Nonlinear ultrasound monitoring of single microcrack propagation in cortical boneReport as inadecuate

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* Corresponding author 1 LIP - Laboratoire d-Imagerie Paramétrique 2 ESRF - European Synchrotron Radiation Facility

Abstract : Accumulation of bone microdamage is suspected to lead to severe impairment of mechanical properties with an increase in skeletal fragility and fracture risk. The objective of the study was to evaluate the sensitivity of nonlinear resonant ultrasound spectroscopy NRUS measurements to the propagation in cortical bone of a single microcrack induced by 4-point bending mechanical loading. Twelve human cortical bone specimens were machined as parallelepiped beams 50*2*2mm to unambiguously identify resonant modes for NRUS measurements. A central notch of 600 µm was made to control crack initiation and propagation during four-point bending loading. During stable crack propagation, load and displacement curves were recorded to extract mechanical parameters J-integral J and stress intensity toughness K. Before and after toughness experiments, the nonlinear ultrasonic elastic coefficient \alphaf was monitored by NRUS for all notched samples. Despite substantial between-sample variability, \alphaf increased significantly up to 50-fold while no significant variation was observed for linear resonant frequency. Moreover, the crack length, assessed under epifluorescence microscope, was found to be significantly correlated to the nonlinear elastic parameter αf r2=0.7, p=0.01. These results strongly suggest that NRUS measurements are sensitive to damage accumulation and can be used as a marker of microcrack length.

Keywords : nonlinear bone microcrack ultrasound

Author: Sylvain Haupert - Sandra Guerard David Mitton Françoise Peyrin - Pascal Laugier -



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