An analytical mathematical model for melting layer thickness of HDPE pipes at thermal butt-fusion welding
High-density polyethylene pipes (HDPE) are widely utilized in everyday applications, such as water, gas, and sewer mains, and more. The proper melting layer thickness ensures adequate material mixing, interface pressure, defect prevention, and strong mechanical properties. However, in most current studies, determining the melting layer thickness typically relies on numerical model, which leads to significantly low cost-effectiveness. The purpose of this study is to develop an analytical mathematical model for predicting melting layer thickness based on heating time, consisting of two governing equations for heat transfer and a coupling equation at the solid-melting phase interface with help of the Neumann moving boundary conditions and the latent heat of fusion. The material properties of HDPE pipes are benchmarked from existing literature, with the heat soaking time set to 180 seconds and the heating temperature set to 240∞C. To verify the reliability of the results from the developed analytical mathematical model, a 2-D numerical model with dimensions of 50 mm in length and 11.8 mm in width was also built in ANSYS Fluent for comparison at heat soaking times of 30, 60, 90, 120, 150, and 180 seconds. Based on the findings of this study, it can be concluded that the developed analytical mathematical model provides a reliable and accurate approach for predicting the melting layer thickness in HDPE pipes during the heat soaking process. The close alignment of the predictions with those obtained from the numerical model validates its effectiveness. In future research, the developed analytical mathematical model in this study can not only assist in the precise control of welded joint quality in HDPE pipes but also offer insights for studies on high-speed welding of polymers.