• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.390-395
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• 2000

The ultrasonic motor have recently begun to be used for certain unique practical utilizations in the fields of industrial medical consumer and automotive applications. Ultrasonic motor stimulated to ultrasonic oscillations by piezoelectrics to drive a rotor via friction contact. The metal and ceramic composite component was used as the stator element to generate ultrasonic vibrations. The ultrasonic motor used here was the windmill type ultrasonic motor operated by single-phase AC source. The windmill type ultrasonic motors has only three components; a stator element of two windmill shape slotted metal endcaps a rotor and a bearing. In this paper a prototype motor with 11.35 mm diameter was fabricated then relationship between the pressing force applied to a rotor and the rotation characteristic of windmill type ultrasonic motor are investigated when stator’s slots was changed from 4, 6, 8 and thickness changed from 0.15, 0.20 mm, respectively. Optimum pressing force applied to a rotor in the six stators was 1.2 mN.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.271-277
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• 2017

In this paper, the amplitude and frequency dependent dynamic characteristics of the equivalent stiffness of a rubber bushing are investigated. A new mathematical model is proposed to explain the large deformation and size effect of a rubber bushing. The proposed model consists of elastic, viscous, and frictional stress components and the equivalent strain. The proposed model is verified using experimental results. The comparison shows that the proposed model can accurately predict the equivalent stiffness values of a rubber bushing under various magnitudes and frequencies. The developed model could be used to predict the dynamic equivalent stiffness of a rubber bushing in automotive engineering.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.94-98
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• 2013

Transfer Path Analysis (TPA) is commonly used, by car makers and parts suppliers, analysis process to root the cause of NVH problems. In general, TPA is an analyzing technique to find the contributing factors of noise/vibration problems, and their transfer path in vehicle. However, not only TPA is used to analyze the source of NVH problems but also is used to predict NVH performance prior to the proto vehicle, or to set the development target for next new vehicle. Automotive parts manufacturing companies have to set NVH performance target when developing new systems just as car makers have NVH target set for new vehicle. Nevertheless, most of components are currently being developed based on subjective evaluation without an objective target. To judge the suitability of using TPA to set NVH target of electric parking brake, this research analyzed the transfer path by setting them in two points of view; Chassis Module and Electric Parking Brake, and comparing the measured value and calculated value. From this result, NVH target of electric parking brake will be approached in level of vehicle, system and component.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.123-134
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• 1999

A new forming technology has been developed to fabricate near-net shape components by using aluminum alloys with globular microstructure. The estimations of filling characteristic in the forging simulation with arbitrarily shaped dies of SSM are calculated by finite element method with proposed algorithm. The proposed model and various boundary conditions for arbitrarily shaped die are investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation processes with arbitrarily shaped dies are performed on the isothermal conditions and axisymmetric problems. To analyze the forging process simulation with SSM, new stress-strain relationship for semi-solid behaviour is described, and forging the liquid flow. Furthermore, For the purpose of getting net shape of SSM, it is important to be obtain a solid fraction in forging process with arbitrarily shaped dies. To produce a automotive part which have good mechanical properties, the filling pattern in accordance with die velocity and solid fraction distribution has to be estimated for arbitrarily shaped die.

• Advances in aircraft and spacecraft science
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• v.3 no.1
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• pp.29-43
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• 2016

Composite materials are rapidly gaining popularity as an alternative to metals for structural and load bearing applications in the aerospace, automotive, alternate energy and consumer industries. With the advent of thermoplastic composites and advances in recycling technologies, fully recyclable composites are gaining ground over traditional thermoset composites. Stamp forming as an alternative processing technique for sheet products has proven to be effective in allowing the fast manufacturing rates required for mass production of components. This study investigates the feasibility of using the stamp forming technique for the processing of thermoplastic, recyclable composite materials. The material system used in this study is a self-reinforced polypropylene composite material (Curv$^{(R)}$). The investigation includes a detailed experimental study based on strain measurements using a non-contact optical measurement system in conjunction with stamping equipment to record and measure the formability of the thermoplastic composites in real time. A Design of Experiments (DOE) methodology was adopted to elucidate the effect of process parameters that included blank holder force, pre heat temperature and feed rate on stamp forming. DOE analyses indicate that feed rate had negligible influence on the strain evolution during stamp forming and blank holder force and preheat temperature had significant effect on strain evolution during forming.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.35-41
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• 2021

A rotor is a crucial component in various mechanical assemblies. Additionally, high-speed and high-efficiency components are required in the automotive industry, manufacturing industry, and turbine systems. In particular, the failure of high-speed rotating bearings has catastrophic effects on auxiliary systems. Therefore, bearing reliability and fault diagnosis are essential for bearing maintenance. In this work, we performed failure mode and effect analysis on bearing rotors and determined that corrosion is the most critical failure type. Furthermore, we conducted experiments to extract vibration characteristic data and preprocess the vibration data through principle component analysis. Finally, we applied a machine learning algorithm called support vector machine to diagnose the failure and observed a classification performance of 98%.

