激光热弹激发超声导波的有限元模拟
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摘要
本文采用有限元法建立了激光点源和环源在铝材料表面热弹激发超声导波的物理模型,通过对激光与材料相互作用产生的温度场和应力场的分析,研究了脉冲激光作用于铝板和铝管表面激发超声导波的物理过程。
基于平面应变的弹性理论,将激光点源和环源的热弹激发超声的物理过程极化在两维平面内进行分析,建立了点源和环状激光源作用于铝材料中的有限元模型,数值模拟了激光脉冲作用于铝材料表面时产生的瞬态温度场,得到了材料内部温度随时间变化的曲线和不同时刻温度沿径向、轴向的变化曲线。进一步分析了温度梯度的形成及随时间、沿径向的变化规律。
针对激光超声技术中如何提高超声信号强度的问题,建立环状阵列激光源作用在铝板材料中激发超声波的理论模型,采用有限元方法对其进行数值模拟。通过调节环状激发源的个数及间距,优化加载模型,得到了超声信号强度和信噪比均较高的加载模型结构。并利用FFT变换提取出超声信号的频率,计算出超声兰姆波波包的群速度。结果表明,该加载模型下激发的超声模式为能量高、频散小、且在整个板内部均有一定振动能量的A0模式兰姆波。
本文的研究结果可以为激光超声理论和数值模拟研究,以及激光超声无损检测中激发光源的选择和模式优化提供理论依据。
Finite element method has been employed to simulate the generation of ultrasonic guided wave generated by the pulsed laser, which has been focused in the Point or ring Pattern. Through the analysis of the temperature field and stress field produced by interaction laser and material, research of the physical process of pulse laser generated Ultrasonic Guided Wave on the surface of aluminum plate and aluminum tubes.
Based on the theoretical model of plane strain, Laser point or ring source irradiation on the aluminum material has been polarized in two dimensional plane, and laser-ultrasonic generated by point or ring laser in aluminum material is established using finite element method based on a theoretical model of thermo-elastic generation of laser-ultrasound. The transient temperature fields generated by a pulse laser radiating on the surface of aluminum material have been simulated. And the evolution curves of the temperature with time, radial variables and axle variables have been gotten. Furthermore, the formation and variation of temperature gradient in the interior of aluminum material have been analyzed.
In order to improve the intensity of ultrasound signal, a laser-ultrasonic excited by ring array laser source is simulated using finite element method based on the theoretical model of laser-ultrasonic generated in aluminum plate.The optimum load model with high signal strength and high signal to noise ratio is obtained through the adjustment of the number of excitation source and spacing.Then,the frequency of ultrasonic signals is extracted by using FFT transform and the ultrasonic packet’s group velocity is calculated.The results indicate that the laser-ultrasonic generated by our ring array laser source is the A0 mode of Lamb wave which has high energy, small dispersion, and always keeps sufficient vibration energy in the entire internal board meanwhile.
The main Practical objective of the Present work is to develop a model of an ultrasonic technique for selecting laser excitation source and optimizing models in the test of laser-ultrasonic nondestructive.
基于平面应变的弹性理论,将激光点源和环源的热弹激发超声的物理过程极化在两维平面内进行分析,建立了点源和环状激光源作用于铝材料中的有限元模型,数值模拟了激光脉冲作用于铝材料表面时产生的瞬态温度场,得到了材料内部温度随时间变化的曲线和不同时刻温度沿径向、轴向的变化曲线。进一步分析了温度梯度的形成及随时间、沿径向的变化规律。
针对激光超声技术中如何提高超声信号强度的问题,建立环状阵列激光源作用在铝板材料中激发超声波的理论模型,采用有限元方法对其进行数值模拟。通过调节环状激发源的个数及间距,优化加载模型,得到了超声信号强度和信噪比均较高的加载模型结构。并利用FFT变换提取出超声信号的频率,计算出超声兰姆波波包的群速度。结果表明,该加载模型下激发的超声模式为能量高、频散小、且在整个板内部均有一定振动能量的A0模式兰姆波。
本文的研究结果可以为激光超声理论和数值模拟研究,以及激光超声无损检测中激发光源的选择和模式优化提供理论依据。
Finite element method has been employed to simulate the generation of ultrasonic guided wave generated by the pulsed laser, which has been focused in the Point or ring Pattern. Through the analysis of the temperature field and stress field produced by interaction laser and material, research of the physical process of pulse laser generated Ultrasonic Guided Wave on the surface of aluminum plate and aluminum tubes.
