Accelerated Fatigue Testing via PSD and FDS Control
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Solution Overview
Problem
Current methods for accelerated vibration testing fail to accurately replicate the fatigue damage of real-world loads due to assumptions about Gaussian amplitude distributions and the loss of kurtosis in system responses, leading to longer testing times and potential changes in failure modes when trying to reduce test duration.
Innovation Solution
A closed-loop control system that simultaneously manages Power Spectral Density (PSD) and Fatigue Damage Spectrum (FDS) to generate non-Gaussian excitation signals with controlled kurtosis, ensuring damage equivalence without altering the PSD levels, thereby accelerating testing while maintaining realistic failure modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PSD upscaling is used to reduce testing time, then productivity is improved, but the failure mode may change and reliability of test results deteriorates
Solution Approach 1:
The patent changes the statistical parameters of the excitation signal by controlling kurtosis while maintaining PSD levels. This allows accelerating the test through non-Gaussian signal characteristics rather than simply increasing vibration amplitude, thus avoiding failure mode changes while reducing test time
Solution Approach 2:
The patent implements a feedback mechanism where the actual kurtosis and PSD of the response are continuously monitored and used to adjust the excitation signal parameters. This closed-loop control ensures that the desired kurtosis level is maintained throughout the test, preserving failure mode accuracy while achieving acceleration
2Ease of operation
If Gaussian random vibration control is used, then ease of operation is improved, but measurement precision of fatigue damage deteriorates due to kurtosis loss
Solution Approach 1:
The system uses feedback control to measure the actual kurtosis of the response and adjust the excitation signal accordingly. This maintains the simplicity of random vibration control while ensuring accurate fatigue damage replication through continuous kurtosis monitoring and adjustment
Solution Approach 2:
The patent replaces the traditional mechanical approach of simply increasing vibration amplitude with a statistical signal processing approach. By using spectral synthesis and kurtosis control algorithms, the system achieves accurate fatigue damage replication without complex mechanical modifications
3Measurement precision
If kurtosis control methods are used to generate non-Gaussian excitation signals, then measurement precision of fatigue damage is improved, but device complexity increases due to additional control requirements
Solution Approach 1:
The patent makes the control system multi-functional by integrating both PSD and kurtosis control capabilities into a single unified system. The same feedback control architecture handles both statistical parameters, reducing overall complexity compared to separate control systems while maintaining high measurement precision
Data Source
Figure 1
AI summary
The invention relates to a method and a system for accelerated fatigue damage testing of an object (DUT), wherein the object (DUT) is excited via an actor (SH), wherein a drive signal (DS) is generated by a control system (CLC) and transmitted to the actor (SH), whereby the acceleration of the object (DUT) or of a mounting base of the actor (SH) is measured and fed back to the control system (CLC) for a cycled closed loop control of the drive signal (DS) in the frequency domain, wherein in the control system (CLC), a Power Spectral Density PSD and a Fatigue Damage Spectrum FDS are calculated from the measured acceleration (AD), whereby the calculated Power Spectral Density PSD is compared with a target Power Spectral Density PSD based on an operational load, whereby the calculated Fatigue Damage Spectrum FDS is compared with a target Fatigue Damage Spectrum FDS, whereby, based on the comparisons, a new drive frequency spectrum is calculated, and, from the new drive frequency spectrum, one or multiple time-domain blocks for the drive signal (DS) for a next cycle are generated and transmitted to the actor (SH). This method accelerates vibration testing without affecting the failure mode, thus coming to more realistic results.