Tennis Strings Research Articles

313 テニスラケットのストリング性能論1 : パワー,コントロール,打球感と性能の寿命に関する考察(テニス・あん馬)

There has been no question that some strings do provide a better grip than others, but that did not guarantee that the ball will produce more spin. Furthermore, experiments with hand-held rackets has been needed to solve the difficult question of how players can tell the difference between different strings when laboratory tests indicate that they should play the same. The previous paper performed an experiment measuring the spin rates of used, notched strings in both their natural condition and after applying a lubricant to the string intersections to facilitate tangential string movement. It found that the lubricated notched strings produced 30% more spin than the unlubricated notched strings. The lubricant materials are effective to the notched strings, because the lateral movement and snap-back of the main strings increase spin. It also showed that the more spin results in the reduction of shock vibrations of the wrist joint during impact. Furthermore, it was shown that the used natural gut with notches decrease 70 % of spin rate compared to the new natural gut without notches in the another experiment, which has remained to be seen whether the same results will be obtained. Recently, International Tennis Federation researchers reported that the same movement that was observed with lubricated strings occurs with copoly as well. Copoly strings-slippery and stiff-generate more spin not because of more friction, but because of less. The old argument was that the better the grip between the strings and the ball, the more spin we would get, but that was not true. Many experiments has started to investigate whether the lateral movement and snap-back of the main strings increase spin, which strings generate the most spin, and so on. The research has also started to investigate the effect of a inter-string friction upon the main strings movement against the cross strings. Furthermore, the research has started to investigate how tennis strings "Go Dead". This paper clarified a mechanism for impact that is able to account for the wide range of string performance seen in the literature.

Elastic Properties of Plasticine, Silly Putty, and Tennis Strings

How would a physicist describe the elastic properties of an apple or a banana? Physics students and teachers are familiar with the elastic properties of metal springs, but are likely to be less familiar with the elastic properties of other common materials. The behavior of a metal spring is commonly examined in the laboratory by adding masses to measure the change in the extension or compression. A banana or an apple or any other relatively soft material could just as easily be examined in the same way, as an additional and entertaining exercise. Even if an apparatus is not readily available to undertake such an experiment, it can easily be constructed.1,2 In this article I compare the elastic properties of Plasticine (a brand of modeling clay), Silly Putty, and tennis strings. All three materials behave in the same qualitative manner when stretched or compressed slowly, despite the fact that they are quite different when stretched or compressed rapidly and despite the fact that Plasticine and Silly Putty are both much softer than a tennis string. Typical results for a slow deformation are shown in Fig. 1.

Effect of inter-string friction on tennis ball rebound

Tennis players report anecdotally that the choice of string material affects the amount of spin applied to the ball by the racket. Previous research on the effect of the coefficient of friction of tennis strings has concluded that ball rebound is mostly, but not always, independent of the string friction. To understand this better, tennis balls were projected at a fixed racket at 25 m·s−1 with backspin varying from 0 to 400 rad·s−1 at an angle of 40° and 60° to the normal with strings made from either nylon or polyester. Each string type was modified by lubricating it to give low friction or sanding it to give high friction. It was shown that the inter-string friction μs had different consequences depending upon whether the strings slid across each other during contact. The ball tended to roll at high μs, unless the inbound backspin was high enough to induce slipping. A decrease in μs allowed slipping of the strings over each other which reduced the horizontal impulse applied to the ball. At very low μs the ball was induced to overspin at steep impacts or slip at shallow angles. It was concluded that the dominant effect of a change in inter-string friction was in the string movement rather than the coefficient of friction between the ball and strings, and that the effect was dependent upon impact angle and spin.

Effect of friction on tennis ball impacts

There are currently no restrictions on the coefficient of friction of tennis courts or strings. The aim of this paper was to determine the effect of friction on tennis ball impacts. Finite element models were used to determine the effect of friction for oblique spinning impacts both between a tennis ball and a rigid surface and between a tennis ball and the string bed of a freely suspended racket. The results showed that during an oblique impact a tennis ball can behave in any of the following ways: first, it can slide, second, it can slide and then ‘overspin’, or, third, it can slide, overspin, and then converge towards rolling. The ball will slide throughout the majority of impacts on the court during play. Therefore, the rebound topspin of the ball will increase with increasing court friction and the horizontal rebound velocity will decrease. The ball will roll off the string bed for the majority of groundstrokes, and the rebound properties will effectively be independent of string bed friction.

