Grain size nondestructive evaluation method based on haar wavelet

Abstract

The invention discloses a grain size nondestructive evaluation method based on haar wavelet. The method comprises the following steps: data acquisition is conducted on a reference test block, time-size distribution is obtained by utilizing haar wavelet transform, furthermore, the average multi-scale attenuation coefficient of all reference blocks is calculated, an ultrasonic multi-scale attenuation evaluation model for the average grain size is built according to the preset size assembly and the preset normalized weight, and finally grain size evaluation of the test block of which the grain size is unknown is realized through the built ultrasonic multi-scale attenuation evaluation model of the average grain size. The method reduces system errors in grain size measurement; for test blocks of which the average grain size is 103.5 [mu]m measured by adopting metallography, the evaluation result is 101.7 [mu]m, and the error is controlled to be + / -2%. Therefore, through multi-scale analysis of original ultrasonic A signals, the method provided by the invention can discover more rich grain size information in the original ultrasonic A signals, and further improves the nondestructive evaluation precision of the grain size.

Description

technical field [0001] The invention relates to the technical field of grain size measurement, in particular to a non-destructive evaluation method for grain size based on Haar wavelet. Background technique [0002] Grain size is an important parameter for the microstructure of reactive metal materials. The Hall-Petch formula describes the relationship between the grain size and yield strength of metal polycrystalline materials. The smaller the grain, the higher the yield strength. In addition, the grain size has an important influence on the plasticity and toughness, fatigue strength, creep strength and corrosion resistance of metal materials. Taking the reboiler commonly used in petrochemical industry as an example, if the grain size of the stainless steel tube sheet is too large, under high temperature and alternating stress, the welded part of the tube sheet and the shell side cylinder will be damaged due to insufficient strength and poor corrosion fatigue resistance. I...

AI Technical Summary

Problems solved by technology

The ultrasonic method can reflect the microstructural characteristics of the deep layer inside the material. When the ultrasonic wave propagates in materials with different average grain sizes, the degree of attenuation of the sound energy is significantly different. Whether it is in the time domain or the frequency domain, the local time is lost. The richer grain size information carried by the spectral information within the range is easily affected by noise signal interference, which in turn affects the accuracy and reliability of grain size evaluation

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