Influence of geometrical parameters of thin pipe bends using FEA

This paper investigates the influence of geometrical and process parameters on thin pipe bends using the rotary draw bending process through finite element analysis (FEA). Four materials aluminium, copper, stainless steel, and Inconel were analyzed to optimize bending quality and predict service life. The results reveal that an optimal bending velocity of 0.2–0.4 rad/s minimizes defects, while die pressure must be maintained at 10–15 MPa for low-yield-strength materials and up to 25–35 MPa for high-strength alloys like Inconel. Boosting velocity significantly affects ovality; optimum values were identified as 20–25 mm/s for aluminium, 15 mm/s for copper, 30 mm/s for stainless steel, and 10–12 mm/s for Inconel. Experimental validation on a CNC rotary draw bending machine confirmed ovality within 7.1% at 90° and 7.48% at 130° bends for stainless steel tubes (OD 50 mm, thickness 4 mm). Life cycle prediction showed that aluminium bends withstand infinite cycles at 10 MPa operating pressure, while Inconel bends sustain infinite life at 310–350 kg/cm², with developed stresses (420 MPa) remaining below the ultimate tensile strength (970 MPa).