Based on the theoretical model of plane strain, Laser point or ring source irradiation on the aluminum material has been polarized in two dimensional plane, and laser-ultrasonic generated by point or ring laser in aluminum material is established using finite element method based on a theoretical model of thermo-elastic generation of laser-ultrasound. The transient temperature fields generated by a pulse laser radiating on the surface of aluminum material have been simulated. And the evolution curves of the temperature with time, radial variables and axle variables have been gotten. Furthermore, the formation and variation of temperature gradient in the interior of aluminum material have been analyzed.
In order to improve the intensity of ultrasound signal, a laser-ultrasonic excited by ring array laser source is simulated using finite element method based on the theoretical model of laser-ultrasonic generated in aluminum plate.The optimum load model with high signal strength and high signal to noise ratio is obtained through the adjustment of the number of excitation source and spacing.Then,the frequency of ultrasonic signals is extracted by using FFT transform and the ultrasonic packet’s group velocity is calculated.The results indicate that the laser-ultrasonic generated by our ring array laser source is the A0 mode of Lamb wave which has high energy, small dispersion, and always keeps sufficient vibration energy in the entire internal board meanwhile.
The main Practical objective of the Present work is to develop a model of an ultrasonic technique for selecting laser excitation source and optimizing models in the test of laser-ultrasonic nondestructive.
引文
[1]罗斯J L (美).固体中的超声波(何存富).北京:科学出版社, 2004: 82~108.
[2]袁易全.近代超声原理与应用.南京:南京出版社, 1996: 25~29.
[3]陆建,倪晓武,贺安之.激光与材料相互作用物理学.北京:机械工业出版社, 1996: 20~41.
[4]张淑仪.激光超声与材料无损评价.应用声学, 1992, 11(4): 1~6.
[5]张淑仪.超声无损检测高新技术.国际学术动态, 1998, 8: 58~60.
[6]章肖融.用激光超声评估复合材料.应用声学, 2000, 19(5): 1~9.
[7]单宁,史仪凯,赵江海,等.正弦脉冲激光热弹激发超声应力脉冲仿真研究.激光杂志, 2007, 28(3): 37~38.
[8] Zhang X R, Zhang W, Wang X D, et al. Laser ultrasound characterization of chemically prepared nano-structured silver. Appl Phys A, 2000, 70: 573~580.
[9] Aussel J D, Brun A L, Baboux J C. Generating acoustic waves by laser: Theoretical and experimental study of the emission source. Ultrasonics, 1998, 26: 245~255.
[10] Farson D F, Kim K R. Generation of optical and acoustic emission in laser weld plumes. J Appl Phys, 1999, 85(3): 1329~1338.
[11] Masahiko H, Hidekazu F. Scattering of Ryaleigh surface waves by edge cracks: Numerical simulation and experiment. Aeoust Soc Am, 1982, 72(2): 602~606.
[12] Kenderian S, Djordjevie B B, Green R E. Point and Line Source Laser generation of Ultrasound for Inspection of Internal and Surface Flaws in Rail and Structural Materials. Res Nondestr Eval, 2001, 13: 189~200.
[13] White R M. Generation of elastic waves by transient surface heating. J Appl, 1963, 34: 3559~3567.
[14] Lamb H. On the Waves in an Elastic Plate. Proceedings of the Royal Society of London, 1917: 293~312.
[15] Worlton D C. Experimental Confirmation of Lamb Waves at Megacycle Frequencies. Journal of Applied Physics, 1961, 32(6): 967~971.
[16]应崇福,张守玉,沈建中.超声在固体中的散射.北京:国防工业出版社, 1994: 10~45.
[17]王小民,李明轩.复合材料的超声检测与评价.应用声学, 1998, 17(6): 39~43.
[18] Zhang X R, Gan C M, Zhang S Y. Ultrasonic velocity and attenuation of nano-scaled copper measured by laser ultrasonic technique. J Acoust Soc Am, 1996, 99: 2469~2500.
