Research on prediction model of forming mechanical behavior of the dimpled tube based on the response surface methodology

Abstract

A new multi-pitch extrusion machine for producing the enhanced heat transfer tube with dimples is proposed for the first time. The goal of the present study is to investigate the forming mechanism and establish a mechanical behavior prediction model for dimpled tubes. The response surface methodology with central composite design was adopted to identify the relationships between independent variables (extrusion depth, pitch, and teeth radius) and responses (stress, plastic strain, and excursion force). The validity of the finite element model and prediction model was verified experimentally and by the analysis of variance technique. The results show that dimples and protrusions are caused by the tube wall bending inward and outward, respectively. The stress, plastic strain, and excursion force increased with increasing extrusion depth, and decreased with increasing extrusion pitch. The changes in teeth radius had no influence on the excursion force.