薄壁铝锂合金材料弹性模量双模式超声体波测量方法研究

Research on Dual-Mode Ultrasonic Bulk Wave Method for Elastic Modulus Measurement of Thin-wall Aluminum-lithium Alloy

弹性模量是航空航天结构静力试验中关键的力学性能参数,能否对其进行快速、准确、无损地测量直接关系结构承载性能的表征及优化。超声法是测量材料力学性能参数的有效方法之一,然而对于薄壁结构,该方法存在回波重叠、传感器频繁更换、脉冲占宽大等问题,导致测量繁琐、精度低。针对该问题,提出了基于声耦合块的双模式超声体波测量薄板弹性模量的方法,并建立了脉冲反射式超声测量模型,分析了超声纵、横波在延迟块和薄板中的传播特性。在验证试验中,采用铝锂合金设计了厚度为3mm的标准拉伸试样,并分别进行了拉伸试验以及超声测量试验。结果表明,所建立的有限元模型能准确模拟声波在延迟块与薄壁材料中的传播过程,可有效指导薄板多次底波的识别;所提出的测量方法可准确表征材料弹性模量,与静态拉伸法相比偏差小于3%。

The elastic modulus is a key parameter in the structural test of the spacecraft,which characterizes the structural bearing performance and determines later optimization.Ultrasonic method is one of the feasible means to measure the mechanical properties of materials.However,for thin-wall aerospace structures,this method has some problems,such as echo overlap,frequent sensor replacement,and large pulse occupancy,which lead to complicated measurement and low accuracy.In this manuscript,a new method for measuring the elastic modulus of thin plates by dual-mode ultrasonic bulk waves with an acoustic coupling block is presented.An ultrasonic pulse reflection model is established,and the propagation characteristics of ultrasonic longitudinal and transverse waves in delay block and thin plate are analyzed.In the validation experiment,a standard tensile sample with a thickness of 3mm is designed using aerospace Al-Li alloy.Meanwhile,the tensile test and ultrasonic measurement experiment are carried out respectively.The results show that the time-domain waveforms calculated from the finite element model are in good agreement with the experimental results,and can be used to identify multiple reflected waves in thin plate.At the same time,the proposed method can accurately characterize the elastic modulus of materials,and the deviation is less than 3%compared with the static tensile method.