Numerical and experimental verification of new method for connecting pipe to flange by cold forming

In this paper a new method of connecting pipe to flange without welding is presented. This method is a cold forming process that is based on plastic expansion/deformation of the pipe into a modified standard flange by use of a cold forming tool. The method is patented by Quickflange Technology AS and represents a highly feasible alternative to welding. The successful use of the method requires the ability to predict dimensional and stress/strain characteristics of the pipe and flange after the connection process in order to evaluate the connectivity to the adjacent flange as well as the leak tightness. In addition the ability to predict the process force during the connection process is needed in order to control the process and design the hydraulically actuated cold forming tool. It is shown that it is possible to simulate this process using the finite element (FE) method and achieve a good accordance with experimental results. For this purpose a non-linear FE model of the flange, pipe and forming tool is developed and analyzed using Abaqus. Experimental work, including tensile material testing and Quickflange joining tests were carried out for material model calibration and Quickflange process model validation, respectively. The FE model results are in good accordance with experimental observations in terms of actuation force for the process, deformations and strains of pipe and flange during and after the process. It is concluded that the developed FE model is a useful tool for simulating the presented process within reasonable computational time as long as careful considerations are given to model complexity, material parameters, friction, and pipe geometry tolerances.