2A70铝合金激光诱导空化强化机理及其抗空蚀性能研究

发布时间：2018-08-09 15:13

【摘要】：空化现象普遍存在于流体机械领域中,当机械部件在液体中高速运动导致近部件区域形成低压区域,低压区域的压力差异形成空泡现象,在空泡脉动周期中冲击波和水射流作用对机械机构造成应力影响。激光诱导空化作为一门前沿的技术方法,因其激光空化泡的可操作性和球对称性,探索利用激光空泡脉动周期产生的力学作用作为强化方法,成为空化研究的重要方法。本文以激光诱导空化作为主要方法,试验研究激光能量变化和叠加作用对2A70铝合金机械性能的改性作用,并论证激光诱导空泡强化材料性能与延长使用寿命的具体效果。通过研究空泡强化在3.5%NaCl溶液中的机械性能变化,对在特殊环境(如海洋环境)中激光诱导空化强化效果的抗空蚀性能开展了论证模拟验证。研究内容和结果如下:(1)以流体力学方程为基础,对空泡空核的惯性生长、溃灭和回弹等动力学方程进行探讨,分析激光诱导空泡的初生与发展机理;以2A70铝合金为实验对象,研究了激光诱导空泡在固液分界面的趋璧效应以及空泡脉动对材料表面的脉动冲击和射流,分析其应力机理和热力学作用的影响。(2)构建了激光诱导空泡实验平台,差异分析研究了相同能量和实验条件下激光入射角度对实验靶材的作用影响;获得了不同激光能量强度和重复影响次数对材料粗糙度,残余应力和硬度的变化规律,证明了使用激光诱导空化强化这一新工艺的可行性;利用重复多次空化强化作用类比群空泡作用,表征了类似群空泡作用下材料强化效果,为群空泡多重作用的应用和推广提供实验参考和机理。(3)选取去离子水和3.5%的NaCl溶液中的材料进行空化空蚀实验,考虑空化的实际应用环境,获得了2A70铝合金的空化空蚀效应,并分析了空蚀后的力学性能,得到空蚀作用和化学作用的相互影响关系;通过对激光诱导空化强化前后的材料进行不同溶液环境中的超声波空蚀实验,测试实验的具体参数(硬度,残余应力和显微形貌)得出激光空化技术对抗空蚀性能的具体效果;对比相同激光强化效果下,在去离子水和3.5%NaCl溶液中抗空蚀实验的具体参数,论证了激光强化在不同液体环境中抗空蚀性能效果,总结获得了激光空化对材料的改性强化规律。
[Abstract]:Cavitation exists generally in the field of fluid machinery. When the mechanical components move at high speed in liquid, the low pressure region is formed in the near component region, and the pressure difference in the low pressure region forms the cavitation phenomenon. The effect of shock wave and water jet on the stress of mechanical mechanism during cavitation pulsation period. Laser induced cavitation is a frontier technique. Because of its maneuverability and spherical symmetry, it has become an important method to study cavitation by using the mechanical effect produced by laser cavitation cycle as a strengthening method. In this paper, laser induced cavitation is used as the main method to study the effect of laser energy change and superposition on the mechanical properties of 2A70 aluminum alloy, and to demonstrate the effect of laser induced cavitation strengthening material properties and prolonging service life. By studying the mechanical properties of cavitation enhancement in 3.5%NaCl solution, the anti-cavitation performance of laser induced cavitation enhancement in special environment (such as marine environment) is demonstrated and verified by simulation. The research contents and results are as follows: (1) based on the hydrodynamic equation, the dynamic equations of cavitation growth, collapse and springback are discussed, and the mechanism of laser induced cavitation is analyzed. The effect of laser induced cavitation on solid-liquid interface and the effect of cavitation pulsation on the pulsating impingement and jet on the material surface were studied. The stress mechanism and thermodynamics of the cavitation were analyzed. (2) an experimental platform for laser-induced cavitation was constructed. The effect of laser incident angle on the experimental target was studied by differential analysis under the same energy and experimental conditions, and the variation of the roughness, residual stress and hardness of the material with different laser energy intensity and repetition times was obtained. The feasibility of laser induced cavitation strengthening is proved, and the effect of material strengthening under similar group cavitation is characterized by repeated cavitation strengthening by analogy with group cavitation. It provides experimental reference and mechanism for the application and popularization of group cavitation multiple action. (3) cavitation erosion effect of 2A70 aluminum alloy is obtained by selecting the materials in deionized water and 3.5% NaCl solution and considering the actual application environment of cavitation. The mechanical properties after cavitation erosion were analyzed and the interaction between cavitation and chemical action was obtained. The ultrasonic cavitation erosion experiments were carried out on the materials before and after laser induced cavitation strengthening in different solution environments. The specific parameters (hardness, residual stress and micromorphology) of the experiment were measured to obtain the specific effect of laser cavitation technology on the cavitation resistance, and the specific parameters of the cavitation resistance experiment in deionized water and 3.5%NaCl solution were compared under the same laser hardening effect. The effect of laser hardening on cavitation corrosion resistance in different liquid environments was demonstrated, and the modification and strengthening rules of laser cavitation materials were summarized.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG665

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