New highly-sensitive and non-contact methods for acoustic recognition and imaging of defects in composites

材料和工业部件的质量保证要求和标准不断提高，以满足现代工程系统对可靠性和安全性的日益增长的需求。该项目旨在通过使用缺陷局部共振的概念来提高声学无损检测技术的效率和灵敏度。该方法的新颖之处在于，它提供了一种选择性的声激励，并通过其机械共振将能量从波直接传递到缺陷。通过探头超声波与缺陷共振之间的频率匹配，验证了超声无损检测技术在效率和灵敏度方面的显著提高。预期超声激活效应(非线性、热效应等)家族将有显著改进。它们通常效率相对较低，因此相应的无损检测和成像技术需要更高的声功率和适应于高功率超声波的特定仪器。该项目致力于开发高效率的非线性超声和超声热像(热声)技术的共振和非接触版本，以避免使用高功率设备，而使用传统的低能量无损检测设备。为此，将对复合材料中基本类型的缺陷的局部共振诱导现象进行详细的理论分析和数值模拟。模拟将包括用于全面振动频谱分析的缺陷的线性和非线性共振模式，用于解决共振声热转换的摩擦加热模型。用于识别缺陷共振的实验方法结合了声(接触和非接触)激励与通过扫描激光测振和红外相机监测局部振动模式和缺陷热响应的实验方法。缺陷振动的共振放大导致了强烈的非线性缺陷响应和局部光谱转换。研究和应用于高灵敏度缺陷识别和成像的非线性共振模式将包括亚谐和超谐参数共振。对线性和非线性振动模式，阐述了具有增强缺陷热响应的共振超声热成像的优点，并进行了实验分析。该项目将重点研究非接触共振技术，目的是创造一种将共振方法的优点与传统超声波探测的简单性相结合的方法。该项目的实施将导致与汽车、航空和航空航天工业相关的复合材料无损检测和缺陷成像的声学技术的实质性改进。

The requirements and standards of quality assurance for materials and industrial components continue to be upgraded constantly to meet the ever-growing demands for reliability and safety in modern engineering systems.The project is aimed at enhancing efficiency and sensitivity of acoustic NDT techniques by using the concept of a local resonance of defects. The novelty of the proposed approach is that it provides a selective acoustic excitation and energy delivery from the wave directly to the defect via its mechanical resonance. By frequency match between a probing ultrasonic wave and the defect resonance, a substantial enhancement in efficiency and sensitivity of ultrasonic NDT techniques is validated. A significant improvement is expected for the family of prospective ultrasound-activated effects (nonlinear, thermal, etc.) which are usually comparatively inefficient so that the corresponding NDT and imaging techniques require an elevated acoustic power and specific instrumentation adapted to high-power ultrasonics. The project is concerned with development of the resonance and non-contact versions for the techniques of nonlinear ultrasonics and ultrasonic thermography (thermosonics) with advanced efficiency that enables to avoid high-power apparatuses and use conventional low-energy NDT equipment instead.To this end, a detailed theoretical analysis and numerical modelling of the local resonance-induced phenomena will be given for basic types of defects in composite materials. The simulation will include both linear and nonlinear resonant modes of defects to be applied for a comprehensive vibration spectrum analysis, the models of frictional heating to address a resonant acousto-thermal conversion.The experimental methodologies to be used for recognition of the defect resonance combine an acoustic (both contact and non/contact) excitation with monitoring a local vibration pattern and a defect thermal response by means of scanning laser vibrometry and IR-camera. A resonance amplification of defect vibrations results in a strong nonlinear defect response and a local spectral conversion. The nonlinear resonance modes to be studied and applied for a highly-sensitive defect recognition and imaging will include sub- and super-harmonic parametric resonances. The advantages of resonance ultrasonic thermography with an enhanced thermal response of defects will be elaborated and experimentally analysed for both linear and nonlinear vibration modes. A special emphasis will be given to investigation of non-contact resonance techniques with objective to create the methods which combine benefits of resonant approach with simplicity of conventional ultrasonic probing.The implementation of the project will result in substantial improvement of acoustic technologies for NDT and imaging of flaws in composite materials relevant to automotive, aviation and aerospace industries.