【作者】 张（亻刍）；

【导师】 杨思乾；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2003， 硕士

【摘要】 本文采用超声穿透法对LY12铝合金板材细小夹杂物进行了检测试验研究，并对超声信号进行了频谱分析，计算了谐波系数和相对有效谱功率。在解剖被检试样的基础上，运用定量金相学的分析方法，估算了被检部位的晶粒直径、夹杂物体积百分数、强化粒子直径及体积百分数。 频谱分析结果表明：1．当LY12铝合金细小夹杂物(小于0.16mm)的体积百分数从0％～0.35％时，在35～50MHz的频带范围内，超声波形的有效谱功率按近似指数曲线快速下降，沿相反方向检测时其变换趋势相同。根据上述变化规律，可对铝合金细小夹杂物进行超声无损检测；2．正向检测(沿轧制方向)时，最高谱线的初相角随夹杂物体积百分数的增加而迅速增加；逆向检测时，最高谱线的初相角随夹杂物体积百分数的增加而迅速减小；3．在正、逆向检测时，随着强化粒子体积百分数的增加，在有效频带范围内谐波系数同时单调增加，但其变化是非线性的，即在临界值以下，谐波系数的变化趋于平缓，而超过临界值以后，随着强化相粒子体积百分数的增加，谐波系数快速增加。 论文的上述研究成果，对于进一步开展LY12铝合金细小夹杂物及强化粒子密度的超声检测提供了重要的理论及实验依据。更多还原

【Abstract】 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.更多还原