Simulation of a Badminton Racket a Parametric Study of Racket Design Parameters Using Finite Element Analysis
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Simulation of a Badminton Racket A parametric study of racket design parameters using Finite Element Analysis. Master's thesis in Applied Mechanics ELIAS BLOMSTRAND MIKE DEMANT Department of Applied Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY G¨oteborg, Sweden 2017 MASTER'S THESIS IN APPLIED MECHANICS Simulation of a Badminton Racket A parametric study of racket design parameters using Finite Element Analysis. ELIAS BLOMSTRAND MIKE DEMANT Department of Applied Mechanics Division of Solid Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY G¨oteborg, Sweden 2017 Simulation of a Badminton Racket A parametric study of racket design parameters using Finite Element Analysis. ELIAS BLOMSTRAND MIKE DEMANT © ELIAS BLOMSTRAND, MIKE DEMANT, 2017 Master's thesis 2017:52 ISSN 1652-8557 Department of Applied Mechanics Division of Solid Mechanics Chalmers University of Technology SE-412 96 G¨oteborg Sweden Telephone: +46 (0)31-772 1000 Cover: Illustration of a smash sequence for a badminton racket. Chalmers Reproservice G¨oteborg, Sweden 2017 Simulation of a Badminton Racket A parametric study of racket design parameters using Finite Element Analysis. Master's thesis in Applied Mechanics ELIAS BLOMSTRAND MIKE DEMANT Department of Applied Mechanics Division of Solid Mechanics Chalmers University of Technology Abstract Badminton, said to be the worlds fastest ball sport, is a fairly unknown sport from a scientific point of view. There has been great progress made to get from the old wooden rackets of the 19th century to the light-weight high performance composite ones used today, but the development process is based on a trial and error method rather than on scientific knowledge. The limited amount of existing studies indicate that racket parameters like shaft stiffness, center of gravity and head geometry affect the performance of the racket greatly. These studies have either been physical test with limit number of data points or simplified computer simulations. In this work a parametric study of racket models is performed with the purpose to find key racket design parameters using Finite Element Analysis, FEA. Eleven racket models are simulated using one smash and one clear swing. One is the reference model, based on a modern isometric racket, and the other ten have one parameter modified to see how this alters the response. In addition to the swing tests, the sweet spots of the racket head is analysed and the eigenmodes of the racket are investigated. The results show that the previously mentioned parameters have a noticeable effect on racket performance. A low shaft stiffness may give higher shuttle velocities if used correctly, and an inconsistent shuttle speed and trajectory if used incorrectly. High center of gravity has a less inconsistent effect but instead would require more effort to swing. Noticeable is that the Y-shaped head introduced by Prince, which since has been removed from the market, perform very well in some aspects. These results show that FEA should be seen as a useful tool in badminton racket development and with further work on the field advances can be made that would make badminton the definitive fastest ball sport in the world. Keywords: Badminton, Racket, Composite, FEA, FEM, LS-Dyna, Smash, Clear, Sweet spot i ii Preface This thesis treat the possibility to adapt an CAE method for design and evaluate badminton racket. The study is performed at the engineering consultant firm FS Dynamics with the sports equipment company Salming as the end costumer. The project was carried out during the spring semester 2017 corresponding 20 week for each of the two participants. The final examination was done at the department of Applied Mechanics at Chalmers University of Technology with Martin Fagerstr¨omas the accountable examiner. Acknowledgements First and foremost our gratitude goes towards FS Dynamics who gave us the opportunity to work with this project together with the end costumer Salming. Many thanks to our supervisors at FS-Dynamics, Bj¨orn Andersson and Mattias W˚angblad,for providing us with valuable feedback and guidance throughout the project. Further we like to thank Linus Lindgren for helping us with several issues in the software LS-Dyna. An additionally gratitude towards Maxine Kwan and John Rasmussen for providing us with the motion capture data. Finally a special thank to our examiner at Chalmers University of Technology, Martin Fagerstr¨om. iii iv Contents Abstract i Preface iii Acknowledgements iii Contents v 1 Introduction 1 1.1 Purpose...................................................1 1.2 Objective..................................................1 1.3 Limitations.................................................2 1.4 