Method for Simultaneous Measurement of Multiple Parameters of Linear Viscoelastic Thin Layer Materials Using Ultrasonic Flat Probe

Abstract

The invention discloses a method for simultaneously measuring multiple parameters of a linear visco-elastic thin layer material by employing an ultrasonic flat probe. The method comprises the steps: 1) immersing a referred base material and the linear visco-elastic thin layer material in water, placing the ultrasonic flat probe respectively right above the referred base material and the linear visco-elastic thin layer material to measure and obtain reflection echo s0(t) and s1(t); 2) performing low-pass filtering on s0(t) and s1(t); 3) performing optimum estimate on echo s11(t) which belongs to s1(t) and comes from the upper surface of the linear visco-elastic thin layer material, so as to obtain an optimum measured value Zm2 of acoustic impedance, and subtracting a corresponding s11(t) from s1(t) when the acoustic impedance is equal to Zm2; and 4) performing optimum estimate on echo s12(t) which belongs to s1(t) and comes from the lower surface of the linear visco-elastic thin layer material, so as to obtain optimum measured values delta tm2 and alpha m2 of transit time and attenuation coefficient. The method helps to avoid the fitting convergence domain problem frequently appeared in conventional measuring methods based on reflection coefficient spectrum fitting, and is suitable for measuring acoustics characteristics of thin layer materials.

Description

technical field [0001] The invention relates to ultrasonic non-destructive testing of properties of thin-layer materials, in particular to a method for simultaneously measuring multiple parameters of linear viscoelastic thin-layer materials by using an ultrasonic flat probe. Background technique [0002] Ultrasonic non-destructive measurement of thin layers, including thin films and coatings, is attracting more and more attention today. It has a wide range of applications in modern manufacturing, civil engineering, food and bioengineering. Since multiple properties of thin-bed sensitive zones can be measured simultaneously and continuously by means of ultrasound, the quantitative measurement of the acoustic and geometric properties of thin-beds has very significant practical value. [0003] The traditional ultrasonic measurement method uses curve fitting techniques to minimize the difference between experimental data and theoretical values ​​based on preliminary estimates o...

AI Technical Summary

Problems solved by technology

The biggest defect in the practical application of this type of method is that it requires the measurer to make a relatively accurate initial estimate of the three unknown parameters in the convergence area. When it is within the range of convergence, it will lead to wrong fitting results

However, this method needs to set up multiple frequency intervals in the calculation to achieve a small relative error, but if the emitted ultrasonic pulse does not have sufficient frequency width, the measurement results will be seriously affected

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