광탄성 실험 하이브리드 법에 의한 접촉응력 해석시 응력형상함수의 영향

신동철(Dong-Chul Shin),황재석(Jai-Sug Hawong) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.3

본 논문에서는 광탄성 실험 하이브리드 법을 이용하여 접촉응력문제를 해석하는 경우의 응력형상함수에 대해서 다루고 있다. 일반적으로 접촉응력문제는 반평면 문제로써 해석 되어지므로, 접촉응력의 경우 Airy 응력함수를 구성하는 두 해석적인 응력함수의 관계는 균열문제에서와 유사하였다. 그러나 이 관계를 그대로 접촉응력문제 (특히 특이점을 가진 경우)에 사용할 수가 없다. 그러므로 정확한 접촉문제의 해석을 위해 이들 두 해석적인 응력함수의 형태에 접촉하는 두 끝점의 조건에 따른 응력형상함수를 반드시 고려하여야만 할 것이다. 두 접촉끝점의 응력 특이성에 따라 4종류로 분류되는 이들 응력형상함수 중에서 오링 해석을 위한 중요한 두 종류의 응력형상함수를 선택하였으며, 이것의 유효성을 검증하였다. In this research, a study on stress shape functions was conducted to analyze the contact stress problem by using a hybrid photoelasticity. Because the contact stress problem is generally solved as a half-plane problem, the relationship between two analytical stress functions, which are compositions of the Airy stress function, was similar to one of the crack problem. However, this relationship in itself could not be used to solve the contact stress problem (especially one with singular points). Therefore, to analyze the contact stress problem more correctly, stress shape functions based on the condition of two contact end points had to be considered in the form of these two analytical stress functions. The four types of stress shape functions were related to the stress singularities at the two contact end points. Among them, the primary two types used for the analysis of an O-ring were selected, and their validities were verified in this work.

광탄성 실험 하이브리드 법을 이용한 접촉응력해석시 응력형상함수에 관한 연구

신동철(Dong-Chul Shin),황재석(Jai-Sug Hawong),남정환(Jeong-Hwan Nam),이준현(Joon-Hyun Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

In this research, in case of analysis of contact stress problems using hybrid method of photoelasticity, the shapes of stress function have been studied. The contact stress problem, in general, have been solved as a half-plane problem. As the results, it is found that the relationship between two analytical stress functions which compose Airy stress function, consequently, is same with one of crack problem, but the forms of the two analytical stress functions of crack problem can't be used as those of contact stress problems. In contact problem, the forms of two analytical stress functions have to be considered stress shape functions according to the condition of two contact end points. The stress shape functions are related to stress singularities in the two contact end points, and divided by four types. Among them, two type stress shape functions used primarily for analysis of O-ring were selected, and those validities were verified in this work.

스퍼기어의 접촉응력 해석

이진환(Jin-Hwan Lee),이동형(Dong-Hyong Lee),이권희(Kwon-Hee Lee) 한국기계가공학회 2010 한국기계가공학회지 Vol.9 No.4

This paper presents the study on the contact stress analysis of a pair of mating spur gears during rotation. Contact stress analysis is performed between two spur gear teeth at different contact positions during rotation. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. The results show that contact stress varies along the contact position and gets maximum values in the beginning and end of the contact. In this study, the gear design considering the contact stress on a pair of mating gears is more severe than that of AGMA standard.

원형 핀과 구멍의 접촉에서 헤르츠 응력장 가정을 위한 조건

김형규(Hyung-Kyu Kim) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.5

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson° Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson° Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