• Korean Journal of Optics and Photonics
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• v.30 no.1
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• pp.8-14
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• 2019

This paper presents methods to correct and evaluate the chromatic aberration occurring on the cut-off line of a headlamp without additional optical components and alignment process. To correct the chromatic aberration using a geometrical concept, the maximum differences in exit-ray angle between wavelengths are reduced by tilting the convex surface of an aspheric projection lens. To evaluate the chromatic aberration, the position and luminous intensity to be measured are suggested, and the criterion for chromatic aberration is presented through color coordinates. From the evaluation of an automotive headlamp designed using this geometrical method, it is found that the chromatic aberration of the cut-off line is significantly reduced.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.893-899
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• 2011

Fabrication of a complex aluminum alloy by the ARB process using dissimilar aluminum alloys has been carried out. Two-layer stack ARB was performed for up to six cycles at ambient temperature without a lubricant according to the conventional procedure. Dissimilar aluminum sheets of AA1050 and AA5052 with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled to 50% reduction such that the thickness became 1 mm again. The sheet was then cut into two pieces of identical length and the same procedure was repeated for up to six cycles. A sound complex aluminum alloy sheet was successfully fabricated by the ARB process. The tensile strength increased as the number of ARB cycles was increased, reaching 298 MPa after 5 cycles, which is about 2.2 times that of the initial material. The average grain size was $24{\mu}m$ after 1 cycle, and became $1.8{\mu}m$ after 6 cycles.

• Advances in nano research
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• v.12 no.1
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• pp.49-63
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• 2022

Nanocatalysts are usually used in the synthesis of petrochemical products, fine chemicals, biofuel production, and automotive exhaust catalysis. Due to high activity and stability, recyclability, and cost-effectiveness, nanocatalysts are a key area in green chemistry. On the other hand, water as a common by-product or undesired element in a range of nanocatalyzed processes may be promoting the deactivation of catalytic systems. The advancement in the field of hydrophobicity in nanocatalysis could relatively solves these problems and improves the efficiency and recyclability of nanocatalysts. Some recent developments in the synthesis of novel nanocatalysts with tunable hydrophilic-hydrophobic character have been reviewed in this article and followed by highlighting their use in catalyzing several processes such as glycerolysis, Fenton, oxidation, reduction, ketalization, and hydrodesulfurization. Zeolites, carbon materials, modified silicas, surfactant-ligands, and polymers are the basic components in the controlling hydrophobicity of new nanocatalysts. Various characterization methods such as N2 adsorption-desorption, scanning and transmission electron microscopy, and contact angle measurement are critical in the understanding of hydrophobicity of materials. Also, in this review, it has been shown that how the hydrophobicity of nanocatalyst is affected by its structure, textural properties, and surface acidity, and discuss the important factors in designing catalysts with high efficiency and recyclability. It is useful for chemists and chemical engineers who are concerned with designing novel types of nanocatalysts with high activity and recyclability for environmentally friendly applications.

• International journal of advanced smart convergence
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• v.11 no.3
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• pp.215-221
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• 2022

In the manufacturing process of the bus treated as the commercial vehicle, after making the bare chassis which is the basic frame of the vehicle body, the part in which passengers ride is connected. In addition, the necessary parts such as the engine and transmission required for the operation of the bus are connected to the bare chassis. The element connecting the parts such as the boarding part of the passengers, the engine, the suspension and the transmission is the bracket. The device required for driving and operating the vehicle is mounted on the bare chassis using the bracket, which should ensure stability during bus operation. In this study, we were performed stress analysis to evaluate the stability of three types of brackets connecting the bare chassis of a new type of 30-seater bus in the development process and components required for driving and operation. The stress analysis should be preceded by the analysis of boundary conditions considering the loads applied to the brackets according to the material of the bracket to be analyzed and the driving type of the bus. The finite element model for structural analysis of brackets according to the driving type of the bus was used by Altair's Hypermesh 2017, and the solver used for structural analysis was Altair's Optistruct. The stress analysis was performed to present the safe and vulnerable parts of the three brackets.