Study On Computer Modelling Of Fabric Contact Thermal Sensation

When human skin touches the fabrics, heat transfer would occur between fabrics and human skin, the skin’s temperature would rise up or fall down, it would stimulate the thermal receptors in the skin, result in the cool or warm feeling. This is called fabric contact thermal sensation. Much work was done on it by the domestic and foreign researchers over the years. Even the test and evaluation methods on it were developed. Such as KES-F7, it evaluates the fabric contact thermal sensation by measuring the maximum heat flux through the fabric. While HES measure it by using the heat absorption ability of test specimens. Some workers analyzed it through building computer modelling. Although the above work makes people know much about fabric contact thermal sensation, there is still some inadequacies. Firstly, most of previous work focuses on two dimensional problems, no matter for modelling or measurement instruments. Secondly, several three dimensional models were developed for skin-fabric contact, while they aims to discuss tactile sensation, not thermal sensation. Finally, they pay more attention to physical process than physiology and psychology. However, in reality, the contact between skin and fabrics starts from a point to a surface. The contact would make deformation between fabrics and skin. The heat transfer couples with the force transmission. It is necessary to establish three dimensional model for this issue. Therefore, this study attempted to modeling on the finger-fabric contact to analyze the fabric contact thermal sensation, for that the finger-fabric contact used to evaluate the quality of fabrics.Modelling is divided into two parts: the thermal-mechanical coupling process during contact and the thermal sensation of fingers. The first part was conducted by two steps: geometry modeling and thermal-mechanical coupling modeling. Geometry modeling was done by applying the tools of Solidworks. After they were built, the geometry models of the finger and three pieces of fabrics were imported into FEM software – ABAQUS. Configured with the material properties, the initial condition and boundary condition, it would start to compute.The second part(the thermal sensation of fingers) was built based on the local dynamic thermal model of Zhang in University of California, Berkeley. Due to the short-time contact and the small contact area, the change of core temperature and mean skin temperature was neglected. Programmed by Matlab, then according to the different temperature sensor position, the corresponding temperature data of simulation of the finger was collected, and the data was brought into the model, the fabric contact thermal sensation would be calculated out.After completing the model, the validation was conducted by comparing with the finger-fabric contact experiments. Computational results shows good agreements with the experiments in terms of the trend of the temperature at finger contact surface and fabric back surface vs. time, although there is some bias for the absolute values. Thermal sensation shows the strongest at the contact moment, but trends down after that. This agrees well with the subjective sensation of subjects.Finally, predicting using this established model was done. Four influence factors was involved, namely textile materials, fabrics initial temperature, warp and weft density and fabric thickness. Prediction results show that the larger thermal conductivity the stronger thermal sensation would be. The more the initial temperature deviates the figure’s skin temperature, the stronger thermal sensation would be. And the smaller the warp and weft density is, the stronger thermal sensation would be. The smaller the thickness is, the stronger thermal sensation would be.