• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.542-545
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• 2004

The vibration reduction process for the driver comfort of a forklift truck is studied in this study since the related driver comfort is a primary design target in the vehicle design recently. However, the underlying study for a vibration analysis regarding to the driver comfort is still an element stage. Thus, a preceding large work has to be needed to apply the CAE technology for the detail vehicle design, and it prevents the vehicle optimal design. To reduce the proceeding large works, the evaluated process and required data are comply with the accumulated trouble shooting experiences in this study. Since the driver comfort is a human related problem, the human vibration index associated with analysis vibration result is additionally introduced as a driver comfort judgement value.

• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.79-88
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• 2008

In this study, we focus on the improvement of the filling efficiency in injection molding by application of ultrasonic vibration. While studies about the filling efficiency of typical filling processes in the injection molding have been widely performed, there have been only few studies about the filling efficiency of an ultrasonic process. The effect of the ultrasonic vibration is an important process condition, which influences the flow characteristics of polymer melt. This new condition even affects well-known injection conditions such as cavity pressure, injection temperature and mold temperature. For this study, we carried out a numerical analysis by appropriate modeling and analysis of the ultrasonic process in the filling process. To verify this numerical analysis, we compared the numerical results with the experimental data. Also, we analyzed the filling process in a thin cavity using this numerical analysis. To understand the flow characteristics of polymer melt in the ultrasonic process, we substituted real and complex vibration conditions with simplified and classified conditions according to the position of vibrating cavity surfaces and the phase difference between two opposing cavity surfaces. We also introduced MFR (melt flow ratio) as a new index to estimate the filling efficiency in the ultrasonic process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.274-278
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• 2014

Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Cutting tooling method is one of major factor to chatter vibration in turning process. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting tooling geometry and clamping method on the onset of chatter vibration. Acquired knowledge from this study will apply the optimal geometry design of cutting tooling and adjusting of machining process.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.17-25
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• 2009

We studied the flow characteristics of the polymer melt in the injection molding process with ultrasonic vibration by using the numerical analysis. To minimize the error between the experimental data and numerical result, we presented a methodology using the design of experiments and the response surface method for reverse engineering. This methodology can be applied to various fields to obtain a valid and accurate numerical analysis. Ultrasonic vibration is generally applied between an extruder and the entrance of a mold for improvement the flow rate in injection molding. In comparison with the general ultrasonic process, the mode shape of the mold must be also considered when the ultrasonic vibration is applied on the mold. The mode shape is defined as the periodic and spatial deformation of the structure owing to the effect of the vibration, and it varies greatly according to vibration conditions such as the forcing frequency. Therefore, we considered new index and found the forcing frequency for obtaining the highest flow rate within the range from 20 to 60 kHz on the basis of the index. Ultimately, we presented the methodology for not only obtaining a valid and accurate numerical analysis, but also for finding the forcing frequency to obtain the highest flow rate in injection molding using ultrasonic vibration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.35-40
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• 2016

End milling process is one of the broadly used manufacturing process for precision machined parts and products. Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting parameters to affect to chatter vibration stability. Acquired knowledge from this study will apply the optimal cutting conditions to improve a machining process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1471-1481
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• 2009

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. The sleeve spring type damper is one of the preventive measures for reducing the torsional vibration. In this study, the closed form equations to predict the spring constant of a sleeve spring and the torsional characteristics of the torsional vibration damper are proposed to calculate stiffness of the damper and verified their availability through the finite element analysis and experiments. And the stability of the sleeve spring torsional vibration damper is verified by analyzing the inner star and outer star, which are the core parts of the damper, and 2-roll bending process is proposed to manufacture sleeve spring. The program to calculate the initial radius including spring-back effect is developed, and the FEA method to analyze elasto-plastic problem was verified through analysis of 90$^{\circ}$bending process. The results of the analysis are in good agreements with those of the experiments. The newly proposed method can be used as an advanced technique that remarkably curtails cost of production and replaces the conventional forming.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.208-211
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• 2005

This paper describes the development process of steering system for reduce idle vibration through the data level of frequency and sensitivity. High stiffness and light weight vehicle is a major target in the refinement of passenger cars to meet customers' contradictable requirements between NVH performance and fuel economy. The target frequency of the steering system is set by benchmarking of a competitive vehicle and the vibration mode map is used to separate steering column modes from resonance of body structure and engine idle rpm. This paper descirbes the analysis approach process for high stiffness of steering system and the design guideline is suggested about steering column and support system by using mother car at initial design stage. We used a patent map in order to analyze accurately a technical trend and suggested the design process using dynamic damper of steering system considering sensitivity. And we established techniques of analysis on steering system and evaluated the level of accuracy of analysis through correlating the test and analysis results. It makes possible to design the good NVH performance vehicle at initial design stage and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

• Journal of the Semiconductor & Display Technology
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• v.2 no.1
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• pp.15-19
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• 2003

Spin etcher can process frontside and backside on the wafer, which is used for etching, stripping, cleaning and wafer reclamation. A new generation of spin etchers has been designed to meet 300mm wafer processing. The larger header and higher spin speed make vibration problem a severe problem in developing equipments. This study shows schematic process of solving practical vibration problems, where it is required to analyze the principal ca uses of vibration problem and find out the method of vibration reduction in spin etcher. The vibration under normal operation is measured in time domain and is analyzed in frequency domain. And modal parameters are obtained through modal test. Using the modal parameters from experiments, the model of finite element method is formulated. From diagnosis using many measurements and analyses, it can be shown that main cause of vibration is unbalance of head.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.736-741
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• 2004

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal (PES) is becoming smaller and smaller. In order to achieve the high TPI disk drive, it is necessary to improve the writing accuracy during the STW(servo track writing) process through the reduction of TMR sources. Among the main contributors of the NRRO(Non-Repeatable Run-out) PES, the disk vibration and the HSA(head-stack assembly) vibration is considered to be one of the most significant factors. Also the most contributors of RRO(Repeatable Run- out) come from the contributors of NRRO which is written-in at the time of STW(servo track writing) process. In this paper, the experimental test result shows that the effect of NRRO on servo written-in RRO effectively can be reduced through a STW process under low dense medium condition such as semi-vacuum.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.85-94
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• 1994

The cutting mechanism of ultrasonic vibration machining is characterized as two phases, that is, an impact at the cutting edge and a reduction of cutting force due to non-contact interval between tool and workpiece. In this paper, in order to identify cutting dynamics of a system with ultrasonically vibrated cutting tool, an ARMA modeling is performed on experimental cutting force signals which have a dominant effect on cutting dynamics. The aim of this study is, through Dynamic Date System methodology, to find the inherent characteristics of an ultrasonic vibration cutting process by considering natural frequency and damping coefficient. Surface roughness and stability of cutting process under ultrasonic vibration are also considered