[20]刘镇清,他得安.用二维傅里叶变换识别兰姆波模式的研究.声学技术, 2000, 19(4):212~219.
[21]倪晓武,陈笑,许伯强,等.激光激发瞬态Lamb波的实验检测与数值模拟.南京理工大学学报, 2003, 27(5): 588~594.
[22] Rose J L. Ultrasonic Waves in Solid Media, BeiJing. Scie~Nce Press, 2004: 125~128.
[23] Ta D A, Liu Z Q, Tian G C. Propagation characteristics of ultrasonic guided-waves in pipes. Technical Acoustics, 2001, 20(3): 131~134.
[24] Song B M, Kim J H , Lee J H. Application of laser-generated ultrasound to evaluate wall thinned pipe. NDT in progress, 2007, 5: 187~195.
[25] Tang L G, Cheng J C , Wang J L, Theoretical investigation of the laser~generated guided waves in hollow cylinders, Acta Acustica, 2001, 26(6): 489~496.
[26] Gao W, Christ G, Jan T. Study of circumferential waves and their interaction with defects on cylindrical shells using line-source laser ultrasonics. J Appl Phys, 2002, 91(9): 6114~6119.
[27]胡文祥,孙伟,钱梦騄.脉冲激光线源热弹激励的圆柱表面波声场.同济大学学报, 2005, 33(3): 400~403.
[28] Zhao Y, Shen Z H, Lu J, et al. Finite element simulation of laser-generated circumferential waves in hollow cylinder. Acta Physica Sinica, 2007, 56(1): 321~325.
[29] He Y J, Zhu R H, Shen Z H, et al. Numerical simulation of laser-induced transient temperature field in cylindrical shell. Laser Technology, 2005, 29(4): 386~388.
[30] Demma A, Cawley P, Lowe M. The Reflection of Guided waves from Notches in pipes: a Guide for Interpreting Corrosion Measurements. NDT&E International, 2004, 37: 167~180.
[31] Cheng A, Murry T W, Achenbach J D. Simulation of laser-generated ultrasonic wave in layered plates. J Acoust Soc Am, 2001, 110(2): 848~854.
[32] Scruby C B, Dewhurst R J, Palmer S B. Quantitative studied of thermally generatedelastic waves in laser-irradiated metals. J Appl Phys, 1980, 51(12): 6210~6216.
[33] Sinclair J E. Epicenter solutions for point multiple sources in an elastic half-space. J Phys D Appl Phys, 1979, 12: 1309~1315.
[34] Rose L R F. Point~Source representation for laser-generated ultrasound.J Aeoust Soe Am, 1984, 75(3): 723~732.
[35] Bresse L F, Hutchins D A. Transient generation by a wide thermoelastic source at a solidsurface. J Appl Phys, 1989, 65(4): 1441~1446.
[36] Cheng J C, Berthelot Y H. Theory of laser-generated transient Lamb waves in orthotropic plates. J Appl Phys D Appl Phys, 1996, 29: 1857~1867.
[37] Kass M, Fukushima S, Gohshi Y, et al. A basic analysis of pulsed photoacoustic signals using thefinite elements method. J Appl Phys, 1988, 64(3): 972~976.
[38] Lee J H, Burger C P. Finite element modeling of laser-generated Lamb waves. Computers& Structures, 1995, 54(3): 499~514.
[39] Xu B Q, Shen Z H, Ni X W, et al. Numerical simulation of laser-induced ultrasonic by finite Element method. Journal of Applied Physics, 2004, 94(4): 2116~2122.
[40] Xu B Q, Shen Z H, Ni X W, et al. Finite element modeling of laser-generated ultrasound in Coating-substrate system. Journal of Applied Physics, 2004, 94(4): 2106~2115.
[41] Arias I, Murry T W, Achenbach J D. Near field analysis of laser-generated ultrasound: the effects of thermal diffusion and optical penetration. Review of Quantitative Nondestructive Evaluation, 2002, CP615: 24~331.
[42] Lee T H, Choi I H, Jhang K Y. Single-mode guided wave technique using ring-arrayed laser beam for thin-tube inspection. NDT&E International, 2008, 41: 632~637.
