多层金属粘接结构粘接质量的超声检测

【作者】 徐猛；

【导师】 徐彦霖；

【作者基本信息】 中国工程物理研究院 ， 机械制造及自动化， 2007， 硕士

【摘要】 粘接结构由于具有比强度、比模量高等特点，被广泛应用于航空航天、军工等重要部门。但是粘接过程中易出现粘接不良、气孔、局部脱粘等缺陷，破坏粘接结构的完整性。目前，超声检测已经成为粘接结构无损检测应用最广的技术之一。对金属-非金属粘接结构的超声检测技术研究较早，已趋于成熟，但是对多层金属粘接结构的超声检测研究较少。本文即是基于实际生产需要，针对多层金属粘接结构粘接质量的超声检测技术展开研究。本文首先根据产品的实际要求，设计了不同层数的金属平板粘接试样，建立了各种粘接试样的声学物理模型。针对不同的粘接试样，分析了不同检测方法的适用性。结合超声波在多层介质中的透射模型，分析了水浸透射法检测过程中不同频率的超声波在三层以上金属粘接结构中的声压透射率及能量损失情况。结果表明：对于两层金属粘接试样，直接接触多次反射底波法和水浸透射法都能够检测出人工缺陷；对于三层金属粘接结构，5MHz、2MHz、1MHz的水浸聚焦探头均能检测第二粘接界面的人工缺陷；对于四层金属粘接结构，5MHz的超声波在粘接层中损失殆尽，难以检测第三粘接界面的缺陷，而2MHz、1MHz的水浸聚焦探头却可以实现。在分析了粘接结构声学特性的基础上，提出了低频水浸聚焦超声换能器的设计方案。从晶片的选择、背衬的设计及优化、声透镜的设计等三个方面展开低频水浸聚焦换能器的设计。并提出了具体的设计指标。采用自行设计的水浸聚焦超声换能器及现有的5MHz的水浸聚焦换能器对粘接试样进行检测实验。实验结果表明：对于两层金属粘接结构，水浸透射法和纵波探头直接接触多次底波法都能检测出Φ6mm缺陷；对于三层金属粘接结构，水浸透射法能够较好的实现第二粘接界面Φ6mm缺陷的检测，但是5MHz的水浸聚焦换能器的缺陷检出能力明显高于2MHz、1MHz的水浸聚焦换能器；对于四层金属粘接结构，2MHz、1MHz的水浸聚焦换能器能够检测出第三粘接界面Φ6mm缺陷，但是5MHz的水浸聚焦换能器由于超声波能量的大幅损失无法完成检测。这与理论分析的结果基本一致。为同类粘接结构粘接质量的超声检测提供了一定的可借鉴经验。更多还原

【Abstract】 Adhesive structure is widely applied in aviation & aerospace, war industry and other important fields, because of its high specific strength and specific modulus characteristics. However, it is easy to appear defects during bonding process, such as weak bonding, air hole, local debonding and so on, to destroy the integrality of the adhesive structure. At present, ultrasonic testing has already become one of the most widely-applied techniques in NDT of adhesive structure. Researches on the ultrasonic testing of multi-layered metal-nonmetal adhesive structure begin earlier, and tend to be ripe, but those of multi-layered metal-metal adhesive structure are less. According to the actual production need, this paper researches on the bonding qualities of multi-layered metal-metal.This paper according to the actual need of production, designed different layered bonding samples of metal-metal plane, established respective acoustic models, and analysed the applicability of different testing methods. Then associated with transmission model of ultrasonic in multi-layered media, this paper analysed its sound pressure transmissivities and energy losses in above three-layered metal-metal adhesive structure by immersion testing under different frequencies. The analysis result showed that both multiple echo method with direct contact and immersion testing could detect the position of the artificial defect in two-layered adhesive structure; immersion focusing probes with frequencies of 5MHz, 2 MHz and 1 MHz all could detect the artificial defect on the second bonding interface of the three-layered adhesive structure; and in four-layered adhesive structure, immersion focusing probe with frequency of 5MHz was difficult to detect the defect because of the attenuation in media, but those of 2 MHz and 1 MHz could be used to detect.On the basis of analysis of the acoustic properties of the adhesive structure, this paper proposed the contrivance of low-frequency immersion focusing probe. According to the contrivance , it planed to design the probe from chips choice, backing design and optimization and acoustic lens design, and specific design index are also proposed.Finally, testing experiments of bonding samples were carried on by self-design immersion focusing probe and 5 MHz probe, the experiments result showed that multiple echo method with direct contact and immersion testing could detect the 06mm defect in two-layered adhesive structure; immersion testing could achieve better detection of 06mm defect on the second bonding interface of the three-layered adhesive structure, but the capacity of detection of 5MHz probe was obviously higher than 2MHz and 1MHz probes; and in four-layered adhesive structure, 2 MHz and 1 MHz probes could detect 06mm defect on the third bonding interface, but 5MHz probe could not complete the detection because of the large energy loss. This was basically consistent with the theoretical analysis result mentioned above, and provided certain available experience for ultrasonic testing of similar adhesive structure.更多还原