• Title/Summary/Keyword: Pressure Distribution

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Mechanical Analysis of golf driving stroke motion (골프드라이빙 스트로크시 역학적 분석)

  • Park, Kwang-Dong
    • Korean Journal of Sport Biomechanics
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    • v.12 no.1
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    • pp.205-219
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    • 2002
  • This research seeks to identify the plantar pressure distribution graph and change in force in connection with effective golf drive strokes and thus to help ordinary golfers have appropriate understanding on the moving of the center of weight and learn desirable drive swing movements. To this end, we conducted surveys on five excellent golfers to analyze the plantar pressure applied when performing golf drive strokes, and suggested dynamic variables quantitatively. 1) Our research presents the desire movements as follows. For the time change in connection with the whole movement, as a golfer raises the club head horizontally low above ground from the address to the top swing, he makes a semicircle using the left elbow joint and shaft and slowly turns his body, thus lengthening the time. And, as the golfer twists the right waist from the middle swing to the impact with the head taking address movement, and does a quick movement, thus shortening the time. 2) For the change in pressure distribution by phase, to strike a strong shot with his weight imposed from the middle swing to the impact, a golfer uses centrifugal force, fixes his left foot, and makes impact. This showed greater pressure distribution on the left sole than on the right sole. 3) For the force distribution graph by phase, the force in the sole from the address to halfway swing movements is distributed to the left foot with 46% and to the right foot with 54%. And, with the starting of down swing, as the weight shifts to the left foot, the force is distributed to the left sole with 58%. Thus, during the impact and follow through movements, it is desirable for a golfer to allow his left foot to take the weight with the right foot balancing the body. 4) The maximum pressure distribution and average of the maximum force in connection with the whole movement changed as the left (foot) and right (foot) supported opposing force, and the maximum pressure distribution also showed much greater on the left sole.

A Study on Pressure Distribution for Uniform Polishing of Sapphire Substrate

  • Park, Chul jin;Jeong, Haedo;Lee, Sangjik;Kim, Doyeon;Kim, Hyoungjae
    • Tribology and Lubricants
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    • v.32 no.2
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    • pp.61-66
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    • 2016
  • Total thickness variation (TTV), BOW, and surface roughness are essential characteristics for high quality sapphire substrates. Many researchers have attempted to increase removal rate by controlling the key process parameters like pressure and velocity owing to the high cost of consumables in sapphire chemical mechanical polishing (CMP). In case of the pressure approach, increased pressure owing to higher deviation of pressure over the wafer leads to significant degradation of the TTV. In this study, the authors focused on reducing TTV under the high-pressure conditions. When the production equipment polishes multiple wafers attached on a carrier, higher loads seem to be concentrated around the leading edge of the head; this occurs because of frictional force generated by the combination of table rotation and the height of the gimbal of the polishing head. We believe the skewed pressure distribution during polishing to be the main reason of within-wafer non-uniformity (WIWNU). The insertion of a hub ring between the polishing head and substrate carrier helped reduce the pressure deviation. Adjusting the location of the hub ring enables tuning of the pressure distribution. The results indicated that the position of the hub ring strongly affected the removal profile, which confirmed that the position of the hub ring changes the pressure distribution. Furthermore, we analyzed the deformation of the head via finite element method (FEM) to verify the pressure non-uniformity over the contact area Based on experiment and FEM results, we determined the optimal position of hub ring for achieving uniform polishing of the substrate.

