摘要：粘接作为一种重要的连接技术而被广泛应用于工业生产领域。然而粘接结构在制造和使用过程中会出现界面缺陷，影响材料使用的寿命和安全性。为了确保粘接结构的产品质量和使用安全，对其粘接强度检测具有重要意义。传统的超声无损检测方法主要基于声波传播过程的声学信息变化来评价宏观损伤和缺陷，对粘接结构的微观性能变化，力学性能退化等不能有效的检测和评估。研究表明，超声波透过微观损伤的粘接界面会产生非线性现象，可以用非线性系数来表征微观损伤。

本文通过对铝合金粘接试件在粘接过程中的超声非线性研究，建立铝合金粘接界面固化性能与非线性系数之间的关系。利用设计的实验平台激励和接收超声波纵波，对得到的纵波信号进行傅里叶变换得到超声波纵波的基波和二次谐波，通过理论公式得到对应的非线性系数，进而分析得到固化时间和激励超声波纵波频率对铝合金粘接界面固化性能的影响。研究表明：选取频率为5MHz的脉冲波作为激发信号源激励粘接界面，得到的非线性系数最大，非线性效果最好；随着固化时间的增加，非线性系数逐渐减小，特别是在固化的初期，非线性系数随固化时间急速下降；环氧树脂粘接剂粘接试件粘接界面固化时间长，AB胶粘接的粘接试件固化时间短。

关键词：铝合金；粘接界面；超声非线性；非线性系数

Abstract：Bonding is widely used in industrial production as an important connection technology. However, the interface defects which appear in interface structure during the manufacture and in-service process would affect the safety and life of the structures. In order to ensure the quality and safety of the adhesive structures , the detection of adhesive strength   is of great significance. Based on the acoustic information changes of the acoustic wave propagation process, the traditional ultrasonic non-destructive testing method can evaluate the macroscopic damage and defects, but can not effectively detect and evaluate the micro-performance of the bonding structure and the degradation of the mechanical properties. Many studies have been shown that when the ultrasonic passes through the interface of the microscopic damage, non-linear phenomenon occurs which can be used to characterize the microscopic damages..

In this paper, the relationship between the curing properties of aluminum alloy bonded interface and the nonlinear coefficient was established by studying in the ultrasonic nonlinearity of the aluminum alloy bonded specimen during the bonding process. The fundamental wave and the second harmonic of the ultrasonic wave are obtained by fast Fourier transforming the obtained longitudinal wave signal . The corresponding nonlinear coefficients are obtained by the theoretical formula, and the influence of curing time and excitation frequence were also discussed.. The results show that 5MHz is the optimum test frequence which can produce maxmum acousic nonlinearity. With the increase of the curing time, the nonlinear coefficient is gradually reduced. Especially in initial stage of curing, the nonlinear coefficient  rapidly decreases with the curing time. The curing time of the adhesive interface of the epoxy resin adhesive is longer than that of AB glue.

Keywords: Aluminum   alloy;   Bonding   interface;   Ultrasonic nonlinearity; Nonlinear coefficient

目录

第一章绪论1

1.1金属粘接的重要作用和基本现状1

1.1.1引言1

1.1.2金属粘接的基本特征 2

1.1.3金属粘接的重要作用..2

1.1.4金属粘接的基本现状..3

1.2非线性超声检测方法的特色及优点.6