• Title, Summary, Keyword: Bridging Effect

Search Result 173, Processing Time 0.04 seconds

Analysis of Bridging Stress Effect of Polycrystalline Aluminas Using Double Cantilever Beam Method II. Development of Double Cantilever Beam Method Considering Bridging Effect (Double Cantilever Beam 방법을 이용한 다결정 알루미나의 Bridging 응력효과 해서 II. Bridging 효과를 고려한 Double cantilever Beam 분석방법의 정립)

  • 손기선;이성학;백성기
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.5
    • /
    • pp.590-601
    • /
    • 1996
  • This study aims at developing the double cantilever beam (DCB) method in order to calculate the bridging stress distribution in polycrystalline aluminas with different grain sizes. In the already existing DCB methods the measured crack opening displacement (COD) in coarse-grained aluminas deviates generally from the calcula-ted one because of the grain-interface bridging in the crack wake. In the current DBC method developed in the present study the effect of the bridging stress was considered in the DCB analysis. whereas the only effect of applied point-loading at the end of DCB specimen was taken into account in the existing DCB analysis The crack closure due to bridging stress was calculated using the power-law relation and the theoretical model developed in Part I of the present paper as bridging stress function and then compared analytically. The limitations of the current DCB methods such as specimen dimensions applied loads and elastic modulus were discussed in detail to provide a reliability of the newly developed DCB analysis for the bridging stress distribu-tion in polycrystalline aluminas.

  • PDF

Analysis of Bridging Stress Effect of Polycrystalline aluminas Using Double Cantilever Beam Method (Double Cantilever Beam 방법을 이용한 다결정 알루미나의 Bridging 응력효과 해석)

  • 손기선;이선학;백성기
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.5
    • /
    • pp.583-589
    • /
    • 1996
  • In this study a new analytical model which can describe the relationship between the bridging stress and microstructure has beenproposed in order to investigate the microstructural effect on the R-curve behavior in polycrystalline aluminas since the R-curve can be derived via the bridging stress function. In the currently developed model function the distribution of grain size is considered as a microstructural factor in modeling of bridging stress function and thus the bridging stress function including three constants PM, n, and Cx, can be established analytically and quantitatively. The results indicate that the n value is closely related to the grain size distribution thereby providing a reliability of the current model for the bridging stress analysis. Thus this model which explains the correlation of the bridging stress distribution and microstructual parame-ters is useful for the systematic interpretation of microfracture mechanism including the R-curve behavior in polycrystalline aluminas.

  • PDF

Effect of the Breathing Methods in Accordance with Surfaces during Bridging Exercises (지지면에 따른 호흡운동 기법이 배근육 두께에 미치는 영향)

  • Bae, Won-Sik;Lee, Keon-Cheol
    • Journal of the Korean Society of Physical Medicine
    • /
    • v.11 no.2
    • /
    • pp.33-40
    • /
    • 2016
  • PURPOSE: The purpose of this study was to determine the impact of stable and unstable surfaces on abdominal muscle thickness and changes in trunk muscle thickness in accordance with breathing methods during bridging exercises. METHODS: Bridging exercise on a stable surface, bridging exercise on an unstable surface, bridging exercise using a drawing-in maneuver on a stable surface, bridging exercise using a drawing-in maneuver on an unstable surface, bridging exercise using bracing on a stable surface, bridging exercise using bracing on an unstable surface. In sequence, the muscles' thickness was measured three times before and after each exercise, and the measured value was averaged. RESULTS: There were significant differences in internal oblique and transversus abdominis muscles' thickness in the drawing-in maneuver in both stable and unstable surface (p<0.05). There were no significant differences in external oblique muscle's thickness in the bridging exercise in both stable and unstable surface. The type of surface did not have a significant influence on the abdominal muscles' thickness. CONCLUSION: As a result of the study, the drawing-in maneuver had a greater effect than bridging or bracing maneuver on muscle thickness. We suggest that drawing-in maneuver will be more effective in a person with a weak abdominal muscle.

