Independent-Study Course Examines Materials in Tennis Rackets and Hockey Sticks
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Independent-Study Course Examines Materials in Tennis Rackets and Hockey Sticks Introduction
For the past seven years I have taught the Engineering Materials course (EM 380) at the United States Military Academy (USMA), Department of Civil and Mechanical Engineering (CME). The course has been modified to introduce modern materials technology to the cadets and to provide the opportunity to fabricate, design, test, and evaluate advanced materials in this course, in capstone design projects, and in independent-study projects. Theoretical and experimental studies of sporting equipment have been a sound and compelling basis to develop student ability in applied mechanics and to gain insight into the importance of materials choice. This article describes the methods and results of several of these projects. Thus far USMA cadets have conducted dynamic characterization of a variety of equipment including basketball hoops, backboards and balls, gymnasium floors, skis, golf clubs, lacrosse sticks, and boxing gloves. Baseball and Softball bats were characterized via resonance apparatus, a Bruel and Kjaer 2034 signal analyzer (apparatus which measures frequencies and mode shapes), excitation "hammer," accelerometers, and associated 386 computer with the StarStruck SMS modal analysis software. Aluminum, wooden, and composite bats were characterized in terms of principal resonant frequencies, mode shapes, and damping behavior. Wooden bats, the classic Louisville sluggers were "doctored " to emulate famous bat tampering incidents, such as drilled hollows filled with cork or metal slugs. Doctoring had virtually no effect on frequency, modal response, or damping behavior! Baseball coefficients of restitution measurements were completed for various support conditions and bat materials. More recently the evolution of tennis rackets and hockey sticks was investigated. Students are currently involved in the study of racket ball rackets, composites in bicycles and kayaks, and other recreational equipment. This article summarizes the results obtained for tennis rackets and hockey sticks as typical examples of the importance of materials choice and structural mechanics response. Tennis
Tennis may be considered a young sport, reputedly first introduced in the mid-1800s by a British army officer, to offer his house guests a pastime other than MRS BULLETIN/MARCH 1998
croquet. While first played on grass courts, it is now played on clay, grass, or cement. Since the first Wimbledon championship tournament in June 1877, tennis rackets have also evolved. Currently the only restrictions placed on manufacture of tennis rackets is that the frame should not exceed 81.3 cm overall length and 30.5 cm in width. There is no limitation on weight. Players seek power, control and comfort in their rackets. Manufacturers have been trying for many decades to improve performance and provide a variety of options for the player. Many types and combinations of materials have been used in pursuit of enhanced performance. To fully optimize materials choice, the
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