Vibration Fatigue Damage Estimation by New Stress Correction Based on Kurtosis Control of Random Excitation Loadings

Abstract

In the pioneer CAE stage, life assessment is the essential part to make the product meet the life requirement. Commonly, the lives of flexible structures are determined by vibration fatigue which accrues at or close to their natural frequencies. However, existing PSD vibration fatigue damage estimation methods have two prerequisites for use: the behavior of the mechanical system must be linear and the probability density function of the response stresses must follow a Gaussian distribution. Under operating conditions, non-Gaussian signals are often recorded as excitation (usually observed through kurtosis), which will result in non-Gaussian response stresses. A new correction is needed to make the PSD approach available for the non-Gaussian vibration to deal with the inevitable extreme value of high kurtosis. This work aims to solve the vibration fatigue estimation under the non-Gaussian vibration; the key is the probability density function of response stress. This work researches the importance of non-Gaussianity numerically and experimentally. The beam specimens with two notches were used in this research. All excitation stays in the frequency range that only affects the second natural frequency, although their kurtosis is different. The results show that the probability density function of response stress under different kurtoses can be obtained by kurtosis correction based on the PSD approach of the frequency domain.

Vibration-Based Fatigue Analysis of Octet-Truss Lattice Infill Blades for Utilization in Turbine Rotors

“…The kurtosis for all the measured signals is above 3.0, which indicates that all the measured signals are non-Gaussian and non-stationary in nature. This indicates the measured signal is identical to the actual conditions of the blade as vibration signals experienced during operational life are usually non-Gaussian [37]. The measured signals are then processed in nCode ® Designlife ® to obtain the power spectral density (PSD) and cycle count for each signal.…”

“…Vibration fatigue analysis is carried out for the structures operating in the vicinity of natural frequencies [ 37 , 38 ]. Vibration fatigue analysis differs from traditional fatigue analysis.…”

Frequency analysis of random fatigue: Setup for an experimental study

“…Gao et al [11] proposed in the same year a new method for spectral analysis of fatigue due to multiaxial random loads with mean stresses, and they verified their method by making some experimental tests on notched plate specimens made of aviation‐grade aluminum alloy. A similar geometry for the specimens was used by Wang and Serra [12], who performed a small number of acceleration‐driven random tests on one‐side constrained double‐notched beam specimens to validate a previously presented numerical method for non‐Gaussian random loading. Finally, Palmieri et al [13] made some experimental fatigue tests on three‐dimensional (3D)‐printed Y‐shaped specimens, with their base mounted on an electrodynamic shaker and two masses fixed on their arms, to check the validity of spectral methods for 3D‐printed polylactic acid samples.…”

“…However, a great part of the frequency methods takes the rainflow count [8] as a reference time-domain cycle counting method and uses the rainflow damage computation as the exact value to emulate. Therefore, very few experimental data for the fatigue life of mechanical components subject to random loads are available in the literature [9][10][11][12][13], and most of them are obtained for particular conditions of loading (multiaxial or non-Gaussian stress state) or for special shapes of the specimen (Y-shaped, notched, etc.). Niesłony et al [9], in 2012, published the results of 107 experimental tests made on tubular specimens with a one-sided hole subjected to complex multiaxial random loads.…”