• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1192-1198
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• 2008

In this paper, the vibration and shock of an HDD car-holder are reduced through vibration analysis and a structural modification. In order to identify the exciting frequency components of vibration and shock, vibration signals are measured and analyzed from the wind shield or dashboard. In addition, the modal test for the current HDD car-holder is performed to investigate the dynamic characteristics of the car-holder. From these experiments, it is found that the exciting frequencies coincide to the natural frequencies of the car-holder. For the purpose of avoiding resonance, some FEM simulations are carried out and then structural modifications are made for the car-holder. Based on the results of simulations, a prototype of new car-holder are manufactured and tested to demonstrate the reduction of vibration and shock. It is verified by the test that a considerable amount of vibration and shock are reduced.

• 한국안전학회지
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• 제26권5호
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• pp.13-16
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• 2011

The vibration and shock of the opto-electronic protective device was induced mechanical failure or fail to work correctly. In order to identify the exciting frequency components of vibration and shock, vibration signals are measured and analyzed from the mechanical power press. In addition, the modal test for the opto-electronic protective device was performed to investigate the dynamic characteristics. Some FEM simulations were carried out and then anti vibration mount was made for opto-electronic protective device. Based on the results of simulations, some kind of rubber mounts were tested to demonstrate the reduction of vibration and shock. It was verified by the test that a considerable amount of vibration and shock were reduced.

• 드라이브 ㆍ 컨트롤
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• 제18권4호
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• pp.65-71
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• 2021

In this paper, the development of a vibration reduction device for hydraulic breakers was studied. Generally, a hydraulic breaker generates shock vibrations while working. When using vibration-proof rubber, shock vibrations are reduced, but without this, shock vibrations are repeatedly generated. Such repeated shock vibrations not only lower the fatigue strength of hydraulic breakers and excavators equipped with them but also increase the fatigue of the workers. This paper proposes the possibility of reducing shock vibration by using a dynamic vibration absorber.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.490-495
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• 2001

This paper deals with an analysis and countermeasure for improving the shock performance of laptop computers. The shock analysis is carried out by using the commercial program of LS-DYNA3D. Also the analysis is verified by the measurements from modal tests and shock tests. The available countermeasures are investigated theoretically and experimentally to find the effective methods of reducing the shock acceleration on hard disk driver during one side fall test. The hard disk drive is the most sensitive part in a laptop computer. This research shows the effects of the spring constant of rubber pad, the reinforcement of mechanical parts and the location of a hard disk driver, on the shock reduction.

• 한국항공우주학회지
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• 제36권3호
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• pp.285-290
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• 2008

파이로 충격은 고주파 영역까지 큰 가속도가 유발되는 천이 진동 현상으로 발사체에서는 주로 화약에 의한 분리 장치의 작동에 의해 발생하게 된다. 일반적인 발사체의 경우 단 분리, 페어링 분리, 위성 분리 이벤트에서 파이로 충격이 발생하게 되는데 이에 의해 위성 또는 발사체의 전자 장비가 비정상적인 기능을 보이거나 작동 불능 상태가 될 수 있다. 본 논문에서는 이러한 파이로 충격의 특성을 소개하고 PEEK 와셔를 적용한 충격저감장치를 실제 전자 장비에 적용하여 그 효과를 살펴보았다. 충격저감장치의 적용에 의해 고주파 영역에서의 충격 저감 효과가 있음을 확인하였고 저주파에서의 진동 특성에는 영향을 끼치지 않음을 시험을 통해 검증하였다.

• 한국소음진동공학회논문집
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• 제13권9호
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• pp.679-687
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• 2003

Shock wave reduction in electrorheological(ER) smart structures is studied. ER insert is a composite structure comprising two elastic outer layers between which is sandwiched layer of ER fluid. When a voltage is applied across the outer layers. the shear modulus and the loss factor of the ER fluid are enabled, and thus the dynamic properties of the composite structure is altered. For the shock wave reduction in a hull mount of a submerged structure, ER inserts are made on the hull mount structure. To investigate the ER insert shape. many types of ER insert pattern are considered. Modal test of ER insert structures is performed to obtain the mode shapes, natural frequencies and the acceleration transmissibility. The acceleration transmissibility is reduced at such a frequency region when an electric field is applied. It is observed that the natural frequencies and mode shapes can be tunable by applying electric field. The ER-inserted hull mount is installed in an integrated system and the overall performance of shock wave reduction is tested. The possibility of shock wave reduction in the hull mount is demonstrated.

