Interfacial micromechanics modeling for bolted joints in ultra-precision machine tools

Yu Chang,Jianguo Ding,Hui Fan,Yuanyuan Ding,Hui Zhuang,Peng Chen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

Bolted joints are widely adopted in various mechanical structures. However, the uncertainty and complexity of the contact surfaces affect accurate modeling. Herein, an interfacial micromechanics model is proposed to characterize the contact behaviors of bolted joints in an ultra-precision machine tool (UMT). The bolted joint is modeled as a virtual material layer with transversely isotropic behaviors, whose constitutive relation is identified by fractal theory. The proposed model accurately formulates the multi-scale contact characteristics and allows convenient integration with the structural dynamic modeling of UMT. Dynamic analysis of the simulation results and the experimental measurements in the time and frequency domains was conducted to identify the most sensitive factor affecting the tool tip vibration. On this basis, the structural optimization for the UMT was further implemented, which effectively reduced vibration by 15.5 %. The dynamic predictions were validated by modal and vibration response tests.

A Linear Control Strategy Using H-infinitive Methodology to an AMB System with a Flexible Rotor

Yu Chang,Joo-Ho Yang,Hwang-Hun Jeong,Gyo-Ho Choi,Young-Wan Kim 한국소음진동공학회 2003 한국소음진동공학회 국제학술대회논문집 Vol.2003 No.8

A Study on Analysis of Industrial Injury Characteristics of Aging Workers in Agriculture

Yuchang Kim,Daesu Kim,Kyunghwan Park,Daesik Kim 대한인간공학회 2014 大韓人間工學會誌 Vol.33 No.6

Objective:This study aims to devise industrial injury prevention measures by analyzing industrial injury characteristics including the status of industrial injuries, source of industrial injury and accident type in order to prevent aging workers" industrial injuries that account for more than half in the workplaces in agriculture. Background: Continuous migration from farm to city takes place among young people in rural areas in Korea, a traditionally agricultural country due to rapid industrialization and economic development. The aging rate in rural areas in 2013 was 37.3%, about three times higher than the total aging rate of 12.2% in Korea. According to industrial injury statistics of the Ministry of Employment and Labor, the number of industrial injuries in agriculture shows an uptrend and the industrial injuries of aging workers account for more than 50% each year. Method: Of the 2,970 industrial injury cases occurred in the workplaces in agriculture for five years during 2008 and 2012 offered by a national agency related to health and safety, this study analyzed 1,767 industrial injury cases of aging workers. Results: As a result of an analysis on aging workers" industrial injuries by company size in agriculture, 89.8% of the total number of industrial injuries were analyzed to occur in small scale company. According to aging workers" industrial injuries by source of industrial injury and accident type, the outdoor floor and a fall were analyzed to be the highest at 16.5% and 26.1%, respectively. Conclusion: This study analyzed aging workers" industrial injuries by company size, age, job duration, accident severity, gender, nationality, the source of industrial injury and accident type in order to identify industrial injury characteristics in agriculture. Application: The identification of industrial injury characteristics of aging workers in agriculture is judged to be helpful to devising effective measures to prevent industrial injuries.

A Study on Analysis of the Industrial Injury Characteristics in the Agriculture

YuChang Kim,DaeSu Kim,KyungHwan Park,DongHyun Seo,KyungSuk Lee 대한인간공학회 2013 대한인간공학회 학술대회논문집 Vol.2013 No.10

