Damage-Equivalent Vibration Testing (FatiResponse)
The fatigue strength of components excited by inertial force under vibration-type loads is often verified by means of vibration tests with broad-band noise signals (power spectral density = PSD). Both OEMs and suppliers need to design and qualify components w loads equivalent to real-life operational loads. For this purpose, they require suitable PSD excitation spectra at an early stage in the design phase. The state of the art for generating the PSD using the fast Fourier transform algorithm with overlapping windows generally delivers spectra which, without further scaling, lead to significant overtesting or undertesting.
IABG FatiResponse Method
The FatiResponse method developed by IABG enables the analysis of operational vibration loads and the derivation of test settings to be used for the design and qualification of vibration-proof components. By means of a comprehensive dynamics and damage model, a PSD test spectrum is created which covers damages equivalent to those caused by the measured operational loads. All relevant operating states are analysed, delivering stress spectra in different application scenarios throughout the service life of a component. The method can take into account the dynamic system behaviour and any relevant failure mechanisms, e.g. fatigue or wear. The associated parameters can usually be derived from previously used components. The software calculates the desired test duration as well as the overtesting or undertesting to be expected based on the maximum load amplitudes.
Acquisition and preparation of load data
- Installation of sensors and measuring equipment on test vehicles
- Execution of measurement campaigns to capture operational loads
- Processing and analysis of measurement results
Derivation of damage-equivalent test settings (“Test Tailoring”)
- Description of load conditions via Fatigue Response Spectra (FRS)
- Combination of user profiles to create individual mission profiles
- Derivation of damage-equivalent test spectra and test time signals using the Fatigue Equivalent Testing module (FET)
- Vibration tests with frequencies ranging up to 2500 Hz on electro-mechanical shakers or servo-hydraulic vibration test benches with test items weighing up to 10 t, optionally under different climate and environmental conditions
- FEM simulation and computational fatigue strength analyses
- Optimisation of components and systems exposed to vibration loads in terms of dynamic behaviour and service life
- Material and damage analyses to identify potential issues and optimise components