• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
• /
• pp.848-853
• /
• 1994

This paper describes the concept and basic technique of measuring torsional operational deflection shapes using a laser-based torsional vibration meter, a dual-channel FFT analyzer and operational deflection shapes software running on a PC. Torsional Operational Deflection Shapes (TODS) is defined similar to ODS (Operational Deflection Shapes), with the exception the TODS designates the operational deflection shapes of structures vibrating in a rotational, or angular, degree of freedom. Thus the TODS measurements can be applied to rotating shafts and the results of such a measurement are shown. In some cases it may be great benefit to apply order tracking and/or synchronous time domain averaging techniques in order to avoid smearing and reduce noise problems.

• Smart Structures and Systems
• /
• 제16권6호
• /
• pp.1049-1068
• /
• 2015

In the paper, the authors propose the application of operational deflection shapes (ODS) for the detection of structural changes in technical objects. The ODS matrix is used to formulate the spatial filter that is further used for damage detection as a classical modal filter (Meirovitch and Baruh 1982, Zhang et al. 1990). The advantage of the approach lies in the fact that no modal analysis is required, even on the reference spatial filter formulation and other components apart from structural ones can be filtered (e.g. harmonics of rotational velocity). The proposed methodology was tested experimentally on a laboratory stand, a frame-like structure, excited from two sources: an impact hammer, which provided a wide-band excitation of all modes, and an electro-dynamic shaker, which simulated a harmonic component in the output spectra. The damage detection capabilities of the proposed method were tested by changing the structural properties of the model and comparing the results with the original ones. The quantitative assessment of damage was performed by employing a damage index (DI) calculation. Comparison of the output of the ODS filter and the classical modal filter is also presented and analyzed in the paper. The closing section of the paper describes the verification of the method on a real structure - a road viaduct.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.232-237
• /
• 2006

Operation deflection shapes(ODS) is defined as a motion of structure at particular frequency. The ODS is eligible to show any types of structural motions while the modes supply solutions only to linear and stationary motion. The principal vibration source of an auto teller machine(ATM) case was occurred due to resonance which was found by modal analysis. To reduce the vibration of ATM case, the motion of the case was visualized using ODS analysis, which can suggest how to modify the structure. As a result the vibration of the ATM case was greatly reduced with a stiffening bar between the opposite plates.

• Journal of Biosystems Engineering
• /
• 제29권2호
• /
• pp.101-108
• /
• 2004

The objectives of this study were to determine the natural frequency of a walking-type cultivator's handle using a modal analysis, to determine whether or not the handle resonates with forcing frequency induced by its engine, and to determine a method to reduce the handle vibration using a technique of the operational deflection shapes(ODS). Results of the study are as follows: The natural frequencies of the handle up to third harmonics were found to be 20.4, 22.5 and 92.1 Hz in the vertical direction and 14.9, 93, and 132 Hz in the horizontal direction. It was found that the handle does not resonate with the forcing frequency of the engine, which is 52 Hz. The operational deflection shape analysis revealed the deflected shapes of the handle in the vertical and horizontal directions and suggested that the handle vibration can be reduced by adding some mass to the place where the largest deflection occurs. Attaching of 1.1 kg mass adjacent to the largely deflected area resulted in reductions of vibration from 9.45 to 8.03 m/s$^2$ in x-axis direction from 3.89 to 3.16 m/s$^2$ in y-axis direction and from 7.89 to 3.09 m/s$^2$ in z-axis direction, which are respectively 15, 19 and 61% reductions. The total vibration level was reduced by 29%, indicating that mass-adding method by the ODS is very effective for reducing the handle vibrations of the cultivators.

• Journal of Biosystems Engineering
• /
• 제31권3호
• /
• pp.139-145
• /
• 2006

A previous study showed that the handle vibration of a walking type cultivator can be reduced by adding a mass to the handle. This study was conducted to determine the optimum magnitude and location of the mass to be added for the same cultivator. The possible locations of added mass were determined by investigating nodal points of the handle vibration by an ODS (operational deflection shapes) test at an engine frequency of 52 Hz. The optimum location was then determined as one that moved the nodal points to the hand grip of the handle bar. To determine the optimum magnitude of the mass, the possible locations were added by a mass from 0.2 to 2.0 kg in an increment of 0.2 kg. The optimum magnitude was then determined as a mass which minimized the vibration level at the hand grip. For the case of this study, the z-axis vibration at the hand grip was reduced from $2.67m/s^2\;to\;0.88m/s^2$ resulting in a reduction of 67% and the total vibration from $4.09m/s^2\;to\;3.27m/s^2$ resulting in a 20% reduction by adding an optimum mass to the optimum location.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.944-949
• /
• 2003

A High-speed cutter, a kind of electric tool is studied to reduce its vibration and noise. The experimental modal analysis, the operational deflection shapes(ODS) and the time domain analysis(TDA) are used in the SMS software to analyze the vibration signals from an operating high-speed cutters under steady state operating condition. The second mode and fifth m,)do of the base plate coincide with the driving frequencies of the motor, And the vibration of the wheel cover is caused by the gap between the main wheel cover and the sub wheel cover. The structural modification for the base plate was done to reduce the vibration. The effect of modification is verified through the test.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2013년도 추계학술대회 논문집
• /
• pp.600-604
• /
• 2013

A CTBA(Coupled Torsion Beam Axle) is a general type for rear suspension of small/compact sedans. It connects left and right knuckles using torsion beam axle and trails rear wheels. Therefore, a CTBA performs a main role of ride & handing. But, a CTBA suspension has main bending mode around 120Hz and causes road booming noise in the interior of a car. Therefore, the mode control of a CTBA is very important for reducing road noise. In this paper, we optimized the shape of a CTBA to reduce road noise considering R&H performance, simultaneously. The vibration mechanism of CTBA was investigated using ODS(Operational Deflection Shape) and mode shape.

• Journal of Biosystems Engineering
• /
• 제32권1호
• /
• pp.6-12
• /
• 2007

This study was conducted to investigate the drying characteristics of oak mushroom using stationary far-infrared dryer. Drying characteristics was measured at drying air velocity 0.4 to 0.6 m/s and drying temperature 50, 60, and 70$^{\circ}C$, respectively. With high temperature of far-infrared heater and fast air velocity, the far-infrared drying rate of double air flow system was better than conventional heated-air drying as much as 39%. The value of color difference (E) of oak mushroom before and after drying was 8.95 by using heated air drying and was in the range of 3.76$\sim$6.98 by the far-infrared drying. The shrinkage rate of oak mushroom after heated air drying was higher than that of air velocity, 0.6 m/s of far-infrared drying conditions, and was lower than that of air velocity, 0.4 m/s of far-infrared drying conditions. The content of free amino acid was higher in far-infrared drying than heated air drying.