• 한국정밀공학회지
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• 제17권10호
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• pp.200-205
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• 2000

This paper presents the vibration characteristics of a rectangular plate with 45$^{\circ}$oblique crack and a smooth plate subjected to a uniaxial tension. The experiment is adopted by the time-average holography method. The natural frequency and mode shape are considered accurate according to the increasement of tensile load in the study. When tensile load is zero, the vibration modes are almost agreed with the smooth and the 45$^{\circ}$obliquely cracked plate. But since then, according to the increasement of load, it is shown that vibration modes are extremely varied. The effects of the crack length in the vibration characteristic are discussed in detail. It is indicated that the increase of the crack length makes the variation of the frequencies and modes complicate in the range of even a small load.

• 대한치과보철학회지
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• 제56권2호
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• pp.105-113
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• 2018

목적: 삼차원 유한요소분석을 이용하여 상악 전치부 즉시하중 임플란트의 식립 깊이가 주위 골의 응력 분포와 임플란트의 미세움직임에 미치는 영향을 알아보고자 하였다. 재료 및 방법: 임플란트 상단이 치조정 피질골 상연을 기준으로 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, 1.00 mm 깊게 위치되도록 총 5개 골모형을 제작하였다. 고정체와 주위 골 계면에 마찰접촉과 35 Ncm의 식립 토크를 재현하였다. 임시 보철물에 178 N의 정하중을 고정체의 중심축에 대하여 축방향의 수직하중과 $30^{\circ}$의 경사하중으로 가하고 유한요소 분석을 시행하였다. 결과: 임플란트의 식립 깊이가 주위 골의 응력 분포에 상당한 영향을 주었다. 임플란트의 가장 큰 미세움직임이 $39.34{\mu}m$로 나타났다. 경사하중이 수직하중에 비해서 응력 분포와 미세움직임의 변화에 크게 기여하였다. 결론: 임플란트 식립 깊이의 증가는 피질골에 집중된 응력을 분산시키는데 유리하였으며, 초기 골유착 실패와 관련이 있는 미세움직임에는 크게 영향을 주지 않았다.

• 대한조선학회논문집
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• 제50권3호
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• pp.138-144
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• 2013

New experimental devices and methods to measure shaft forces of ships are proposed in this paper. The strain gauge type six-component load cell was newly designed and installed to the end of the propeller shaft. The signals generated from the sensor in the propeller rotating are transferred to the new data amplifying and processing board on the shaft and the data is transmitted to the self-made wireless receiver. To find out the characteristics of shaft forces during port and starboard turning motions in sea trial, oblique and combined yaw maneuvering tests at straight, transient, maximum yaw rate, steady conditions were performed with the model ship installed the shaft forces measuring device using circular motion tester of Samsung Ship Model Basin. Characteristics of the measured shaft forces in model tests show quantitatively good agreement with the computed values obtained by the CFD programs using the measured wake data in oblique towing conditions. In the near future, It is hoped that the estimated shaft forces for a ship from this experimental method could be validated through comparison with directly measured values of a ship.

• 한국전문물리치료학회지
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• 제24권2호
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• pp.19-26
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• 2017

Background: To improve lumbo-pelvic stability, passive support devices (i.e., a pelvic belt) are recommended clinically. Nevertheless, to understand the influence of passive support on lumbo-pelvic stability, it is necessary to examine the influence of a pelvic belt on the abdominal and hip abductor muscles. Objects: To examine the effects of a pelvic belt on the forces of the hip adductor and abductor muscles and activity of the abdominal muscles during isometric hip adduction and abduction. Methods: This study recruited 14 healthy men. All subjects performed isometric hip adduction and abduction with and without a pelvic belt in a neutral hip position. Load cells, wrapped with a non-elastic belt, were placed above the medial and lateral malleoli of the dominant leg to measure the muscle forces of the hip adductors and abductors, respectively. The forces of the hip adductors and abductors were measured using a load cell during isometric hip adduction and abduction, while the electromyographic activities of the bilateral rectus abdominis, internal oblique, and external oblique muscles were measured. Results: The forces generated by the hip adductors and abductors were significantly greater with the pelvic belt than without (p<.05). No significant differences in abdominal muscle activities between the two conditions were found (p>.05). Conclusion: These findings suggest that use of a pelvic belt could lead to effective strengthening exercise of hip muscles in individuals with sacroiliac joint pain.