Non-destructive testing of tennis strings

The paper aims to illustrate three advantages of infrared thermography as a non-destructive, non-contact and in real time technique (a) to detect the occurrence of intrinsic dissipation localisation, (b) to observe the progressive damage processes and mechanisms of gut failure, and to determine the optimal tensions for each type of tennis strings. Experimental results evidence a limit of acceptable damage beyond which string will fail due to coalescence of defects and/or weakness zones.

Experimental designs in sport implement research: Application to the tension loss in tennis strings

The aim of this study was to quantify the influence of five experimental variables (style of play, sheath and central structure of synthetic strings, racket frame, and game court) on the tension loss in tennis strings in field situations, using experimental design methodology. Sixteen experiments were defined using a fractional factorial design 2(5–1). The tension loss in tennis strings was calculated by the difference between the tension measured just before and just after one hour of play. Multiple linear regression was performed to express the tension loss as a function of the five experimental variables and their first‐order interactions. The results showed that the tension loss was influenced by three main experimental variables: game court, racket frame, and string‐sheath, and by four two‐factor interactions, including the style of play and string central structure interaction term. The tension loss in tennis strings was minimal when playing with an 18‐main‐string racket frame strung with an S1‐coated string on a hard court. This work suggested that experimental designs could help researchers to highlight the sport implements’ behaviour in field situations.

Evaluation of the Restitution Characteristics of the Strings for Racket.

The restitution characteristic of fiber string in axial direction was analyzed with considering the visco-elasticity of yarns. An impact test was developed that one side of string was fixed in load cell, the other side was fixed in hammer. The hammer moves along the slide rail. When the hammer was struck, the impact speed of hammer was measured with the laser sensor, and the restoration ratio was obtained. In experimental range for all samples, the restoration ratio became small with the impact speed. A dynamic restitution model considering tensile non-linear visco-elasticity of materials was suggested. The good agreement was obtained between the experimental and the theoretical values. It was also shown that the repulsion of tennis strings could be evaluated with the parameter of the proposed model.

Laboratory testing of tennis strings

Most tennis strings have a performance rating of almost 10 out of 10 if one can believe the manufacturers’ claims. Laboratory tests of tennis strings provide a different picture. The test methods and the results of testing 90 different strings are described. This type of information is needed if players, coaches and stringers wish to make an informed comparison between different strings, and it is also needed if one wishes to model the interaction between a tennis racket and a tennis ball.

Measurement of Restitution Behavior of Strings and Rigid Body.

The relationship between restitution behavior of strings and its mechanical properties was measured and discussed. An impact test device that could control the initial tension and impact velocity on speed area of less than 10 m/s was developed for measuring the restitution behavior of hammer and tensioned strings. About this device, influence to the measurement results of mass and materials of the hamnler and slipping on the clamps was examined. Using this device, restitution behavior of tennis strings was measured. A dynamic restitution model considering tensile viscoelasticity of materials was suggested with approximating it by Voigt model. The restitution behavior was simulated by numerical computation. In experimental range for all samples, coefficient of restitution increases with initial tension and decreases with initial velocity, and when the mass of a hammer is small, the coefficient becomes big. The calculation results of the model could show the tendency of experimental results well.

Tennis strings and methods of making them (review)

-- Analysis of the patent literature has shown that to obtain synthetic strings with playing properties close to those of strings from natural raw material and with a good lifetime, one uses a construction which includes a core and winding of monofilaments or complex yarns and an envelope (coating). To obtain flexible elastic strings, it is preferable to use complex yarns, especially in the core. To wind the core, thin textile monofilaments are recommended most often.

Evaluating the elastic properties of tennis strings

-- Characteristics of the clastic properties of specimens of domestic tennis string and strings from certain foreign companies have been analyzed.

Estimating the lifetime of tennis strings

-- The static and dynamic strength characteristics of experimental specimens of tennis string have been studied; these were prepared on a basis of nylon complex yarn with a polyamide coating.

Characteristics of Nylon and Gut Tennis Strings

Characteristics of Nylon and Gut Tennis Strings