세 물체 간 마찰 완전 접촉 문제의 응력 특이성 거동

김형규 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.4

This study investigates the stress singularity that occurs at the contact edge of three bodies in a frictional complete contact. We use the asymptotic analysis method, wherein we constitute an eigenvalue problem and observe the eigenvalue behavior, which we use to obtain the order of the stress singularity. For the present geometry of three bodies in contact, a contact between a cracked indenter and half plane is considered. This is a typical geometry of the PCMI problem of a nuclear fuel rod. Thus, this paper, specifically presents the characteristics of the PCMI problem from the perspective of stress singularity. Consequently, it is noted that the behavior of the stress singularity varies with the difference in the crack angle, coefficient of friction, and material dissimilarity, as is observed in a frictional complete contact of two bodies. In addition, we find that the stress singularity changes essentially linearly with respect to the coefficient of friction, regardless of the variation in the crack angle and material dissimilarity. Concurrently, we find the order of singularity to be 0.5 at a certain coefficient of friction, irrespective of the crack angle, which we also observe in the crack problem of a homogeneous and isotropic body. The order of singularity can also exceed 0.5 in the frictional complete contact problem of three bodies. This implies that the propensity for failure when three bodies are in frictional complete contact can be even worse than that in case of a failure induced by a crack.

터보블로워용 헬리컬 기어의 접촉응력 해석

황석철(Seok-Cheol Hwang),이동형(Dong-Hyong Lee),박영철(Young-Chul Park),이권희(Kwon-Hee Lee) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.2

This paper presents the study on the contact stress analysis of a pair of mating helical gears for turbo blower during rotation. Turbo blowers need high speed rotation of impeller in structure and high rate gear ratio. The use of helical gear indicated that noise was an important problem when the application involves high speeds and large power transmission. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at the lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. In this study, the gear design considering the contact stress on a pair of mating gear is more severe than that of AGMA standard.

후판 4단 압연기에서 백업롤과 워크롤의 접촉응력에 관한 연구

김상록(S. R. Kim),송승호(S. H. Song),권용덕(Y. D. Kwon) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10

We examined the contact pressure between back up roll surface and work roll surface in a 4-high plate-rolling mill and adopted submodeling method in order to predict contact pressure. This method was able to predict contact pressure distribution on barrel length and max contact pressure on local stress concentration region. We investigated the change of contact pressure according to change of the plate width and specific force. The result show that increase of plate width and specific force influenced the increase of overall contact pressure distribution on roll barrel length and max contact pressure. Change of plate width and specific force influenced contact pressure deviation between roll barrel center and chamfer starting point of back up roll.

스프링요소를 이용한 풍력발전기용 슬루잉 베어링의 유한요소해석

한기봉,강종훈 한국융합학회 2020 한국융합학회논문지 Vol.11 No.11

This study is about design and verification of stress reduction of bearings for wind turbines. In a slewing bearing having a typical four-contact structure, the contact point moves to the end of the raceway due to a large moment load, resulting in a stress concentration. A bearing was designed to reduce such contact point movement. The deformation behavior of typical ball bearings and newly designed bearings was calculated through finite element analysis under ultimate load by replacing the ball with a spring element. The contact stress between the ball and the raceway was calculated by finite element analysis by inputting the deformation behavior analysis result as a boundary condition. The effectiveness of the bearing stress analysis method using spring elements was verified through comparison of the contact stress according to the bearing structure. 본 연구는 풍력발전기용 베어링의 응력저감을 위한 설계와 검증에 관한 것이다. 일반적인 4점 접촉 볼베어링의 구조를 가지고 있는 슬루잉 베어링은 큰 모멘트 하중이 작용하면 접촉점이 레이스웨이 끝단부로 이동하여 국부적인 응력상승 문제가 발생한다. 본 연구에서는 이러한 접점 이동을 줄이기 위한 베어링을 설계하였다. 전통적인 볼베어링과 새로인 설계된 베어링의 극한하중 하에서의 변형거동을 볼을 스프링요소로 치환하여 유한요소해석을 통하여 계산하였다. 볼과 레이스웨이의 접촉응력은 변형거동 해석결과를 경계조건으로 입력하여 유한요소해석으로 계산하였다. 베어링 구조에 따른 접촉부 응력 비교를 통하여 베어링의 응력해석 방법의 효용성을 검증하였다.