• 한국기계가공학회지
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• 제9권1호
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• pp.25-34
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• 2010

Fretting damage reduces fatigue life of the material due to low amplitude cyclic sliding and changes in the contact surfaces of strongly connected machine and structures such as bolt, key, fixed rivet and connected shaft, which have relative slip of repeatedly very low frequency amplitude. In this study, the fretting fatigue behavior of 7050-T7451 aluminum alloys used mainly in aircraft and automobile industry were evaluated. The plain fatigue test and fretting fatigue test under cyclic bending load carried out commercial bending fatigue tester and specially devised equipments to cause fretting damage. From these experimental work, the following results obtained: (1) The plain fatigue limit for stress ratio R=-l was about 151MPa. (2) In case of fretting fatigue, fatigue limit for stress ratio R=-l about 72MPa, the fatigue limit for R=0 about 81MPa, and the fatigue limit for R=0.3 about 93MPa. (3) The fatigue limit reduction rates by the fretting damage were about 52%(R=-1), 46%(R=0) and 38%(R=0.3) respectively. (4) The fatigue limit reduction rate decreased with stress ratio increase. In fretting bending test, as stress ratio increased, occurrence of initial oblique crack by fretting decreased or phased out, so that fracture surfaces were formed by plain fatigue crack occurrence, and such tendency was notable as stress amplitude increased. (5) Tire tracks and rubbed scars were observed in the fracture surface and contacted surface.

• PNF and Movement
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• 제21권2호
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• pp.243-253
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• 2023

Purpose: This study aimed to investigate the effects of an abdominal drawing-in maneuver (ADIM) with a light load while sitting on transverse abdominis contraction in subjects with and without low back pain. Methods: In this study, 20 participants with chronic low back pain and 20 controls participated. Ultrasonography was used to assess the thickness of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) muscles. Muscle thickness was measured at rest and during ADIM in three different sitting postures: (1) just sitting, (2) sitting loaded position (holding a 1 or 2 kg dumbbell in each hand), and (3) sitting loaded shoulder flexion position (holding a 1 or 2 kg dumbbell in each hand). Results: The contraction ratio (CR) and preferential activation ratio (PAR) of the TrA during ADIM had no significant interactional effect between the group and the sitting postures. However, the CR and PRA of the TrA during the ADIM showed significant differences among the three different sitting postures. The CR of the TrA during the ADIM in the sitting loaded shoulder flexion position was significantly increased compared to that in the sitting position (p<0.05). Moreover, the PRA of the TrA muscle during ADIM in sitting loaded and sitting loaded shoulder flexion positions was significantly higher than that in the sitting position (p<0.05). Conclusion: The findings suggest that ADIM in the sitting-loaded shoulder flexion position should be implemented to facilitate TrA activity.

• 대한조선학회지
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• 제22권3호
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• pp.1-8
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• 1985

In this paper, the motion response and wave load of a container ship are treated by a nonlinear motion theory, which is similar to that used by Yamamoto et. al.[1]. This paper deals with the vertical motion response in oblique waves and the effect of the Smith correction in buoyancy force calculation. In the present computation, for S-175 container ship model our result also shows that the ratio of the motion peak to peak value to the wave height decreases as the wave height increases, which was obtained earlier by Yamamoto et.al.[3]. On the other hand the nondimensional midship bending moment increases as the wave height increases. These nonlinear effects are dominant near the resonance frequency, and depend on the hull form and forward speed. However, it is found that these nonlinear effects are significant for tanker model.

