非均匀材料热物性参数的定量光声层析成像

Quantitative characterization of thermophysical properties of engineering materials can realize industrial quality control by evaluating the adaptability of materials in specific thermally working environments, as well as provide references for fundamental research and engineering design of functionally graded materials. Photoacoustic and photothermal techniques have been developed to be among the most important nondestructive testing methodologies and widely applied to parameter evaluation, component analysis, and structure imaging of various materials. In view of the fact that the photoacoustic technique has been able to quantitatively and accurately determine the effective thermophysical parameters and able to achieve qualitative tomography, this proposal aims at further developing it to be able to realize quantitative tomography of thermophysical parameters of inhomogeneous materials. We plan to establish a theory and corresponding algorithms for the inversion problem in the frequency-domain photoacoustic piezoelectric field. The radar signal processing principles and methods will be introduced into the photoacoustic imaging technique by using pulse compression and matched filtering in lieu of the traditional single-frequency modulation and lock-in detection, which allows for in-time and fast time-domain quantitative tomographic imaging as well as designs and optimization of waveform engineering problems. The uniqueness problem in the photoacoustic inversion procedures, which is one of the most fundamental problems in photoacoustics, will be addressed by direct investigation on the mathematical structure of the base function space determined by the PA theoretical model. By this study we hope to provide new ideas for the innovation in the photoacoustic and photothermal area as well as advanced characterization methodologies for studying of new materials.

对工程材料的热物理性能进行定量表征，既可以衡量材料能否适应具体热工作环境、为工业生产提供安全保障，也可以为功能性梯度材料的基础研究和工程设计提供学术参考。光声光热技术已发展成为无损检测领域的一类重要技术手段，广泛应用于参数测量、成分分析、和结构成像。针对光声技术目前已经可以实现等效热物性参数定量表征、可以实现定性层析成像的现状，本项目拟将其发展成为可实现非均匀材料热物性参数定量层析成像的技术：研究热物性非均匀材料的频域光声压电反演理论及算法；拟结合雷达信号处理方法，用脉冲压缩和自相关匹配滤波取代传统单频激励和锁相检测，在实现时域快检的同时，研究波形工程最优化问题和最佳调制解调参数设计；拟从光声理论模型的数学空间结构出发，尝试从本质上研究逆问题的唯一性理论以及反演精度。本项目的研究不仅可以为光声光热技术的创新研究提供参考，也力争为新型材料研究提供先进的表征与评价方法。

光声技术已广泛应用于参数测量、成分分析和结构成像，本项目将其发展成为可初步实现非均匀材料热物性参数定量层析成像的技术。本项目开展了如下研究：（1）热物性深度非均匀材料在单频激光激励下的频域光声压电热物性参数测量理论和热物性深度分布测量及定量层析成像实验研究；（2）热物性深度非均匀分布材料基于光声中间量-光热信号的频域光热反射、频域光热辐射热物性参数测量理论及热物性参数测量实验研究；（3）多频激光激励下的时域光声压电热物性参数测量理论和热物性深度分布测量及定量层析成像实验研究。通过本项目理论和实验研究，建立了频域、时域光声压电热扩散率测量和定量分层成像实验系统、频域光热反射热扩散率测量系统、频域光热辐射热扩散率测量系统，实现了热物性参数测量，初步实现了热物性参数深度分布反演和热物性参数定量层析成像，为新型材料研究提供先进的表征与评价方法。