【摘要】：加筋板是工程領(lǐng)域常見的輕量化結(jié)構(gòu),既能減輕結(jié)構(gòu)自重又能滿足結(jié)構(gòu)強度和剛度要求,被廣泛運用于航空航天等工業(yè)領(lǐng)域。目前采用機械噴丸工藝對加筋板進行成形時,存在帶筋板區(qū)域彎曲變形量不足的問題,亟需開展加筋板新型噴丸成形工藝研究。超聲波噴丸技術(shù)作為一種新型噴丸工藝,可以獲得比傳統(tǒng)機械噴丸更大更深的殘余壓應(yīng)力場,能大幅提高加筋板噴丸成形彎曲變形量,同時表面質(zhì)量和成形后綜合性能也優(yōu)于傳統(tǒng)機械噴丸,為加筋板提供了一種成形新途徑。本文運用超聲波噴丸成形工藝,以加筋板為研究對象,在超聲波噴丸板件成形理論分析的基礎(chǔ)之上,對超聲波噴丸加筋板成形的成形量、成形特性以及表面性能進行了研究,并結(jié)合數(shù)值分析方法對超聲波噴丸加筋板成形過程進行了模擬,主要研究工作如下:1.理論分析了超聲波噴丸的成形過程�；贖ertz碰撞理論,研究了超聲波噴丸過程中板件的變形情況和受力情況,探討了彈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,分析了殘余壓應(yīng)力場的產(chǎn)生過程以及板件彎曲變形和殘余應(yīng)力場的關(guān)系,推導(dǎo)了板件成形曲率半徑與殘余壓應(yīng)力的計算公式。2.對無筋壁板進行了超聲波噴丸成形試驗,分析了不同噴丸軌跡對無筋壁板曲率半徑的影響,研究發(fā)現(xiàn)采用展向噴丸軌跡可以在提高壁板弦向變形程度的同時降低展向變形程度,有利于改善壁板球面變形趨勢�；谡瓜驀娡柢壽E,對加筋板進行了超聲波噴丸成形試驗,對影響加筋板成形曲率半徑的主要噴丸工藝參數(shù)進行了研究,分析了加筋板基本彎曲變形規(guī)律。結(jié)果表明:在展向噴丸軌跡下,加筋板展向與弦向曲率半徑的比值基本在11倍以上,此時加筋板展向變形很小可忽略不計,加筋板近似呈現(xiàn)弦向單曲率變形趨勢。同時,還獲得了加筋板較優(yōu)成形工藝參數(shù)。3.對超聲波噴丸后加筋板試件的表面性能進行了研究,分析了不同噴丸工藝參數(shù)對試件表面形貌、表面粗糙度、顯微硬度以及殘余應(yīng)力場的影響。結(jié)果表明,與未噴丸試件相比,超聲波噴丸后,成形件的表面粗糙度有所增加、表面硬度得到增大、并在材料表層產(chǎn)生了呈“√”狀分布的有益殘余壓應(yīng)力場,這表明了超聲波噴丸成形技術(shù)是集塑性成形和沖擊強化為一體的新工藝。同時,還獲得了加筋板較優(yōu)表面性能參數(shù)。4.通過動態(tài)仿真與靜態(tài)仿真相結(jié)合的方法,建立了超聲波噴丸加筋板成形數(shù)值分析模型,利用有限元分析方法,研究了不同噴丸工藝參數(shù)對加筋板成形曲率半徑以及殘余應(yīng)力場的影響,并將數(shù)值分析結(jié)果和試驗結(jié)果進行比較,二者的數(shù)據(jù)誤差很小,驗證了有限元模型的可靠性,為研制開發(fā)大變形機翼壁板的超聲波噴丸成形工藝提供理論及數(shù)據(jù)參考。
[Abstract]:Stiffened plate is a common lightweight structure in engineering field. It can not only reduce the structural weight but also meet the requirements of structural strength and stiffness. It is widely used in aerospace and other industrial fields. In the process of mechanical shot peening, there is a problem of insufficient bending deformation in the stiffened plate area, so it is urgent to study the new shot peening process of stiffened plate. As a new type of shot peening technology, ultrasonic shot peening technology can obtain a larger and deeper residual compressive stress field than traditional mechanical shot peening, and can greatly increase the bending deformation of shot peening of stiffened plate. At the same time, the surface quality and the comprehensive properties after forming are better than those of traditional mechanical shot peening, which provides a new way for forming stiffened plate. Based on the theoretical analysis of ultrasonic shot peening plate forming, the forming quantity, forming characteristics and surface properties of ultrasonic shot peening plate are studied in this paper. Combined with numerical analysis method, the forming process of ultrasonic shot peening stiffened plate is simulated. The main research work is as follows: 1. The forming process of ultrasonic shot peening is analyzed theoretically. Based on Hertz collision theory, the deformation and stress of plate during ultrasonic shot peening are studied, and the diameter of crater before and after elastoplastic 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 analyzed. The process of producing the residual compressive stress field and the relationship between the bending deformation and the residual stress field of the plate are analyzed. The formula of curvature radius and residual compressive stress of sheet metal forming is derived. The ultrasonic shot peening test was carried out on the unstiffened wall plate, and the influence of different shot peening locus on the curvature radius of the unstiffened wall plate was analyzed. It was found that the spanned shot peening trajectory could increase the chordal deformation degree of the wall plate and reduce the spreading deformation degree at the same time. It is beneficial to improve the deformation trend of wall surface. Based on the trajectory of spanned shot peening, the ultrasonic shot peening test of stiffened plate was carried out. The main parameters affecting the curvature radius of stiffened plate were studied, and the basic bending deformation law of stiffened plate was analyzed. The results show that under the trajectory of shot peening, the ratio of spanned and chordal curvature radius of stiffened plate is above 11 times, at this time, the span deformation of stiffened plate can be neglected, and the stiffened plate approximately shows the tendency of chordal single curvature rate deformation. At the same time, the optimum forming process parameters of stiffened plate are obtained. The surface properties of stiffened plate after ultrasonic shot peening were studied. The effects of different parameters of shot peening on the surface morphology, surface roughness, microhardness and residual stress field were analyzed. The results show that after ultrasonic peening, the surface roughness and hardness of the formed parts are increased, and the beneficial residual compressive stress field is produced in the surface layer of the material. This indicates that ultrasonic shot peening is a new technology which integrates plastic forming and impact strengthening. At the same time, the optimum surface performance parameters of stiffened plate. By combining dynamic simulation with static simulation, the numerical analysis model of ultrasonic shot peening plate forming is established, and the finite element analysis method is used. The effects of different parameters of shot peening on the curvature radius and residual stress field of stiffened plate are studied. The numerical analysis results are compared with the experimental results. The data error between them is very small, which verifies the reliability of the finite element model. It provides a theoretical and data reference for the research and development of ultrasonic shot peening process for large deformed wing panels.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG668

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