Abstract:

Objective In order to study the mechanism of interaction between clothing pressure and various layers of lower body tissues, including skin layer, other soft tissue layer and muscle layer, a finite element layered model was established using ANSYS to predict the deformation and stress distribution of each layer tissue under clothing pressure.

Method Two-dimensional tomography images of human lower limbs was obtained by CT scanner, and a three-dimensional layered model of human lower limbs by Mimics was established and was imported into ANSYS to improve the model. Material properties of the model were defined, and boundary conditions were set to obtain finite element prediction models. In order to verify the accuracy of the model, 44 collection points were selected in the lower limbs to collect the measured clothing pressure data, and SPSS were utilized to analyze the correlation between the predicted data and the measured data,useing multiple correlation coefficient R to measure the model fit degree. The closer the R value was to 1, the higher the accuracy of the model was proved.

Results The least obvious part of the skin layer was found to be the medial front of the calf, the least obvious part of the other soft tissue layer was basically the same as the skin layer, and the least obvious part of the muscle layer was the medial front of the calf. The most obvious deformation part of the skin layer was basically the same as that of other soft tissue layers, which was on the upper part of the inner middle of the thigh. The maximum shape variations were 2.73×10^-2 mm and 5.19×10^-4 mm, respectively, with a difference of nearly two orders of magnitude. The muscle layer deformation mainly occurred in the inner thigh, front internal, back internal and back leg. The most obvious part of the deformation was in the middle of the inner thigh, with a maximum value of 7.30×10^-5 mm. By comparing the skin layer with other soft tissue layers, it was found that in the area where the skin layer shape variation is less than 2.73´10^-3 mm, the other soft tissue layers hardly deformed. Compared with the deformation prediction curve and stress prediction curve, although there are some differences between them, the inflection point was basically the same. When the stress reached the peak, the deformation also reached the maximum value, and when the stress dropped to the trough, the deformation is also at the minimum value, indicating that the deformation was affected by the change of stress and was positively correlated with the stress. On the whole, the thigh deformation was more obvious than the calf deformation, the middle thigh deformation difference was the largest, the ankle deformation difference was the smallest.

Conclusion By comparing the prediction results of clothing pressure of skin layer, other soft tissue layer and muscle layer, it is found that the pressure of clothing pressure on each layer of human lower limbs gradually decreases from the outside to the inside, and the influence of clothing pressure on muscle layer is little, and the main object of clothing pressure is skin layer and other soft tissue layer. In a certain range, the body surface shape variations are affected by stress changes and maintain a positive correlation with stress. The surface stresses of human lower limbs are inner, rear, front and outer in order from large to small. The goodness of fit of multiple correlation coefficients between the predicted clothing pressure data and the measured data R is 1, indicating that the layered clothing pressure prediction model can be used to study the deformation prediction of skin, other soft tissues and muscles under clothing pressure. In practical application, this finite element prediction model can be used to obtain the appropriate garment pressure comfort threshold, reduce muscle fatigue, improve exercise efficiency, and provide theoretical guidance for the product development of functional tight sports pants.

Key words: clothing pressure, lower limb stratification model, clothing pressure prediction, deformation displacement, functional clothing, ANSYS software