| 摘要 |
A method is disclosed for evaluating the physical properties of a sample, f or example, the grain size in a polycrystalline material. An ultrasound field i s generated in a local region of the sample with a non-contact source, such as a pulsed laser, such that the generated ultrasound diffuses away from said loc al region. After waiting until the generated ultrasound field has reached a diffusion regime, the resulting ultrasound field is measured with a non-contact detector. Parameters are adjusted in a mathematical model describing the predicte d behaviour of the ultrasound field in the diffusion regime to fit the detecte d ultrasound field to the mathematical model. In this way, parameters dependen t on the physical properties of the sample, such as the diffusion coefficient and absorption coefficient, can be derived. The grain size, for example, can be estimated from these parameters preferably by calibrating the diffusion coefficient to grain size.
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