections and shear forces are presented and the effects of the type of model on the response are discussed.