蜂窝夹芯结构多次低速冲击损伤空间与时频效应研究

Honeycomb sandwich structure has been widely used in many fields, such as aeronautics, astronautics. However, this kind of structure is susceptible and vulnerable to multiple low-velocity impact. Therefore, to do better work on safety design, reliability assessment and service life prediction, non-contact and accurate measurement on damage states and damage propagation behaviors of honeycomb sandwich structures under multiple low-velocity impact is of great importance. A novel dynamic measurement system, which can achieve synchronous data acquisition and has a high speed-up during deformation calculation, is developed to determine the damage evolvement process accurately in real time. The proposed system is combined with ultrasonic C-scan method to obtain spatial and time-frequency effects on damage evolution and mechanical properties of honeycomb sandwich structures under multiple low-velocity impact. Impact energy, constraint, impact location, the number of impact and interval are also considered during the investigation. Furthermore, a strain field estimation method based on global information is proposed and combined with micro damage characteristics to investigate the failure mechanism of honeycomb sandwich structures. Moreover, the load capacity evaluation method for damaged structure is developed after scale-span analysis. Effects of different multiple damage modes on vibration characteristics are studied, the free vibration model is also established in the research. It is very useful to apply the proposed system and method for investigation on the failure mechanism, damage resistance and damage tolerance behavior of honeycomb sandwich structures under multiple low-velocity impact. And the results can provide experimental basis for both scientific research and engineering.

蜂窝夹芯结构是航空航天等领域常用的结构，多次低速冲击是其服役时常见的损伤来源。对蜂窝夹芯结构多次低速冲击损伤状态和扩展特性进行高精度测量对于结构的安全设计、可靠性评价和使用寿命预测有着重要意义。本项目拟开发一套采集数据同步、变形计算加速比高的动态测量系统，结合超声C扫描法，并充分考虑冲击能量、约束条件、冲击点位置、冲击次数和时间间隔等因素，揭示空间效应和时频效应对冲击损伤演化、损伤后力学特性的影响规律。提出基于全局统计信息的精确应变场的分析方法，结合结构微观损伤特征，揭示蜂窝夹芯试件多次低速冲击损伤扩展失效机理。由微观宏观跨尺度综合分析，提取含冲击损伤结构的承载力计算方法；揭示不同混合损伤模式对结构振动特性的影响规律，建立蜂窝夹芯板的自由振动模型。本项目的研究成果可为蜂窝夹芯结构多次低速冲击下损伤阻抗及损伤容限性能的分析和预测提供科学的实验依据。

蜂窝夹芯结构是航空航天等领域常用的结构，多次低速冲击是其服役时常见的损伤来源。多次低速冲击在在夹芯结构表面和内部产生损伤，使其力学性能大为降低，影响其服役安全。本研究针对多次低速冲击作用下夹芯结构动态响应的实验研究需要，开发了一套采集数据同步、变形计算加速比高的动态测量系统，包括发展了一种基于单相机的三维变形测量方法，发展了一种适合动态测量的数字图像相关快速计算方法，提出了基于自然纹理的标定方法，发展了基于径向基函数和应变片导向的逆向非均匀应变计算方法。通过实验和有限元仿真对蜂窝夹芯板在不同能量、不同频次冲击和准静态压缩作用下的应力传播、损伤产生、裂纹扩展等动态响应进行了研究，通过实验和数值计算对损伤后的剩余强度和振动特性进行了研究，为蜂窝夹芯结构多次低速冲击下损伤阻抗及损伤容限性能的分析和预测提供科学的实验依据。

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