本文選題：柔性成形 + 拉伸成形　； 參考：《吉林大學(xué)》2017年博士論文

【摘要】：拉伸成形是大尺寸、小曲率蒙皮類件的主要成形方法,與傳統(tǒng)模具沖壓成形比較,具有零件回彈小、成形精度高的優(yōu)點(diǎn),但設(shè)備研制成本高,一般只用于航空、航天領(lǐng)域。隨著航空、航天工業(yè)的快速發(fā)展,蒙皮的生產(chǎn)周期要求越來越短,形狀更是向著個(gè)性化、復(fù)雜化的方向發(fā)展,這對傳統(tǒng)拉伸成形方法提出了新的挑戰(zhàn)。傳統(tǒng)拉伸成形存在兩方面弊端:一方面整體模具體積大、數(shù)量多,生產(chǎn)周期長,儲(chǔ)運(yùn)成本高,重復(fù)利用率低;另一方面拉伸成形機(jī)柔性程度低,成形過程板料不易貼模,材料利用率低,變形不均勻,易出現(xiàn)拉裂、起皺等缺陷。可見,沿用傳統(tǒng)拉伸成形技術(shù)已經(jīng)無法滿足新形式下的蒙皮生產(chǎn)需要。此外,國內(nèi)拉伸成形設(shè)備以進(jìn)口為主,歐美等發(fā)達(dá)國家掌控設(shè)備制造的核心技術(shù),高昂的設(shè)備售價(jià)令中小企業(yè)難以承受。因此,生產(chǎn)具有自主知識(shí)產(chǎn)權(quán)的柔性化拉伸成形設(shè)備已經(jīng)成為我國工業(yè)發(fā)展的迫切需求。高柔性拉伸成形設(shè)備是由我國自主研發(fā)的新型拉伸成形設(shè)備,包括高柔性模具和高柔性拉伸成形機(jī)。高柔性模具使用多點(diǎn)數(shù)字化模具代替?zhèn)鹘y(tǒng)的整體模具,可以一模多用、降低模具制造成本和縮短模具生產(chǎn)周期。高柔性拉伸成形機(jī)通過離散夾鉗的自協(xié)調(diào)作用實(shí)現(xiàn)板料貼模,能夠提高成形質(zhì)量、材料利用率和生產(chǎn)效率。另外高柔性拉伸成形設(shè)備簡化了控制系統(tǒng),制造成本降低,價(jià)格便于中小企業(yè)接受,有利于該技術(shù)在其它領(lǐng)域的應(yīng)用推廣。本課題以多點(diǎn)模具和高柔性拉伸成形機(jī)為主線展開研究,采用有限元數(shù)值模擬和試驗(yàn)相結(jié)合的方法分析板料拉伸成形過程,旨在優(yōu)化加工工藝、提高零件的成形質(zhì)量,同時(shí)也為工業(yè)生產(chǎn)和新型拉伸成形設(shè)備的研制提供科學(xué)的指導(dǎo)。本文的主要內(nèi)容和結(jié)論如下:1.高柔性拉伸成形原理及成形過程力學(xué)分析對高柔性拉伸成形原理、技術(shù)特點(diǎn)及成形過程進(jìn)行分析;分析高柔性拉伸成形時(shí)板料內(nèi)部的應(yīng)力、應(yīng)變變化過程;對板料內(nèi)部拉力以及卸載回彈量進(jìn)行推導(dǎo)計(jì)算;給出毛坯尺寸的選擇依據(jù)和成形質(zhì)量的評定標(biāo)準(zhǔn)。2.建立高柔性拉伸成形有限元模型對有限元數(shù)值模擬的動(dòng)力顯式、靜力隱式的求解算法以及材料的彈塑性本構(gòu)關(guān)系進(jìn)行探討;建立高柔性拉伸成形有限元模型及板料回彈模型。3.拉伸成形機(jī)的結(jié)構(gòu)分析及數(shù)值模擬對高柔性拉伸成形機(jī)的主要部件(夾料機(jī)構(gòu)、拉料機(jī)構(gòu)、萬向結(jié)構(gòu))進(jìn)行結(jié)構(gòu)分析;采用有限元數(shù)值模擬方法分析夾鉗離散化程度、夾鉗間隙、加載幅值對成形結(jié)果的影響。分析表明:隨著夾鉗數(shù)量的增加,板料貼模效果逐漸變好,成形質(zhì)量提高;隨著夾鉗間隙的增加,成形件的應(yīng)力、應(yīng)變分布均勻程度先提高后降低,間隙過大,成形區(qū)出現(xiàn)起皺現(xiàn)象,在板料寬度為1200mm,10個(gè)夾鉗的工況下,夾鉗間隙為其寬度的1/9時(shí),成形效果最佳;成形力按合理的幅值加載能夠提高成形質(zhì)量。4.高柔性拉伸成形時(shí)基本體排列方式的研究對高柔性拉伸成形件的壓痕形式及其產(chǎn)生原因進(jìn)行分析,提出了通過改變基本體排列方式抑制成形件表面缺陷的方法。以球形件、鞍形件為研究對象,采用有限元數(shù)值模擬和拉伸成形試驗(yàn)相結(jié)合的方法比較了常規(guī)排列、傾斜交錯(cuò)排列、平行交錯(cuò)排列的多點(diǎn)模具對成形結(jié)果的影響。結(jié)果表明:球頭壓窩和拉伸溝是成形件表面的主要缺陷,交錯(cuò)排列的多點(diǎn)模具能夠有效地抑制壓痕缺陷,提高成形件的表面質(zhì)量和成形精度,比常規(guī)排列的多點(diǎn)模具成形效果更好。5.研究基本體球頭形式對成形結(jié)果的影響推導(dǎo)出球頭與板料相切的幾何條件,基于擺動(dòng)球頭多點(diǎn)模具建立拉伸成形有限元模型,采用有限元數(shù)值模擬和拉伸成形試驗(yàn)相結(jié)合的方法分析擺動(dòng)球頭對成形結(jié)果的影響。分析表明:基本體球頭半徑小于與板料相切的臨界半徑時(shí),隨著球頭半徑增加,成形質(zhì)量提高,球頭半徑大于臨界半徑時(shí),隨著球頭半徑增加,表面質(zhì)量下降。擺動(dòng)球頭模具代替固定球頭模具能夠有效抑制成形件表面壓痕,降低回彈,提高了成形質(zhì)量。交錯(cuò)排列的多點(diǎn)模具使用擺動(dòng)球頭的成形效果優(yōu)于常規(guī)排列的多點(diǎn)模具。6.研究摩擦條件對成形結(jié)果的影響通過摩擦試驗(yàn)測定不同摩擦接觸對在干摩擦和油潤滑條件下的摩擦系數(shù);采用有限元數(shù)值模擬方法研究板料與模具之間的摩擦條件對成形結(jié)果的影響;通過有限元數(shù)值模擬和拉伸成形試驗(yàn)相結(jié)合的方法研究多點(diǎn)模具和彈性墊、彈性墊與彈性墊之間的摩擦條件組合對成形結(jié)果的影響。結(jié)果表明:板料與模具之間為干摩擦?xí)r,成形件有效成形區(qū)成形效果更好,但過渡區(qū)的應(yīng)力、應(yīng)變較大,用油潤滑的方法可以有效降低過渡區(qū)的應(yīng)力、應(yīng)變;在存在多個(gè)接觸對時(shí),保持各接觸對之間為干摩擦,有效成形區(qū)成形效果更好,彈性墊與彈性墊之間使用油潤滑時(shí),成形效果較差。7.研究彈性墊對高柔性拉伸成形的影響以球形件為研究對象,采用有限元數(shù)值模擬方法分析彈性墊厚度、硬度、層數(shù)對成形件表面質(zhì)量和成形誤差的影響;對板料貼模的判定方法和誤差補(bǔ)償?shù)膶?shí)現(xiàn)方法進(jìn)行探討。結(jié)果表明:彈性墊厚度增加,成形件表面質(zhì)量提高,但成形誤差增大;彈性墊硬度越大,成形件表面質(zhì)量和成形精度越高;相同厚度的彈性墊,隨著層數(shù)增加,成形件表面質(zhì)量和成形精度降低,但回彈量同時(shí)減小;使用剖面法判斷板料貼模更簡單;多點(diǎn)模具通過模具型面修正法可以快速實(shí)現(xiàn)誤差補(bǔ)償。
[Abstract]:Tensile forming is the main forming method of large size and small curvature skin parts. Compared with traditional die stamping, it has the advantages of small springback and high forming precision. But the cost of the equipment is high, and the equipment is usually used in aviation and space industry. With the rapid development of aerospace industry, the production cycle of the skin is shorter and more shaped. In the direction of individualization and complicating, it poses a new challenge to the traditional drawing method. There are two disadvantages