다축피로하에 응력 구배효과를 고려한 구름 접촉모델의 피로수명해석에 관한 연구

조인제(I.J.Cho),조용주(Y.J.Cho),유용훈(Y.H.Yu),이보라(B.R.Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

In this paper, a new formulation of gradient fatigue criteria is proposed in the context of multiaxial high-cycle fatigue (HCF). To predict exact fatigue life, it is necessary to calculate contact sress and subsurface stresses accurately. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface stress field is obtained using rectangular patch solutions. Based on these stress values, a new gradient fatigue criteria which extended from classical ones with stress gradient terms introduced not only in the normal stress but also in the shear stress components is used. The results show fatigue life calculated and compared between considered gradient criteria and not considered gradient criteria.

치근접촉이 마이크로 임플란트 인접골 응력에 미치는 영향에 대한 유한요소해석

유원재(Won-Jae Yu),김미령(Mi-Ryoung Kim),박효상(Hyo-Sang Park),경희문(Hee-Moon Kyung),권오원(Oh-Won Kwon) 대한치과교정학회 2011 대한치과교정학회지 Vol.41 No.1

마이크로 임플란트 시술의 중요한 위험요인 중 하나로 치근접촉 문제가 있으나, 관련 연구는 결과 분석에 치중되어 있고, 치근접촉이 마이크로 임플란트 안정성 상실로 이어지는 기전에 대한 연구는 아직 미흡한 것으로 보인다. 이에, 본 연구에서는 생역학적 측면에서 그 영향을 분석하였다. Absoanchor 마이크로 임플란트(SH1312-7, Dentos Inc., Daegu, Korea) 첨부가 치근에 접촉되어 있을 때, 저작압 전달에 의한 마이크로 임플란트 변위가 인접골에 가하는 압축응력을 축대칭 유한요소모델을 사용하여 계산하였다. 요소별 응력이 해면골의 최대압축강도나, 치밀골의 비정상 골개조 임계응력을 넘을 경우 해당 요소를 순차적으로 해석모델에서 제거하며 실행한 6단계해석의 결과, 마이크로 임플란트에 인접한 해면골의 전체적인 파절과 과부하에 따른 치밀골의 비정상 골개조가 임플란트 지지력 상실에 주요인이 될 것으로 평가되었다. 치밀골의 과부하 영역은 초기에는 치밀골판의 하부에 존재하였으나 상부로 확장되었고, 응력 재분포로 인한 감소효과 없이 양성 되먹임(positive feedback)으로 결국 치밀골 전 두께로 확대됨을 관찰하였다. 본 연구를 통해 치근접촉된 마이크로 임플란트가 인접골을 훼손시켜 안정성 상실로 이어지는 과정을 모사할 수 있었으며, 이로부터 치근접촉에 따른 마이크로 임플란트의 불량한 예후에 대한 생역학적 측면의 원인을 파악할 수 있었다. (대치교정지 2011;41(1):6-15) Objective: The aim of this study was to evaluate the biomechanical aspects of peri-implant bone upon root contact of orthodontic microimplant. Methods: Axisymmetric finite element modeling scheme was used to analyze the compressive strength of the orthodontic microimplant (Absoanchor SH1312-7, Dentos Inc., Daegu, Korea) placed into inter-radicular bone covered by 1 mm thick cortical bone, with its apical tip contacting adjacent root surface. A stepwise analysis technique was adopted to simulate the response of peri-implant bone. Areas of the bone that were subject to higher stresses than the maximum compressive strength (in case of cancellous bone) or threshold stress of 54.8MPa, which was assumed to impair the physiological remodeling of cortical bone, were removed from the FE mesh in a stepwise manner. For comparison, a control model was analyzed which simulated normal orthodontic force of 5 N at the head of the microimplant. Results: Stresses in cancellous bone were high enough to cause mechanical failure across its entire thickness. Stresses in cortical bone were more likely to cause resorptive bone remodeling than mechanical failure. The overloaded zone, initially located at the lower part of cortical plate, proliferated upward in a positive feedback mode, unaffected by stress redistribution, until the whole thickness was engaged. Conclusions: Stresses induced around a microimplant by root contact may lead to a irreversible loss of microimplant stability. (Korean J Orthod 2011;41(1):6-15)