考虑晶粒分布的多晶体材料超声散射统一理论  

Ultrasonic sacttering unified theory for polycrystal material with grain sizes distribution

作　　者：李珊 李雄兵[1] 宋永锋[1] 陈超[2] Li Shan;Li Xiong-Bing;Song Yong-Feng;Chen Chao(School of Traffic and Transportation Engineering,Central South University,Changsha 410075,China;State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China)

机构地区：[1]中南大学交通运输工程学院,长沙410075 [2]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《物理学报》2018年第23期99-110,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51575541;51711530231);中南大学中央高校基本科研业务费(批准号:2018zzts515)资助的课题~~

摘　　要：现有超声散射统一理论可通过多晶体材料的微观结构和力学特性,实现全频域范围内衰减和相速度的正演建模,但其忽略晶粒尺寸分布的影响,进而降低了正演模型的计算精度.本文对不均匀介质的波动方程进行二阶Keller近似,用全频域格林函数推导介质中的平均波;以截断对数正态分布描述晶粒分布,构建加权的空间相关函数;结合材料的弹性模量协方差,建立含晶粒分布的超声散射统一理论,揭示晶粒分布对超声散射的影响规律;制备304不锈钢试块并开展超声散射实验.结果表明考虑晶粒分布特性后,纵波衰减谱和相速度谱相对于实验结果的相异性降低约49%和64%,横波衰减谱和相速度谱相对于实验结果的相异性降低约12%和4%.可见,本文的统一理论模型能有效修正晶粒分布导致的衰减谱和相速度谱偏差,为晶粒分布反演评价提供理论基础.The existing unified theory of ultrasonic scattering can model the attenuation and phase velocity in the frequency domain by using the microstructure and mechanical properties of polycrystalline materials.However,this theory does not consider the influence of grain size distribution,thus degrading the calculation accuracy in the forward modeling.A new unified theory,which is mainly corrected by considering the grain size distribution,is developed.First,the second-order Keller approximation and the full-field Green's function are used to calculate the wave equation of inhomogeneous medium and derive the average wave in the medium,respectively.Second,the method of the truncated lognormal distribution is used to describe the grain size distribution and construct the weighted spatial correlation function.Finally,the new unified theory of ultrasonic scattering is established to reveal the influence of grain distribution on ultrasonic scattering. Using the new unified model,the effects of the grain distribution widening on the ultrasonic scattering while the average grain size is unchanged,are analyzed for the longitudinal wave and the shear wave.The attenuation increases in the Rayleigh scattering region and the geometric scattering region,while there is less attenuation variation in the stochastic scattering region and two adjacent transition regions.The phase velocity varies strongly in the stochasticgeometric transition region,while the variation is relatively small in other scattering zones.Experiments are conducted by using a 304stainless steel specimen.The results show that when the grain distribution characteristics are considered, the discrepancy between the longitudinal wave attenuation spectrum and experimental results, and that between the phase velocity spectrum and experimental results are reduced by 49%and 64%,respectively;for the shear wave,these discrepancies are reduced by 12%and 4%,respectively. From all above aspects,the accuracy of the new model is higher than that of the traditional model.The new

关 键 词：超声散射 统一理论 晶粒尺寸 截断对数正态分布 

分 类 号：TB30[一般工业技术—材料科学与工程]