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采用接触法和水浸聚焦法分别对平底孔、通孔、槽伤三类半固态用铝合金人工缺陷进行超声检测并提取特征参量进行分类识别。用频谱分析方法分析静态超声A扫信号,对缺陷信号段进行快速傅里叶变换,以偏度值、峰度值、主频率峰值、谐振频率间隔作为特征参量判断缺陷类型。槽伤的偏度值、峰度值最大,通孔次之,平底孔最小,随着缺陷埋深的增加频谱图趋于对称和正态分布的特征;主频率峰值通孔最大,平底孔次之,槽伤最小;谐振频率间隔平底孔最大,槽伤次之,通孔最小。分析动态超声C扫描信号随着缺陷埋深增加的衰减情况,根据图像边缘形状特征可判断出缺陷类型,并且测量值/实际值(ρ/ρ0)图表明,平底孔缺陷尺寸测量误差最小达到40μm,通孔最小误差达到30μm,槽伤误差最小达到50μm。人工缺陷检测结果为自然缺陷的类型识别提供了可靠的判断依据。
Using contact method and immersion focus method, the artificial defects of three kinds of semi-solid aluminum alloy such as flat-bottomed hole, through-hole and slot injury were detected by ultrasound and the characteristic parameters were extracted for classification and recognition. A-scan signal of static ultrasonic was analyzed by spectrum analysis method, fast Fourier transform was performed on the defective signal segment, and the type of defect was judged by taking skewness value, kurtosis value, main frequency peak and resonant frequency interval as characteristic parameters. Skeletal injury skewness value, kurtosis value is the largest, followed by the hole, flat bottom hole smallest, with the increase of the defect depth of the spectrum tends to be symmetrical and normal distribution characteristics; the main frequency peak through hole maximum, The smallest slot injury; resonant frequency interval flat-bottomed hole maximum, followed by slot injury, the smallest hole. According to the edge shape feature of the image, the type of defect can be judged according to the decay of the dynamic ultrasonic C-scan signal with the increasing depth of the defect, and the measured value / actual value (ρ / ρ0) shows that the measurement error of the flat bottom hole defect size is 40 μm , The minimum error of the through hole reached 30μm, the smallest slot injury error reached 50μm. The results of artificial defect detection provide a reliable basis for the type identification of natural defects.