A Study on the Features of the Velocity Distribution and the Static Pressure Distribution of Oil on a Low-velocity Piston (저속용 피스톤에 가해지는 오일의 속도분포와 정압분포 특성)

  • Park, Hei-Jae;Choi, Jae-Wook;Kim, Sang-Do
    • Korean Chemical Engineering Research
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    • v.48 no.4
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    • pp.450-456
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    • 2010
  • This study was conducted in order to design a piston, part of a shock absorber, and the findings after examining the features of the velocity distribution and the static pressure distribution of oil on a low-velocity piston are as follow. The compression speed of oil passing through an 0.9 mm orifice was 0.0156~0.0642 m/s, and the velocity vector of the velocity distribution and the static pressure distribution had a greater tendency to rotate when the velocity increased. In case of the velocity vector of the velocity distribution and the static pressure distribution with an 0.8mm orifice, the speed changed secondarily, the second pressure-drop was observed and as for the distribution of the streamline around the orifice, a vortex was produced around the center. As for the velocity distribution of oil passing from the compression cylinder to the compact pipe, the velocity was greater in orifice of small diameter. Also, the greater the pressure difference was between the compression cylinder and the compact cylinder, the greater the force it was upon the piston.

Contact Pressure Distribution of Pin Bushing Bearings Depending on the Friction Conditions (마찰조건에 따른 핀부싱 베어링의 접촉면압분포에 관한 연구)

  • Kim, Chung-Kyun;Kim, Do-Hyun
    • Tribology and Lubricants
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    • v.23 no.6
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    • pp.255-260
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    • 2007
  • This paper presents the contact pressure distribution of pin bushing bearings for various lubrication friction modes such as oil film and elastohydrodynamic lubrication contacts, a mixed lubrication contact, a boundary contact, and a dry contact. During a sliding contact of a plain bearing, the boundary and dry rubbing contacts are dominated between a piston pin and a pin bushing bearing. This may come from a micro-scale clearance, an explosive impact pressures from the piston head, and an oscillatory motion of a pin bearing. The computed results show that as the oil film parameter $h/{\sigma}$ is increased from the dry rubbing contact to the oil film lubrication friction, the maximum oil film pressure is radically increased due to an increased viscous friction with a thin oil film thickness and the maximum asperity contact pressure is reduced due to a decreased asperity contact of the rubbing surfaces.

Seismic lateral earth pressure analysis of retaining walls

  • Ismeik, Muhannad;Shaqour, Fathi
    • Geomechanics and Engineering
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    • v.8 no.4
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    • pp.523-540
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    • 2015
  • Based on limit equilibrium principles, this study presents a theoretical derivation of a new analytical formulation for estimating magnitude and lateral earth pressure distribution on a retaining wall subjected to seismic loads. The proposed solution accounts for failure wedge inclination, unit weight and friction angle of backfill soil, wall roughness, and horizontal and vertical seismic ground accelerations. The current analysis predicts a nonlinear lateral earth pressure variation along the wall with and without seismic loads. A parametric study is conducted to examine the influence of various parameters on lateral earth pressure distribution. Findings reveal that lateral earth pressure increases with the increase of horizontal ground acceleration while it decreases with the increase of vertical ground acceleration. Compared to classical theory, the position of resultant lateral earth force is located at a higher distance from wall base which in turn has a direct impact on wall stability and economy. A numerical example is presented to illustrate the computations of lateral earth pressure distribution based on the suggested analytical method.

Development and Application of System for Pressure Distribution Measurement (압력분포 측정용 시스템 개발 및 응용)

  • 김용환;박성하
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.6
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    • pp.134-140
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    • 2003
  • The film sensor is used for measuring pressure distribution at planar area, especially at a small space or gap. The present paper deals with the development of film type sensors and system for pressure distribution measuring. The developed system is consist of (1)film sensor with 40/sup */40 array, (2)PCI interface card with maximum sampling rate of 100㎐, and (3)software for data processing and real-time display. The contact pressure test of wiper blade and front glass of vehicle was performed with wiper blade by 40cm. Generally spring force of wiper arm is designed at 0.7∼1kN. Test results of total force was 9.4N and 7.1N in each driver and passenger toward. The paper suggested possibility for base definition in wiper design. A windshield wiper blade experiment revealed that the system successfully measured the contact force distribution during static state, showing the usefulness of the developed system.

