• 한국표면공학회지
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• 제35권6호
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• pp.357-362
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• 2002

In this study, to improve the effect of the surface treatment, the shape design of shot ball is proposed. The fatigue effects of shot peening by the cut wire shot ball and the rounded cut wire shot ball are compared. The rotary bending and tensile fatigue tests are conducted on a spring steel to evaluate fatigue lives. The residual compressive stresses by the rounded cut wire shot ball is higher than by the rounded cut wire shot ball. This consequently increase the fatigue life and the reliability of surface treatment. Thus, to obtain optimum, repeatable and reliable shot peening effect the shape of the shot ball must be round.

• 한국운동역학회지
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• 제22권3호
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• pp.269-276
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• 2012

The purpose of This study's aim is to examine the difference in the changes of body segment movement, variables for ball quality, and carry at golf driver swing according to the ball quality using comparative analysis. Regarding the impact variables according to the ball quality using the track man and carry, club speed was the fastest at draw shot, ball speed was the fastest at straight shot, and smash factor was the lowest at draw shot. About the vertical launch angle, the fade shot showed the highest launch angle while the max height of the ground and ball was the highest at fade shot. And carry was the longest at draw shot. For the flight time, it was the longest at draw shot. The landing angle was the largest at fade shot. About the club head position change and trajectory, at the overall event point, the fade shot drew a more outer trajectory at the point of the follow through(E6) than the straight or draw shot. Regarding the angular speed of shoulder rotation, at the overall event point, the fade shot showed the greatest angular speed change in the follow through(E6). Also, about the angular speed of pelvic rotation, at the overall event point, the draw shot showed the greatest angular speed change at the point of down swing(E4). Concerning the stance angle change, both straight and fade shots were open as the concept of open stance whereas the draw shot was close as that of close stance. Regarding the previous study, the most important factor of deciding Ball Quality is the club face angle's open and close state at Impact. In short, the Ball Quality and carry were decided by this factor.

• 한국기계기술학회지
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• 제20권6호
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• pp.844-851
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• 2018

In this study, the regression equation was suggested to predict of the shot ball velocity according to blade shapes based on discrete element (DE) analysis. First, the flat type blade DE model was used in the analysis, the validity of the DE model was verified by giving that the velocity of the shot ball almost equal to the theoretical one. Next, the DE analyses for curved and combined blade models was accomplished, and their analytical velocities of shot ball were compared with the theoretical one. The velocity of combined blade model was greatest. From this, the regression equation for velocity of shot ball according to the blade shape based on the DE analysis was derived. Additionally, the wind speed measurement experiment was carried out, and the experimental result and analytical one were the same. Ultimately, it was confirmed that the prediction method of the velocity of shot ball based on DE analysis was effective.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1590-1596
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• 2001

The shot peening process is most often used to improve fatigue properties of metal parts. The single most critical parameter of the shot peening process is the shot ball itself. Without the correct quality media, all other shut peening parameters are extraneous and the desired fatigue improvement and consistency of improvement will not be achieved. Shot peening involves modifications of the surface and subsurface condition of a material that can be described by the change of the residual stresses, the hardness, and the surface roughness. This Paper Presents the shot peening to optimize the shot ball parameters. The effect of shot peening parameter on the surface roughness, surface hardness and residual stress are investigated.

• Tribology and Lubricants
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• 제13권2호
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• pp.39-45
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• 1997

The shot peening treatment were conducted for improving the strength of rolling contact fatigue of machine element like a gear. This paper was undertaken to analyze the influence of shot peening treatment for inner race of ball bearing on the rolling contact fatigue. Shot peening treatment were applied to the full hardened and the carbonitrided bearing. And the rolling contact fatigue life test and X-ray diffraction test were carried out. The results of this study showed that the fatigue life of ball bearing in the clean and the contaminated oil could be improved by shot peening treatment. This effect was found to be more pronounced to the full hardened bearing. These facts might be due to the generation of compressive residual stress and the strain hardening of surface layer by shot peening treatment. The failure of the shot peened bearing were presumed to initiate at surface.