• 한국농공학회지
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• 제17권4호
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• pp.3962-3969
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• 1975

1. When the frame of the experimental apparatus was directly fixed on the platform, result from the spectrum density analysis showed that the generated vibration frequecy of the system was nearly-same as the system's own characteristic vibration frequency, 80Hz, in the case of the forcing vibration frequency was 7.5 to 22.5Hz. The reduction ratio of acceleration by balanced type model compare to non-balanced type one was 26.66 percent. 2. When the frame of experimental apparatus was fixed on the platform with putting a shock absorbing rubber between the frame and the platform, the generated vibration frequency of the system was same as forcing vibration frequency. When either frequency or the amplitude of the forcing vibration was increased, the acceleration ratio was increased too. The average reduction ratio was resulted 44.77 per cent. It was concluded that this method of acceleration measurement(the method using a shock absorbing rubber) was a reaonable method, because actual machine will work under such condition. As the vibration frequency and aptitude were increased, the absolute magnitude of acceleration was increased. 3. unbalanced rotating parts, and unbalanced moment of inertia of links were supposed to be causing factors of residual vibration in spite of using the balanced type oscillating mole drainer. This fact suggested that the attachment of the counter weight on the rotating parts which satisfy the condition mw$.$rw=m0e, was necessary. And also, it was expected that the shock absorbing effect could be improved by putting the shock absorbing materials between the moving parts and their supports.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.92-97
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• 2003

By using a centerbody injection, an effort to reduce shock assoicated noise is made in an underexpanded sonic nozzle with an exit diameter of 10mm. The centerbody or micro nozzle, aligned with the axis of the main jet has an o.d. of 2mm and i.d. of 1.5mm. When measured at 90$^{\circ}$ relative to the main jet the farfield noise spectra showed that the screech tones and broadband shock associated noise can be significantly reduced simply by varying the length of the centerbody and/or mass fraction of the microjet. The maximum reduction in overall sound pressure level (OASPL) was as much as 9 and 4 ㏈ at fully expanded jet Mach numbers Mi of 1.3 and 1.5, respectively, when the length of the centerbody was varied from 0 to 4 main nozzle diameters without blowing. With the aid of the blowing, the maximum reduction in OASPL increased to 12 and 7 ㏈ at M$\sub$j/=1.3 and 1.5, respectively. The impact pressure field in the main jet plume strongly suggested that the reduced periodic pressure distribution in the shear layers and/or centerline is responsible for the reduced screech and broadband shock associated noise. Therefore, the steady blowing by a micro centerbody is a promising technique for shock noise reduction in a supersonic jet.

• 한국소음진동공학회논문집
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• 제19권9호
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• pp.892-898
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• 2009

In this paper, a cause of a shock of an industrial chop saw is identified by experimental method and the shock is reduced by structural modifications. For the shock identification, vibration signals are measured by an accelerometer when the chop saw operates. Through some experiments, it is found that the shock is occurred by a slip between a spindle and a wheelwasher of the chop saw. To reduce the shock, One method is to lower the mass moment of inertia of the wheelwasher and the angular rotating acceleration of it. Another method is to broaden a contact area between the wheelwasher and the spindle. After designing and analyzing the wheelwasher and the spindle mechanically, a prototype of them is built. With the manufactured prototype, the performances and design requirements of them are experimentally verified by the response measurements.

• 한국포장학회지
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• 제11권1호
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• pp.17-24
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• 2005

During handling unitized products, they are subjected to a variety environmental hazards. Shock and vibration hazards are generally considered the most damaging of the environmental hazards on a product, and it may encounter while passing through the distribution environment. A major cause of shock damage to products is drops during manual handling. The increasing use of unitization on pallets has been resulted in a reduction in the manual handling of products and with it a reduction in the shock hazards. This has caused and increasing interest in research focused on vibration caused damage. the use of pallets as a base for unitizing loads, aids in the mechanical handling, transportation and storage of products. Besides aiding in the handling, transportation and storage of products, a pallet also acts on and interface between the packaged goods and the distribution environment. The determination of the impact deformation of the cushioning materials such as tray cup (polymeric foam) and corrugated fiberboard pad must be carried out to design the proper packaging system providing adequate protection for the fruit, and to understand the complex interaction between the components of fruit when they relate to expected transportation vibration inputs. In this study, the theoretical analysis of impact deformation for cushioning materials by dynamic vibration. The impact deformations of SW and DW corrugated fiberboard pad in acceleration amplitudes of 0.25 G-rms and 0.5 G-rms that were usually generated in transport vehicles during distribution environments were very small compare with the thickness of corrugated fiberboard pad. The maximum of vibration acceleration level of tray cup by vibration impact was about 3.2 G-rms. The theoretical allowable acceleration (G-factor) of the pear was 0.7102 G-rms, and the maximum dynamic deformation estimated within G-factor was about 1 mm.