軟式網球線粗糙度對球拍特性影響－前導實驗

Influence of Soft Tennis String Roughness on the Racket Performance-Preliminary Study

廖英宏(Ying-Hung Liao) ； 方同賢(Tung-Hsien Fang) ； 劉強(Chiang Liu)

《華人運動生物力學期刊》 5期 (2011/10) Pp. 15-21

摘要

前言：本研究目的在於探討改變軟式網球線表面粗糙度對球線摩擦力、球撞擊球拍後震動響應、球速、轉數之影響。方法：實驗區分為材料及人體測試兩階段，第一階段先使用氧化鋁砂布No150#摩擦球拍甜區，以改變表面粗糙度，再利用白光干涉儀器測試球線表面粗糙度差異，並在球拍裝置Biopac三軸加速規後固定於夾鉗鋏器，球體由100公分處以自由落體落下於拍面甜區，以測得震動響應；第二階段為實際揮拍擊球，受試對象為台北體院軟式網球隊3名優秀選手，分別以未改變及以改變表面粗糙度之球拍，揮擊上旋球、平擊球及下旋球，利用Mega高速攝影機（1000Hz）分析球速及轉速。統計方法因樣本數量較少而採用敘述性統計。結果：未改變與已改變球線表面粗糙度之球線數值分別為3.12 ± 0.37微米、6.81 ± 2.50微米，震動響應減少14.59伏特，上旋球球速減少60%、平擊球減少33%、下旋球減少15%，上旋球轉數增加50%、平擊球增加34%，下旋球增加34%。結論：改變球線表面粗糙度後，會使球線表面粗糙度增加、震動響應減少、球速減低，球轉數增加等現象，因此軟網選手可利用此方法達到運動生物力學優勢。

關鍵字

球線 ； 摩擦 ； 震動響應 ； 揮拍運動

並列摘要

Purpose: The aim of this study was to exam effects of surface roughness changes of soft tennis string on friction of string, vibration response, ball velocity and number of revolutions. Method: Material and hitting measurements were conducted, respectively. In first measurement, one emery cloth, No150#, was used to rub the sweet spot of the racket for changing its roughness. Friction of tennis string was measured by using a friction tester (ALGOL-HF-100). Vibration response of racket was measured by using a tri-axial accelerometer when the bounce response after a soft tennis ball, fall down from 100 cm height, hits against on the sweet spot of racket. In second measurement, 3 elite players hit top-spin, flat strike and back-spin by using the string with and without roughness changes. Mega high-speed camera at 1000Hz was collected batted ball for analyzing ball velocity and number of revolutions. Result: After surface roughness changes of soft tennis string, the friction of string increased about 0.02 kg, vibration response decreased about 14.59 v, ball velocity decreased (60% for topspin, 33% for flat strike and 15% for backspin), and number of revolutions increased (50% for topspin, 34% for flat strike and 34% for backspin). Conclusion: Increased string roughness resulted in higher friction, lower vibration response, lower ball velocity and higher ball spin. Therefore, soft tennis player could get biomechanical benefit after adopting this method.

並列關鍵字

string ； friction ； vibration response ； racket sport