小试件材料弹性常数超声测量线聚焦PVDF探头的研制

Design of line-focus PVDF ultrasonic transducer for elastic constant measurement of limited-size samples

本文针对小试件材料力学性能测试的特殊需求,利用PVDF压电薄膜设计制作了无透镜柱面线聚焦超声探头。文中介绍了探头材料的选择和结构参数的确定,对探头性能进行了数值模拟。该探头具有孔径角大、频带宽、中心频率高等特点。采用线聚焦PVDF探头的弹性常数超声测量系统对多种小试件材料进行了弹性常数测量,测量结果表明,本系统具有波形清晰,信噪比大。分辨率高,测量误差小,结果准确等特点,能够满足工程实验和科学研究的需要。由于线聚焦探头可以发射与聚焦线垂直的表面波,因此,基于线聚焦PVDF探头的小试件材料弹性常数超声精密测量系统,不仅适用于各向同性材料,而且适用于各向异性材料。

A line-focus PVDF transducer for material elastic constant measurement of small samples was developed, which aims at the especial needs of testing mechanical properties of bulk nano-materials. This paper presents the design and fabrication of the transducer. Simulations for several specifications of the transducer are carried out. This line-focus PVDF transducer is a large aperture angle, wideband, high-frequency line-focus beam transducer, and is constructed using 28um thick piezoelectric polyvinylidene fluoride （PVDF） film. An ultrasonic measurement system was built, which adopts the line-focus PVDF transducer and is based on acoustic microscope technology. Using this system, the material elastic constants are determined by measuring the longitudinal wave and leak surface wave velocities simultaneously. Experimental results show that this system works well and can satisfy the requirement of engineering and scientific research. Besides, the line-focus PVDF transducer can launch surface acoustic wave in the specific direction perpendicular to the focus line, so it can be further applied for the study of anisotropic material.