복합하중을 받는 원통형 적층복합재 구조의 파괴에 대한 열응력의 영향

조희근 한국생산제조학회 2023 한국생산제조학회지 Vol.32 No.6

As the mechanical behavior of cylindrical structures subjected to complex loads is very complex, predicting phenomena such as displacement, stress, and failure is very difficult. In this study, the effect of thermal stress due to temperature on the failure of a laminated composite cylindrical structure, in which tension, bending, and torsion are applied simultaneously, was evaluated through FEA numerical analysis. Five types of models: Tsai-Wu, Tsai-Hill, Puck, Hoffman, and Hashin, were used to predict the failure of a cylindrical laminated composite shell structure having eight layers. The type of composite failures appeared very different owing to the influence of thermal stress. Contrary to general predictions, we confirmed that thermal stress has a positive effect on failure in certain combinations of layer stacking angles in the case of cylinders.

비선형 복합재 좌굴 해석

조희근 한국복합신소재구조학회 2019 복합신소재구조학회 학술발표회 Vol.2019 No.04

복합재 복합좌굴 해석

조희근 한국복합신소재구조학회 2019 복합신소재구조학회 학술발표회 Vol.2019 No.04

열-습윤에 노출된 적층복합재의 정적-동적 최적화

조희근,안진효 한국복합신소재구조학회 2018 복합신소재구조학회 학술발표회 Vol.2018 No.04

Optimization was performed on the static dynamic behavior of a simply supported laminated composite plate. Thickness optimization was performed with respect to Gr/E laminated composites with simultaneous mechanical load, thermal load and hygro-load. Displacement, fundamental frequency and composite damping were imposed as constraints for optimization. The results of the optimization were much better than those of the conventional methods.

웨이블렛 필터뱅크를 이용한 동적 엔드밀 절삭력 필터링

조희근,진도훈,윤문철,Cho, Hee-Geun,Chin, Do-Hun,Yoon, Moon-Chul 한국생산제조학회 2009 한국생산제조학회지 Vol.26 No.3

The end-milling force behaviour is very complex and it is related to a de-noising phenomenon, so it is very difficult to detect and diagnose this static cutting force phenomenon. This paper presents a new method of filtering of end-milling force in end-milling operation using filter bank technique, based on the wavelet transform. In this paper by comparing the history of end-milling force using wavelet filtering the fundamental end-milling property of the wavelet transform is well reviewed and analyzed. This result of wavelet transform using filter bank shows the possible static prediction of end-milling force with severe dynamic properties such as chatter in end-milling operation.

그레이트바 코팅층 성능평가

조희근,조은경,최준영,박원규 한국복합신소재구조학회 2016 복합신소재구조학회 학술발표회 Vol.2016 No.04

Grate bar is a metal part being used in the sintering process in a steel company. It is exposed to severe operating conditions such as high temperature, corrosion, wear and chemical reaction and etc. In this paper, the surface of the grate bar is coated with high performance materials. They are Al2O3, Cr2O3, WC. These materials have enhanced grate bar’s performances of life time, corrosion, thermal resistance, abrasion, chemical resistance and etc. These high quality characteristics are verified through experimental tests. The results are presented and discussed.

GFRP 적층 복합재 패널의 비선형 좌굴 해석

조희근 한국복합신소재구조학회 2018 복합신소재구조학회논문집 Vol.9 No.4

A thin paneled structure is susceptible to buckling due to its geometric shape. Numerous studies have been conducted on the analysis of the buckling for isotropic materials. However, in the case of composites, the buckling phenomenon is very complicated and difficult to converge. In order to numerically analyze the buckling behavior of GFRP laminated composites, 3D shell elements were applied to analyze the buckling behavior. In this study, nonlinear composite buckling analysis is conducted for three types of layups and the load-displacement characteristics of buckling behavior are investigated. In the case of laminated composites, the buckling behavior exhibits severe nonlinear behavior and is difficult to converge numerically. The arc-length method was used to analyze the buckling behavior of three layup laminated composites. The force-displacement curves of the nonlinear buckling behavior were calculated and the failure of the laminate composite was calculated based on the Tsai-Wu failure theory. 앏은 패널 형태의 구조물은 그 형상의 특성상 좌굴이 발생하기 쉽다. 등방성 재료에 대한 좌굴의 해석은 그동안 많은 연구가 이루어졌다. 그러나 복합재의 경우는 좌굴 현상의 거동이 매우 복잡하고 난해하기 때문에 많은 연구가 이루어지지않았다. 적층복합재의 좌굴거동을 수치적으로 해석하기 위하여 3D 쉘요소를 적용하여 해석을 수행하였다. 본 연구에서는 3가지종류의 layup에 대하여 비선형 좌굴 현상을 계산하였고 좌굴거동의 하중-변위 특성 관계를 규명하였다. 적층복합재의 경우 좌굴거동이 극심한 비선형 현상을 나타내며, 또한 수치적으로 수렴하기 어렵다. 3가지 layup 적층복합재의 좌굴 거동을 해석하기 위하여 arc-length 방법을 사용하였다. 비선형 좌굴 거동의 힘-변위 곡선을 계산 하였고 또한 Tsai-Wu 파괴이론에 의하여 좌굴거동이 발생하면서 복합재의 파괴를 계산하였다.

