Experimental Method for Durability Evaluation of a Chisel Mounted on a Composite Working Implement

Han, Jeongwoo,Moon, Sanggon,Lee, Geunho,Kang, Daesik Korean Society for Agricultural Machinery 2017 바이오시스템공학 Vol.42 No.4

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

Experimental Method for Durability Evaluation of a Chisel Mounted on a Composite Working Implement

( Jeongwoo Han ),( Sanggon Moon ),( Geunho Lee ),( Daesik Kang ) 한국농업기계학회 2017 바이오시스템공학 Vol.42 No.4

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner’s Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

Soil Moisture Drought Forecasting Using Neural Network Ordinary Differential Equations: The Case Study for California

Jeongwoo Han,Vijay P. Singh 대한토목학회 2023 대한토목학회 학술대회 Vol.2023 No.10

Simulink Model Implementation of MVDR Adaptive Beamformer for GPS Anti-Jamming

Jeongwoo Han,Hoon Park,김복기,Jin-Hee Han 사단법인 항법시스템학회 2020 Journal of Positioning, Navigation, and Timing Vol.9 No.2

For the purpose of development of anti-jamming GPS receiver we have developed an anti-jamming algorithm and its Simulink implementation model. The algorithm used here is a form of Space-Time Adaptive Processing (STAP) filter which is well known as an effective way to remove wideband jamming signals. We have chosen Minimum Variance Distortionless Response (MVDR) block-adaptive beamforming algorithm for our development since it can provide relatively fast convergence speed to reach optimal weights, stable and high suppression capability on various types of jamming signals. We will show modeling results for this MVDR type adaptive beamformer and some simulation results. We also show the integrity of the demodulated satellite signals and the accuracy of resulting navigation solutions after anti-jamming operation.

고민 나눔을 위한 대화형 익명 플랫폼 어플리케이션

한정우(Jeongwoo Han),곽명섭(Myeongsub Kwak),강찬혁(Chanhyuk Kang),한경식(Kyungsik Han) 한국HCI학회 2020 한국HCI학회 학술대회 Vol.2020 No.2

본 연구의 목적은 고민을 나누며 불안감과 스트레스 해소를 도와주는 플랫폼 시스템을 디자인하는 것이다. 고민 없이 살아가는 사람들은 없다. 세상은 점점 각박해지고 누구에게도 털어놓을 수 없는 고민들이 늘어나고 스트레스와 우울감을 느끼는 사람들이 많아졌다.[1] 이런 세상 속에서 부담과 거부감 없이 고민을 털어놓을 수 있는 플랫폼을 제공하고 일상 속의 피난처와 같은 역할을 이번 서비스를 통해 해내고자 한다. 이 서비스를 통해 비슷한 고민을 가진 많은 사람들을 대화를 통해 서로 연결해준다. 이 서비스는 전 연령대 중에서 가장 스트레스와 고민이 많은 20 대를 타겟 사용자로 설정했다. 많은 20 대 사용자가 이 서비스를 통해 소통하며 심리적인 위로를 얻을 것이다. 또 이 서비스는 사용자가 직접 조건을 설정해 만나고자 하는 사람을 필터링 할 수 있게 해 익명이라는 요소가 주는 불안감을 낮추고 신뢰성을 높인다. 그리고 플랫폼 속에서 서로의 고민을 나누며 스스로를 되돌아보고 발전하는 효과도 기대할 수 있다.

용접잔류응력 이완 및 노치변형률법을 적용한 십자형 필렛용접 이음부의 피로수명 평가

한정우(Jeongwoo Han),한승호(Seungho Han),신병천(Byungchun Shin),김재훈(Jaehoon Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

The fatigue strength of welded joint is influenced by the welding residual stress which is relaxed depending<br/> on local stress distributed in vicinity of stress raisers, eg. under cut, overlap and blow hole. To evaluate its<br/> fatigue life the geometry of the stress raisers and the welding residual stress should be taken into account.<br/> The several methods based on notch strain approach have been proposed in order to consider the two factors<br/> above mentioned. These methods, however, have shown considerable differences between analytical and<br/> experimental results. It is due to the fact that the amount of the relaxed welding residual stress evaluated by<br/> the cyclic stress-strain relationship do not correspond with that occurred in reality. In this paper the residual<br/> stress relaxation model based on experimental results was used in order to reduce the discrepancy of the<br/> estimated amount of the relaxed welding residual stress. Under an assumption of the superimposition of the<br/> relaxed welding residual stress and the local stress, a modified notch strain approach was proposed and<br/> verified to the cruciform welded joint.

