• Journal of Welding and Joining
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• 제22권5호
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• pp.4-8
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• 2004

• Journal of Welding and Joining
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• 제22권6호
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• pp.3-5
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• 2004

• Geomechanics and Engineering
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• 제11권2호
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• pp.253-267
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• 2016

The stability of surrounding rock will be poor when the tunnel is excavated through nearly horizontal stratum. In this paper, the instability mechanism of local nearly horizontal stratum in super-large section and deep buried tunnel is revealed by the analysis of the macro failure and micro fracture. A structural model is proposed to explain the mechanics of surrounding rock collapse under the action of stress redistribution and shed light on the macroscopic analytical approach of the stability of surrounding rock. Then, some highly effective formulas applied in the tunnel engineering are developed according to the theory of mixed-mode micro fracture. And well-documented field case is made to demonstrate the effectiveness and accuracy of the proposed analytical methods of mixed-mode fracture. Meanwhile, in order to make the more accurate judgment about yield failure of rock mass, a series of comprehensive failure criteria are formed. In addition, the relationship between the nonlinear failure criterion and $K_I$ and $K_{II}$ of micro fracture is established to make the surrounding rock failure criterion more comprehensive and accurate. Further, the influence of the parameters related to the tension-shear mixed-mode fracture and compression-shear mixed-mode fracture on the propagation of rock crack is analyzed. Results show that ${\sigma}_3$ changes linearly with the change of ${\sigma}_1$. And the change rate is related to ${\beta}$, angle between the cracks and ${\sigma}_1$. The proposed simple analytical approach is economical and efficient, and suitable for the analysis of local nearly horizontal stratum in super-large section and deep buried tunnel.

• 비파괴검사학회지
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• 제21권3호
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• pp.251-260
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• 2001

단조인장시험하에서 CFRP적층재의 손상과정을 음향방출과 초음파시험에 의해 평가하였다. 시험편으로부터의 음항방출신호의 진폭 분포는 기지재 균열(matrix crack), 박리(debonding), 섬유 pull-out 및 섬유 과단(fiber fracture)과 같은 CFRP에서의 파괴기구를 분석하는데 도움을 주며, 초음파 진폭감쇠의 특성 또한 각각의 파괴기구를 분석하는데 유용하다. 여러종류의 CFRP시험편을 사용하여 음향방출신호와 초음파신호의 진폭감쇠를 조사하였다. 끝으로 하중 제하중(loading-unloading) 시험이 초음파내의 진폭비에 대한 Felicity effect와 감쇠를 조사하기 위해서 수행되었다. 전 실험에 걸쳐 초음파신호의 진폭감쇠와 음향방출 파라미터(parameter)들은 동시에 검출되었다. 이로써 음향방출과 초음파시험의 두 파라미터들이 CERP에서의 파괴기구를 분석하기 위해 효과적으로 사용될 수 있음이 확인되었다.

• 대한족부족관절학회지
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• 제17권3호
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• pp.182-188
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• 2013

Purpose: We evaluate clinical manifestations and radiologic features of ankle fracture & dislocation, as well as the usefulness of computed tomography on posterior ankle fracture & dislocation to study factors contributing to ankle fracture & dislocation. Material and Methods: Ankle dislocation was defined as the center of talar body being translated over the cortex of tibia on AP or lateral view on simple X-ray. Surgical treatments of 30 patients from January 2007 to March 2012 were categorized according to the injury mechanism, the direction of dislocation and fracture site. Joint involvement of posterior malleoalr fracture was evaluated through simple x-ray and computed tomography. We treated surgically if posterior malleolus fracture involves more than 25% of dital tibial articular surface. Thereafter, clinical outcomes were identified through radiographs and by using the AOFAS score. Results: The mean age was 42(13-78) years old, and slip down was the most common injury mechanism (13 cases). Car accident (6 cases) and fall accident (4 cases) were the next frequently found injury mechanisms. As for the types of ankle fracture, posterior fracture and dislocation (21 cases, 43.3%) was most commonly found. Out of these 21 cases, 15 cases involved trimalleolar fracture, and 19 cases were associated with posterior malleolar fracture. Danis-weber type B and C patients were 11 cases and 10 cases respectively. Articular involvement of posterior malleolar fracture turned out to be average 27.9%(5.1%~49.1%) on simple x-ray. The rate was evaluated as average 31.7%(12.6%~55.3%) on computed tomography which was conducted 15 times, and led us to more meaningful data. Conclusion: Anterolateral fracture and dislocation often accompanied open dislocation. Posterior fracture dislocation was most commonly found. Posterior malleolus was an important factor that ensures posterior stability of the ankle joint. Computed tomograph is useful to evaluate the articular involvement of posterior malleolar fracture.

• 대한기계학회논문집A
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• 제29권5호
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• pp.689-697
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• 2005

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, $B_{10}$ life and its lower bound with $90\%$ confidence at worst case use condition are estimated by analyzing the accelerated life test data.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.303-311
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• 2004

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, B$_{10}$ life and its lower bound with 90% confidence at worst case use condition are estimated by analyzing the accelerated life test data.a.

• 대한기계학회논문집
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• 제18권6호
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• pp.1388-1398
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• 1994

The fracture toughness and micro-fracture mechanisms of the porous glass and stainless fiber reinforced glass composite were evaluated by using the acoustice mission(AE) technique, fracture toughness $test(K_{IC})$ and the macroscopic observation of the specimen surface which was being under the loading. At initial portion of the loading, the AE signals with low energy, of which origins were considered as the micro-cracks formated at the crack tip, were emitted. With increasing the applied load, AE signals having higher energies were generated due to the coalesence of micro-cracks and fast fracture. Based on the such relationship between AE emission and loading condition, fracture toughness $K_{IAE}$ could be defined successfully be using the $K_I$ value corresponding to an abrupt change of the accumulated AE signal energies emitted during the fracture toughness test. In spite of its brittleness of glass material, nonlinear deformation behavior before maximum load was observed due to the formation of micro-cracks. Further, the stainless fiber may have attributed to the improvement of fracture toughness and the resistance to crack propagation comparing to noncomposited materials Finally, models of the micro-fracture process combined with the AE sources for the porous glass material and its composite were proposed paying attention to the micro-crack nucleation and its coalescence at the crack tip. Fiber fracture and its Pullout, deformation of fiber itself were also delinated from the model.

• 대한족부족관절학회지
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• 제15권1호
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• pp.36-38
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• 2011

Ankle fracture and Achilles tendon rupture are common as an isolated injury. However, Achilles tendon rupture with ipsilateral ankle fracture is uncommon, and occurs by a different injury mechanism with a risk of negligence. We report a case of Achilles tendon rupture with ipsilateral medial malleolar fracture.

• Wind and Structures
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• 제4권2호
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• pp.147-162
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• 2001

This paper presents an analytical method which takes into account the non-linearity of individual members, and discusses some case study results. It also discusses the relationship between member non-elastic behavior and excitation duration, and the relationship between member fracture and overall structure behavior. It is clearly demonstrated that the frame already shows almost unstable behavior due to long-columnization just before the occurrence of a column fracture. Then, a column fracture immediately induces a structural collapse mechanism.