DBEM and FEM Analysis of an Extrusion Press Fatigue Failure

1 Introduction This paper illustrates an application of the Dual Boundary Element Method (DBEM) [1, 2], as implemented in a commercial code [3], to the simulation of a fatigue crack propagation phenomenon affecting the main cylinder of an extrusion press for aluminum sections (Figs. 1, 2, 3 and 4). Such methodology is particularly effective for simulation of three-dimensional single/multiple crack propagation under the hypothesis of isotropic and linear elastic material properties [4–8, 9]. The aforementioned crack propagates through the thickness, causing a leakage of the pressurized oil and consequent production stop after 1,310,400 cycles (the extrusion press had been working for 11 years, 240 working days per year, 5 days per week, 24 h per day, with basic cycles lasting 3 min each). The fatigue load is induced by the pressure variation inside the cylinder from 0 to 300 bar for each cycle, as needed to push each section through the extrusion hole. The main aim of the simulation is to assess the most probable initial crack dimensions that, after the recorded in service fatigue cycles, lead to the final crack scenario. Once assessed the initial crack scenario it is possible to understand if there was any possibility to detect such crack before the assembly phase, by using non destructive detection techniques, and if there was a rogue flaw introduced by the manufacturing process.