On force control of an engine order type excitation applied to a bladed disk with underplatform dampers

The paper presents an original multiple excitation system based on electromagnets with force control. The system is specifically designed in order to investigate the dynamics of bladed disks since it mimics the excitation existing in a real engine. Moreover the system is suitable for forced response tests of bladed disks with nonlinear dynamic response like in the case of presence of friction contacts since the amplitude of the exciting force is known with good precision. For this purpose a device called Force Measuring ElectroMagnet (FMEM), was designed and employed during the system calibration. The excitation system is applied to the test rig Octopus (see ASME Turbo Expo GT2010-22879) which includes underplatform dampers (UPDs). Tests were carried out under different excitation force amplitude values. The tests put in evidence the presence of mistuning and the UPDs capability of attenuating the mistuning phenomena.