3-Dimensional Stress Calculation of Competitive Swimwear Using Anisotropic Hyperelastic Model Considering Stress Softening

AbstractThree dimensional stress calculation of competitive swimwear using anisotropic hyperelastic model considering stress softening was investigated in this paper. An anisotropic hyperelastic model considering stress softening of swimwear fabrics was introduced in order to reproduce the mechanical characteristics of swimwear fabrics on the analysis. The cyclic tensile loading test was carried out to evaluate the mechanical characteristics of the swimwear fabrics. From the test results, the mechanical characteristics of swimwear fabrics show strong-anisotropy and the stiffness of the fabrics shows hardening along with the increase of stretch. Also, the test results show reduction of stiffness which depended on the maximum deformation previously reached in the history of the swimwear fabrics. From the test results, material parameters of the anisotropic hyperelastic model and the stress softening model were approximated. The theoretical calculations were in good agreements with experimental data. In addition, the pressure measurement tests were conducted to measure the pressure of swimwear tightening the cylinder. The theoretical pressure calculated by the proposed model showed similar trend of pressure measurement tests. Finally, 3-dimentional stress calculation of swimwear was conducted using the anisotropic hyperelastic model considering stress softening. The stress calculation enabled the visualization of stress distributions of swimwear. In addition, the torque generated in right and left hip joints were calculated by stress calculation of swimwear. The stress calculation investigated in this study enabled the new design of competitive swimwear considering the torque generated in hip joint

A New Method for Designing Sportswear by Using Three Dimensional Computer Graphic Based Anisotropic Hyperelastic Models and Musculoskeletal Simulations

AbstractThe purpose of this study is to develop a new method for designing compression sportswear from the viewpoint of force by simulation. Applied simulation techniques are 1) skin strain simulation, 2) fabric strain simulation using the anisotropic hyperelastic model, and 3) musculoskeletal simulation. For skin strain simulations, a three dimensional computer graphic (3D-CG) polygon strain was calculated as a skin strain using a 3D-CG model that simulates the human body (CG-Human-Model). The initial strain and the strain caused by physical exercise were given to the polygon model representing the shape of the sportswear (CG-Sportswear-Model). For compression sportswear, the strain of the fabric is approximately the same as skin strain, thus the strain of the CG-Human-Model was given to the CG-Sportswear-Model. In-plane and out-of-plane forces resulting from the CG-Sportswear-Model are calculated using anisotropic hyperelastic models. These forces were given to the musculoskeletal simulation as the external forces, and muscle activity required for any given physical exercise (e.g. swimming motion) was calculated. Information of forces and muscle activity are very useful in designing compression sportswear. It is believed that this new method for designing compression sportswear based on simulation is a sophisticated technique because this method takes into account not only forces resulting from sportswear but also the effect of these forces on physical exercise

A METHOD FOR ESTIMATING ELBOW VARUS TORQUE USING ONLY A BASEBALL WITH AN EMBEDDED SENSOR

Currently, to measure the elbow varus torque during baseball pitching, it is necessary to attach markers and sensors to the body. The purpose of this study is to develop the method for estimating elbow varus torque by only a baseball with an embedded sensor, and examine the accuracy. Eight baseball pitchers threw a four-seam fastball with maximum effort. The varus torque was estimated using one-link-segment model by an accelerometer and gyro sensor placed in the baseball. The Intraclass Correlation Coefficients between the maximum values of the varus torque calculated by the proposed method and the values calculated by the motion capture system was high (ICC(3,1) = 0.73).This result indicates that proof of concept by one-link model is success and warrants future research to potentially develop a system with greater accuracy

Musculoskeletal Simulation of Sports Motion Considering Tension Distribution in a Whole Body Compression Garment

AbstractCompression garments are widely used in various sports activities. Since the cloths in a compression garment are sufficiently attached to the human body, it is possible for a compression garment to have particular mechanical functions by appropriately arranging the tension distribution in the garment. However, the effects of such garment on muscle activity have not been sufficiently investigated yet. Therefore, a method of musculoskeletal simulation for such problems were developed in the present study. In the developed musculoskeletal model, particular belt-like parts of cloths which had larger tension against stretch were modelled as virtual ligaments. In order to distribute the virtual ligaments, 403 reference points for upper half of the body were defined on the whole body in the musculoskeletal model. These points could be used as start, end and via points for the virtual ligaments. As an example of analysis, a running motion was analyzed in the present study. The running motion was acquired from the experiment using motion capture system, and put into the simulation model. One simple pattern of tension distribution was examined by the simulation. From the simulation, it was confirmed that the muscle activity changed according to the tension of the belt-like cloths. Therefore the developed simulation method will be useful for the design (the arrangement of the belt-like cloths) of the whole body compression garments