• Structural Monitoring and Maintenance
• /
• v.6 no.1
• /
• pp.33-46
• /
• 2019

In present study, Operational Modal Analysis (OMA) was employed to carry out the dynamic and vibration analysis of the threshing unit of the combine harvester thresher as a mechanical component. The main study is to find the causes of vibration and to decrease it to enhance the lifetime and efficiency of the threshing unit. By utilizing OMA, structural modal parameters such as mode shapes, natural frequencies, and damping ratio was calculated. The combine harvester was excited by engine to vibrate different parts and accelerometer sensor collected acceleration signals at different speeds, and OMA was utilized by nonparametric and frequency analysis methods to obtain modal parameters while vibrating in real working conditions. Afterwards, finite element model was designed from the thresher and updated using the data obtained from the modal analysis. Using the conducted analyses, it was specified that proximity of the thresher pass frequency to one of the natural frequencies (16.64 Hz) was the most important effect of vibration in the thresher. Modification process of the structure was carried out by increasing mass required for changing the natural frequency location of the first mode to 12.4 Hz in order to reduce resonance and vibration of the thresher.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.04a
• /
• pp.481-488
• /
• 2001

The HANARO in-chimney bracket was proposed as a structure which supports the guide tubes of irradiation facilities at the irradiation sites of CT, IR and OR4/5 in HANARO core for the reduction of flow-induced vibration and seismic response of the irradiation facilities. For the evaluation of the structural integrity of the in-chimney bracket, its finite element model is developed. The seismic response analysis was performed for the in-chimney bracket and related reactor structures, under the response spectrum of OBE and SSE. The analysis results show that stress values of the in-chimney bracket and reactor structures for the seismic loads are within the ASME code limits. It is also confirmed that its fatigue usage factor is much less than 1.0. For the verification of the implementation effects of the in-chimney bracket, the vibration level of the guide tube of the instrumented fuel assembly, which is subjected to fluid-induced vibration, was measured and analyzed. The vibration analysis results demonstrate that the vibration level of the instrumented fuel assembly has been remarkably reduced after installing the in-chimney bracket. Therefore, when the in-chimney bracket is installed at the reactor chimney, any damage on the structural integrity is not expected.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.3 s.21
• /
• pp.43-50
• /
• 2006

This paper is concerned with the natural periods of ambient vibration and eigenvalue analysis. Ambient vibration tests were conducted to four bearing-wall reinforced concrete buildings ranging from twelve to nineteen stories. The performance of modeling in eigenvalue analysis was investigated using consideration of rigidity out of the plane in the slab and the non-structural bearing wall. Measured natural period was also compared with the value by the KBC2005. Natural period of the short direction in eigenvalue analysis is well fitted with the measured one. In the other hand, Natural period of the long direction in eigenvalue analysis is slightly more overestimated than the measured one. Natural period of the long direction in eigenvalue analysis was found to be enhanced by considering the effect of the stiffness out of the plane of the slab and non-structural wall in the structural modeling.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1998.04a
• /
• pp.357-364
• /
• 1998

In this paper, ground vibration analysis methods for train transit on bridges are studied. Train loads acting on the piers are evaluated considering the interactions between the trains and the bridge. The 2D in-plane wave propagation method and the axisymmetric wave propagation method are used in the ground vibration analysis, and then the results of the ground vibration are compared. A modified axisymmetric method is presented, which can consider the effect of the train loadings on a series of piers as the train moves.

• Journal of the Semiconductor & Display Technology
• /
• v.2 no.2
• /
• pp.25-30
• /
• 2003

In the case of a vibration sensitive equipment, it require a vibration free environment to provide its proper function. Especially, lithography and inspection device, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved Giga Class semi conductor wafers. This high technology equipments require very strict environmental vibration criteria in proportion to the accuracy of the manufacturing. In this paper, the dynamic analysis and modal test were performed to evaluate the dynamic properties of the constructing clean room structure. Based on these results, a structural dynamic modification(SDM) were required to satisfiy the vibration allowable limit for pression machine. Therefore, in order to improve the dynamic stiffness of clean room structure, the VSD system which can control the force applied on structure, were adopted and its utility were proved from dynamic test results of the improved structure after a modification work.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.105-112
• /
• 1994

In a local vibration analysis of a large steel frame, a large eigenvalue problem results. Due to computer storage and the expense of a complete solution, it is desirable to minimize the size of the resulting matrices. A new and efficient method of local vibration analysis for large steel frames is presented. It reduces the order of dynamic matrices by dynamic condensation method. Examples are given for local vibration of a plane frame. Results are compared to the complete solution of the full eigenvalue problem.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.89-94
• /
• 1994

Latticed domes take form a curved surface by arranged members with certain patterns. For this reason, it is possible for the characteristics of vibration to complicate by change of various parameters of dome; grid-pattern, boundary condition and ratio of radius-height etc. Therefore, it is important to clarify the effect by these parameters before generalized dynamic response analysis. So this study deals with free vibration analysis of latticed domes and makes clear an effect of shape coefficient, that is, geometrical characteristics of latticed domes, on the vibration characteristics.

• Structural Engineering and Mechanics
• /
• v.6 no.5
• /
• pp.517-527
• /
• 1998

This paper describes an exact method of analysis for natural vibration of diagonal networks by considering an equivalent cyclic periodic structure and adopting the double U-transformation technique. Both a lumped mass system and a distributed mass system are considered to investigate the diagonal networks. The exact solution for the frequency equations and the natural modes of the networks can be derived. As numerical examples, square diagonal cable networks with different meshes are worked out.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.281-284
• /
• 2014

Unlike ordinary vehicle chassis frame, chassis frame of military vehicle is long and that is operated in harsh driving environment in middle of war. Thus, because large dynamic loads is acting on the frame, it is important to secure the durability of the frame based on the structural dynamic characteristic analysis. The purpose of the study is that the chassis frame is optimized to secure durability of the chassis frame of the military vehicle according to the structural dynamic characteristic analysis. Also, structure optimization are performed using parametric optimization and topology optimization methods.

• Journal of the korean Society of Automotive Engineers
• /
• v.14 no.5
• /
• pp.69-82
• /
• 1992

Vibration of intake menifold is important as it could worsen the noise levels radiated from surface itself and support bracket, and it eventually leads to the failures of a Throttle Position Sensor and an Idle Air Control Valve. In this study, structural modification method is proposed to reduce structural vibration of an intake manifold system. At first, vibration problems are identified through tests on a running engine. Then modal data acquired by modal testing and finite element analysis are helpful to understand vibration mechanism of the system, and used as the design guide when structural modifications are attempted. After the system model is validated by comparison of the modal data obtained from analysis and experiment, iterative calculations are performed to find optimized structure of the system by finite element analysis. As a result, a newly designed plenum bracket is suggested in such a way that the intake manifold is stiffened, and that design of the support bracket is suggested in such a way that the intake manifold is stiffened, and that design of the support bracket is changed in terms of bolting position, thickness, shape, and minimum weight increase. Finally, it is shown that a new design achieves a significant reduction of vibration of an intake manifold system and it is confirmed by tests on a running engine.