Ultrasonic Detection Of Small Inclusions In Aluminum Alloy By Frequency Analysis

It is studied that small inclusions in aluminum alloy are detected by ultrasonic transmission method in this paper. Frequency analysis of the ultrasonic signal is done. Harmonic factor and relative valid spectral power are calculated. Using the method in Quantification Metallography, the size of grain and hardening particles, volume percentage of inclusions and hardening particles are estimated according to samples.The frequency analysis results show conclusions as follows: 1. The relative valid spectral power is declined with the volume percentage of inclusions in terms of exponent curve and the tendency of negative direction is same to that of forward direction. The small inclusions -in aluminum alloy can be detected according to this rule. 2. The initial phase angle of the highest spectral line mushrooms with the growth of volume percentage of inclusions while forward direction, but it goes down while negative direction.3. The harmonic factor raises with the growth of volume percentage of hardening particles no mater what detecting direction is. But it is not a linear variation course. The harmonic factor mounts up slowly under the critical value but increases rapidly while exceeds the critical value.The above-mentioned research results will supply valuable foundation of theory and experiment for ultrasonic detection of small inclusions and hardening particles density.