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박용재(Yongjai Park),남일광(Riguang Nam),강연준(Yeonjune Kang),박철민(Chulmin Park),채기상(Kisang Chae) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Statistical Energy Analysis has been widely applied to improve the accuracy of the prediction of vehicle interior noise. Especially, in airborne noise cases, SEA is very useful for predicting the Interior noise ofa vehicle if some parts of the vehicle model are changed. In this paper, a building and validating process of the full vehicle SEA model is presented. First, Sound Transmission Loss and Absorption Coefficient (α) of vehicle components were measured using a real vehicle. An airborne SEA model was built using the geometry information, and the component characteristics were modeled using STLs, and α's, which were measured or calculated. Then, the interior and exterior noises of a full vehicle were measured for various experimental conditions such as WOT (wide open throttle) condition and loudspeaker loading conditions, which were used for the validation of the SEA model. Finally, the predicted and the measured interior noises were compared, and the accuracies of the SEA model were identified for several loading conditions.
A Study on Sound Transmission Loss Measurement of Vehicle Components
Riguang Nan,Yongjai Park,Yeonjune Kang,Chulmin Park,Kisang Chae 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The measurement method of Sound Transmission Loss (STL) both in the reverberation room and the semi-anechoic room at the vehicle component level is presented. The sound intensity method was used to measure the STL, and the Statistical Energy Analysis (SEA) models were used to predict the acoustic performance of the system. Since the dash and the floor system mainly affect the NVH performance in the car compartment, the analysis process requires detailed SEA modeling and accurate measurement in these parts. The measured data was in good agreement with the predicted data obtained by using SEA model, and the results were helpful in determining the reliability of the measurement method and the SEA modeling.
초정밀장비 미진동제어를 위한 기계식 가변감쇠시스템의 진동제어성능 연구
심다솔(DaSol Shim),전종균(ChongKeun Chun),박용재(YongJai Park),박상곤(SangGon Park),한현희(HyenHee Han) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.4
The precision equipment for precision processing, manufacturing, and inspection process are usually managed in a strictly vibration-controlled environment that uses vibration isolators. To complement the weaknesses of these isolators, we designed and tested two types of mechanical adjustable dampers with helical gear: a box-like adjustable damper with a comb-type orifice and a round damper with a wing-type orifice. Additionally, we designed two versions for the latter: a standard version and an enhanced version to improve the variable performance. We then compared the performance of these two versions during their modal tests. Not surprisingly, the test showed that the enhanced version was superior to the standard version in variable damping. For this reason, we expect this damper to be particularly useful to semiconductor manufacturing facilities where the precision equipment are located.
해양플랜트용 500 MPa급 후판강의 모재 및 HAZ의 미세조직과 기계적 특성의 상관관계
박지원,조성규,조영욱,신건철,권용재,이정구,신상용,Park, Jiwon,Cho, Sung Kyu,Cho, Young Wook,Shin, Gunchul,Kwon, Yongjai,Lee, Jung Gu,Shin, Sang Yong 한국재료학회 2020 한국재료학회지 Vol.30 No.3
In this study, two types of thick steel plates are prepared by controlling carbon equivalent and nickel content, and their microstructures are analyzed. Tensile tests, Vickers hardness tests, and Charpy impact tests are conducted to investigate the correlation between microstructure and mechanical properties of the steels. The H steel, which has high carbon equivalent and nickel content, has lower volume fraction of granular bainite (GB) and smaller GB packet size than those of L steel, which has low carbon equivalent and nickel content. However, the volume fraction of secondary phases is higher in the H steel than in the L steel. As a result, the strength of the L steel is higher than that of the H steel, while the Charpy absorbed energy at -40 ℃ is higher than that of the L steel. The heat affected zone (HAZ) simulated H-H specimen has higher volume fraction of acicular ferrite (AF) and lower volume fraction of GB than the HAZ simulated L-H specimen. In addition, the grain size of AF and the packet sizes of GB and BF are smaller in the H-H specimen than in the L-H specimen. For this reason, the Charpy absorbed energy at -20 ℃ is higher for the H-H specimen than for the L-H specimen.
금속고화체용 STS304-Zr 합금의 미세조직과 파괴거동에 미치는 열처리의 영향
김종우,장선아,한승엽,박환서,이정훈,이성학,권용재,이정구,신상용,Kim, Jongwoo,Jang, Seon Ah,Han, Seung Youb,Park, Hwan Seo,Lee, Junghoon,Lee, Sunghak,Kwon, Yongjai,Lee, Jung Gu,Shin, Sang Yong 한국재료학회 2018 한국재료학회지 Vol.28 No.3
Three kinds of STS304-Zr alloys were fabricated by varying the Zr content, and their microstructure and fracture properties were analyzed. Moreover, we performed heat treatment to improve their properties and studied their microstructure and fracture properties. The microstructure of the STS304-Zr alloys before and after the heat treatment process consisted of ${\alpha}-Fe$ and intermetallics: Zr(Cr, Ni, Fe)2 and Zr6Fe23. The volume fraction of the intermetallics increased with an increasing Zr content. The 11Zr specimen exhibited the lowest hardness and fine dimples and cleavage facets in a fractured surface. The 15Zr specimen had high hardness and fine cleavage facets. The 19Zr specimen had the highest hardness and large cleavage facets. After the heat treatment process, the intermetallics were spheroidized and their volume fraction increased. In addition, the specimens after the heat treatment process, the Laves phase (Zr(Cr, Ni, Fe) 2) decreased, the Zr6Fe23 phase increased and the Ni concentration in the intermetallics decreased. The hardness of all the specimens after the heat treatment process decreased because of the dislocations and residual stresses in ${\alpha}-Fe$, and the fine lamellar shaped eutectic microstructures changed into large ${\alpha}-Fe$ and spheroidized intermetallics. The cleavage facet size increased because of the decomposition of the fine lamellar-shaped eutectic microstructures and the increase in spheroidized intermetallics.
980 MPa급 이상조직강의 신장 플랜지성에 미치는 템퍼링의 영향
이건희,백종희,송은지,나선형,박봉준,김주영,권용재,신상용,이정구,Lee, Gun-Hee,Baek, Jong-Hee,Song, Eunji,Na, Seon-Hyeong,Park, Bongjune,Kim, Ju-Young,Kwon, Yongjai,Shin, Sang Yong,Lee, Jung Gu 한국재료학회 2020 한국재료학회지 Vol.30 No.6
In this study, the effect of tempering on the stretch-flangeability is investigated in 980 MPa grade dual-phase steel consisting of ferrite and martensite phases. During tempering at 300 ℃, the strength of ferrite increases due to the pinning of dislocations by carbon atoms released from martensite, while martensite is softened as a consequence of a reduction in its carbon super-saturation. This strength variation results in a considerable increase in yield strength of the steel, without loss of tensile strength. The hole expansion test shows that steel tempered for 20 min (T20 steel) exhibits a higher hole expansion ratio than that of steel without tempering (T0 steel). In T0 steel, severe plastic localization in ferrite causes easy pore formation at the ferrite-martensite interface and subsequent brittle crack propagation through the highly deformed ferrite area during hole expansion testing; this propagation is mainly attributed to the large difference in hardness between ferrite and martensite. When the difference in hardness is not so large (T20 steel), on the other hand, tempered martensite can be considerably deformed together with ferrite, thereby delaying pore formation and hindering crack propagation by crack blunting. Eventually, these different deformation and fracture behaviors contribute to the superior stretch-flangeability of T20 steel.