Excitation-dependent nonlinear behavior of distributed microcracks

Kathrin Hoffmann, Jin Yeon Kim, Katherine Scott, Jianmin Qu, Laurence J. Jacobs

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations

Abstract

It is well known that microcracks generate strong higher harmonics in propagating monochromatic waves. There is a large amount of literature on modeling this phenomenon, but most of these existing papers only describe one specific mechanism. For example, Zhao et al. [1] assumes that the crack faces are either open under tension or closed under compression, and in the latter case they may slide against each other. On the other hand, the Nazarov and Sutin [2] model assumes microcracks as an elastic contact of two rough surfaces, which are never completely separated by an external load. All these mechanisms depend on the level of excitation. In this research, a micromechanical model for the acoustic nonlinearity generation of microcracks is developed by combining the bilinear stiffness model and the rough surface contact model to describe the excitation-dependent nonlinear behavior of distributed microcracks. It is shown that the first and second harmonic amplitudes have the relationship: A2~A1n, with n dependent on the amplitude of excitation, and 2 ≥ n ≥ 1 for non-adhesive crack surfaces. Nanostructured ferritic alloys (NFAs) [3] are considered as an example. These materials exhibit outstanding high-temperature properties, irradiation tolerance and thermal stability, making them a leading candidate for advanced nuclear fission and fusion applications. One characteristic property of mechanically processed NFAs is their layer-like structure, with a large number of microcracks aligned in a specific direction. Nonlinear ultrasound measurements (acoustic nonlinearity, β) with longitudinal waves are used to characterize this material. The results show that these measurement techniques are sensitive to the orientation of the cracks. The model developed in this research is then used to interpret these experimental measurements and used to characterize the microcracks in a NFA specimen.

Original languageEnglish
Title of host publication45th Annual Review of Progress in Quantitative Nondestructive Evaluation, Volume 38
EditorsSimon Laflamme, Stephen Holland, Leonard J. Bond
ISBN (Electronic)9780735418325
DOIs
StatePublished - 8 May 2019
Event45th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2018 - Burlington, United States
Duration: 15 Jul 201819 Jul 2018

Publication series

NameAIP Conference Proceedings
Volume2102
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

Conference45th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2018
Country/TerritoryUnited States
CityBurlington
Period15/07/1819/07/18

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