【摘要】：熱障涂層(Thermal Barrier Coatings,簡(jiǎn)稱TBCs)的隔熱性能優(yōu)異,能夠顯著降低發(fā)動(dòng)機(jī)的油耗并延長(zhǎng)服役壽命,目前已經(jīng)廣泛應(yīng)用于航空發(fā)動(dòng)機(jī)。發(fā)動(dòng)機(jī)在工作時(shí),涂層不可避免的會(huì)受到粉塵、硬質(zhì)顆粒的撞擊,使得涂層剝落,這一失效方式被稱為沖蝕失效。物理氣相沉積(Electron Beam-Physical Vapor Deposition,簡(jiǎn)稱EB-PVD)TBCs高溫沖蝕的典型特征為塑性區(qū)、密實(shí)區(qū)以及拐彎帶,其中拐彎帶是最有可能萌生裂紋的位置之一,因此引起了學(xué)術(shù)界的廣泛關(guān)注。傳統(tǒng)的EB-PVD沖蝕有限元模型都是用平行的規(guī)則柱狀晶來(lái)表示陶瓷層,忽略了陶瓷層的真實(shí)形貌和存在的缺陷,因此本文考慮了陶瓷層的真實(shí)形貌,建立了真實(shí)微觀結(jié)構(gòu)EB-PVD沖蝕模型,從拐彎帶和應(yīng)力場(chǎng)等方面分析了簡(jiǎn)單模型和真實(shí)模型的區(qū)別。主要研究?jī)?nèi)容如下:第一:利用CAD軟件以及圖像處理技術(shù)建立了真實(shí)微觀結(jié)構(gòu)沖蝕有限元模型。確立了陶瓷層的材料模型,由于陶瓷層是多孔的結(jié)構(gòu),因此選用GTN模型來(lái)表示柱狀晶,間隙則用低密度的泡沫模型來(lái)表示。第二:從應(yīng)力場(chǎng)、粒子壓入深度等方面分析了簡(jiǎn)單模型和真實(shí)微觀結(jié)構(gòu)模型的沖蝕差異,結(jié)果表明由于兩種模型的柱狀晶材料均采用理想彈塑性模型,因此兩種模型的無(wú)量綱粒子最大壓入深度和速度隨時(shí)間的變化是基本相同的;應(yīng)力場(chǎng)分析表明,幾何形貌對(duì)碰撞后的應(yīng)力影響很大,相同條件下真實(shí)微觀結(jié)構(gòu)模型的應(yīng)力明顯的大于簡(jiǎn)單模型的,裂紋擴(kuò)展的粒子臨界無(wú)量綱動(dòng)能也小于簡(jiǎn)單模型的無(wú)量綱動(dòng)能。這些結(jié)果表明在模擬涂層的沖蝕失效時(shí),我們有必要將EB-PVD的真實(shí)微觀形貌考慮進(jìn)去。第三:拐彎帶是EB-PVD熱障涂層高溫沖蝕的典型特征,本文首先研究了簡(jiǎn)單模型沖蝕參數(shù)對(duì)拐彎帶形成的影響,模擬發(fā)現(xiàn)粒子的初速度越大、半徑越大時(shí),拐彎帶傾斜的程度越嚴(yán)重;柱狀晶的長(zhǎng)細(xì)比越大,粒子的壓入深度越大,拐彎帶形成越明顯;其次對(duì)比分析了簡(jiǎn)單模型和真實(shí)模型拐彎帶形成規(guī)律,結(jié)果表明由于真實(shí)模型柱狀晶的尺寸不均勻,模型中柱狀晶越大,拐彎帶越難形成;垂直入射時(shí),簡(jiǎn)單模型的拐彎帶是對(duì)稱分布的,而真實(shí)模型拐彎帶分布并不是對(duì)稱分布的。
[Abstract]:Thermal barrier coating (Thermal Barrier Coatings,) has been widely used in aero-engines due to its excellent thermal insulation performance, which can significantly reduce engine fuel consumption and prolong service life. When the engine is working, the coating will inevitably be hit by dust and hard particles, which makes the coating flake. This failure mode is called erosion failure. The typical characteristics of Electron Beam-Physical Vapor Deposition, (EB-PVD) TBCs high temperature erosion are plastic zone, dense zone and bend zone, among which the bend zone is one of the most likely crack initiation sites. As a result, the academic community has attracted wide attention. The traditional finite element model of EB-PVD erosion is to represent the ceramic layer by parallel regular columnar crystals, ignoring the true morphology and defects of the ceramic layer, so the true morphology of the ceramic layer is considered in this paper. The EB-PVD erosion model of real microstructure is established, and the difference between the simple model and the real model is analyzed in terms of bend zone and stress field. The main research contents are as follows: first, the real microstructure erosion finite element model is established by using CAD software and image processing technology. The material model of the ceramic layer is established. Because the ceramic layer is porous, the GTN model is used to represent the columnar crystal and the gap is expressed by the low-density foam model. Second, the erosion difference between the simple model and the real microstructure model is analyzed in terms of stress field, particle indentation depth and so on. The results show that the ideal elastic-plastic model is used in the columnar materials of the two models. Therefore, the maximum depth and velocity of dimensionless particles in the two models are basically the same as those of time. The results of stress field analysis show that the geometrical morphology has a great influence on the stress after collision, and the stress of the real microstructure model is obviously larger than that of the simple model under the same conditions. The critical dimensionless kinetic energy of the crack propagation is also smaller than that of the simple model. These results indicate that it is necessary to take the true microstructure of EB-PVD into account when simulating the erosion failure of the coating. Third, the bending zone is a typical feature of EB-PVD thermal barrier coating erosion at high temperature. In this paper, the influence of the erosion parameters of the simple model on the formation of the curved zone is studied. The simulation results show that the larger the initial velocity of particles is, the larger the radius is. The degree of inclination in the bend zone is more serious; The larger the slenderness ratio of columnar crystals is, the greater the depth of impingement is, and the more obvious the bend zone is. The results show that the bigger the columnar crystal in the real model is, the more difficult it is to form the corner zone because of the uneven size of the columnar crystal in the real model. When the incidence is perpendicular, the curve distribution of the simple model is symmetrical, but the distribution of the real model is not symmetrical.
【學(xué)位授予單位】：湘潭大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG174.4

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本文編號(hào)：2298528