The Comparison of Plantar Foot Pressure Distribution in Adult and Elderly according Obstacle Heights (장애물 높이에 따른 성인과 노인의 족저압 분포 비교)

  • Chang, Jong-Sung;Lee, Myoung-Hee
    • The Journal of Korean Physical Therapy
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    • v.26 no.4
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    • pp.257-261
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    • 2014
  • Purpose: The purpose of this study was to compare plantar foot pressure distribution in adults and elderly according to obstacle height. Methods: Nine healthy adults and nine older adults were recruited and the subjects provided written informed consent consent prior to participation. Both groups walked and crossed obstacles with heights of 0%, 10%, 20%, and 30% of their height. Foot pressure was measured by peak pressure using the Pedar System (Novel Gmbh, Germany) during obstacle walking with barefeet in shoes. Three trails were calculated on eight areas and then averaged for data analysis. Results: A significant difference in great toe, little toes, and lateral metatarsal area was observed between adults and elderly groups, but other areas did not show significant differences. Foot pressure was increased in groups according to obstacle height. Conclusion: These findings showed that change in foot pressure distribution is more lateral in elderly in order to maintain postural control during obstacle crossing.

Development of a Pressure Distribution Measurement System (압력분포 측정시스템의 개발)

  • 정진호;이기원;김영호
    • Journal of Biomedical Engineering Research
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    • v.21 no.2
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    • pp.213-218
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    • 2000
  • Pressure distributions of the soft tissue are valuable for understanding and diagnosing the disease characteristics due to the mechanical loading. Our system measures dynamic pressure distributions in real-time under the general PC environment, and analyzes various foot disorders. Main features of the developed system are as follows: (1) With the resistive pressure sensor matrix of 40${\times}$40 cells, the data is sent to the PC with the maximum sampling rate of 40 frames/sec. (2) For each frame, contact area, pressure and force are analyzed by graphic forms. Thus, various biomechanical parameters are easily determined at specific areas of interests. (3) A certain stance phase can be chosen for the analysis from the continuous walking, and the detailed biomechanical analysis can be done according to an arbitrary line dividing anterior/posterior or medial/lateral plantar areas. (4) The center of pressure (COP) is calculated and traced from the pressure distribution data, and thus the movement of the COP is monitored in detail. A few experiments revealed that our system successfully measured the dynamic plantar distribution during normal walking.

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Fluctuating wind loads across gable-end buildings with planar and curved roofs

  • Ginger, J.D.
    • Wind and Structures
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    • v.7 no.6
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    • pp.359-372
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    • 2004
  • Wind tunnel model studies were carried out to determine the wind load distribution on tributary areas near the gable-end of large, low-rise buildings with high pitch planar and curved roof shapes. Background pressure fluctuations on each tributary area are described by a series of uncorrelated modes given by the eigenvectors of the force covariance matrix. Analysis of eigenvalues shows that the dominant first mode contributes around 40% to the fluctuating pressures, and the eigenvector mode-shape generally follows the mean pressure distribution. The first mode contributes significantly to the fluctuating load effect, when its influence line is similar to the mode-shape. For such cases, the effective static pressure distribution closely follows the mean pressure distribution on the tributary area, and the quasi-static method would provide a good estimate of peak load effects.

Contact Pressure Distribution Measurement of PVA Brush for Post CMP Cleaning (CMP 후 세정용 PVA 브러쉬의 접촉압력 분포 측정)

  • Ryu, Sun-Joong;Kim, Doeg Jung
    • Journal of the Semiconductor & Display Technology
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    • v.15 no.4
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    • pp.73-78
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    • 2016
  • Contact pressure distribution between PVA brush and semiconductor wafer was measured by developing a test setup which could simulates the post CMP cleaning process. The test set-up used thin film type pressure sensor which could measure the pressure distribution of contact area with the resolution of $15.5ea/cm^2$. As the experimental results, it was verified that there had been severe contact pressure non-uniformity along the axis of the brush and between the adjacent projections on the brush's surface. These results should be considered when developing post CMP cleaning stage or designing the PVA brush.