An Analytical Modeling for Bridging Stress Function Involving Grain Size Distribution in a Polycrystalline Alumina (다결정 알루미나에서 결정립 크기 분포를 포함하는 Bridging 응력함수의 해석적 모델링)

  • 손기선;이성학;백성기
    • Journal of the Korean Ceramic Society
    • /
    • v.31 no.12
    • /
    • pp.1449-1458
    • /
    • 1994
  • A new analytical model which can discribe the relationship between the bridging stress and the crack opening displacement was proposed to investigate the microstructural effect on the R-curve behavior in a polycrystalline alumina. The crack opening displacement according to the distance behind the stationary crack tip was measured using in-situ fracture technique in an SEM, and then used for a fitting procedure to obtain the distribution of bridging stress. The current model and an empirical power law relation were introduced into the fitting procedure. The results indicated that the bridging stress function and R-curve computed by the current model were consistent with those computed by the power law relation. The microstructural factor, e.g., the distribution of grain size, was also found to be closely related to the bridging stress. Thus, this model explained well the interaction effect between the distribution of bridging stress and the local-fracture-controlling microstructure, providing important information for the systematic interpretation of microfracture mechanism including R-curve behavior of a monolithic alumina.

  • PDF

Effect of surfactant adsorption on the rheology of suspensions flocculated by associating polymers

  • Otsubo, Yasufumi;Horigome, Misao
    • Korea-Australia Rheology Journal
    • /
    • v.15 no.4
    • /
    • pp.179-185
    • /
    • 2003
  • Associating polymers act as flocculants in colloidal suspensions, because the hydrophobic groups (hydrophobes) can adsorb onto particle surfaces and create intermolecular cross-linking. The steady-shear viscosity and dynamic viscoelasticity were measured for suspensions flocculated by multichain bridging of associating polymers. The effects of surfactant on the suspension rheology are studied in relation to the bridging conformation. The surfactant molecule behaves as a displacer and the polymer chains are forced to desorb from the particle surfaces. The overall effect of surfactant is the reduction of suspension viscosity. However, the additions of a small amount of surfactant to suspensions, in which the degree of bridging is low, cause a viscosity increase, although the number of chains forming one bridge is decreased by the forced desorption of associating polymer. Since the polymer chains desorbed from one bridge can form another bridge between bare particles, the bridging density over the system is increased. Therefore, the surfactant adsorption leads to a viscosity increase. The surfactant influences the viscosity in two opposing ways depending on the degree of bridging.

The Effect of Lower Extremity Muscle Activity on Bridging Exercise and Combined Lifting pattern Bridging Exercise (교각운동과 들어올리기 패턴결합 교각운동이 하지 근 활성도에 미치는 영향)

  • Youn, Hye-Jin;Kim, Kyung-Hwan;Park, Sung-Hun;Yi, Min-Young
    • PNF and Movement
    • /
    • v.10 no.4
    • /
    • pp.49-55
    • /
    • 2012
  • Purpose : The purpose of this study was to assess the effects of bridging exercise and combined lifting pattern bridging exercise on the lower extremity muscle activity. Methods : Twenty-five healthy adults volunteered to participate in this study. Subjects were required to complete following bridging exercises. Muscle activity was measured by QEMG-4 system(LXM 3204, Laxtha Korea). A paired t test was used to determine the influence of muscle activity for each exercise and descriptive statistics was used to characteristics of the subjects. Results : The biceps femoris, tibialis anterior, gastrocnemius of combined lifting pattern bridging exercise showed significance excepted vastus medialis(p<.05). In the case of men, biceps femoris showed significance in the combined lifting pattern bridging exercise(p<.05). In the case of women, biceps femoris and tibialis anterior showed significance in the combined lifting pattern bridging exercise(p<.05). Conclusion : The combined lifting pattern bridging exercise was more increased than bridging in lower extremity muscle activation. This result will be used for knee joint stabilizing exercises and biceps femoris strength training.

  • PDF

Analysis of bridging Stress Effect of Polycrystlline Aluminas Using Double Cantilever Beam Method (Double Cantilever Beam 방법을 이용한 다결정 알루미나의 Bridging 응력효과 해석 III. 다결정 알루미나의 Bridging 응력분포)

  • 손기선;이성학;백성기
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.5
    • /
    • pp.602-615
    • /
    • 1996
  • The purpose of the present study is to investigate the microstructural effect on the R-curve behavior in three aluminas with different grain size distributions by analyzing the bridging stress distribution. The crack opening displacement (COD) according to the distance behind the stationary crack tip was measured using an in situ SEM fracture method. The measured COD values in the fine-grained alumina agreed well with Wiederhorn's sollution while they deviated from Wiederhorn's solution in the two coarse-grained aluminas because of the increase of the crack closure due to the grain interface bridging in the crack wake. A numerical fitting procedure was conducted by the introduction of the power-law relation and the current theoretical model together with the measured COD's in order to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R-curve computed by the current model were consistent with those computed by the power-law relation providing a reliable evidence for the bridging stress analysis of the current model. The strain-softening exponent in the power-law relation n, was calculated to be in the range from 2 to 3 and was closely related to the grain size distribution. Thus it was concluded from the current theoretical model that the grain size distribution affected greatly the bridging stress distribution thereby resulting in the quantitative analysis of microfracture of polycrystalline aluminas through correlating the local-fracture-cont-rolling microstructure.

