Acoustic detection method for defects of cast iron material

Abstract

The invention discloses an acoustic detection method for defects of a cast iron material. The method comprises the following steps of manufacturing a comparison test board and a maximum allowable defect test board; performing ultrasonic detection on the comparison test board and the maximum allowable defect test board respectively, and then performing ultrasonic detection on a board to be tested; performing normalization on amplitude attenuation of the comparison test board, the maximum allowable defect test board and the board to be tested to obtain a maximum difference value close to the end of a measurement range between a normalized amplitude attenuation curve of the maximum allowable defect test board and a normalized amplitude attenuation curve of the comparison test board; and comparing an attenuation variation value of the board to be tested relative to the normalized amplitude attenuation curve of the comparison test board with the maximum difference value, and judging whether a defect which is larger than a maximum allowable defect exists on the board to be tested. The defect detection method has the advantages of high detection speed and low cost.

Description

technical field [0001] The invention relates to the technical field of non-destructive testing, in particular to an acoustic testing method for defects in cast iron materials. Background technique [0002] Cast iron materials have been widely used in urban gas pipelines, paper drying cylinders, automobiles and other equipment or components due to their excellent castability, wear resistance and shock absorption, high yield and low cost. However, the inherent characteristics of cast iron materials and the particularity of the casting process make it inevitable that there will be defects in cast iron components and equipment. Common defects include: porosity, slag inclusion, cold shut, shrinkage cavity and porosity, cracks, etc. At present, the non-destructive testing techniques for internal defects of cast iron materials mainly include radiographic testing and pulse reflection ultrasonic testing. Radiographic testing can detect manufacturing defects such as porosity, porosit...

AI Technical Summary

Problems solved by technology

However, the inherent characteristics of cast iron materials and the particularity of the casting process make it inevitable that there will be defects in cast iron components and equipment.

Affected by the complexity of multiple propagation modes of ultrasonic waves and the existence of wave mode conversion (mutual conversion between transverse and longitudinal waves, mutual conversion between Lamb wave and Rayleigh wave, etc.), when it is applied to composite materials, in order to make The propagation mode of the sound wave is simple, and the emission, propagation and reception are mainly low-order Lamb waves, so that a higher ultrasonic frequency above the MHz level is usually used on a composite material plate with a thickness of several millimeters, which makes the detection distance Short, only measure the overall sound attenuation of the material within a certain distance

When the thickness of the composite material plate increases, the propagation mode of the ultrasonic wave inside the material increases, and the waveform signal obtained is complex, difficult to explain and not easy to apply

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