환자 안전을 위한 경추 및 요추부 도침시술 전후 체크리스트 제안: 예비연구

조희근,송민영,윤상훈,정신영,김종환,백은혜,임정태 한방재활의학과학회 2018 한방재활의학과학회지 Vol.28 No.1

Objectives The authors propose a new checklist model adapted for safety miniscalpel acupuncture procedure of cervical and lumbar spine. Methods On the basis of available literature and expert opinion, a prototype checklist was developed. The checklist was adapted on the basis of observation of daily practice. Results The checklist has three parts: 1. prevention and management of healthcare associated infections, 2. verification list before and after miniscalpel acupuncture treatment, 3. adverse event monitoring after procedure. We presented a summary checklist based on the above contents. Conclusions We propose the first patient safety checklist for minicalpel acupuncture treatment of cervical and lumbar spine. The checklist will be complemented using further research methodologies. (J Korean Med Rehabil 2018;28(1):61-72)

Antioxidant and laxative effects of taurine-xylose, a synthetic taurine-carbohydrate derivative, in loperamide-induced constipation in Sprague-Dawley rats

조희근,김민지,문보영,정선희 한국운동영양학회 2019 Physical Activity and Nutrition (Phys Act Nutr) Vol.23 No.4

[Purpose] In this study, we examined the in vitro antioxidant activities and laxative effects of taurine-xylose (T-X), a synthetic taurine-carbohydrate derivative, in a rat model of constipation induced by loperamide. [Methods] The animals were divided into four treatment groups: normal untreated rats (NOR group), loperamide-treated control rats (CON group), loperamide and taurine-xylose (15 mg/kg)-treated rats (T-X group), and loperamide and commercial Dulcolax S (5.5 mg/kg)-treated rats (DS group). [Results] In the present study, T-X exhibited potent reducing power and free radical scavenging activities for DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS+ (2,2′-azino-bis (3-ethylbenzothiazoline 6-sulfonic acid ammonium salt) radicals. The laxative effects of T-X were dependent on food, body weight, fecal properties, gastrointestinal transit (GIT) ratio, and serum metabolic parameters. In the T-X group, the number, wet weight, and water content of fecal pellets were noticeably increased compared to those in the loperamide-induced group. T-X treatment significantly increased the activities of hepatic antioxidant enzymes, including those of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT), relative to those in loperamide-induced constipated rats. Furthermore, the GIT ratio and loperamide-induced metabolic parameters in serum, including gastrin (GAS), motilin (MTL), and somatostatin (SS) levels, were significantly improved by T-X treatment. [Conclusion] These results suggest that taurine-xylose exerts antioxidant activities and laxative effects on loperamide-induced constipation by promoting gastrointestinal motility.

Optimization of Laminated Composite Cylindrical Shells to Maximize Resistance to Buckling and Failure When Subjected to Axial and Torsional Loads

조희근 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.1

The most frequently encountered structure in design is the cylindrical shell. This study analyzed, methods to optimize the design of a composite cylindrical shell against buckling and failure. Buckling and failure characteristics were investigated when an axial load, a torsional load or both loads were applied simultaneously. Optimization of the composite cylindrical shell was performed with respect to a loading boundary condition using a genetic algorithm. All analyses were performed numerically using finite element analysis. By optimizing the layer angle of the laminate composite, the buckling load of the cylindrical shell was maximized. The thinwalled shell with the strongest resistance to failure was achieved by optimizing the angle of the composite layer based on the Tsai- Wu composite failure theory. The optimized composite cylindrical shell exhibited significantly improved mechanical properties compared to the conventional design.