• 한국자동차공학회논문집
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• 제12권1호
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• pp.145-152
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• 2004

This paper compares seat vibrations of a small passenger car and a SUV. The results also include the comparison of the human body accelerations and the ride values, such as the component ride values, and SEAT values of 12 axis accelerations obtained at the human body and seat track. The ride comfort evaluation is usually carried out by experiments of real cars which are expensive and sometimes may contain errors by passenger's postures. Simulations by computer, on the other hand, enable to solve these problems when the accuracy is proven. This paper, thus, also shows the correlation of human body vibration between experiments and computer simulations. For the computer simulation, korean dummy models are developed from the Hybrid III models by scaling the body data of Hybrid III to those of Korean men and women. From the comparison between the test data and simulation data, a nice correlation in trends was shown.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.671-675
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• 2001

Elastomers, which are engine mounts and body mounting rubbers, are traditionally designed for NVH use in vehicles, and they are designed to isolate specific unwanted frequencies. According to the measurement of the characteristics of engine mounts and body mounting rubbers, dynamic stiffness changes with respect to the driving miles accumulated in engine mounts and initial load in body mounting. This study looks at the variability in same engine mount properties, and the desired dynamic stiffness may increased with driving miles accumulated. And the dynamic stiffness of body mounting rubber changes very stiff above 150Hz.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.325.2-325
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• 2002

A new methodology is presented for the multi-degree-of-freedom vibration absorber for an elastically suspended rigid body with the planes of symmetry in general motion. Unlike the common single degree-of-freedom vibration absorber, the presented methodology makes use of both linear and rotational properties of the absorber. It is suggested that an absorber is designed separately for the in-plane and out-of-plane axes of vibration and combined the two cases for a six-degree-of-freedom absorber. (omitted)

• Journal of Advanced Marine Engineering and Technology
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• 제26권6호
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• pp.631-637
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• 2002

Two stroke low speed diesel engines are used as a power supplier not only for marine vessel but also diesel power plant with a benefit of its higher mobility and durability than the other thermal engines. However, there are some disadvantages such as the bigger vibrating excitation forces generated by high combustion pressure in cylinders which various kinds of vibrations are caused. In this paper, it is theoretically studied to control engine body vibration using dynamic vibration absorber. As an actual case, dynamic absorbers are designed for controlling X-mode vibration of 9K80MC-S engine on the diesel power plant and its performance is identified by the vibration test both in shop and site

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.409-414
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• 2007

Nowadays, with the advancement of computational mechanics, and vehicle dynamics simulation linked up with virtual testing laboratory(VTL) and virtual proving ground(VPG) technologies has become a useful method for analyzing numerous driving performances and diverse noise/vibration characteristics. In this paper, the analytical vehicle model based on multi-body dynamics theory was developed to investigate the vibration characteristics according to various road conditions. For the purpose, the whole vehicle parameters, each vehicle's part parameter, and part connecting elements such as spring, damper, and bush were measured by an experiment. Also, the vehicle dynamics model, which includes the front suspension, rear suspension, steering, front wheel, rear wheel, and body subsystems has been constructed for computer simulation. With the developed vehicle dynamics model, three forces and three moments measured at each wheel center were applied to evaluate and analyze dynamics and vibration characteristics for miscellaneous road conditions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.443-446
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• 2014

Recently the demand for natural gas as clean and safe energy due to concerns about global warming and interests in green ship is increasing. The dual fuel(DF) engine, one of environmentally friendly engines, is preferred for general merchant ships and power plants as well as LNG carriers. This is for the reasons of having higher efficiency and lower nitrogen and sulfur oxides emissions by operating on LNG fuel with a small amount of light fuel oil. In this study, the engine body vibration characteristics of 12V50DF in a generator set with engine-resilient-mounted, generator-rigid-mounted and flexible-coupling configuration are investigated through theoretical analysis and comprehensive vibration measurement. This analysis showed the dynamic behavior of engine excitation forces and seismic waves. And the suitable countermeasures for reducing vibration and safe operation are proposed.

