냉간가공된 알루미늄 점용접의 피로수명 개선

임병수(Byeongsoo Lim),류승진(Seungjin Ryu),김대욱(D. Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_2

The use of aluminum alloys is an attractive possible option in order to reduce the weight of automobile body structures to achieve the subsequent improvement of fuel economy and driving performance. Aluminum resistance spot welding(Al RSW), similar to current steel automobile body construction, may be considered one of the manufacturing methods for an aluminum body structure. Due to the unreliable durability of weld-bonded joints, applications of Al RSW are limited. A patented post-weld cold working process was used to improve the fatigue strength of Al RSW. The post-weld cold working process includes that special shaped indenters are pressed or driven into the structure in order to induce the compressive residual stresses. The effect of the post-weld cold working process parameters on the fatigue strength of the Al RSW was investigated. Comparisons of the fatigue properties and qualitative results between the as-welded RSW specimens and the post-weld cold worked RSW specimens are discussed.

냉간가공 된 알루미늄 점용접의 피로거동에 관한 연구

김범준(Bumjoon Kim),임병수(Byeongsoo Lim),류승진(Seungjin Ryu),김대욱(D. Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3

The use of aluminum alloys is an attractive possible option in order to reduce the weight of automobile body structures and to achieve the subsequent improvement of fuel economy and driving performance. In this study, the post-weld cold working process was used to improve the fatigue strength of aluminum resistant spot welds (Al RSW). The post-weld cold working process includes the special shaped indenters that are pressed or driven into the weld nugget area in order to induce the compressive residual stresses. Comparisons of the fatigue life and the failure modes between the as-welded specimens and the post-weld cold worked Al RSW specimens are discussed. Also, in order to analyze the failure behavior, finite elements method (FEM) was employed to compare the results with the experimental results.

냉간가공에 의한 자동차 차체용 강 점용접의 피로수명 향상

김민혁(Minhyuk Kim),임병수(Byeongsoo Lim),류승진(Seungjin Ryu),김대욱(D. Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Resistance spot welding (RSW), or spot-welding, is still the most frequently used sheet metal fabrication process for automotive body applications. The optimization of the number, location, and quality of spot welds is a major economic consideration. In order to improve fatigue strength of low carbon steel RSWs, a post-weld cold working processhas been recently introduced. The post-weld cold working process on the spot weld joints generates uniform and consistent large zones of compressive residual stresses using a specially designed indentation device. The compressive residual stress distributions on the RSWs can be modified through the cold working process parameters including cold working pressure and indenter size. The effect of the indenting pressure during the cold working process on the fatigue properties of the low carbon steel spot weldments is investigated. Comparisons of the fatigue strength and fractography between the as-resistance spot-welded specimens and the post-weld cold worked resistance spot-weld specimens are made in this investigation.

배터리 팩을 위한 Boost 컨버터 기반 셀 밸런싱 토폴로지 및 스위칭 제어 전략

백인수(Insu Baek),이평연(Pyeongyeon Lee),류승진(Seungjin Ryu),김종훈(Jonghoon Kim) 전력전자학회 2021 전력전자학술대회 논문집 Vol.2021 No.11

배터리 팩을 안전하고 효율적으로 운용하기 위해서는 어플리케이션에서 요구하는 운용 범위에 맞게 출력을 제어할 수 있어야 하며, 운용 중 발생하는 배터리 팩 내부 셀 간 불균형의 최소화가 필요하다. 이의 목적을 달성하기 위해 배터리 팩에 DC/DC 컨버터와 셀 밸런싱 회로 등, 많은 보조 회로를 탑재해야 한다. 본 논문에서는 기존에 셀 밸런싱과는 다르게 셀 간 에너지 교환이 아닌, DC/DC 컨버터의 기능을 수행하면서 셀 밸런싱을 수행하는 Boost 컨버터 기반 셀 밸런싱 토폴로지를 제안한다. PSIM 툴을 사용하여 제안하는 DC/DC 컨버터와 셀 벨런싱 기능을 가진 토폴로지의 성능을 검증한다.

