Method for measuring attenuation coefficients of ultrasonic cylindrical surface guided waves at different temperatures

Abstract

The invention discloses a method for measuring the attenuation coefficients of ultrasonic cylindrical surface guided waves at different temperatures, which comprises the steps of 1) preparing a measurement test block containing n cylindrical propagation paths with different lengths, wherein the two end surfaces of the measurement test block are planes and being perpendicular to the axis directionof a cylinder, a fixing device for fixing cylindrical test blocks with different lengths is arranged on the measurement test block, and the lower end of the measurement test block forms a stepped structure; 2) adjusting the temperature of the lower end surface of the test block to a to-be-measured temperature, and keeping the constant temperature; (3) exciting by utilizing an ultrasonic transducerto generate ultrasonic cylindrical surface guided waves, propagating li to the lower end surface of the test block along the direction vertical to the upper surface of the test block, reflecting by the lower end surface of the test block, returning to the ultrasonic transducer along the original path to be received, adjusting the gain of an ultrasonic instrument to enable the echo amplitude to be80% full screen, and recording a gain value Bi at the moment; and 4) calculating the attenuation coefficient of the ultrasonic cylindrical surface guided waves. The method can accurately measure theattenuation coefficients of the ultrasonic cylindrical surface guided waves under different workpieces and temperatures.

Description

technical field [0001] The invention relates to a method for measuring attenuation coefficients, in particular to a method for measuring attenuation coefficients of ultrasonic cylindrical guided waves at different temperatures. Background technique [0002] Ultrasonic cylindrical guided wave exists in the whole inspected part, and can find internal and surface defects. It has an important application in ultrasonic inspection, especially in the non-destructive inspection of rod-shaped structures such as bolts and ground anchors, because of its large detection distance, It is not subject to side wall interference and has high detection efficiency, so it is widely used. [0003] Commonly used ultrasonic transverse waves and longitudinal waves can be regarded as propagating in an infinitely large homogeneous isotropic elastic medium, and there is no waveform coupling between them. When the propagation medium is rod-shaped or rod-shaped, the ultrasonic transverse wave or longitu...

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Problems solved by technology

[0005] At present, the method of measuring the ultrasonic attenuation coefficient is mainly to obtain the multiple reflection bottom waves of the ultrasonic wave passing through the workpiece and reaching the bottom surface at room temperature, and the ultrasonic energy loss caused by the reflection is processed by estimation, and the measurement accuracy needs to be further improved

In addition, the attenuation of ultrasonic waves increases at high temperatures, and it is difficult to meet the measurement requirements when using piezoelectric ultrasonic transducers for indirect coupling or electromagnetic ultrasonic methods. When using direct coupling methods, special high-temperature ultrasonic transducers are required, and because of the presence of couplant It makes it difficult to control the temperature uniformity of the part to be measured, so the current commonly used method is not suitable for the determination of the attenuation coefficient of ultrasonic cylindrical guided wave at high temperature

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