• 대한기계학회논문집A
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• 제31권1호
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• pp.97-104
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• 2007

Vibration analysis of a rigid body supported by in-parallel linear springs can be greatly simplified by utilizing the conditions for a plane of symmetry. The vibration modes of an oscillatory system having plane of symmetry are classified into the in-plane and out-of-plane modes. From the viewpoint of screw theory, they represent respectively the vibration axes perpendicular to the plane of symmetry and lying in the plane of symmetry. In this paper, the sets of orthogonal and mutually intersecting three springs are used as resilient support of a rigid body. The geometrical conditions for the system to have a plane of symmetry and diagonalized stiffness matrix are presented. From the orthogonality of the vibration modes with respect to the inertia matrix, the geometrical relation between the reaction wrenches and the vibration modes are derived. This geometrical relation is then used to get the cubic design equation for the design of out-of-plane modes. The numerical design example of engine mounts is presented in order to explain the suggested design technique.

• 한국공작기계학회논문집
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• 제12권4호
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• pp.57-62
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• 2003

A fundamental structural design consideration for a vehicle system is the overall vibration characteristics in bending and torsion. Vibration characteristics of such vehicle system are mainly influenced by the static and dynamic stiffness of the vehicle body structure and also by the material and physical properties of the components attached to the vehicle body structure. In this paper, modeling techniques for the vehicle components are presented and the flexibility and mass effects of the components for the vibration characteristics of the vehicle are investigated. The $1^{st}$ torsional frequency is increased by attaching windshields to the B.I.W. (body-in-white), but the $1^{st}$ bending frequency is decreased by the mass effect. And also, the natural frequencies of the vehicle are large decreased by attaching bumpers, seats, doors, trunk-lid etc. But, suspension system rarely affects the natural frequencies of the vehicle. The study shows thai the dynamic characteristics of the vehicle system can be effectively predicted in the initial design stage.

• Physical Therapy Rehabilitation Science
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• 제10권3호
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• pp.278-288
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• 2021

Objective: The purpose of this study is to investigate the effect of stabilization exercise on whole-body vibration on pain, dysfunction, psychosocial factors, balance ability, and abdominal contraction with patients with low back pain. Design: A randomized controlled trial Methods: A total of 34 patients with low back pain were assigned randomly to experimental group (n=17) and control group (n=17). Both groups underwent a neuromuscular stabilization exercise program. In addition, the experimental group implemented the neuromuscular stabilization exercise program using whole-body vibration. All interventions were applied 60 min per session, 3 times per week for total 4 weeks. Numeric Rating Scale (NRS), Korean version of Oswestry Disability Index (K-ODI), Fear-Avoidance Beliefs Questionnaire (FABQ), balance ability, muscle thickness and contraction ratio were compared to evaluate the effect on intervention. Results: Both groups showed significant differences in NRS, balance ability, and muscle thickness in contraction, contraction ratio before and after intervention (p<0.05). In addition, the experimental group showed significant difference in the amount of change in NRS, balance ability and muscle thickness in contraction, contraction ratio values than the control group (p<0.05). Conclusions: Neuromuscular stabilization exercise program combined with whole-body vibration stimulation has been proven to be an effective and clinically useful method to decrease pain, dysfunction, increase balance ablilty, and transverse abdominis muscle thickness in contraction and contraction ratio for patients with low back pain.

• 한국소음진동공학회논문집
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• 제22권4호
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• pp.335-343
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• 2012

As a matter of fact, it has been not allowed to modify the shape of a vehicle body skeleton since the technical definition for the structure was fixed and the corresponding molds were developed. By the way, if it is available to apply an alternative to reinforce the skeleton without changing its mold, it must be much flexible to improve the performance qualities relevant to not only NVH(noise, vibration and harshness) but also crash and durability. Recently, a solution of so-called composite body becomes available for the need. We present a design method to insert the composite body inside a vehicle body skeleton in order to improve a structure-borne noise at the idle condition. The algorithms, topology optimization and design sensitivity analysis, are applied to mainly search the sensitive structural sections in the body skeleton and to extract the target stiffness of the sections. Inserting the composite bodies into the sensitive portions, it is predicted to achieve the countermeasures which can compromize the design availability in terms of the idle noise and weight. According to the validation result with test vehicles, the concerned noise transfer function is reduced and the idle booming noise is resultantly improved.