Re-examination of NIST acoustic emission absolute sensor calibration: Part II--finite element modeling of acoustic emission signal from glass capillary fracture

• Published in: Journal of acoustic emission 2011-01, Vol.29, p.175
• Main Author: Hamstad, M.A
• Format: Article
• Language: English
• Subjects: Acoustic emission testing; Finite element method
• ISSN: 0730-0050

A validated axisymmetric finite-element code was used to model the out-of-plane displacement acoustic emission (AE) signal at 100 mm from a glass capillary fracture on the surface of a large steel block under the control of National Institute of Standards and Technology (NIST). This situation corresponds to the absolute sensor calibration approach described in the test method ASTM E1106-07. A number of source parameters relating to the fracture of the glass capillary source were studied: (i) value of the rise-time of the force release, (ii) temporal shape of the force release, (iii) spatial size and spatial distribution of the normal stress on the block surface, and (iv) the magnitude of the force. The results of the dynamic finite-element model (FEM) were compared to the signal from the capacitance sensor used in the AE sensor calibration at NIST. The FEM results indicate that the magnitude of the signal is a linear function of the force released, and that all other source parameters change the magnitude of the Rayleigh wave that dominates the displacement signal. During calibration, only the force at fracture is measured. It is not clear at present how the other parameters can be measured. Based on the results in this study, recommendations are made relative to the content of ASTM E1106-07. Keywords: Absolute AE sensor calibration, ASTM E1106-07, finite-element modeling, glass-capillary fracture, NIST steel block, Rayleigh wave