Estimation of Fatigue Crack AE Emissivity Based on the Palmer–Heald Model

Abstract

This article is devoted to materials testing by the acoustic emission (AE) method, which is the analysis of models and diagnostic parameters to assess the probability of detection of a defect in steel structures. The paper proposes to evaluate the emissivity of the material quantitatively by the number and dynamics of the accumulation of acoustic emission impulses. Experimental studies were carried out on pearlitic structural steels, including the loading of samples with fatigue cracks. It was established that the number of AE impulses emitted during loading of an object with a fatigue crack is a random variable corresponding to the normal distribution law. The results show that an estimate of the number of AE impulses emitted during the loading of samples with fatigue cracks can be obtained by distributing the multiplicative parameter D of the Palmer-Heald model by taking into account the maximum value of the applied load.

Empirical Approach to Defect Detection Probability by Acoustic Emission Testing

“…We have studied the notched samples made from hot-rolled sheets with a thickness of 3-5 mm made of industrial steels 09G2S (similar to steel A 516-55) and 45 (similar to steel 1045) with a ferrite-pearlite structure and nominal chemical composition shown in Table 1 [12]. The samples were tested under static tension using a loading schedule described in [23].…”

“…The fourth stage is carried out with a stress exceeding σ max by 25%. A more detailed description of the experiment is given in [12].…”

“…The total effect of these stochastic factors explains the great variability of AE signals even for the typical testing structures and defects of similar type and size [10,11]. The second reason is the absence of a direct correlation between AE data and defect size [12]. A defect in AE testing is considered not as a discontinuity, but as an active source of elastic waves.…”

“…In [12], it was proposed to predict the number of AE hits emitted by an object with crack during the loading procedure using the Palmer-Heald model, which represents the relationship of the number of AE hits vs. the applied load up to a multiplicative parameter D, which is a constant of the inspected material. Based on the analysis of experimental data for different steels of the same structural class, it was shown that this parameter can be interpreted as a random variable with a normal distribution with constant parameters (mean value and variance) for certain steel grades.…”

Structural Health Monitoring of Walking Dragline Excavator Using Acoustic Emission

“…It is presented in [19] that the multiplicative coefficient of the Palmer-Heald model D can be considered as parameters that may be applied to describe the material AE emissivity independent of loading conditions, crack length, and stress intensity factor. Dependence of cumulative AE hits vs. time was approximated using the Palmer-Heald equation for the data obtained after testing of each 10 specimens in the series.…”