Objective: The aim of this study is to analyze the industrial injury characteristic and prepare the effective counterplan about the industrial accident prevention of the workplace in the agriculture sector. Background: Recently government support for agricultural policy-oriented individual to assist in the workplace was changed to business support. Because of this many businesses increased, the number injured in the agriculture sector is increasing. However, because the studies on the characteristics and causes of injury have not been performed, the effective measure for the prevention of industrial injury is difficult to establish. Method: In study methods, 2,970 cases of industrial injury during the last five years (2008-2012) in the agriculture sector were analyzed. The data was offered by Korean Occupational Safety and Health Agency. Results: The results of analyze the industrial injury characteristic of the workplace in the agriculture sector, number of industrial injury for source of industrial injury was 12.3% in the outdoor floor and for accident type was 23.1% in the fall. Conclusion: This study analyzed industrial injury characteristic which size and type of business, accident type and source of industrial injury through the case of industrial injury in agriculture sector. Application: The result of this study will be helpful when it grasps the industrial injury characteristic in the agriculture and prepares the effective industrial injury prevention method.

NEW RESULTS TO BDD TRUNCATION METHOD FOR EFFICIENT TOP EVENT PROBABILITY CALCULATION

YUCHANG MO 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.7

A Binary Decision Diagram (BDD) is a graph-based data structure that calculates an exact top event probability (TEP). It has been a very difficult task to develop an efficient BDD algorithm that can solve a large problem since its memory consumption is very high. Recently, in order to solve a large reliability problem within limited computational resources, Jung presented an efficient method to maintain a small BDD size by a BDD truncation during a BDD calculation. In this paper, it is first identified that Jung’s BDD truncation algorithm can be improved for a more practical use. Then, a more efficient truncation algorithm is proposed in this paper, which can generate truncated BDD with smaller size and approximate TEP with smaller truncation error. Empirical results showed this new algorithm uses slightly less running time and slightly more storage usage than Jung’s algorithm. It was also found, that designing a truncation algorithm with ideal features for every possible fault tree is very difficult, if not impossible. The so-called ideal features of this paper would be that with the decrease of truncation limits, the size of truncated BDD converges to the size of exact BDD, but should never be larger than exact BDD.

가축에 의한 산업재해 원인분석에 대한 연구

Yuchang Kim,Juhyun Park,Donguk Shin,Wonsik Choi 대한인간공학회 2016 대한인간공학회 학술대회논문집 Vol.2016 No.06

Objective: In this study, the analysis of industrial injury situation by livestock looks in the direction of reduction proposals of specific animal husbandry industrial injury and tries to actually presenting the basics of safety education and management in order to reduce the industrial injury caused by livestock in the livestock industry. Background: Recently, as agricultural workers number of Korea continuously increase. However, measures for prevention of agricultural industry are sufficient because the industrial injury prevention focuses on the manufacturing. So in order to prepare an effective industrial injury prevention measures in animal husbandry business field, there is a need for research in order to ensure the basic data. Method: Through statistical analysis and literature review of 191 cases in the last five years (2008-2012) of occupational injury, this study investigated animal husbandry workers including by the animals for occupation, by size, number of days per seniority, age, etc. Result: The results of the analysis of the characteristics of the industrial injury caused by livestock in the livestock industry. In the job-specific affected population labor workers was the highest in 88.5 percent. In the scale by affected people, injury in the workshop of less than five people was the highest at 42.9 percent. Conclusion: Analysis of the livestock industry occupational injury case analyzed the characteristics of the livestock industry occupational injury at the various classification. Application: The results of this study is determined that it becomes useful to prepare an effective livestock industry injury prevention measures by understanding the characteristics of the industrial injury.

A Study on Characteristics of Fatal Industrial Injuries and Illnesses Among Older Workers