초분광 영상을 이용한 꿀벌과 꿀벌응애의 분광 특성 구명

한정우 ( Jeongwoo Han ),김민지 ( Min-jee Kim ),이홍구 ( Hong-gu Lee ),김수배 ( Su-bae Kim ),이아영 ( Ah-yeong Lee ),모창연 ( Changyeun Mo ) 한국농업기계학회 2022 한국농업기계학회 학술발표논문집 Vol.27 No.1

꿀벌응애(Varroa jacobsoni)는 주로 꿀벌의 체액을 영양분으로 기생하며 살아가는 진드기의 일종이다. 크기는 1.6 mm x 1.1 mm로서 육안으로 쉽게 구별되지 않으며, 양봉 농가의 고령화로 인해 꿀벌응애 판별이 어려운 문제가 있다. 최근 영상 기술을 통한 꿀벌응애 판별 연구가 수행되고 있으나 꿀벌응애를 RGB영상으로 분석할 경우 화질에 따라 정확도 차이가 발생하는 등 여러 한계점이 존재한다. 초분광 영상 기술은 분광 기술과 영상기술이 융합된 기술로서 측정 대상물들의 구성 성분까지 측정가능하다. 위 한계점들을 극복하기 위해 초분광 영상(Hypersectral Images)를 활용하여 꿀벌과 정상 꿀벌의 분광적 특성을 구명하고자 한다. 본 연구에서 595 ~ 860nm 파장영역의 초분광 영상 데이터를 획득할 수 있는 초분광 카메라(MQ022HG-IM-SM4X4-RN2, Ximea, Germany)를 사용하여 400mm 거리에서 초분광 데이터를 획득했다. HSI Studio(Imec, Belgium) 초분광 영상 데이터 분석 프로그램을 사용하여 정상 꿀벌과 꿀벌응애가 존재하는 꿀벌 각 1마리를 총 8 부위로 나누어 각 부위에 대한 Balanced value를 구하여 비교 분석했다. 주변 환경(소비)에도 고유 파장대가 존재하여 간섭이 발생할 경우를 대비하여 꿀벌응애를 검출할 수 있도록 꿀벌과 소비 주변 환경과의 Balanced value를 구하였다. 본 연구를 통해 꿀벌응애와 꿀벌의 초분광 스펙트럼의 차이를 확인하였으며, 이는 추후 모니터링 시스템에 적용하여 꿀벌응애 판별에 기여할 것으로 판단된다. 추후 꿀벌응애 초분광 영상 데이터를 추가하고, 이를 기계학습을 활용한 꿀벌응애 판별 알고리즘 개발 연구를 진행 할 것이다.

다균열 간섭, 합체, 성장이론을 고려한 십자형 필렛용접 이음부의 피로균열진전수명 평가

한정우(Jeongwoo Han),한승호(Seungho Han),신병천(Byungchoen Shin),임전(Jeon Rim),김재훈(Jaehoon Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

Fatigue life of welded joints are governed by the propagation of multiple collinear surface cracks distributed randomly along weld bead. These cracks propagate in mutual interaction and coalescence of them. To estimate the fatigue life, the influences of above two mechanisms on the fatigue life should be taken into account. These two mechanisms appear through the stress intensity factors disturbed mutually. However, it is difficult to calculate the stress intensity factors of multiple surface cracks located in vicinity of weld toe. The stress intensity factors are calculated normally by using the Mk -factors, but such Mk-factors are very rare in literature. In this study, the Mk-factors were obtained from a parametric study on crack length and depth, in which a finite element method is used. A fatigue test for a cruciform welded joint was conducted. The fatigue life of the tested specimen was estimated through present method with the informations obtained from the test, e.g. the number, size and locations of the cracks. The estimated and measured fatigue life showed a good agreement.

산업통상자원부 화학산업분야 정책방향 및 RND 전략

한정우(Jeongwoo Han) 한국고분자학회 2023 한국고분자학회 학술대회 연구논문 초록집 Vol.48 No.2

다양한 용접구조상세의 피로균열진전수명 평가

한승호(Seungho Han),한정우(Jeongwoo Han),신병천(Byungchun Shin) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

To estimate fatigue crack propagation life for the representative welding details, i.e. non-load carrying cruciform, cover plate and longitudinal stiffener joint, the stress intensity factors at the front of the surface cracks have to be calculated, which are influenced strongly by the geometry of attachments, weld toes and the crack shapes. However, it is difficult to obtain the stress intensity factors of the multiple surface cracks located in vicinity of the weld toe due to their geometrical complexity. For the effective calculation of the stress intensity factors the M<SUB>k</SUB>-factor was introduced which can be derived by a parametric study performed by FEM considering influence of the geometrical effects. The fatigue life of the welding details was estimated through considering the mechanisms of mutual interaction and coalescence of multiple collinear surface cracks distributed randomly along the weld toe. The estimated results for the fatigue life had a good agreement with that of experiment.