發(fā)布時(shí)間：2018-11-15 08:32

【摘要】：超聲波噴丸成形技術(shù)具有設(shè)備簡(jiǎn)單、操作便攜、綠色無污染、能耗少、成形后材料綜合性能好等諸多優(yōu)勢(shì),在航空航天、國(guó)防工業(yè)、船舶汽車工業(yè)、建筑等眾多領(lǐng)域中具有非常廣闊的應(yīng)用前景。但是在自由狀態(tài)下,超聲波噴丸成形也易發(fā)生球面變形,而實(shí)際需要的零件外形并不總是要求是球面的,一旦發(fā)生球面變形,想要消除或改變非常困難,而預(yù)應(yīng)力噴丸成形不僅能夠提高零件的成形曲率,還能在一定程度上減小球面變形趨勢(shì)。本文結(jié)合預(yù)應(yīng)力噴丸成形和超聲波噴丸成形兩種工藝方法,以薄壁板為研究對(duì)象,在超聲波噴丸成形過程理論分析的基礎(chǔ)上,對(duì)預(yù)應(yīng)力超聲波噴丸成形的成形機(jī)理、成形特性以及表面層性能進(jìn)行了系統(tǒng)的研究,并結(jié)合數(shù)值分析方法對(duì)預(yù)應(yīng)力超聲波噴丸的成形過程進(jìn)行了模擬,主要研究工作如下:(1)理論分析了超聲波噴丸的成形過程。以碰撞理論為依據(jù),對(duì)超聲波噴丸過程中板料的力學(xué)狀態(tài)進(jìn)行分析,推導(dǎo)出了板料分別發(fā)生彈性變形和彈塑性變形時(shí)撞針的臨界速度,探討了塑性變形前后凹坑直徑、凹坑深度和沖擊力的大小以及回彈后殘余應(yīng)力沿深度方向的分布關(guān)系,并推導(dǎo)出了預(yù)應(yīng)力狀態(tài)下殘余應(yīng)力的計(jì)算公式,對(duì)比分析了自由狀態(tài)和預(yù)應(yīng)力狀態(tài)成形曲率半徑。(2)對(duì)2024-T351鋁合金薄壁板進(jìn)行了預(yù)應(yīng)力超聲波噴丸成形試驗(yàn)研究,分析了預(yù)彎曲率、成形軌跡、撞針?biāo)俣取⑵镁嚯x以及壁板厚度對(duì)壁板成形曲率半徑的影響,結(jié)果表明了預(yù)應(yīng)力超聲波噴丸能夠大幅度增大壁板展向(預(yù)彎方向)的成形曲率并減小弦向的成形曲率,隨著預(yù)彎曲率的增加,減小和增大的效應(yīng)隨之逐漸增大,大幅度減小了球面變形趨勢(shì)。(3)對(duì)預(yù)應(yīng)力超聲波噴丸后成形件的表面層性能進(jìn)行了研究,分析了不同工藝參數(shù)對(duì)試樣件的表面形貌、表面粗糙度、顯微硬度以及殘余應(yīng)力場(chǎng)的影響,與自由狀態(tài)相比,預(yù)應(yīng)力狀態(tài)下成形件的表面粗糙度值略有減小,表面硬度增大,并在材料的表面層產(chǎn)生了更大更深的呈典型的“√”狀分布的殘余壓應(yīng)力場(chǎng),表明了預(yù)應(yīng)力超聲波噴丸能夠獲得更好的表面性能。(4)利用ABAQUS軟件建立了預(yù)應(yīng)力超聲波噴丸成形數(shù)值分析模型,分析了不同參數(shù)對(duì)壁板成形曲率以及殘余應(yīng)力場(chǎng)的影響,并將數(shù)值分析結(jié)果和試驗(yàn)結(jié)果進(jìn)行比較,二者的數(shù)據(jù)誤差很小,驗(yàn)證了預(yù)應(yīng)力超聲波噴丸成形有限元模型的可靠性,為研制開發(fā)機(jī)翼整體壁板的超聲波噴丸成形工藝提供理論及數(shù)據(jù)參考。
[Abstract]:Ultrasonic shot peening technology has many advantages, such as simple equipment, portable operation, no pollution, less energy consumption, good comprehensive properties of materials after forming, and so on. Architecture and many other fields have a very broad application prospects. But in the free state, the ultrasonic shot peening is also prone to spherical deformation, and the actual part shape is not always required to be spherical, once the spherical deformation occurs, it is very difficult to eliminate or change. Prestressed shot peening can not only improve the forming curvature of parts, but also reduce the deformation trend of spherical surface to a certain extent. In this paper, based on the theoretical analysis of the ultrasonic shot peening process, the forming mechanism of pre-stressed ultrasonic shot peening is analyzed, which is based on the pre-stressed shot peening and ultrasonic shot peening, and the thin-walled plate is taken as the research object. The forming characteristics and surface layer properties are studied systematically, and the pre-stressed ultrasonic shot peening process is simulated with numerical analysis method. The main research work is as follows: (1) the forming process of ultrasonic shot peening is analyzed theoretically. Based on the collision theory, the mechanical state of sheet metal during ultrasonic shot peening is analyzed, and the critical velocity of crashing needle in elastic deformation and elastoplastic deformation of sheet metal is deduced, and the diameter of crater before and after plastic deformation is discussed. The relationship between the depth of the pit and the impact force and the distribution of the residual stress along the depth after springback is derived, and the formula for calculating the residual stress in the state of prestress is derived. The curvature radius of 2024-T351 aluminum alloy thin-walled plate was compared and analyzed. (2) the pre-bending rate, forming track and pin speed of 2024-T351 aluminum alloy thin-walled plate were studied by prestressing ultrasonic shot peening. The results show that prestressed ultrasonic shot peening can greatly increase the forming curvature and decrease the chord curvature of the wall plate, which is influenced by the offset distance and the thickness of the wall plate, and the results show that the ultrasonic shot peening can greatly increase the shape curvature of the plate in the development direction (prebending direction) and decrease the forming curvature in the chord direction. With the increase of prebending ratio, the effect of decreasing and increasing gradually increases, which greatly reduces the tendency of spherical deformation. (3) the surface layer properties of prestressing ultrasonic shot peening are studied. The effects of different process parameters on the surface morphology, surface roughness, microhardness and residual stress field of the specimen are analyzed. Compared with the free state, the surface roughness value of the formed part in the prestressing state is slightly reduced, and the surface hardness increases. A larger and deeper residual compressive stress field is produced in the surface layer of the material with a typical "squared" distribution. The results show that the prestressing ultrasonic shot peening can obtain better surface performance. (4) the numerical analysis model of pre-stressed ultrasonic shot peening is established by using ABAQUS software, and the influence of different parameters on the curvature and residual stress field of slabs is analyzed. The numerical analysis results are compared with the experimental results, and the data error between them is very small, which verifies the reliability of the finite element model of pre-stressed ultrasonic shot peening. It provides theoretical and data reference for the research and development of ultrasonic shot peening process for wing integral panel.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG668

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