Simulation Of A Breast And A Sports Bra Interaction During Exercise

Breast displacement of a female body during exercise might cause discomfort, breast pain and even other injury to breast tissue. Sports bras usually tight-fit and made of elastic materials are used to provide firm support to the breast and reduce the displacement. The tension caused by stretched fabrics provides the breast support through compression which might cause another problem, pressure discomfort. The different design of sports bra in terms of materials and styles might have various effects on the breast support both in static and dynamic states. A model to simulate the mechanical between a breast and a bra, and thus predict the breast displacement and pressure distribution on breast surface will be helpful in developing sports bra products. In this study, we aimed to build such a model.A 3-D female body manikin was scanned by using SYMCAD 3-D body scanner system, the obtained point cloud data was processed with the reverse engineering software Geomagic Studio. A 3-D surface model of the breast was built and a bra model was generated from the breast surface. The breast surface model was further filled as a solid model by using Solid Works package. The geometric model of the breast and bra were input into the FEM package of Abaqus, the biomechanical properties of human body tissues were assigned to the breast, and the mechanical properties obtained by a bi-axial extension test of a knitted fabric for the bra was assigned to the bra. On the other hand, the 3-D breast displacements of four subjects wearing a sports bra during running were recorded at five points including left nipple and four surrounding points by using an 8-camera Vicon motion capturing system. At the same time, the pressure at the five points was also measured by using air pack pressure sensors. The measured movement data of the breast was assign to the thorax of the body model, a dynamic model was further generated. The mechanical interaction between the breast and the bra was simulated statically and dynamically(running) as well. In the static simulation, the average static pressure error of five points is 15%. In the dynamic simulation, the breast point displacement and measured displacement changes has better consistency, among them, X direction changes are the biggest difference, less than 1 cm. In addition, except for the BL dynamic pressure error is too large, the L1 dynamic pressure error below 20%, the other three average errors less than 10%. The simulated pressure and breast displacement were compared with the respective measured ones. Good agreement obtained validated the modeling.