A simplified experimental technique to measure the acoustic radiation induced static strain during the longitudinal acoustic wave propagation in solids is proposed. Experiments have been carried out to extract the static displacement (dc) component without resorting to electronic filters, as in the case of previously reported experimental measurements. This prevents the influence of the filter time response characteristics on the measurement. The dependence of the static displacement amplitude on the square of the fundamental amplitude of the input wave, its being independent of the burst width of the tone burst, and its abnormal variation at low input amplitudes are reported. © 2007 American Institute of Physics.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Elankumaran Kannan

Acoustic wave propagation

ELECTRIC FILTERS

STRAIN CONTROL

Acoustic radiation

DISPLACEMENT AMPLITUDE

INPUT WAVE

Time response

Acoustic waves

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Simplified experimental technique to extract the acoustic radiation induced static strain in solids

Applied Physics Letters

Sensitivity of nonlinear ultrasonic method towards isothermal annealing in pure copper is investigated in this study. It was reported that, recovery, recrystallization and grain growth associated with annealing has profound influence on nonlinearity parameter. Presence of precipitates and secondary phase particles, and its effect on nonlinearity parameter was considered by many authors. However, in this study, focus is on the influence of grain-growth on nonlinearity parameter. Variation of non-linearity parameter, β, with different holding durations were analyzed. All the samples were annealed at a temperature above its recrystallization temperature. Further, metallography studies as well as hardness measurements were performed to understand the relationship between microstructural changes and ultrasonic nonlinearity parameter. © 2014 AIP Publishing LLC.

AIP Conference Proceedings

Characterization of annealing in polycrystalline copper using harmonic generation technique

This paper describes a new nonlinear ultrasonic (NLU) technique for creep damage characterization. Traditionally, nonlinear material response is evaluated at high amplitude levels. The present paper evaluates the nonlinear response of samples at much lower amplitude levels than used in any previous study of nonlinear material behavior. The newly observed nonlinear behavior occurs when dislocations are constrained between two quiescent lattice planes as defined by Cantrell. Three parameters are used to characterize the low amplitude nonlinear response during the progression of creep damage in 99.98% pure copper specimens studied here; these are parameters that characterize (a) the static displacement, (b) the second harmonic and (c) the third harmonic components of the ultrasonic through-transmitted signal. Various features of the received NLU amplitude vs. input amplitude to the ultrasonic transducer were observed to correlate well with micro-void concentrations caused by creep damage. © 2010 Elsevier Inc. All rights reserved.

Materials Characterization

Creep damage characterization using a low amplitude nonlinear ultrasonic technique

This paper describes the use of non-linear ultrasonic techniques for the characterization of material degradation in 99.98% pure copper due to high-temperature creep. Flat dog-bone-shaped specimens were subjected to constant load creep testing at different stress and temperature levels. Creep damage progression was monitored by conducting continuous and interrupted mode creep tests. In the case of continuous loading non-linear ultrasonic (NLU) measurements were conducted after fracture at different locations along the gage length of the sample. For interrupted tests the NLU measurements were conducted on different creep life fractions, through periodic interruption of the creep test. In all cases a through transmission NLU measurement technique was employed. Three different non-linear measurements, namely static displacement, second harmonic and third harmonic, were taken and their responses compared. The NLU measurements were found to be significantly sensitive to the extent of creep damage (∼200-2500% of base level), while the linear ultrasonic measurements, representing the change in longitudinal velocities, were only in the range 10-30% for a comparable creep damage level. NLU measurements carried out on fractured samples suggest that the NLU response was locally high at locations where the creep damage was concentrated, compared with other locations, even within the gage length of the specimen. This was confirmed using micrograph observations. Of the three non-linear measurements, the third harmonic data was most sensitive to creep damage. © 2009 Acta Materialia Inc.

Acta Materialia

Creep damage characterization using non-linear ultrasonic techniques

Recent experimental results showing the pulse width independence and the flat topped shape of static displacement generated during finite amplitude sinusoidal ultrasonic tone burst propagation in solids and the contradicting previous results reported in the literature are considered. The pulse width independence is analytically confirmed and the flat topped shape is explained by considering the progressive spatial and time domain shapes of the static strain and displacement pulses. A numerical simulation of the finite amplitude longitudinal ultrasonic wave propagation in solids has been performed to further verify the pulse width independence of the static displacement pulse. © 2009 American Institute of Physics.

Journal	Applied Physics Letters
ISSN	00036951
Open Access	No