不同網球拍拍線截面對擊球時所產生之動力響應

The Response of Dynamic during the Different Section of Tennis String with Ball Impact

林寶城(Pao-Chen Lin)

《體育學報》 21期 (1996/06) Pp. 137-149

https://doi.org/10.6222/pej.0021.199606.2113

摘要

本研究使用一支空拍重295公克之Wilson廠牌Profile 2.9型之大拍面網球拍，並以橫線張力53磅，直線張力為55磅分別穿以prince廠牌之15L號線(1.38mm)、16號線(1.30mm)、16L號線(1.22mm)等三種不同截面之半羊腸拍線。每種截面網線皆經由網球實際二十次自由下落碰撞實驗測試，並透過高速攝影機以每秒250赫茲取樣率收集網球碰撞球拍後之反彈影片資料，同時透過B＆K 8200壓電力量轉換計(Force Transducer)以每秒512個樣點之取樣率收集球拍受碰撞時之振動響應(The Response Of Vibration)資料。三種不同截面網線反彈之回復係數(The Coefficient Of Restitution)，經由SAS之統計分析軟體作變異數分析，考驗三種不同截面網線回復係數之差異，而振動響應是應用頻譜分析(Spectrum Analysis)方法加以分析。研究結果發現：三種不同截面網線碰撞之回復係數達到顯著差異，經事後比較結果也發現各組間皆達顯著差異。顯然的，16L號線(1.22mm)在回復係數方面優於16號線(1.30mm)之回復係數和15L號線(1.38mm)之回復係數。同樣的，16號線(1.30mm)在回復係數方面也優於15L號線(1.38mm)之回復係數。而三種不同截面網線受碰撞時拍柄之振動響應(The Response Of Vibration)經功率頻譜分析(Power Spectrum Analysis)同樣的發現16L號線(1.22mm)在振動響應方面優於16號線(1.30mm)之振動響應和15L號線(1.38mm)之振動響應。同樣的，16號線(1.30mm)在振動響應方面也優於15L號線(1.38mm)之振動響應。就本研究所得到的研究結論建議：如果不考慮經濟層面因素，網球拍穿以較細之網線擊球時，不論是對反彈球速或振動響應皆會產生較佳的擊球反應。

關鍵字

網球 ； 拍線 ； 回復系數 ； 振動響應

並列摘要

The influences of the tensile forces and the cross sections of wires to the dynamic responses of tennis racket and balls are examine. By the use of a Wilson's profile 2.9model oversize tennis racket that is 295 gram of the weight, three different cross sections of the Prince's synthetic gut, number 15L (1.38mm), 16 (1.30mm), and 16L (1.22mm) , are consider. The three different wires are mount on the same racket using the Babolat's machine respectively and the tensile forces are all keep at 53 pounds in transverse axis and 55 pounds in longitudinal axis. Every case is testing experimentally via free-fall ball impacts twenty times by tennis ball from a distance of four meters high. Shooting the rebound pictures of balls via high speed camera in 250Hz sampling frequency and collecting the vibration responses of the rackets via force transducer in 512Hz sampling frequency simultaneously. Using the digital image analyzer to digitize the rebound films of balls and analyze the rebound height, via the equations of the coefficients of restitution, one can get the coefficients of restitution of the balls for the three different wires. Then using the SAS of statistical analysis software, to consider whether the differences of the coefficients of restitution of the balls among the three different wires considered have reached the level of significance. Finally, using the spectrum analysis to get the forced responses of the racket after impact testing. The experimental results show that the differences of the coefficients of restitution of the balls between the three different wires considered have reached the level of significance, and that the thinner the cross section of the wires are, the higher the coefficients of restitution of the balls have, in our considering cases, the numbers 16L (1.22mm) have the highest coefficient of restitution of the balls and the number 15L (1.38mm) have the lowest one. In the view of the responses of vibration of the rackets, the thinner the cross section of the wires are, the lower the vibration responses of the rackets have, in our considering cases, the number 16L (1.22mm) have the lowest vibration response of the racket and the number 15L (1.38mm)have the highest one. Altogether, whichever in the view of the rebound speed for the balls or in the view of the comforts for users, the thin wires are more good than the thick ones. Via this research, the present writers have some commends. For the users, thin wires are more good choice whichever in the view of the rebound speed for the balls or in the view of the comforts if not consider the economics. It is worth researching how to improve the technologies of mounting wires to reduce the wear of wires when mounting on the racket and to elongate the life of the wires. In the view of the technologies of manufactures, it is worth considering how to enforce the ductility and the patience for wear of the wires. Finally, how to design the densities of the wire apertures of a racket to produce more affect tive restitution effects.

並列關鍵字

Tennis ； String ； Coefficients of restitution ； Vibration Response