• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.21-28
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• 2001

Analysis of squeal noise generated during brake operation is an important task for the improvement of brake noise prob-lem. By the use of measuring instrument and techniques, test and evaluation process are to be developed systematically in quantitative analysis. The cost far test and evaluation 7an be reduced, and the technical power can be raised by the devel- oped system.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.117-124
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• 2007

The pressure ripple in most hydraulic systems is the root cause of their noise and vibration. This paper reduced the pressure ripple using side branch hose for an axial piston pump applied to small excavator. First, in calculating open area, a new method using groove area of valve plate is proposed. Simulation model in AMESim environment is developed to verify proposed method, find effective length and diameter of branch hose. Finally, the comparisons with experiment results show that the proposed method is more effective than previous method in reducing the pressure ripple.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.140-145
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• 2007

To improve productivity of a metal cutting process, it is required to monitor machining stability in real time. Since cutting environment is harsh against sensing conditions due to vibration, chip, and cutting fluid, etc., it is necessary to develop a robust and reliable sensing system for the practical application. In this work, a chatter monitoring system was developed and its effectiveness was proved. Spindle displacement caused by cutting was selected as a main monitoring parameter. A cylindrical capacitive displacement sensor was adopted. Chatter frequencies were identified through modal analysis. To quantify chatter vibrations, chatter correlation coefficient was introduced. The identification of the monitoring system showed a good agreement with the result of experiment.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.7-12
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• 2008

In the design of modem rotating machinery, it is often necessary to increase the performance of rotor-bearing system. Since a critical speed range influences the performance and safety of the whole system, it should be necessary to constrain the critical speed and thus resonance response in design process to result in large vibration. Consequently the minimization of resonance response amplitudes within the operation range of the rotor system becomes the most primary design objective. In this paper, based on the assumption that the external shape of rotating-shaft, bearing supporting positions and etc, the natural frequency analysis of spindle is performed by ANSYS $10.0^{(R)}$ Optimum design is conducted using the RBF model.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.117-123
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• 2003

This paper deals with pressure ripple and noise reduction characteristics for a hydrostatic transmission(HST) consisting of a variable axial piston pump connected in an open loop to a fixed displacement axial piston motor. Pressure ripples in HST is major source of vibration, which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube type hydraulic filter proposes to absorb pressure ripples with the high frequencies components to achieve better noise attenuation in HST. The basic principle tube is applied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimently confirmed that a hydraulic filter is absorbed to be about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and here, should provide a means of designing a quieter HST.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.52-60
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• 1997

This paper proposes the effective method of the software based motion control by using lenear, exponential and bell type discrete filters for acceleration and deceleration of servo motors. Recursive filters are designed in discrete time domain which can reduce computation time and vibration of motors due to load disturbance. Also it deals with the method which decides the time constants of filters when a machine tool is driven at rapid, cutting and jog feedrate. Validity of the proposed method is verified by corner cutting experiments.

• Journal of Practical Engineering Education
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• v.14 no.1
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• pp.119-125
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• 2022

Materials used for education are materials such as SM20C, Al6061, and acrylic. SM20C materials are carbon steel and are often used in certification tests and functional competitions, but are also widely used in industrial sites. The Al6061 material is said to be a material that has lower hardness and stronger flexibility than carbon steel, so it is a material that generates a lot of compositional selection of tools. If students are taught practical training using acrylic materials, vibration occurs due to excessive cutting in some parts and damage to the tool occurs. In this process, we examine to what extent the impact on the 2NC head, which is a five-axis equipment, can affect precision control. The weakest part of the five-axis equipment can be said to be the weakest part of the head that controls the AC axis. When the accuracy and cumulative tolerance of this part occur, the accuracy of all products decreases. Therefore, the core part of the 2NC head, the spindle housing, was carried out using an Al7075 T6 (Alcoa, USA) material. In the process of vibration and cutting applied to this material, the analysis was conducted to find out the value applied to the finite element analysis under extreme conditions. It is hoped that this analysis data will help students see and understand the structure of 5-axis machining rather than 5-axis cutting.

• Composites Research
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• v.13 no.6
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• pp.39-46
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• 2000

Electrical discharge machining (EDM) cuts metal by discharging electric current across a thin gap between tool and workpiece. Electrical discharge wire cutting, a special form of EDM, uses a continuously moving conductive wire as an electrode, and is widely used for the manufacture of punches, dies and stripper plates. In the wire cutting process, the moving wire is usually supported by cantilever arm and wire guides. As the wire traveling speed has been increased in recent years to improve productivity, the vibration of the cantilever arm occurs, which reduces the positional accuracy of the machine. Therefore, the design and manufacture of the cantilever arm with high dynamic characteristics have become important as the machining speed increases. In this paper, the cantilever arm for guiding the moving wire was designed and manufactured using carbon fiber epoxy composite in order to improve the static and dynamic characteristics. Specimens for the composite cantilever arm were manufactured and tested to investigate the effect of the number of reinforcing plies and length fitted to steel flange on the load capacity. Also, the finite element analysis using layer and contact elements was performed to compare the calculated results with the experimental ones. From the results, the prototype of the composite cantilever arm for the electrical discharge wire cutting machine was manufactured and the static and dynamic characteristics were compared with those of the conventional steel cantilever arm.

• Steel and Composite Structures
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• v.19 no.3
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• pp.569-583
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• 2015

Recent years, explosive welding structures have been widely used in many engineering fields. The bonding state detection of explosive welding structures is significant to prevent unscheduled failures and even catastrophic accidents. However, this task still faces challenges due to the complexity of the bonding interface. In this paper, a new method called dual-tree complex wavelet transform based permutation entropy (DTCWT-PE) is proposed to detect bonding state of such structures. Benefiting from the complex analytical wavelet function, the dual-tree complex wavelet transform (DTCWT) has better shift invariance and reduced spectral aliasing compared with the traditional wavelet transform. All those characters are good for characterizing the vibration response signals. Furthermore, as a statistical measure, permutation entropy (PE) quantifies the complexity of non-stationary signals through phase space reconstruction, and thus it can be used as a viable tool to detect the change of bonding state. In order to more accurate identification and detection of bonding state, PE values derived from DTCWT coefficients are proposed to extract the state information from the vibration response signal of explosive welding structure, and then the extracted PE values serve as input vectors of support vector machine (SVM) to identify the bonding state of the structure. The experiments on bonding state detection of explosive welding pipes are presented to illustrate the feasibility and effectiveness of the proposed method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.1
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• pp.116-121
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• 2009

Thermosonic flip chip bonding is an important technology for the electronic packaging due to its simplicity, cost effectiveness and clean and dry process. Mechanical properties of the horn and the shank, such as the natural frequency and the amplitude, have a great effect on the bonding capability of the transverse flip chip bonding system. In this research, two kinds of study are performed. The first is the new design of the clamp and the second is the effect of tolerance parameters to the performance of the system. The clamp with a bent shape is newly designed to hold the nodal point of the flip chip. The second is the effect of the design parameters on the vibration amplitude and planarity at the end of the shank. The variation of the tolerance parameters changes the amplitude and the frequency of the vibration of the shank. They, in turn, have an effect on the quantity of the plastic deformation of the gold ball bump, which determined the quality of the flip chip bonding. The tolerance parameters that give the great effect on the amplitude of the shank are determined using Taguchi's method. Error of set-up angle, the length and diameter of horn and error of the length of the shank are determined to be the parameters that have peat effect on the amplitude of the system.