Yuchang Kim,Daesu Kim,Wonsik Choi 대한인간공학회 2015 대한인간공학회 학술대회논문집 Vol.2015 No.10

Objective: 본 연구의 목적은 사망 산업재해에서 비 고령작업자와 고령작업자의 재해특성을 비교하여 고령작업자의 재해특성을 찾아내어 예방대책과 정책대안을 마련하고자 하는 것이다. Background: 고령화 사회가 되어감에 따라 전체 산업재해자 중에서 고령작업자가 차지하는 비율이 증가하고 있는 추세이다. 고용노동부의 산업재해통계에 따르면 산업재해자수 중 50대 이상의 고령작업자 수는 2010년 42,598명, 2011년 43,241명, 2012년 44,783명으로 증가추세를 보이는 반면, 50대 미만의 비 고령작업자 수는 2010년 56,047명, 2011년 50,051명, 2012년 47,468명으로 감소추세를 보이고 있다. 국내 사망 산업재해 분석결과, 2012년에는 전체 사망재해의 58.5%, 2011년 60.1%, 2010년 56.0%가 50세 이상의 고령작업자에서 발생한다는 것을 알 수 있었다. 이를 통해 전체 사망재해에서 고령작업자의 사망재해가 많은 비중을 차지하는 것을 알 수 있다. Method: 3년간 (2010~2012)의 사례 4,664건에 대한 사망 산업재해 통계분석과 문헌조사 등을 통해 고령작업자와 비 고령작업자의 발생형태별, 업종별, 규모별 등의 재해특성을 조사하였다. Results: 고령작업자의 사망 산업재해 특성을 분석한 결과, 발생형태별 사망재해자수에서는 떨어짐이 37.5%로 가장 높게 나타났고 입사근속기간별 사망재해자수에서는 1년 미만이 48.3%로 가장 높게 나타났다. Conclusion: 사망재해 사례 분석을 통하여 업종별 사망재해자수, 규모별 사망재해자수, 발생형태별 사망재해자수 등의 다양한 분류에서 고령작업자의 사망 산업재해 특성을 파악하였다. Application: 본 연구의 결과는 고령작업자의 사망 산업재해 특성을 통하여 효과적인 고령작업자의 산업재해예방 방안을 마련하는데 도움이 될 것이라 판단된다.

중소규모 해상 이동식 담수화 선박 기술 개발 및 사업화

임유창(Yuchang Lim),김성규(Sungkyu Kim),김기홍(Keehong Kim),강하늘(Haneul Kang) 대한환경공학회 2022 대한환경공학회 학술발표논문집 Vol.2022 No.11

NEW RESULTS TO BDD TRUNCATION METHOD FOR EFFICIENT TOP EVENT PROBABILITY CALCULATION

Mo, Yuchang,Zhong, Farong,Zhao, Xiangfu,Yang, Quansheng,Cui, Gang Korean Nuclear Society 2012 Nuclear Engineering and Technology Vol.44 No.7

A Binary Decision Diagram (BDD) is a graph-based data structure that calculates an exact top event probability (TEP). It has been a very difficult task to develop an efficient BDD algorithm that can solve a large problem since its memory consumption is very high. Recently, in order to solve a large reliability problem within limited computational resources, Jung presented an efficient method to maintain a small BDD size by a BDD truncation during a BDD calculation. In this paper, it is first identified that Jung's BDD truncation algorithm can be improved for a more practical use. Then, a more efficient truncation algorithm is proposed in this paper, which can generate truncated BDD with smaller size and approximate TEP with smaller truncation error. Empirical results showed this new algorithm uses slightly less running time and slightly more storage usage than Jung's algorithm. It was also found, that designing a truncation algorithm with ideal features for every possible fault tree is very difficult, if not impossible. The so-called ideal features of this paper would be that with the decrease of truncation limits, the size of truncated BDD converges to the size of exact BDD, but should never be larger than exact BDD.

스파크 점화시스템을 적용한 하이브리드 로켓 설계

길유창(Yuchang Gil),최나린(Narin Choi),원동민(Dongmin Won),구평회(Pyeonghoe Goo),하재형(Jaehyeong Ha),이서진(Seojin Lee),김민석(Minseok Kim),박진혁(Jinhyeok Park),전하상(Hasang Jun),하정원(Jeongwon Ha),변건일(Gunil Byun),고수한(Suhan Ko 한국추진공학회 2021 한국추진공학회 학술대회논문집 Vol.2021 No.11