• Steel and Composite Structures
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• v.22 no.5
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• pp.1001-1018
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• 2016

The purpose of this paper is to compare the structural responses obtained from the stochastic analysis of a suspension bridge subjected to uniform and partially correlated seismic ground motions, using different spatial correlation functions commonly used in the earthquake engineering. The spatial correlation function employed in this study consists of a term that characterizes the loss of coherency. To account for the spatial variability of ground motions, the widely used four loss of coherency models in the literature has been taken into account in this study. Because each of these models has its own characteristics, it is intended to determine the sensitivity of a suspension bridge due to these losses of coherency models which represent the spatial variability of ground motions. Bosporus Suspension Bridge connects Europe to Asia in Istanbul is selected as a numerical example. The bridge has steel towers that are flexible, inclined hangers and a steel box-deck of 1074 m main span, with side spans of 231 and 255 m on the European and Asian sides, respectively. For the ground motion the filtered white noise model is considered and applied in the vertical direction, the intensity parameter of this model is obtained by using the S16E component of Pacoima Dam record of 1971 San Fernando earthquake. An analytically simple model called as filtered white noise ground motion model is chosen to represent the earthquake ground motion. When compared with the uniform ground motion case, the results obtained from the spatial variability models with partial correlation outline the necessity to include the spatial variability of ground motions in the stochastic dynamic analysis of suspension bridges. It is observed that while the largest response values are obtained for the model proposed by Harichandran and Vanmarcke, the model proposed by Uscinski produces the smallest responses among the considered partially correlated ground motion models. The response values obtained from the uniform ground motion case are usually smaller than those of the responses obtained from the partially correlated ground motion cases. While the response values at the flexible parts of the bridge are totally dominated by the dynamic component, the pseudo-static component also has significant contributions for the response values at the rigid parts of the bridge. The results also show the consistency of the spatial variability models, which have different characteristics, considered in this study.

• Elastomers and Composites
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• v.52 no.4
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• pp.303-308
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• 2017

In this study, finite element modeling and material property tests are performed for the finite element analysis of rubber isolator parts which support the engine and isolate the vibration. As a result of the P direction analysis of the rubber isolator parts, the static stiffness in the P direction was 44.2 kg/mm, which is well within the error of 5% as compared with the test result of 46.1 kg/mm. The static stiffness of the rubber isolator parts in the Q direction was calculated to be 7.9 kg/mm, which is comparable to the test result of 8.6 kg/mm, with an error of less than 8%. As a result of the analysis on the Z direction, the static stiffness was calculated as 57.7 kg/mm, and the test results were not available. Through this study, it is expected that the time and cost for prototype development can be reduced through nonlinear finite element analysis for rubber isolator parts.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.299-307
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• 2002

In this proposed study, a new emerging shape forming technique Direct Coagulation Casting(DCC) which enables to fabricate complex-shaped ceramic parts has been investigated using colloid surface chemistry. Various process variables affected by dispersant, coagulation agent and sintering additives, have been evaluated in order to achieve highly concentrated stabilized silicon nitride suspensions. A high solid loading of 51 vol% in the dispersed silicon nitride suspension was prepared with 1.0wt% Tetraethylammonium Hydroxide (TEAH), which obtained a stable silicon nitride suspension with sintering additives $(Al_2O_3\;and\;Y_2O_3)$ in alkaline regions. The addition of hydroxyaluminium diacetate into the suspension, which decomposed at elevated temperatures, led to coagulate of a silicon nitride suspension. In a basic medium, aluminum ions precipitated to aluminum hydroxide $(Al(OH)_3)$, leading to decreased $OH^-$ concentration and, thus, coagulated suspension.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.571-575
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• 2008

An engine cradle is a quite important structural assembly for supporting the engine, suspension and steering parts of vehicle and absorbing the vibrations during the drive and the shock in the car crash. Recently, the engine cradle having structural stiffness enough to support the surrounding parts and absorbing the shock of collision has been widely used. The hydroforming technology may cause many advantages to automotive applications in terms of better structural integrity of parts, reduction of production cost, weight reduction, material saving, reduction in the number of joining processes and improvement of reliability. We focus on increasing the durability and the dynamic performance of engine cradle. For realizing this objective, several optimization design techniques such as shape, size, and topology optimization are performed. This optimization scheme based on the sensitivity can provide distinguished performance improvement in using hydroforming.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1023-1028
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• 2010

