中部地方의 複合營農시스템의 模型化 硏究

張東日,金基鐵 충남대학교 새마을연구소 1985 새마음 논문집 Vol.6 No.-

This study was a basic research for developing a computer program which could be used for designing the optimum systems of diversified farming by region. The objective of study was to model the diversified farming systems including the regional characteristics and applicable to the central regions of Korea. For this purpose, the three villages of plain, hilly and mountainous region were selected, and farming survey and systems analysis were conducted for mainly 1984 agriculture. Surveys were carried out on January and July 1985 for the following villages: 1) Plain region­­­Jungjung­Ri, Buyeor­Eup, Buyeor Contry, Chungnam Province 2) Hilly region­­­Bonggi­Ri, Kumnam­Myon, Yunki Country, CHungnam Province 3) Mountainous region­­­Sungsan­Ri, Ohchang­Myon, Chungwon Country, Chungbuk Province The surveyed data were analyzed by systems analysis. Then, the diversified farming systems were modeled for three areas not only with the analyzed results, but also with the modeling objectives, the crop selection criteria and assumptions. They consist of cropping systems and farm machinery system. The former in­cludes four cropping patterns for paddy, six cropping patterns for upland, two kinds of fruit crop and three kinds of livestock. The latter comprises seven farm machinery for each work system. The basic cropping systems was “Rice(Barley) + Special crop + Supplementary crop”. The special crops were selected by the nature of the optimum cultivating conditions and the supplementarys were choosed and combined with the specials to increase their mutual benefits. The introducing priority of the selected crops was decided by their profitability and the cropping patterns were modeled by the combination methods emphasizing the maximum utilization of agricultural resources. Agricultural machinery system was modeled that the major machinery was included for each work system as follows: 1) Plowing and harrowing ­­­Power tiller 2) Transplanting ­­­Power transplanter 3) Pest control ­­­Power sprayer 4) Irrigation and drainage ­­­Water pump 5) Harvesting ­­­Binder 6) Threshing ­­­Power thresher 7) Drying ­­­Continous dryer

균열재(龜裂材)의 불안정연성파괴(不安定延性破壞)에 대한 J 적분(J積分) 평가(評價)를 위한 탄소성해석(彈塑性解析)

장동일,정경섭,Chang, Dong Il,Jung, Kyoung Sup 대한토목학회 1987 대한토목학회논문집 Vol.7 No.1

본(本) 연구(硏究)는 소규모강복범위(小規模降伏範圍)를 벗어나는 대규모강복조건하(大規模降伏條件下)에서 구조안정성(構造安定性)에 관(關)한 중요(重要)한 문제(問題)인 불안정연성파괴(不安定延性破壞)를 평가(評價)할 수 있는 파괴역학인자(破壞力學因子)로서의 J 적분(積分)을 수치해(數値解)로서 구하는데 그 목적(目的)을 두었다. 이를 위해 균열재(龜裂材)의 균열선단요소(龜裂先端要素)로 8절점등방특이요소(節點等方特異要素)를 사용(使用)하고, 균열발생(發生)은 파괴인성(破壞靭性) $J_{IC}$를 초과할 때 일어나도록 하였으며, 그리고 균열성장(成長)의 취급(取級)은 균열개구각(龜裂開口角)을 이용(利用)했다. 본(本) 연구(硏究)에 의해 해석(解析)된 J 적분치(積分値)를 사용(使用)하여 균열재의 균열발생 과 안정성장(安定成長), 불안정(不安定) 발생점(發生點)을 찾은 결과(結果) 다른 연구결과(硏究結果)와 잘 일치(一致)하고 있어 탄소성(彈塑性)을 고려(考慮)한 J 적분치(積分値)가 균열의 안정성장(安定成長) 및 불안정연성파괴(不安定延性破壞) 문제(問題)를 다루는 파괴역학인자(破壞力學因子)로서 직접(直接) 이용(利用)될 수 있음을 보였다. It is the objective of this study to estimate J-integral by numerical analysis, in which J-integral as aparameters in fracture mechanics can be used to evaluate unstable ductile fracture which is a important problem with respect to structural stability when the scope is beyond small scale yielding criteria. For this, 8-node isoparametric singular element as crack tip element of a cracked material was used to solve plastic blunting phenomenon at crack tip, and crack opening was forced to start when J-value was exceeding fracture toughness $J_{IC}$ of the material. And crack propagation behaviour was treated by using crack opening angle. From this study, it was shown that crack opening, stable propagation and unstable opening point of the cracked material found by using J-value obtained from this study were accord with the other study, so think, J-value obtained from this study can be directly used as a parameter in fracture mechanics to deal with the problem of stable propagation of crack and unstable ductile fracture.

용접(鎔接) 강부재(鋼部材)의 피로균열성장(疲勞龜裂成長)에 대한 잔류응력특성(殘留應力特性)에 관한 연구(硏究)

