Study Of Contact Pressure And Breast Displacement Of Sports Bra Based On Finite Element Method

Comfort and function are important factors for consumers to buy sports bra.Therefore,it is very necessary to further explore the pressure comfort of sports bra and its protective effect on breast shaking,which is necessary to meet the understanding of sports bra of consumers and the comfort\functional design of sports bra.The traditional objective measurement method has poor stability and is prone to human errors,while computer simulation can make up for this defect to a certain extent.Simulation of bra contact pressure and breast displacement has become an important development trend at present.This topic starts with two main factors that affect the pressure and displacement of breast—support intensity of bra and movement velocity,and use the "torso-breast-bra" model to explore its influence on breast contact pressure and breast displacement.The main research contents and conclusions are as follows:(1)The physical parameters such as thickness,density,elastic modulus and Poisson’s ratio of the main fabric,cup and lower elastic belt of W-1(ordinary soft support bra),W-2(medium support sports bra)and W-3(high support sports bra)were measured respectively.Then three subjects were selected to test the pressure and the displacement of breast,and the data of dynamic and static pressure and displacement of the breast at 5 points were obtained.In the displacement test,it is necessary to use 3points in the torso to establish a new torso coordinate system to obtain the relative displacement differentiation which can characterize the intensity of breast shaking.Based on the correlation analysis between the pressure and displacement data and the elastic modulus,it is found that the pressure increases with the increase of the elastic modulus,and the displacement decreases with the increase of the elastic modulus.(2)The finite element contact mechanical model of "torso-breast-bra" was established.Firstly,the 3D point cloud data of human chest and bra were obtained through 3D scanning system,and use the Geomagic reverse engineering software to process the geometric model to obtain the chest geometric model and the bra geometric model composed of three parts,and then the chest geometric model materialization and segmentation were completed in Solid Works.The "torso-breast" model and the bra model were imported into the ABAQUS finite element software,and the "auxiliary tool" was used to lift the breast and complete the process of wearing the bra,in which the contact between the bra and the "torso-breast" was defined as the contact T,and the contact between the torso and the breast was defined as binding B.By assigning the material parameters of the three parts of the bra,3 different support intensity of bra models can be obtained.The displacement trajectories of the xiphoid process point Ob at 4km/h,6km/h and 8km/h were used as the three-dimensional motion boundary conditions of the torso to simulate the three-dimensional motion of the human body at different velocities.Finally,the finite element contact mechanical model is solved by applying gravity and geometric thermal expansion.(3)The pressure and displacement of breast under different support intensity and different movement velocity were simulated and analyzed,and the following conclusions are obtained:1)Compared with the objective test results,it is found that the error between the finite element contact pressure simulation results of different bra support intensity and different movement velocity models and the human test results is within ±0.25 k Pa,the total average error is-0.01 k Pa,and the total RMSE value is 0.12.The error between the displacement simulation results is within ±5mm,the total average error is-0.19 mm,and the total RMSE value is 1.58.The simulation results are good,which can be used to evaluate and predict the comfort and function of the bra.2)The pressure cloud map directly shows that there are some differences in the contact pressure in different regions of the breast,that is,the lower and lateral areas of the breast are larger,while the upper and medial areas are smaller;the breast displacement of the upper and marginal areas is larger,while the breast displacement in the middle of the breast is smaller.Therefore,when studying bra comfort,you can’t just take the nipple point instead of the whole breast.3)Under 3 different support intensities of bra,the contact pressure of the breast was W-3 > W-2 > W-1.With the increase of movement velocity,the breast contact pressure increased,but the contact pressure of the three bras was still W-3 > W-2 > W-1,and the maximum contact pressure area and minimum contact pressure area did not change.Therefore,in the design of sports bra,we should ensure that within the range of pressure threshold,the material with larger elastic modulus should be selected as far as possible to improve the protective effect of sports bra on breast.4)With the increase of movement velocity,the shaking amplitude of breast becomes more intense,and the breast shaking intensity in different directions is Z(up and down)> Y(left and right)> X(before and after).When the speed increases from4km/h to 6km/h,the variation of the relative displacement differentiation of different areas of the breast is more consistent,and the increase is small;and from 6km/h to8km/h,the breast shaking is obviously intensified,and the relative displacement differentiation between different areas is significantly different,while the increase of bra support intensity can effectively slow the breast shaking amplitude and the displacement difference between different areas of the breast.Therefore,in the exercise and fitness,we should try to choose a bra with good support intensity to slow down the breast shaking.This study can provide some technical support for the exploration of pressure comfort and function of sports bra.Finite element simulation and prediction can not only effectively and intuitively show the breast contact pressure distribution and breast displacement,but also simplify the traditional testing process.It is expected to be used to optimize the pressure comfort and function of sports bra in the design and development stage.