To investigate the fatigue crack propagation phenomenon affecting the main cylinder of an extrusion press for aluminum sections. The crack had propagated through the thickness, causing a leakage of the pressurized oil and consequent production stop. The fatigue load was induced by the pressure variation inside the cylinder from 0 to 300 bar for each cycle, as needed to push each section of material through the extrusion hole. The main aim of the simulation was to assess the most probable initial crack dimensions that would lead to the final crack scenario experienced in practice.
A three dimensional model was developed to simulate the growth of the crack through the wall thickness. A fatigue load was applied to the model to simulate the extrusion press basic loading cycle (240 working days per year, 5 days per week, 24h per day, every 3 min).
The main aim of the simulation was to assess the most probable initial crack dimensions that would lead to the final crack failure scenario. This information provides the data to determine the critical defect size which must be detected during inspection after the manufacturing process, prior to assembly of the press.