• 제목/요약/키워드: Ball speed

검색결과 627건 처리시간 0.033초

열처리 금형강의 볼엔드밀 고속가공 (High Speed Ball End Milling of Hardened Mold Steel)

  • 양진석;허영무
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2004년도 추계학술대회 논문집
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    • pp.1418-1423
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    • 2004
  • High speed machining experiment on the heat-treated mold steel(STAVAX and CALMAX of hardness HRc 53) is carried using TiAlN coated ball endmill. Tool life and wear characteristics under the various machining parameters and cooling methods are investigated. Effect of cooling method on life and wear of the tool was compared. For most cases, tool life was not determined by the amount of wear but by th chipping on the cutting edge. It is found that tool manufacturer's cutting parameters generally agrees with the results of this experiment.

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공작기계용 리니어 볼 부쉬의 소음수준에 관한 실험적 연구 (An Experimental Study on the moise level of Linear Ball Bushes for Machine Tools)

  • 최영휴
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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    • pp.704-707
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    • 2000
  • In this experimental study, noise level measurements were conducted on physical LBB(Linear Ball Bush) samples in a semi-anechoic chamber. Evaluation of the measured data demonstrates that LBB's noise level is proportional to the logarithmic of its speed multiplied by the ball diameter. Furthermore details of implementations and process for measuring noise level and operating speed of LBB are also presented.

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베어링-축계의 부정정계 해석 및 볼베어링의 거동예측 (Analysis of Statically Indeterminate Bearing-Shaft System and Prediction of the Behavior of Ball Bearing)

  • 김완두;한동철
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1993년도 제18회 학술대회 초록집
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    • pp.70-76
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    • 1993
  • From the analysis of shaft-bearing indeterminate system, moment and misalingment angle which was generated in bearing were determined. And the influence of span length between bearings on the fatigue life was established. The equation to estimate the cage rotational speed was proposed, and this equation was verified by the measuring of cage speed and shaft speed. And accoding to quasi-static analysis, the spinning speed of ball was determined.

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On the wave propagations of football game ball after contacting with the player foot

  • Lei Sun;Cancan Wei;Fei Liu;Lijun Wang;Bo Ren
    • Geomechanics and Engineering
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    • 재33권6호
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    • pp.529-542
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    • 2023
  • Wave propagation with high transverse deflection could affect the stability of the ball in its trajectory. For low stiffness balls similar to soccer and volleyball balls, the waves are more noticeable in comparison to other balls like ping-pong ball. On the other hand, the soccer balls are under heavy impact loads from shoots and contacting different objects in the field. The maximum recorded speed of a soccer ball after kicking is the 211 km/hr and the average maximum speed is around 112 km/hr. Therefore, in such speeds the aerodynamic forces become important which are directly related to geometrical shape of the ball. In this regard, the wave propagation in soccer ball is examined in the current study using large deformation shear deformable formulations. Classical relations of stress-strain components are taken into consideration along with minimum total energy principle. The final derived relations were solved by using harmonic differential quadrature method. The results are generally presented ion term of phase velocity as function of different influencing parameters of the materials, geometry and mass of the ball.

Effects of pelvic stability on instep shooting speed and accuracy in junior soccer players

  • Sung, Ha-Rim;Shin, Won-Seob
    • Physical Therapy Rehabilitation Science
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    • 제7권2호
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    • pp.78-82
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    • 2018
  • Objective: The purpose of this study was to determine the effect of wearing a pelvic compression belt on ball speed and accuracy in instep shoots of youth soccer players. Design: Randomized cross-over design. Methods: We included 20 male junior soccer players with experience of more than 5 years. Participants were randomly assigned to two conditions: application of a pelvic compression belt and instep shooting or no application. Instep shooting was performed three times at a distance of 20 meters from the position of the goal post, and the ball speed was measured using a speed gun at a position 5 meters behind the goal post. The shooting accuracy was measured based on a 5-point scale. The shooting accuracy was measured by scoring 5 points at 2.44 meters in the middle of the goal area of area A, 3 points at 2.44 meters in the goal area of area B, and 0 in the case of shooting outside the goal area C. Results: After applying a pelvic compression belt, the mean speed of the ball was significantly increased (p<0.05). The maximum speed of the ball was significantly increased (p<0.05). The accuracy of the ball was significantly increased (p<0.05). Conclusions: Through this study, we expect that the use of the pelvic compression belt can be applied as a training method to improve the shooting ability of soccer players. Clinically, pelvic compression belts are expected to help rehabilitation soccer players to improve their shooting accuracy.

공구경로 변화에 따른 고속 볼 엔드밀 가공에서 경사면의 특성(I) (Characteristics of Inclined Plane Constructed by High speed Ball End Milling according to the Variation of Cutting Direction(I))

  • 강명창
    • 한국생산제조학회지
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    • 제8권2호
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    • pp.137-143
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    • 1999
  • The study of the high speed machining of inclined plane using ball end mill is performed. The use of ball end mill is rapidly growing in die and mold manufacturing. The cutting characteristics, such as cuttin g force, surface roughness and surface profile, are varied according to the variation of cutting directions. Free surface is cut using ball end mill, the surface profile is greatly varied depending upon the cutting direction. So this study will deal with the characteristics of cutting such as cutting efficiency according to the inclined plane of the workpiece, the cutting force according to tool path, surface profile and the roughness of surface. The optimal cutting direction to be applied the cutting for 3-D sculptured surfaces can be show through the results of this study.

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볼-유정압 복합베어링을 갖는 고정밀 주축의 회전특성에 관한 연구 (Rotational Characteristics of High Precision Spindle Unit with Ball-Hydrostatic Bearing)

  • 이찬홍;이후상
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2000년도 춘계학술대회 논문집
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    • pp.663-667
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    • 2000
  • The spindle unit is core parts in high precision machine tools. Diverse static and dynamic charateristics of spindle unit are needed for special purpose of machine tools. Specially, high damping ability may be very useful to high precision and high speed spindle unit. But commercial bearing system has very low damping value and high stiffness. In this paper, the combined bearing system with ball-hydrostatic bearing is suggested for high damping spindle unit. The suggested bearing system has 30% damping ability more than general ball bearing's. The average rotational accuracy of spindle with combined bearing in working speed is 24% better than with ball bearing. The unbalance rotating experiment in spindle show that rotating error with combined bearing is only half value of with ball bearing.

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