• 전자공학회논문지 IE
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• 제47권2호
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• pp.47-53
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• 2010

본 논문은 PLC를 이용하여 자동으로 제어되는 쇼트볼 이송 호이스트에 대해 연구하였다. 대형 선박 표면에 페인트를 다시 칠할 때 기존의 페인트를 제거하는데 이때 찌꺼기들을 완전히 제거하기 위해서 사용하는 것이 쇼트볼이다. 고철에서 쇳물을 만들고 냉각 시켜서 작은 쇼트볼을 만든 후 호이스트와 연결 된 전자석을 이용하여 호퍼로 이동하게 된다. 현재 쇼트 볼을 호퍼에 옮기는 과정을 살펴보면 조작기를 사용하여 사람이 수동으로 호이스트를 조작하고 있어서 쇼트볼을 이동하는데 비효율적이며 기기를 작동하는데 대충 감으로 작업을 하고 있다. 그래서 수동으로 조작되고 있는 호이스트를 정확하게 위치제어를 하고 효율적인 작업을 할 수 있도록 무인 자동화 장치를 개발하였다.

• 한국운동역학회지
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• 제20권1호
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• pp.49-55
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• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2656-2661
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• 2002

Multiple impact models to examine the effect of stress interference are proposed and investigated. The single shot model analysis, which used various shot ball conditions, was carried out to compare with multiple impacts analysis. Then the multiple impact analysis were performed to predict the effect of the shot ball distances. The results showed that the stress interference in the multiple impact model significantly reduced the maximum value of the compressive residual stresses. The residual stress profiles were strongly effected by the shot ball distances. The multiple impact model can simulate a realistic shot peening process rather than a single shot model does. It is concluded that the proposed model predicts the real process more accurately.

• 방송공학회논문지
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• 제25권4호
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• pp.576-586
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• 2020

레이더나 라이더 센서를 활용한 야구 경기 분석은 많은 비용이 요구된다. 본 논문에서는 중계 비디오에서 피치 샷과 타구 샷을 검출하고, 카메라의 움직임 기반 타구 궤적 생성 알고리즘을 제안한다. 제안하는 알고리즘은 객체 검출과 옵티컬 플로우 기반 피치 샷과 타구 샷 검출 이후, 프레임 간 변환 관계를 통해 프레임 내 타구 위치와 타구 궤적을 계산한다. 제안 방법은 KBO 중계 영상 시퀀스 3개에 대해 성능을 평가하였고 피치 샷과 타구 샷 검출 정확도와 검출률은 89-95[%] 이내의 성능을 보였으며, 평균 타구 위치 거리차이는 13.6[m], 방향 차이 7.5°, 파울 분류 정확도 98.6%의 성능을 보였다.

• 한국운동역학회지
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• 제17권2호
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• pp.177-185
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• 2007

Even though there were no clear definitions of the short game and short game distance, short game capability is crucial for a good golf score. Generally, chip shot and pitch shot are regarded as two principal components of the short game. Chip shot is a short, low trajectory shot played to the green or from trouble back into play. Pitch shot is a high trajectory shot of short length. Biomechanical studies were conducted usually to analyze full swing and putting motions. The purpose of the study was to reveal the kinematical differences between professional golfers' 30 yard $53^{\circ}wedge$ chip shot and $56^{\circ}wedge$ pitch shot motions. Fifteen male professional golfers were recruited for the study. Kinematical data were collected by the 60 Hz three-dimensional motion analysis system. Statistical comparisons were made by paired t-test, ANOVA, and Duncan of the SPSS 12.0K with the $\alpha$ value of .05. Results show that both the left hand and the ball were placed left of the center of the left and right foot at address. The left hand position of the chip shot was significantly left side of that of the pitch shot. But the ball position of the pitch shot was significantly right side of that of the chip shot. All body segments aligned to the left of the target line, open, at address. Except shoulder, there were no significant pelvis, knee, and feet alignment differences between chip shot and pitch shot. These differences at address seem for the ball height control. Pitch shot swing motions(the shoulder and pelvis rotation and the club head travel distance) were significantly bigger than those of the chip shot. Club head velocity of the pitch shot was significantly faster than that of the chip shot at the moment of impact. This was for the same shot length control with different lofted clubs. Swing motion differences seem mainly caused by the same shot length control with different ball height control.