液态金属薄层中的超声波空化特征及其效应研究

发布时间：2018-04-21 18:02

本文选题：超声波钎焊 + 超声空化　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：本文主要研究了超声波作用下窄间隙液态金属内部的超声波空化效应及其对母材表面的空蚀作用。目的在于揭示超声波辅助钎焊过程当中的超声物理现象，深化认识母材表面氧化膜破除的机制以及影响空蚀效果的因素，丰富超声波辅助钎焊的理论研究。首先采用高速摄像技术观察窄间隙钎料池内空化行为，主要观察空化泡的形态、分布以及随时间变化的特征并分析了影响空化强弱的因素，包括间隙、振幅及钎料种类。结果发现，在窄间隙金属内部空化泡的形态主要为瞬态空化泡，并且在板表面振幅均匀时，空化泡呈现中间多两边少的情况。空化泡在瞬态分布呈现不均匀性并且不是在所有位置都出现，但是在一段时间内空化泡的分布比较均匀，基本所有位置都会出现。研究了超声波钎焊过程当中的核心问题，即去除材料表面的氧化膜，超声波钎焊之所以能够焊接一些难焊的材料正是利用此点。分析了钎料池表面氧化膜的破除过程，即在氧化膜表面产生微裂纹—空蚀坑—空蚀坑扩大—氧化膜完全破除，分析在超声钎焊过程中影响空蚀的因素。采用ANSYS模拟板表面的振幅分布，FLUENT模拟间隙内部的声压分布情况，解释之前观察到的关于空化泡分布以及空蚀坑分布的现象。认为板表面振幅越大导致间隙内的声压越大，，造成空化效应越强导致空蚀效果越明显。
[Abstract]:In this paper, the ultrasonic cavitation effect of liquid metal with narrow gap and its cavitation erosion on the base metal surface under the action of ultrasonic wave are studied. The purpose of this paper is to reveal the ultrasonic physical phenomena in the process of ultrasonic assisted brazing, to deepen the understanding of the mechanism of oxide film breaking on the base metal surface and the factors affecting the cavitation corrosion effect, and to enrich the theoretical study of ultrasonic assisted brazing. The cavitation behavior in the narrow gap brazing pool was observed by high speed camera technique. The morphology, distribution and variation characteristics of cavitation bubbles with time were observed, and the factors affecting the cavitation intensity, including clearance, amplitude and type of solder, were analyzed. The results show that the cavitation bubble in the narrow gap metal is mainly transient cavitation bubble, and when the amplitude of the plate surface is uniform, the cavitation bubble appears to be more and less in the middle. Cavitation bubbles are distributed inhomogeneously in transient state and not in all locations, but they are more uniform in a certain period of time, and almost all of them will appear. The core problem of ultrasonic brazing is to remove the oxide film from the surface of materials. The reason why ultrasonic brazing can weld some difficult materials is to make use of this point. The process of breaking the oxide film on the surface of the solder pool is analyzed, that is, the micro-crack, the cavitation pit, the expansion of the cavitation pit and the oxide film are completely broken on the surface of the oxide film, and the factors affecting the cavitation erosion in the ultrasonic brazing process are analyzed. The amplitude distribution on the surface of the plate was simulated by ANSYS and fluent was used to simulate the sound pressure distribution inside the gap to explain the phenomena of cavitation bubble distribution and cavitation pit distribution observed before. It is considered that the larger the amplitude of the plate surface is, the greater the sound pressure in the gap is, and the stronger the cavitation effect is, the more obvious the cavitation effect is.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TG454;TB559

【参考文献】