장동일,김두환,Chang, Dong Il,Kim, Doo Hwan 대한토목학회 1987 대한토목학회논문집 Vol.7 No.2

용접(鎔接) 강구조물(鋼構造物)의 피로균열성장거동(疲勞龜裂成長擧動)에 관(關)한 용접잔류응력(鎔擬殘留應力)의 거동(擧動)을 파악(把握)키 위하여 열처리(熱處理)를 실시(實施)하고 피로균열성장(疲勞龜裂成長) 및 검토(檢討)한 결과(結果) 용접부(鎔接部)는 경화(硬化)되어 늑성(勒性)이 감소(減少)되므로 소재부(素材部)보다 피로균열성장율(疲勞龜裂成長率)이 높았으며 이를 열처리(熱處理)한 결과(結果) 경도(硬度)나 저항력(抵抗力)이 증가(增加)되어 개선(改善)되었으며 $650^{\circ}C$ 정도(程度)에서 가장 이상적(理想的) 이었다. Elber 식(式)은 Paris-Erdogan 식(式)에 비(比)해 균열(龜裂)닫힘현상(現狀)을 고려(考廬)하므로 더 낮은 균열성장율(龜裂成長率)을 가지며 각(各) 열처리(熱處理)에 의한 곡선(曲線)들이 서로 비슷하므로 잔류응력(殘留應力)의 효과(?果)를 고려(考慮)할 수 없었다. 균열(龜裂)길이에 따른 개구하중(開口荷重)은 경도(硬度)가 높을수록 큰 값을 가지나 열처리(熱處理) 후(後)는 경도(硬度)값의 저하(低下)로 피로균열(疲勞龜裂) 성장율(成長率)이 낮아지며 흡수(吸收)에너지와 파괴늑성(破壞勒性)을 증대(增大)시켜 균열저지능력(龜裂沮止能力)을 가져 파괴(破壞)의 위험성(危險性)을 감소(減少)시킨다. Annealing were performed to investigate the behaviors of the residual stress remaining on the member of a steel structure. According to the fatigue test, the welding part has higher fatigue crack growth rate than the base metal part because the hardening of welding part reduce fracture toughness. However, the heat treatment decrease the hardness and increase the resistance to failure. Thus, the fatigue crack growth rate is improved and it reaches the minimum at $650^{\circ}C$. Elber' s equation includes the effect of the crack-close so that this equation provides a lower the fatigue crack growth rate than Paris-Erdogan' s equation, the Elber's curves show no significant difference to indentify the effect of the residual stress. The Pop loading along the crack length increases as the hardness goes higher. The heat treatment not only decrease the hardness, and the fatigue crack growth rate, but increase the absorption energy and fracture toughness on the member of a steel structure. As the result, the heat treatment produces the resistant ability to cracking which can reduce the degree of danger to failure.

Torque Shear형 고장력 볼트 이음부의 피로거동에 관한 실험적 연구

장동일,이성욱 한국강구조학회 1996 韓國鋼構造學會誌 Vol.8 No.4

개회사

장동일 한국강구조학회 1997 韓國鋼構造學會誌 Vol.9 No.2

단순변동하중(單純變動荷重)을 받는 용접구조용강(鎔接構造用鋼)의 피로균열성장(疲勞龜裂成長)

장동일,박용걸,이봉학,Chang, Dong Il,Bak, Yong Gul,Lee, Bong Hak 대한토목학회 1987 대한토목학회논문집 Vol.7 No.4

Fatigue tests using a single-peak loading and a two-step loading were carried out to examine the fatigue crack growth behaviar and to find the appropriate analysis method. C-T specimens were made using structural steel SWS58 for the tests. From this, just after a single-peak loading acceleration effect was occured and after some times retardation effect was found. And eminent retardation effect was found after High-Low two-step loading. The transition effect of crack growth due to this variable loading was occured owing to the residual stress and the plastic zone size at the crack tip. And the behaviors of these are well explained by Elber's Crack Closure Model. Also I could find that the Wheeler's Retardation Model is a simple and appropriate theory among analysis methods of fatigue crack growth under the variable loading. 본(本) 연구(硏究)는 단순변동하중하(單純變動荷重下)에서의 피로균열성장거동(疲勞龜裂成長擧動)을 고찰하고 해석방법(解析方法)을 구하고자, 용접구조용강(鎔接構造用鋼) SWS 58을 사용하여 CT 시험편을 제작하고 간단한 하중모델을 설정(設定)하여 피로실험(疲勞實驗)을 행했다. 그 결과 단일과하중작용직후(單一過荷重作用直後)에는 가속효과(加速效果)가 경미(輕微)하게 발생하였으며 그후 상당한 지연효과(遲延效果)가 발생했다. 2단중복하중하(段重復荷重下)에서는 low-high인 경우 약간의 가속효과(加速效果)가 발생하나 high-low인 경우는 상당한 지연효과(遲延效果)가 발생했다. 이러한 하중변화(荷重變化)에 따른 균열성장율(龜裂成長率)(da/dN)은 균열선단(龜裂先端)의 잔류응력(殘留應力)과 소성영역(塑性領域)으로 인한 상호영향(相互影響)때문이며, 이러한 미시적(微視的) 균열성장거동(龜裂成長擧動)은 Elber의 crack closure model로 잘 설명(說明)될 수 있으나 피로균열성장해석방법(疲勞龜裂成長解析方法)으로는 불충분(不充分)하다. 반면 변동하중하(變動荷重下)에서의 피로균열성장해석방법(疲勞龜裂成長解析方法) 중(中) Wheeler의 retardation model은 간편하면서도 적합한 이론임을 알 수 있었다.

미곡의 산물이송을 위한 이동식 오거의 개발

장동일,장규섭,김재홍,김진영 ( D . I . Chang,K . S . Chang,J . H . Kim,J . Y . Kim ) 한국농업기계학회 1989 바이오시스템공학 Vol.14 No.2

RPF 합성보의 실험 연구

장동일,황윤국,김정호,조태준 한국강구조학회 1998 韓國鋼構造學會誌 Vol.10 No.1

강구조 협의회 창립축사

장동일 한국강구조학회 1996 韓國鋼構造學會誌 Vol.8 No.4

횡방향 맞대기 용접부를 가진 고장력볼트 마찰이음부의 역학적 특성에 관한 연구

장동일,김학재 한국강구조학회 1998 韓國鋼構造學會誌 Vol.10 No.2