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링 프로젝션 돌기의 용입정도가 ECV 조립공차에 미치는 영향
장희석,원웅연,최덕준,김종호,김진상,남택현,강희종,Chang, Hee-Seok,Won, Woong-Yeon,Choi, Duk-Jun,Kim, Jong-Ho,Kim, Jin-Sang,Nahm, Tak-Hyun,Kang, Hee-Jong 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.1
Due to the inherent dimensional uncertainty, tolerances accumulate in the final assembly. Tolerance accumulation has serious effect on the performance of ECV assembly. This paper proposes a method of tolerance accumulation analysis using Monte Carlo simulation, which includes welding process in assemble process. This method can predict the final tolerance distributions of the completed assembly with the prescribed statistical tolerance distribution of each part to be assembled. With the inclusion of welding, another dimensional uncertainties due to partial melting is to be accounted as well. Partial melting of projection height was included in the tolerance propagation analysis. Verification of the proposed method was performed by making use of Monte Carlo simulation. Monte Carlo simulation results showed promising results in that we can predict the final tolerance distributions in advance before actual assembly process of precision machinery.
In-Process Monitoring of Micro Resistance Spot Weld Quality using Accelerometer
장희석,권효철,Chang, Hee-Seok,Kwon, Hyo-Chul The Korean Welding and Joining Society 2011 대한용접·접합학회지 Vol.29 No.1
This study is to propose an in-process monitoring system for micro resistance spot welding processes using minute accelerometer. A minute accelerometer is mounted on the upper moving electrode tip holder. With its high sensitivity and frequency response characteristics, accelerometer output signal has been successfully recorded and integrated twice to reflect electrode expansion during micro spot welding processes. The analysis of electrode expansion pattern was attempted to find its correlation with spot weld quality. Major previous findings1-6) regarding spot weld quality assessment with the electrode expansion signal in large scale resistance spot welding processes were proved to be true in this in-process monitoring system.
정선녀,장희석,이목영,Jung, Sun-Nyeo,Chang, Hee-Seok,Lee, Mok-Young 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.1
Weldability of Mg alloy was investigated using servo-actuated DC resistance spot welder. Due to its uncommon electrical and mechanical properties, lots of voids and cracks were observed inside nugget with conventional weld schedule. Lobe curve was proposed to clarify proper electrode force and weld current, which guarantee reasonable weld strength and fatigue life. Macro structure of sectioned specimen was examined to count total number of void and crack. Post weld schedule is also proposed to reduce micro victors hardness value of weld zone.
Dynamic Model for Electrode Expansion in Resistance Spot Welding Machines
아사드 샤,장희석,Shah, Syed Asad Ullah,Chang, Hee-Seok The Korean Welding and Joining Society 2011 대한용접·접합학회지 Vol.29 No.2
A lumped mass damped vibratory model was proposed for quantitative understanding of welding machine characteristics. An experimental setup was developed to determine the mechanical parameters (moving mass m, equivalent stiffness k and damping c) which govern the dynamic mechanical response of the resistance spot welding machine. During the test, acceleration of the electrodes for each level of applied load was measured by accelerometer, filtered and numerically integrated to find the corresponding velocity and displacement. The machine dynamic parameters were determined by finding the unknowns of the proposed model with experimental data. A Simulink model was proposed to investigate the influence of these mechanical parameters on the welding process. The electrode response was simulated by changing values of stiffness and damping. It was observed that both of the machine parameters(c, k) have significant effect on the response of electrode head.