【摘要】：空化現(xiàn)象普遍存在于流體機(jī)械領(lǐng)域中,當(dāng)機(jī)械部件在液體中高速運(yùn)動(dòng)導(dǎo)致近部件區(qū)域形成低壓區(qū)域,低壓區(qū)域的壓力差異形成空泡現(xiàn)象,在空泡脈動(dòng)周期中沖擊波和水射流作用對(duì)機(jī)械機(jī)構(gòu)造成應(yīng)力影響。激光誘導(dǎo)空化作為一門前沿的技術(shù)方法,因其激光空化泡的可操作性和球?qū)ΨQ性,探索利用激光空泡脈動(dòng)周期產(chǎn)生的力學(xué)作用作為強(qiáng)化方法,成為空化研究的重要方法。本文以激光誘導(dǎo)空化作為主要方法,試驗(yàn)研究激光能量變化和疊加作用對(duì)2A70鋁合金機(jī)械性能的改性作用,并論證激光誘導(dǎo)空泡強(qiáng)化材料性能與延長(zhǎng)使用壽命的具體效果。通過研究空泡強(qiáng)化在3.5%NaCl溶液中的機(jī)械性能變化,對(duì)在特殊環(huán)境(如海洋環(huán)境)中激光誘導(dǎo)空化強(qiáng)化效果的抗空蝕性能開展了論證模擬驗(yàn)證。研究?jī)?nèi)容和結(jié)果如下:(1)以流體力學(xué)方程為基礎(chǔ),對(duì)空泡空核的慣性生長(zhǎng)、潰滅和回彈等動(dòng)力學(xué)方程進(jìn)行探討,分析激光誘導(dǎo)空泡的初生與發(fā)展機(jī)理;以2A70鋁合金為實(shí)驗(yàn)對(duì)象,研究了激光誘導(dǎo)空泡在固液分界面的趨璧效應(yīng)以及空泡脈動(dòng)對(duì)材料表面的脈動(dòng)沖擊和射流,分析其應(yīng)力機(jī)理和熱力學(xué)作用的影響。(2)構(gòu)建了激光誘導(dǎo)空泡實(shí)驗(yàn)平臺(tái),差異分析研究了相同能量和實(shí)驗(yàn)條件下激光入射角度對(duì)實(shí)驗(yàn)靶材的作用影響;獲得了不同激光能量強(qiáng)度和重復(fù)影響次數(shù)對(duì)材料粗糙度,殘余應(yīng)力和硬度的變化規(guī)律,證明了使用激光誘導(dǎo)空化強(qiáng)化這一新工藝的可行性;利用重復(fù)多次空化強(qiáng)化作用類比群空泡作用,表征了類似群空泡作用下材料強(qiáng)化效果,為群空泡多重作用的應(yīng)用和推廣提供實(shí)驗(yàn)參考和機(jī)理。(3)選取去離子水和3.5%的NaCl溶液中的材料進(jìn)行空化空蝕實(shí)驗(yàn),考慮空化的實(shí)際應(yīng)用環(huán)境,獲得了2A70鋁合金的空化空蝕效應(yīng),并分析了空蝕后的力學(xué)性能,得到空蝕作用和化學(xué)作用的相互影響關(guān)系;通過對(duì)激光誘導(dǎo)空化強(qiáng)化前后的材料進(jìn)行不同溶液環(huán)境中的超聲波空蝕實(shí)驗(yàn),測(cè)試實(shí)驗(yàn)的具體參數(shù)(硬度,殘余應(yīng)力和顯微形貌)得出激光空化技術(shù)對(duì)抗空蝕性能的具體效果;對(duì)比相同激光強(qiáng)化效果下,在去離子水和3.5%NaCl溶液中抗空蝕實(shí)驗(yàn)的具體參數(shù),論證了激光強(qiáng)化在不同液體環(huán)境中抗空蝕性能效果,總結(jié)獲得了激光空化對(duì)材料的改性強(qiáng)化規(guī)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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG146.21;TG665

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