Accurate coil springs axial and transverse stiffness measurements with multicomponent testing machines

Accurate characterization of coil springs, typically in terms of axial and transverse stiffness, is crucial in many applications, in particular in automotive engineering, such as suspensions, vibration reduction, seating, exhaust valves, gear engagement controls, transmission hose, fuel panels, car trunks, and engine hoods. These measurements are usually performed in spring testing machines along the vertical axis in quasi-static conditions. However, when springs are stressed along the main vertical axis, side forces, bending and torsion moments are generated, thus have to be evaluated. For this reason, a hexapod-shaped multicomponent force and moment transducer has been recently devised, realized and integrated into standard spring testing machines capable to measure the displacement along the main and transverse axes. In this way, forces, moments and displacement components generated by the springs can be measured and axial and transverse stiffness derived. In this work, two multicomponent spring testing machines with the hexapod-shaped force and moment transducer are described and measurements on different large coil springs are presented.