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Thermo-Elastic Analysis for Chattering Phenomenon of Automotive Disk Brake
Cho, Chongdu,Ahn, Sooick The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.5
This study investigates the effects of operating conditions on the chattering of an automotive disk brake by experimental and computational methods. Design factors, which cause chattering in automobiles, have attracted great attentions for long time; but they are not well understood yet. For this study, we construct a brake dynamometer for measuring the disk surface temperature during chattering, and propose an efficient hybrid algorithm (combining FFT-FEA and traditional FEA program) for analyzing the thermo-elastic behavior of three-dimensional brake system. We successfully measure the judder in a brake system via the dynamometer and efficiently simulate the contact pressure variation by the hybrid algorithm. The three-dimensional simulation of thermo-mechanical interactions on the automotive brake, showing the transient thermo-elastic instability phenomenon, is presented for the first time in this academic community. We also find from the experimental study that the disk bulk temperature strongly influences the brake chattering in the automotive disk brakes.
Computational mechanics of laser cladding process
Cho, Chongdu,Zhao, Guiping,Kwak, Si-Young,Kim, Chang Boo Elsevier 2004 Journal of materials processing technology Vol. No.
<P><B>Abstract</B></P><P>Laser cladding process accompanies phase transformations through melting (on heating) and solidifying (on cooling), which is an irreversible thermodynamic process. Most of analyses on material processing by laser as a heat source have been conducted on models of neglecting the latent heat in the process just for the reason of simplification. In this study the previous important works are summarized. And to further investigate the effects of latent heat on laser cladding process, this study develops a program accommodating an algorithm for enforcing the latent heat to run with ABAQUS™. The simulation technique of this study is verified by direct comparison of the present prediction with experimental publications elsewhere; the numerical results agreed accurately with the experiments. As a result, it is found that more accurate conclusions come out when considering the latent heat in process analyses.</P>
노종두,안효경 公州大學校 産業開發硏究所 1998 産業開發硏究 Vol.6 No.-
ita'is defined as an adjective considering following morphlogical, semantical and funtional factors. First, 'ita'is an inflected word and it shows same inflection of adjective's. Second, 'ita' has the predicative function in a sentence. Third, 'ita' specifies content of noun phrase and has a meaning that a certain noun phrase belongs to other's.
Printing the products: An overview of the Three Dimensional Printing (3DP) process
Mohib(모힙),Chongdu Cho(조종두) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This paper work presents an overview of the three dimensional printing process (3DP), its features, capabilities and applications. 3DP has generated a lot of interest in recent years as a tool for creating rapid prototypes, and thereby reducing the design cycle of product development. With the advances in the field, nowadays, it is being used for many purposes other than rapid prototyping, and in fields as diverse as medicine, automobile engineering and art-restoration. Several such case studies covering a wide range of applications are discussed in this paper work. It also analyses the future of 3DP in view of recent developments, and its transformation from rapid prototyping to rapid manufacturing.
THE INVESTIGATION OF PSEUDOELASTIC NITI WIRES FOR DAMPING USES
Qiang Pan,Chongdu Cho,Sheng Lu 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Some shape memory alloys like NiTi show noticeable high damping property in pseudoelastic range. Due to its instinct characteristics, a NiTi alloy is commonly used for passive damping applications, in which the energy may be dissipated by the conversion from mechanical to thermal energy. Previous researches found the NiTi wires own higher damping property than the bars; therefore the wire form is adopted in this study. A loss factor is introduced for measuring the damping property of the NiTi wires. The experimental observation shows the mechanical behaviors of NiTi wires are dependent on temperature, strain rate and strain amplitude. Moreover, it is found the first several decades of loading-unloading cycles can obviously influence the property of NiTi wires under the same working conditions.
STUDY ON DYNAMIC CRACK PROPAGATION AT IMPACT LOADED 3PB STEEL SPECIMENS
Jaeung Cho,Chongdu Cho,Moonsik Han 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The crack propagation in ductile steel is investigated by means of impact loaded 3 point bending specimens. Results from experiments and numerical simulations are compared. The specimen has the size 320×75 ㎜ with a thickness of 10 ㎜. A newly designed 3PB specimen design with reduced width at the ends has been developed to avoid the influence of the uncertain boundary conditions at the impact heads. One static and two dynamic experiments with impact velocities of 30.2 ㎧ and 45.2 ㎧ are carried out. High speed photography is used to obtain crack growth and crack tip opening displacement data. Direct measurement of the relative rotation of the two specimen halves is made using by Moire interference pattern. The fracture surfaces of shear lip are obtained for all three loading conditions. The experiments indicate no or only a slight influence of the loading rate on the crack propagation.
HM Graphite/Epoxy와 Silicon/Epoxy의 비강성에 관한 이론적 연구
김동화(Donghwa Kim),조종두(Chongdu Cho) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Unidirectional fiber-reinforced Graphite/Epoxy and Silicon carbide/Epoxy have high values of stiffness and strength. This paper is performed to analyze longitudinal and transverse specific stiffness of Graphite/Epoxy and Silicon carbide/Epoxy using the mathematical method. Specific stiffnesses of the composites are compared and results suggest which composite can be taken as a proper choice when it is used for manufactures.