[43] Kim H J, Jhang K Y, Shin M J, et al. A noncontact NDE method using a laser generated focused-Lamb wave with enhanced defect-detection ability and spatial resolution. NDT&E International, 2006, 39: 312~319.
[44] Noroy M H, Royer D, Fink M. The laser-generated ultrasonic phased array: analysis and experiments. J Aeoust Soc Am, 1993, 94(4): 1934~1943.
[45] Baldwin K C, Berndt T P, Ehrlich M J. Narrow band laser generation/air-coupled detection: ultrasonic system for on~line process control of composites. Ultrasonics, 1999, 37(5): 329~334.
[46] Jhang K Y, Shin M J, Lim B O. Application of the laser generated focused-Lamb wave for non-contact imaging of defects in plate. Ultrasonics, 2006, 44: e985~e989.
[2]袁易全.近代超声原理与应用.南京:南京出版社, 1996: 25~29.
[3]陆建,倪晓武,贺安之.激光与材料相互作用物理学.北京:机械工业出版社, 1996: 20~41.
[4]张淑仪.激光超声与材料无损评价.应用声学, 1992, 11(4): 1~6.
[5]张淑仪.超声无损检测高新技术.国际学术动态, 1998, 8: 58~60.
[6]章肖融.用激光超声评估复合材料.应用声学, 2000, 19(5): 1~9.
[7]单宁,史仪凯,赵江海,等.正弦脉冲激光热弹激发超声应力脉冲仿真研究.激光杂志, 2007, 28(3): 37~38.
[8] Zhang X R, Zhang W, Wang X D, et al. Laser ultrasound characterization of chemically prepared nano-structured silver. Appl Phys A, 2000, 70: 573~580.
[9] Aussel J D, Brun A L, Baboux J C. Generating acoustic waves by laser: Theoretical and experimental study of the emission source. Ultrasonics, 1998, 26: 245~255.
[10] Farson D F, Kim K R. Generation of optical and acoustic emission in laser weld plumes. J Appl Phys, 1999, 85(3): 1329~1338.
[11] Masahiko H, Hidekazu F. Scattering of Ryaleigh surface waves by edge cracks: Numerical simulation and experiment. Aeoust Soc Am, 1982, 72(2): 602~606.
[12] Kenderian S, Djordjevie B B, Green R E. Point and Line Source Laser generation of Ultrasound for Inspection of Internal and Surface Flaws in Rail and Structural Materials. Res Nondestr Eval, 2001, 13: 189~200.
[13] White R M. Generation of elastic waves by transient surface heating. J Appl, 1963, 34: 3559~3567.
[14] Lamb H. On the Waves in an Elastic Plate. Proceedings of the Royal Society of London, 1917: 293~312.
[15] Worlton D C. Experimental Confirmation of Lamb Waves at Megacycle Frequencies. Journal of Applied Physics, 1961, 32(6): 967~971.
[16]应崇福,张守玉,沈建中.超声在固体中的散射.北京:国防工业出版社, 1994: 10~45.
[17]王小民,李明轩.复合材料的超声检测与评价.应用声学, 1998, 17(6): 39~43.
[18] Zhang X R, Gan C M, Zhang S Y. Ultrasonic velocity and attenuation of nano-scaled copper measured by laser ultrasonic technique. J Acoust Soc Am, 1996, 99: 2469~2500.
[20]刘镇清,他得安.用二维傅里叶变换识别兰姆波模式的研究.声学技术, 2000, 19(4):212~219.
[21]倪晓武,陈笑,许伯强,等.激光激发瞬态Lamb波的实验检测与数值模拟.南京理工大学学报, 2003, 27(5): 588~594.
[22] Rose J L. Ultrasonic Waves in Solid Media, BeiJing. Scie~Nce Press, 2004: 125~128.
[23] Ta D A, Liu Z Q, Tian G C. Propagation characteristics of ultrasonic guided-waves in pipes. Technical Acoustics, 2001, 20(3): 131~134.
[24] Song B M, Kim J H , Lee J H. Application of laser-generated ultrasound to evaluate wall thinned pipe. NDT in progress, 2007, 5: 187~195.
