TY - JOUR
T1 - Frequency spectrum spatially resolved acoustic spectroscopy for microstructure imaging
AU - Li, Wenqi
AU - Sharples, Steve D.
AU - Clark, Matt
AU - Somekh, Michael Geoffrey
PY - 2011/1/1
Y1 - 2011/1/1
N2 - The microstructure of a material influences the characteristics of a component such as its strength and stiffness. A previously described laser ultrasonic technique known as spatially resolved acoustic spectroscopy (SRAS) can image surface microstructure, using the local surface acoustic wave (SAW) velocity as a contrast mechanism. The technique is robust and tolerant of acoustic aberrations. Compared to other existing methods such as electron backscattered diffraction, SRAS is completely non-contact, non-destructive (as samples do not need to be polished and sectioned), fast, and is capable of inspecting very large components. The SAW velocity, propagating in multiple directions, can in theory be used to determine the crystallographic orientation of grains. SRAS can be implemented by using a fixed grating period with a broadband laser excitation source; the velocity is determined by analysing the measured frequency spectrum. Experimental results acquired using this "frequency spectrum SRAS" (f-SRAS) method are presented. The instrumentation has been improved such that velocity data can be acquired at 1000 points per second. The results are illustrated as velocity maps of material microstructure in two orthogonal directions. We compare velocities measured in multiple propagation direction with those predicted by the numerical model, for several cubic crystals of known orientations.
AB - The microstructure of a material influences the characteristics of a component such as its strength and stiffness. A previously described laser ultrasonic technique known as spatially resolved acoustic spectroscopy (SRAS) can image surface microstructure, using the local surface acoustic wave (SAW) velocity as a contrast mechanism. The technique is robust and tolerant of acoustic aberrations. Compared to other existing methods such as electron backscattered diffraction, SRAS is completely non-contact, non-destructive (as samples do not need to be polished and sectioned), fast, and is capable of inspecting very large components. The SAW velocity, propagating in multiple directions, can in theory be used to determine the crystallographic orientation of grains. SRAS can be implemented by using a fixed grating period with a broadband laser excitation source; the velocity is determined by analysing the measured frequency spectrum. Experimental results acquired using this "frequency spectrum SRAS" (f-SRAS) method are presented. The instrumentation has been improved such that velocity data can be acquired at 1000 points per second. The results are illustrated as velocity maps of material microstructure in two orthogonal directions. We compare velocities measured in multiple propagation direction with those predicted by the numerical model, for several cubic crystals of known orientations.
UR - http://www.scopus.com/inward/record.url?scp=79953789696&partnerID=8YFLogxK
U2 - 10.1088/1742-6596/278/1/012026
DO - 10.1088/1742-6596/278/1/012026
M3 - Journal article
SN - 1742-6588
VL - 278
JO - Journal of Physics: Conference Series
JF - Journal of Physics: Conference Series
IS - 1
M1 - 012026
ER -