사면불상의 의미 재고 -전 대구 동화사 비로암 삼층석탑 출토 사리장엄을 중심으로-

류승진 한국고고미술연구소 2021 동원학술논문집 Vol.22 No.-

The four gilt-bronze Buddhist plaques currently on display at the Daegu National Museum and the agalmatolite sarira reliquary owned by the Dongguk University Museum in Seoul form part of the same sarira reliquary set enshrined in the Three-story Stone Pagoda of Biroam Hermitage at Donghwasa Temple in 863, third year of the reign of King Gyeongmun of Silla, to commemorate King Minae (r. 838-839). The four gilt-bronze plaques forming the casket surrounding the sarira jar are inscribed with Buddha triads, respectively featuring the Medicine Buddha holding a medicine case in the left hand, a Buddha with hands held together, a Buddha with hands in the bhumisparsa (earth-touching) mudra, and a Buddha wearing a resplendent crown and hands in the bodhasri (wisdom-fist) mudra, each with an attendant bodhisattva on either side. According to their iconographic characteristics and conventional interpretations, the Buddha holding the medicine case has been identified as the Medicine Buddha of the east, the Buddha making the bhumisparsa mudra as Sakyamuni of the south, the Buddha with hands together as the Amitabha of the west, and the Buddha wearing a crown and making the bodhasri mudra as Vairocana of the north. More specifically, the Buddha wearing a crown and with hands in the bodhasri mudra has been interpreted as Mahavairocana of Vajradhatu (diamond realm), the principal icon of esoteric Buddhism. the principal icon of esoteric Buddhism. Hence these four icons have been considered the major example of the four Buddhas of the four directions of esoteric Buddhism dating to the Silla period. In terms of iconographic characteristics, however, they do not correspond at all to the four Buddhas of the four directions of esoteric Buddhism, which are featured in the center of the Mandala of the Two Realms (K. Yanggye mandara) along with the Buddha of the center, comprising the five Buddhas of the five directions. Therefore, to properly understand their meaning and characteristics, rather than approaching them from the perspective of esoteric Buddhist art, they should be placed in the same context as similar examples of the “four-sided Buddhas,” which represent the four Buddhas on four sides. Among the four-sided Buddha images of Korea, the largest number are relief carvings on stone pagodas. The four-sided Buddhas of stone pagodas are highly varied as if living beings, and there is not a single instance of two identical image. But they have been found to be naturally connected to each other according to several rules. First, the axis of time and place exists, so the Medicine Buddha of the east and Amitabha Buddha of the west form the horizontal axis of place, while Sakyamuni, the present Buddha, and Maitreya, the future Buddha, form the vertical axis of time. Considering the funerary nature of a stone pagoda, where the relics (sarira) of Sakyamuni are enshrined, in many cases Sakyamuni making the bhumisparsa mudra is carved on the southern side, which is the front of the pagoda. But the growing popularity of images of Vairocana making the bodhasri mudra gradually influenced the composition of the four-sided Buddhas on stone pagodas, and Sakyamuni, who had occupied the front of the pagoda, eventually gave way to Vairocana. Around the time Vairocana making the bodhasri mudra began to appear among the four-sided Buddhas carved in relief on stone pagodas, there emerged cases of Vairocana images with the same iconography being created simultaneously in the same worship space. Sudoam Hermitage at Cheongamsa Temple in Gimcheon has a stone pagoda decorated with four Buddhas on four sides, including a Buddha making the bodhasri mudra. In the same compound, a stone seated image of Vairocana making the bodhasri mudra was enshrined as the principal icon of Daejeokgwangjeon Hall. Likewise, the principal icon of Biroam Hermitage at Donghwasa Temple in Daegu is a seated statue of Vairocana making the bodhasri mudra, similar to the Buddha wearing a crown and making the bodhasri mudra found among the four gilt bronze Buddhist plaques from the pagoda at the same hermitage. It is clear that an attempt was made to differentiate between the two with iconographic features such as the addition of the crown and variation of the robes. Within this new order, appropriate iconographic features of esoteric Buddhism were selected to differentiate the Buddhas because the four-sided Buddhas are symbolic of the countless Buddhas of all directions throughout the world (K. sibangjebul, literally “buddhas of the ten directions”). The Buddhas of the four sides, all different from each other, would have been an effective way of helping people to contemplate the Buddhas of the ten directions when circumambulating the pagoda. In the case of the Three-story Stone Pagoda of Biroam Hermitage at Donghwasa Temple where the four-sided Buddhas are not carved on the exterior, the inscription on the sarira jar mentions haengdo, a type of spiritual practice indicating circumambulation of the pagoda. The purpose of this practice would have been to circle the pagoda while imagining the four Buddhas protecting the sarira inside the pagoda and thereby attain the same virtue attained by contemplating the Buddhas of the ten directions. Originally, the Buddhas of the ten directions described in Mahayana Buddhism refer to a countless number of Buddhas of infinite variety. As if reflecting this description, it is not easy to define the characteristics and meaning of the four-sided Buddhas, which are infinitely varied as if living beings. They are generally found on the exterior of stone pagodas but are sometimes hidden on the inside; without a single, defined direction they seem to be in constant flux and change, which is the inherent nature of the four sided Buddhas as symbols of the Buddhas of the ten directions. This is also why they cannot be regarded as images of esoteric Buddhist art.