[25] Tang L G, Cheng J C , Wang J L, Theoretical investigation of the laser~generated guided waves in hollow cylinders, Acta Acustica, 2001, 26(6): 489~496.
[26] Gao W, Christ G, Jan T. Study of circumferential waves and their interaction with defects on cylindrical shells using line-source laser ultrasonics. J Appl Phys, 2002, 91(9): 6114~6119.
[27]胡文祥,孙伟,钱梦騄.脉冲激光线源热弹激励的圆柱表面波声场.同济大学学报, 2005, 33(3): 400~403.
[28] Zhao Y, Shen Z H, Lu J, et al. Finite element simulation of laser-generated circumferential waves in hollow cylinder. Acta Physica Sinica, 2007, 56(1): 321~325.
[29] He Y J, Zhu R H, Shen Z H, et al. Numerical simulation of laser-induced transient temperature field in cylindrical shell. Laser Technology, 2005, 29(4): 386~388.
[30] Demma A, Cawley P, Lowe M. The Reflection of Guided waves from Notches in pipes: a Guide for Interpreting Corrosion Measurements. NDT&E International, 2004, 37: 167~180.
[31] Cheng A, Murry T W, Achenbach J D. Simulation of laser-generated ultrasonic wave in layered plates. J Acoust Soc Am, 2001, 110(2): 848~854.
[32] Scruby C B, Dewhurst R J, Palmer S B. Quantitative studied of thermally generatedelastic waves in laser-irradiated metals. J Appl Phys, 1980, 51(12): 6210~6216.
[33] Sinclair J E. Epicenter solutions for point multiple sources in an elastic half-space. J Phys D Appl Phys, 1979, 12: 1309~1315.
[34] Rose L R F. Point~Source representation for laser-generated ultrasound.J Aeoust Soe Am, 1984, 75(3): 723~732.
[35] Bresse L F, Hutchins D A. Transient generation by a wide thermoelastic source at a solidsurface. J Appl Phys, 1989, 65(4): 1441~1446.
[36] Cheng J C, Berthelot Y H. Theory of laser-generated transient Lamb waves in orthotropic plates. J Appl Phys D Appl Phys, 1996, 29: 1857~1867.
[37] Kass M, Fukushima S, Gohshi Y, et al. A basic analysis of pulsed photoacoustic signals using thefinite elements method. J Appl Phys, 1988, 64(3): 972~976.
[38] Lee J H, Burger C P. Finite element modeling of laser-generated Lamb waves. Computers& Structures, 1995, 54(3): 499~514.
[39] Xu B Q, Shen Z H, Ni X W, et al. Numerical simulation of laser-induced ultrasonic by finite Element method. Journal of Applied Physics, 2004, 94(4): 2116~2122.
[40] Xu B Q, Shen Z H, Ni X W, et al. Finite element modeling of laser-generated ultrasound in Coating-substrate system. Journal of Applied Physics, 2004, 94(4): 2106~2115.
[41] Arias I, Murry T W, Achenbach J D. Near field analysis of laser-generated ultrasound: the effects of thermal diffusion and optical penetration. Review of Quantitative Nondestructive Evaluation, 2002, CP615: 24~331.
[42] Lee T H, Choi I H, Jhang K Y. Single-mode guided wave technique using ring-arrayed laser beam for thin-tube inspection. NDT&E International, 2008, 41: 632~637.
[43] Kim H J, Jhang K Y, Shin M J, et al. A noncontact NDE method using a laser generated focused-Lamb wave with enhanced defect-detection ability and spatial resolution. NDT&E International, 2006, 39: 312~319.
[44] Noroy M H, Royer D, Fink M. The laser-generated ultrasonic phased array: analysis and experiments. J Aeoust Soc Am, 1993, 94(4): 1934~1943.
[45] Baldwin K C, Berndt T P, Ehrlich M J. Narrow band laser generation/air-coupled detection: ultrasonic system for on~line process control of composites. Ultrasonics, 1999, 37(5): 329~334.
[46] Jhang K Y, Shin M J, Lim B O. Application of the laser generated focused-Lamb wave for non-contact imaging of defects in plate. Ultrasonics, 2006, 44: e985~e989.