Abstract
Measurement of elastic anisotropy in textured polycrystalline metals is very difficult, especially the nondestructive testing of the elastic anisotropy of micro-regions. In this paper, the angular dependence of surface acoustic wave velocity affected by texture in micro-regions is measured by the laser ultrasonic method, and a method for calculating elastic anisotropy based on angular dependence of surface acoustic wave velocity is discussed. The results show that the elastic anisotropy calculated by the angular dependence of the surface acoustic wave velocity fits well with the measured elastic anisotropy, and the elastic anisotropy in micro-scale regions can be characterized well by the laser ultrasonic method. In addition, a calculation model of the elastic modulus at different temperatures based on the elastic modulus at 25 °C is given, and the elastic modulus at different temperatures is also calculated, which fits well with the experiment results. This model can be used for nondestructive testing of the elastic modulus in micro-regions.
Highlights
Elastic anisotropy of polycrystalline metals provides some information about single crystal anisotropy in the textured state.1 the anisotropy of polycrystalline metals has two obvious characteristics:2 (1) the anisotropy is weak; that is, they merely superimpose a weak anisotropy on the basis of isotropy, and (2) anisotropic images are complex; that is, the symmetry of polycrystalline metals is not as strict as that of single crystals
Texture is mathematically described by the orientation distribution function (ODF)
The angular dependence of the surface acoustic wave velocity in the micro-region is detected by the laser ultrasonic method
Summary
Elastic anisotropy of polycrystalline metals provides some information about single crystal anisotropy in the textured state. the anisotropy of polycrystalline metals has two obvious characteristics: (1) the anisotropy is weak; that is, they merely superimpose a weak anisotropy on the basis of isotropy, and (2) anisotropic images are complex; that is, the symmetry of polycrystalline metals is not as strict as that of single crystals. The anisotropy of polycrystalline metals has two obvious characteristics: (1) the anisotropy is weak; that is, they merely superimpose a weak anisotropy on the basis of isotropy, and (2) anisotropic images are complex; that is, the symmetry of polycrystalline metals is not as strict as that of single crystals Because their anisotropy is very weak, it is hard to measure it accurately.. In most experiments, ultrasonic waves are excited by piezoelectric, piezomagnetic, or electromagnetic acoustic transducers (EMATs) These methods have a limited bandwidth and have difficulty exciting high-frequency ultrasound and evaluating material properties in the micro-scale region.. The angular dependence of SAW velocity in the micro-region of textured metals is measured by the laserultrasonic method. Using the verified formula, the elastic anisotropy at different temperatures is predicted
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