Non-Contact Characterization of Acoustoelastic Parameters of Advanced Materials by Laser-Ultrasound

Abstract

In advanced functional materials, where the prestress can initialize phase transitions or other structural changes, the effect of the increasing load on an acoustic wave velocity is substantial and can provide important information on the undergoing physical phenomena. In this paper, a novel method for contactless measurements of acousto-elastic parameters is presented. The contactless arrangement, based on the concept of laser-ultrasound, enables an accurate detection of small changes of the velocities of surface acoustic waves in various directions. Because of this contactless arrangement, the changes of the sample shape during the loading do not affect the results, which can be assumed as the main source of inaccuracy for classical contact methods. The experimental device and its control system is described in detail, and its application possibilities and limits are shown on examples of shape memory alloys.

<em>In Situ</em> Characterization of the Elasticity and Stress-Induced Phase Transformation of NiTi Shape-Memory Alloy

“…1. Stress-strain curve obtained during the measurement (note that the stress is compressional and correspondingly the strain is negative) [14].…”

Detection of Drilled Hole on Subsurface of Aluminum Plate with Rayleigh Ultrasonic Wave Field by Laser Probing

“…On the other hand, ultrasonic measurement using a laser has been widely performed. (3)(4)(5)(6)(7)(8) It is used to study defects and other physical properties, such as cracks in materials, using the interaction between laser light and ultrasonic waves, and to inspect composite materials using Lamb waves. (9)(10)(11) Laser light is concentrated in a small area using an optical fiber, (12,13) and it is used as a sound source or a sensor such as Lamb waves.…”

“…This method is called 'laser probing', which has already been used to measure residual stress in glass and plastic materials. (2,(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) This method enables us to observe the characteristics of a smaller area than other imaging methods, such as the photoelasticity method. In addition, in this method, contact with the sample is unnecessary and there is no problem of spatial signal averaging described above.…”