摘要
为了研究镍基高温合金声学表面波(SAW)的传播速度与晶向之间的关系,介绍了一种基于波前调控的新型激光超声技术。该技术采用光栅将激发光调制成周期排列的线性光源,从而在样品表面激发出具有特定波长且定向传播的SAW。通过对SAW传播速度的提取实现样品各向异性的分析。结合数值仿真与实验验证,实现了单晶镍基高温合金SAW速度的定量检测与各向异性分析。提出了基于波前调控的激光超声有限元数值仿真模型,通过数值仿真得到单晶镍基高温合金在(100)晶面和(001)晶面内的SAW速度各向异性比分别为0.073和0.18。基于镍基高温合金声速对晶向的依赖性,采用激光超声显微成像系统对单晶以及多晶镍基高温合金表面声速进行扫描成像,实现了表面缺陷以及晶粒分布状态的可视化分析。研究结果表明基于波前调控的激光超声显微成像技术为特种金属缺陷以及声速检测提供了一种新型快速的无损检测手段。
Objective Nickel-based superalloys have already been extensively used in aviation manufacturing,particularly in the production of jet engine components such as turbine blades,airframe parts,and nuclear power plant components.The mechanical properties of these alloys make them highly desirable for these applications.To ensure the successful application of single crystal nickel-based superalloys,it is crucial to have a comprehensive understanding of their anisotropic properties.This includes knowledge of the elastic coefficients,thermal expansivity,and thermal conductivity.For these purposes,acoustic wave velocity is often employed as a primary quantity to access the parameters of these alloys since it is influenced by the module of elasticity and density.Any variation in material properties like porosity,residual stress,or even coating thickness in the case of surface waves can lead to changes in acoustic wave velocity.Monitoring the acoustic wave velocity can provide valuable information about the ongoing processes and their effects on material properties.Measuring the changes in acoustic wave velocity makes it possible to assess and track the progress of these processes.This information is important in evaluating the quality and integrity of manufactured components,as it helps in identifying deviations or abnormalities that may affect the final product.Methods Nondestructive testing(NDT)has offered a powerful approach for safety critical material inspections such as those in aerospace and nuclear industries by minimizing the risk of failure,thereby reducing costs and maximizing safety.Laser ultrasound technology(LUT)uses a pulsed laser source to locally heat the sample,and acoustic waves are then generated due to thermal elastic processes.A second laser is used to probe the generated acoustic wave.As thermal elastic constants are highly related to samples density,stress,as well as crystallographic structures,one can then access the macroscopic or microscopic information of the sample and thus find the defects at both scales.As a consequence,LUT is receiving growing attention thanks to its great potential in the evaluation of defects,crystallographic orientation,and residual stress.Moreover,as LUT uses lasers to excite and detect the signals,the entire process is contactless,and it thus shows great advantages when inspecting samples with complex geometric structures and brings great convenience when used in environments with elevated temperatures or toxicity.In addition,LUT can inspect small specimens with high spatial revolution by using lenticular systems that allow the pump and probe lasers to focus on the surface of the sample.In recent years,laser ultrasound systems combined with wavefront modulation techniques have shown the capability of generating and detecting surface acoustic wave(SAW)with a specific frequency,which makes the mathematical modeling much simpler during data processing and in turn leads to an easier approach to access critical material properties such as crystallographic structures.Results and Discussions We discuss a new LUT that utilizes wavefront control to investigate the relationship between SAW velocity and crystal orientation in nickel-based superalloys.Nickel-based superalloys are widely used in aerospace turbofan blades due to their thermal resistance.Understanding the mechanical anisotropy of these materials is crucial for ensuring the mechanical performance and flight safety of turbofan blades.The technology combines numerical simulation and experiments to accurately measure the propagation velocity of SAWs and analyze the material s mechanical properties.A laser ultrasonic finite element numerical simulation model based on wavefront control is proposed.The simulation results reveal that the anisotropy ratios of SAW velocity in single crystal nickel-based superalloys in the(100)and(001)planes are 0.073 and 0.18,respectively(Fig.4&Fig.6).To further investigate the relationship between crystal orientation and acoustic velocity in nickel-based superalloys,a laser ultrasonic microscopy system is employed(Fig.7).This system enables the scanning and imaging of the surface acoustic velocity in both single crystal and polycrystalline nickel-based superalloys,facilitating the visualization analysis of surface defects and grain distribution(Fig.10).Conclusions The simulation and experiment results indicate that the SAW velocity is sensitive to the orientation of the crystalline axis,which proves the capability of laser ultrasound systems combined with wavefront modulation techniques in the field of crystalline orientation determination and defect detection in an NDT manner.
作者
乔杰
冯甫
黄子嫣
胡斌
李江艳
马海祥
霍德旺
袁小聪
Qiao Jie;Feng Fu;Huang Ziyan;Hu Bin;Li Jiangyan;Ma Haixiang;Huo Dewang;Yuan Xiaocong(Research Center for Frontier Fundamental Studies,Zhejianglab,Hangzhou 310000,Zhejiang;Institute of Microscale Optoelectronics,Shenzhen University,Shenzhen 518000,Guangdong,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2024年第10期328-337,共10页
Acta Optica Sinica
基金
国家自然科学基金(62205215,62275167,12304330)
浙江省自然科学基金(LQ23F050009)
浙江省实验室重点研究项目(2022MG0AC05)
之江实验室中心立项项目(113014-AL2209)
中国博士后科学基金会(2022M722906)。
关键词
成像系统
镍基高温合金
声学表面波
激光超声
波前调控
声速各向异性
imaging systems
nickel-based superalloy
acoustic surface wave
laser ultrasound
wavefront control
acoustic velocity anisotropy
