利用Lamb波检测垢层厚度的数值分析
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摘要
针对锅炉垢层厚度检测的问题,提出一种通过Lamb波的频散特性检测垢层厚度的方法。首先,建立Lamb波在铝板-垢层双层弹性结构中的波动模型,利用半解析有限元法求解Lamb波的特征方程,绘制Lamb波的频散曲线。其次,建立铝板-垢层二维电磁超声仿真模型,通过电磁超声换能器在铝板中激发S0模态的Lamb波,得到不同采集点下的波形曲线。最后,通过对频散曲线和波形曲线的分析得知,随着垢层厚度的增加,低频S0模态Lamb波群速度变慢,高频S0模态Lamb波群速度变快,信号波群的幅值减小。结果表明,可利用S0模态Lamb波群速度变化及幅值变化进行锅炉垢层厚度检测。
A thickness detection method based on the dispersion characteristics of the Lamb wave is proposed to solve the detection problem of the boiler scale thickness. Firstly,the fluctuation model of Lamb wave in the aluminum-scale double-layer elastic structure is established,and the semi-analytical finite element method is adopted to solve the characteristic equation of Lamb wave in the model,and the dispersion curve of the Lamb wave which changed with the scale thickness is plotted. Secondly,a two-dimensional electromagnetic ultrasonic simulation model of aluminum-scale is established. The Lamb wave of S0 mode is excited by electromagnetic ultrasonic transducer in aluminum plate,and the waveform curve under different acquisition points is got. Finally,through the analysis of the dispersion curve and the waveform curve,the Lamb wave velocity of the low frequency S0 mode becomes slower with the increase of the thickness of the scale,and the Lamb wave velocity of the high frequency S0 mode becomes faster and the amplitude of the signal wave group decreases. The results show that the thickness of the boiler scale can be detected by S0 modal Lamb wave velocity and amplitude change.
A thickness detection method based on the dispersion characteristics of the Lamb wave is proposed to solve the detection problem of the boiler scale thickness. Firstly,the fluctuation model of Lamb wave in the aluminum-scale double-layer elastic structure is established,and the semi-analytical finite element method is adopted to solve the characteristic equation of Lamb wave in the model,and the dispersion curve of the Lamb wave which changed with the scale thickness is plotted. Secondly,a two-dimensional electromagnetic ultrasonic simulation model of aluminum-scale is established. The Lamb wave of S0 mode is excited by electromagnetic ultrasonic transducer in aluminum plate,and the waveform curve under different acquisition points is got. Finally,through the analysis of the dispersion curve and the waveform curve,the Lamb wave velocity of the low frequency S0 mode becomes slower with the increase of the thickness of the scale,and the Lamb wave velocity of the high frequency S0 mode becomes faster and the amplitude of the signal wave group decreases. The results show that the thickness of the boiler scale can be detected by S0 modal Lamb wave velocity and amplitude change.
引文
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[2]林宇铃.工业锅炉水垢的形成、危害及处理方法[J].装备制造技术,2014(8):131-133.
[3]陈欣.锅炉受热面损坏的常见原因及防范措施探讨[J].科技创新与应用,2017(5):135.
[4]刘焱.锅炉形成水垢原因及其处理措施[J].中国新技术新产品,2010(11):121.
[5]吴斌,李杨,郑阳.水平剪切波在板表面附着物厚度检测中的应用[J].机械工程学报,2012(18):78-84.
[6] PUTHILLATH P,GALAN J M,REN B,et al. Ultrasonic guided wave propagation across wave guide Transitions:Energy transfer and mode conversion[J]. Journal of the Acoustical Society of America,2013,133(5):2624-2633.
[7]许西宁,余祖俊.半解析有限元分析兰姆波特性[J].仪器仪表学报,2013,34(2):247-253.
[8]李忠芳.半解析有限元方法在超声波传播模拟中的应用[J].机械强度,2015,37(3):413-417.
[9] ROSE J L. A Baseline and vision of ultrasonic guided wave inspection potential[J]. Journal of Pressure Vessel Technology,2002,124(3):273-282.
[10]何存富,李隆涛,吴斌.空心圆柱体中的周向超声导波[J].机械工程学报,2004(8):7-12.
[11] PREDOI Mihai V,CASTAINGS Michel,HOSTEN Bernard,et al. Wave propagation along transversely periodic structures[J]. Acoustical Society of America,2007,121(4):1935-1944.