Analytical process design for interference-fit joining of rectangular profiles

Abstract The classical joining of round tubes by die-less hydroforming is extended to joining of rectangular profiles. A new analytical approach for the calculation of required process parameters is developed. It allows the calculation of the interference pressure p and the required fluid pressure range given by a lower and upper limit ( p i , m i n and p i , m a x ). These limits are the result of the deformation state of the inner and outer joining partner. The minimum pressure, where plastic deformation of the inner joining partner occurs first, characterizes the value at which the joint formation starts. The maximum pressure is the value, at which plastic deformation of the outer joining partner occurs. The analytical model is validated by experimental studies where two rectangular aluminum profiles (EN AW-6060) with different heat treatment conditions were joined. Above p i , m a x , the increase of the achievable joint strength with respect to the internal pressure is not significant anymore. The maximum deviation between the analytically and experimentally determined maximum fluid pressure p i , m a x is about 12 % in case of a wall thickness of 3 mm and 11 % in case of a wall thickness of 5 mm.