The Game of Badminton.........................................2 1.4.1 Badminton Racket............................................3 1.4.2 Shuttlecock................................................3 1.4.3 Badminton Strokes............................................4 1.4.4 The Player................................................4 2 Theory 5 2.1 Racket Properties.............................................5 2.1.1 Racket Mass and Swing-Weight.....................................5 2.1.2 Racket Stiffness.............................................6 2.1.3 String Properties.............................................7 2.2 Key Parameters for Racket Design....................................7 2.3 Challenges Due to Individual Player Characteristics..........................8 2.4 Finite Element Method..........................................8 2.4.1 Mesh...................................................8 2.4.2 Hourglass.................................................9 2.4.3 Elements................................................. 10 2.5 Composite Mechanics........................................... 10 2.5.1 FE-model of Composite Materials................................... 11 2.6 Motion Capture............................................... 12 3 Method 13 3.1 Used Software Products.......................................... 13 3.2 Racket Motion............................................... 14 3.3 CAD Model for the Racket........................................ 14 3.3.1 CAD Model for the Head and the Shaft................................ 15 3.3.2 CAD Model for the Net......................................... 15 3.3.3 CAD Model for the Handle....................................... 15 3.3.4 CAD Model for the Shuttle....................................... 16 3.4 Material Properties............................................. 16 3.4.1 Static Bending Test for Material Verification............................. 16 3.4.2 Composite Material for Frame..................................... 17 3.4.3 Wood Material for Handle........................................ 17 3.4.4 Material for Strings........................................... 17 3.4.5 Cork Material for Shuttle........................................ 17 3.5 The Finite Element Model of the Racket................................. 18 3.5.1 Defining Part Identities (PID)..................................... 18 3.5.2 Meshing Procedure and Used Element Formulations......................... 18 3.5.3 FE-model of the Badminton Racket.................................. 19 3.5.4 Alternations for Model Used in the Implicit Eigenmode Analysis.................. 22 3.5.5 Alternations for Rigid FE-model.................................... 22 3.6 Parameter Study.............................................. 22 3.7 Simulations................................................. 23 3.7.1 Simulation Settings........................................... 23 3.7.2 Execute Simulation........................................... 24 3.7.3 Eigenfrequency Analysis......................................... 24 3.7.4 Deflection Analysis............................................ 25 v 3.7.5 Sweet Spot Analysis for Swing..................................... 25 3.7.6 Sweet Spot for Clamped Racket.................................... 25 3.7.7 Time Window Analysis for Shuttle Impact.............................. 26 3.8 Method for Post-process and Organise Data............................... 26 3.8.1 Post-processing Result in Meta..................................... 26 3.9 Post-processing in MATLAB....................................... 27 3.9.1 Comparison of Input and Output.................................... 27 3.9.2 Deflection of the Racket......................................... 27 3.9.3 Shuttle Motion and Contact...................................... 28 3.9.4 Sweet Spot Analysis........................................... 28 4 Result 29 4.1 Racket Motion............................................... 29 4.2 Static Deflection Test........................................... 30 4.3 Mesh Convergence............................................. 31 4.4 Frequency Response and Eigenfrequencies................................ 31 4.5 Clear - Racket Behaviour and Parameter Influence........................... 32 4.5.1 Deflection of Racket During Swing and Hit.............................. 32 4.5.2 Racket Velocity at Impact........................................ 33 4.5.3 Momentum During Stroke........................................ 35 4.5.4 Contact Time and Duration....................................... 35 4.5.5 Shuttle Velocity and Direction..................................... 37 4.5.6 Repositioned Ball............................................ 37 4.6 Smash - Racket Behaviour and Parameter Influence.......................... 38 4.6.1 Deflection................................................. 38 4.6.2 Racket Velocity