Recently, an intelligent service robot is being developed for use in guiding and providing information to visitors about the building at public institutions. The intelligent robot has a sensor at the bottom to recognize its location. Four wheels, which are arranged in the form of a lozenge, support the robot. This robot cannot be operated on uneven ground because its driving parts are attached to its main body that contains the important internal components. Continuous impact with the ground can change the precise positions of the components and weaken the connection between each structural part. In this paper, the design of the suspension system for such a robot is described. The dynamic model of the robot is created, and the driving characteristics of the robot with the designed suspension system are simulated. Additionally, the suspension system is optimized to reduce the impact for the robot components.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.137-142
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• 2009

Impact noise is induced in a car when it is driven on a harsh road or over some bumps. This noise occurs with the very high level of sound, which affects passengers in some way or other. Although it is impossible to clearly remove such noise. It is necessary to research an improvement in sound quality for impact noise. A new sound metric for impact sound is presented in the previous work. This metric is verified by comparison between mean subjective ratings and several sound metrics. In this paper, more objective attributes are considered, which are the attributes expressing the level and modulation of sound. Three sound metrics are employed to get impact sound indexes for each course by the method of multiple linear regressions. The indexes are verified by considering the correlation between the estimated values from the multiple linear regressions and the mean subjective ratings by evaluators. Also, the subjective ratings on the indexes are estimated for the case in which some parts of suspension system are changed. The estimated ratings represent more reasonable or acceptable ratings. Thus, such indexes can be used for modification of the parts of suspension system under considering a good sound quality.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.198-204
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• 2005

Seeds of neem were collected from different parts of India and analyzed for their azadirachtin content by High Performance Liquid Chromatography (HPLC). In order to assess the effects of genotypic and geographical variation on azadirachtin content in cell cultures, callus development was attempted in the seeds containing high and low concentration of azadirachtin. The concentration of azadirachtin in callus cultures was significantly affected by the explant source. Seed kernels with higher azadirachtin content produced higher azadirachtin content in callus cultures and lower azadirachtin content was seen in callus cultures produced from seed kernels with low azadirachtin content. The protocol for development of elite stock culture of Azadirachta indica was established with the objective of selecting a high azadirachtin-producing cell line. The highest azadirachtin-producing cell line was selected and the effects of different media and illumination conditions on growth and azadirachtin production were studied in shake flask suspension culture. Detailed batch growth kinetics was also established. These studies provided elite starter culture and associated protocols for cultivation of A. indica plant cell culture in the bioreactor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.69-74
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• 2006

It is known that the various noise sources which are engine, transmission, tire, intake system, etc exist at vehicle driving status. Specially noises which cannot be expected by a driver induce unpleasantness to all passengers. These noises are difficult to distinguish noise sources or specifications because of too many vehicle parts. Therefore in this paper, study on abnormal noise of bush on suspension system is performed by the measurement and analysis of the noises of bushings that are generated artificially. The measured noises are analyzed by two points-view of spectrum and sound quality. Finally, it is shown that the noise sources of bushings on the suspension system which are the pillow ball joint bush of a control arm and the rubber bush of a lower arm could be distinguished by the spectrum distribution and a index value based on tonality.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.79-90
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• 2012

The torsion beam type of rear suspension has been adopted by most manufactures of small to medium front wheel drive passenger cars. Previous studies analyzed only the load characteristics of CTBA(the coupled torsion beam axle)'s components. This paper analyzed the results of measurement after measuring loads and displacements, angles when a car equipped with the coupled torsion beam axle is driving in various roads. The most important durability factors for CTBA part are the force and direction of rear CTBA trailing arm. If there are design changes, it was difficult to make a sensor and install each time for measuring the trailing arm forces. After analyzing the loading histories between body and chassis, we developed the transformation matrix that can be converted to mutual force. This paper also deals with the analysis of the force behavior through the analysis of the influence and correlation between the body and chassis parts of cars.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.352-359
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• 2023

Recently, independent suspension systems have been applied not only to passenger cars but also to large commercial vehicles. Therefore, the need for research to domestically produce such independent suspensions for large commercial vehicles is gradually increasing. In this paper, we conducted research on the manufacturing technology of the relay lever, which are integral components of independent suspension systems for large commercial vehicles. Our goal was to reduce the flash volume generated during the forging process. The shape variables of the initial billet were adjusted to find proper forming conditions that could minimize flash volume while performing product forming smoothly. Shape variables were set as input variables and the flash volume was set as an output variable, and simulations were carried out to analytically predict the volume of the flash area for each variable condition. Based on the data obtained through numerical simulations, a regression model and an artificial neural network model were used to develop a prediction model that can easily predict the flash volume for variable conditions. For the corresponding prediction model, a goodness of-fit test was performed to confirm a high level of fit. By comparing and analyzing the two prediction models, the high level of fit of the ANN model was confirmed.