  • PDF

Effect of Abdominal Hollowing on Muscle Activity of Gluteus Maximus and Erector Spinae during Bridging Exercise (교각 운동 시 복부 넣기가 큰볼기근과 척추세움근의 활성도에 미치는 영향)

  • Koh, Eun-Kyung;Jang, Jin-Ho;Jung, Do-Young
    • The Journal of Korean Physical Therapy
    • /
    • v.24 no.5
    • /
    • pp.319-324
    • /
    • 2012
  • Purpose: This study examined the muscle activities of the erector spinae (ES) and gluteus maximus (GM) during bridging exercises with and without abdominal-hollowing. Methods: Nineteen healthy subjects with no medical history of low back pain or hip flexion contracture were enrolled in this study. The subjects performed bridging exercises with and without abdominal hollowing or with and without a one-leg lift. The muscle activities of the ES and GM were measured by surface electromyography during bridging exercises under each condition. A 2 (abdominal hollowing)X2 (one-leg lift) repeated ANOVA was used to compare the normalized muscle activities of the ES and GM. Results: The muscle activity of the ES during bridging exercise with abdominal-hollowing was significantly smaller than that without abdominal-hollowing (p=0.00). The muscle activities of the GM during bridging exercise with abdominal-hollowing were significantly greater than those without abdominal-hollowing (p=0.00). In addition, the muscle activities of the GM during bridging exercise with one-leg lifting was significantly greater than that without one-leg lifting (p=0.00). Conclusion: Bridging exercise with abdominal-hollowing appears to be more effective on activating the GM muscle than that without abdominal-hollowing minimizing the activation of the ES muscle.

Effect of Bridging Stabilization Exercises on Trunk Muscles Activity On and Off a Swiss Ball (교각운동 시 공 적용이 체간근 활동에 미치는 영향)

  • Kim, Moung-Jin
    • Physical Therapy Korea
    • /
    • v.16 no.1
    • /
    • pp.18-24
    • /
    • 2009
  • The purpose of this study was to assess the effect of bridging stabilization exercises on trunk muscles activity on and off a Swiss ball. 20 healthy university students volunteered to participate in this study. Subjects were required to complete following four exercises: exercise 1, single bridging exercise; exercise 2, feet on ball bridging exercise; exercise 3, calf on ball bridging exercise; exercise 4, back on ball bridging exercise. Surface electromyography from selected trunk muscles was normalized to maximum voluntary isometric contraction. A repeated measures of ANOVA with post-hoc Bonferroni's correction was used to determine the influence of exercise type on muscle activity for each muscle and descriptive statistics was used to determine local/global muscle ratios. The rectus abdominis of exercise 4 showed significantly higher muscle activity than rectus abdominis of exercise 1, 2, 3 (p<.05). The external oblique of exercise 2, 4 showed significantly higher muscle activity than external oblique of exercise 1 (p<.05). The internal oblique of exercise 2, 4 showed significantly higher muscle activity than internal oblique of exercise 1 (p<.05). The erector spinae of exercise 2, 3, 4 showed significantly higher muscle activity than erector spinae of exercise 1 (p<.05). Median of internal oblique/rectus abdominis ratio of exercise 1 was 1.16, exercise 2 was 2.43, exercise 3 was 2.45, exercise and 4 was 1.27. Median of internal oblique/external oblique ratio of exercise 1 was 1.01, exercise 2 was .91, exercise 3 was .99, and exercise 4 was .93. Muscle activity can be influenced by addition of a Swiss ball in bridging exercises. It is recommend to use a Swiss ball for trunk stabilization exercise.

  • PDF

In Situ Observation of Slow Crack Growth in a Whisker-Reinforced Alumina Matrix Composite (SiC 휘스커 보강 알루미나 복합재료에서 Slow Crack Growth 현상의 직접관찰 연구)

  • 손기선;김우상;이성학
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.2
    • /
    • pp.203-213
    • /
    • 1996
  • In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

  • PDF