• 구강회복응용과학지
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• 제22권1호
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• pp.37-53
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• 2006

Purpose: The purpose of this study was to investigate the influences of the jaw dimension on the bone stress. Materials and Methods: Root analogue implant of Frialit-2 Synchro model in the jaw bone of various thickness from 8mm to 13mm were modelled axisymmetrically for a series of finite element analyses. As load conditions, non-axisymmetric lateral load of 20N and an oblique load of 50N, as well as an axisymmetric vertical load of 50N were taken into consideration. Results: The cervical area of implant under the axisymmetric load and the base cortical bone under the non axisymmetric load condition were the areas of main concern where the higher level of stress were likely to be obtained. Conclusion: The results indicated that at the two concerned areas drastically different stress distribution could take place as a function of the load conditions. Under the vertical load, the lower level of stress was observed for the narrow jaw bone at the cervical cortical bone whereas stress at the base cortical bone remained virtually unchanged. Under the non axisymmetric load condition, however, the stress at the base cortical bone increased very rapidly as the jaw bone width increased without inducing any significant change in the stress level at the cervical area.

• 대한치과보철학회지
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• 제42권2호
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• pp.226-237
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• 2004

Purpose: Four finite element models were constructed in the mandible having a single implant fixture connected to the first premolar-shaped superstructure, in order to evaluate how the shape of the fixture and the implant-abutment connection would influence the stress level of the supporting tissues fixtures, and prosthethic components. Material and methods : The superstructures were constructed using UCLA type abutment, ADA type III gold alloy was used to fabricate a crown and then connected to the fixture with an abutment screw. The models BRA, END , FRI, ITI were constructed from the mandible implanted with Branemark, Endopore, Frialit-2, I.T.I. systems respectively. In each model, 150 N of vertical load was placed on the central pit of an occlusal plane and 150 N of $40^{\circ}$ oblique load was placed on the buccal cusp. The displacement and stress distribution in the supporting tissues and the other components were analysed using a 2-dimensional finite element analysis . The maximum stress in each reference area was compared. Results : 1. Under $40^{\circ}$ oblique loading, the maximum stress was larger in the implant, superstructure and supporting tissue, compared to the stress pattern under vertical loading. 2. In the implant, prosthesis and supporting tissue, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 3. In the superstructure and implant/abutment interface, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 4. In the implant fixture, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 5 The stress was more evenly distributed in the bone/implant interface through the FRI of trapezoidal step design. Especially Under $40^{\circ}$ oblique loading, The maximum stress was smallest in the bone/implant interface. 6. In the implant and superstructure and supporting tissue, the maximum stress occured at the crown loading point through the ITI. Conclusion: The stress distribution of the supporting tissue was affected by shape of a fixture and implant-abutment connection. The magnitude of maximum stress was reduced with the internal connection type (FRI) and the morse taper type (ITI) in the implant, prosthesis and supporting tissue. Trapezoidal step design of FRI showed evenly distributed the stress at the bone/implant interface.

• 구강회복응용과학지
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• 제33권3호
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• pp.189-198
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• 2017

목적: 외측 육각형과 내측 원추형 연결부로 설계된 임플란트 지지 하악 구치 수복물에 교합력을 가할때 발생하는 생역학 현상을 분석하고자 한다. 연구 재료 및 방법: 외측 연결형 임플란트(EXHEX)와 내측 연결형 임플란트(INCON) 그리고 이와 결합할 해당 나사와 지대주 및 크라운을 제작하였고, 하악 무치악 치조골을 설계하였다. 각 부분을 조립하여 2종의 유한요소 모형을 제작하였다. 총 120 N 크기의 수직력(L1)과 45도 측방력(L2)을 가하였고, 유한요소 응력 분석을 시행하였다. 결과: L2 측방력 하중에 의해 발생한 최대 응력은 L1 수직력 하중에 의한 것 보다 6 - 15배 더 컸다. INCON 모델은 EXHEX 모델보다 크라운 교두부에서 2.2배 더 큰 변위량을 보여 주었다. 측방력에 의해 EXHEX 모델은 나사에서, INCON 모델은 임플란트 고정체의 상단 변연부에서 폰미세스 응력의 최대값이 관찰 되었다. INCON 모델에서는 임플란트 내부 계면에서 긴밀한 접촉이 유지 되었다. 결론: 측방력이 큰 변형과 응력을 발생하였으나, 임플란트에서의 최대 응력 발생부위는 INCON과 EXHEX 모델이 서로 상이하였다.