in traditional drawing forming. On the one hand, the whole mold has large volume, large quantity, long production cycle, high cost of storage and transportation, low reuse rate, low flexibility of the other side stretch forming machine, and the forming process is not easy to paste. The material utilization rate is low, the deformation is not uniform, it is easy to crack, wrinkle and so on. It can be seen that the traditional drawing technology has been unable to meet the needs of the skin production in the new form. In addition, the domestic tensile forming equipment is mainly imported, the European and American developed countries control the core technology of the equipment manufacturing, and the high price of the equipment makes the small and medium enterprises. It is difficult to bear. Therefore, the production of flexible tensile forming equipment with independent intellectual property has become an urgent demand for the development of China's industry. The high flexible stretch forming equipment is a new type of tensile forming equipment developed by our country, including high flexible die and high flexible stretch forming machine. For the whole traditional mold, can use the first mock exam, reduce the manufacturing cost and shorten the manufacturing cycle of the mould. High flexible stretch forming machine by discrete clamp self coordinating role in the process of sheet metal punch, can improve the forming quality, material utilization and production efficiency. In addition high flexible stretch forming device simplifies the control system. Manufacturing cost The price is easy to be accepted by small and medium enterprises and is beneficial to the application and popularization of the technology in other fields. This subject is to study the main line of multi point die and high flexible stretch forming machine, and analyze the drawing process by combining the finite element numerical simulation and experiment. The aim is to optimize the processing technology and improve the forming quality of the parts. At the same time, it also provides scientific guidance for the development of industrial production and new type of tensile forming equipment. The main contents and conclusions of this paper are as follows: 1. the principle of high flexible tensile forming and the analysis of the mechanical analysis of the forming process, the technical characteristics and the forming process of the high flexible stretch forming, and the analysis of the internal stress in the sheet material during the high flexible stretch forming. The strain change process is derived, and the internal tension of the sheet material and the unloading and rebound are derived and calculated. The selection basis of the blank size and the evaluation standard of the forming quality.2. are given to establish the dynamic explicit formula of the finite element model for the finite element numerical simulation, the static implicit solution algorithm and the elastoplastic constitutive relation of the material. The structure analysis and numerical simulation of the high flexible stretch forming finite element model and the springback model.3. stretch forming machine are set up to analyze the main components of the high flexible stretch forming machine (the clamping mechanism, the pulling mechanism, the universal structure), and the finite element numerical simulation method is used to analyze the degree of the clamp discretization, the clamp gap, and the loading. The effect of the amplitude on the forming result shows that with the increase of the clamp number, the effect of the sheet material is gradually better and the forming quality is improved. With the increase of the gap of the clamp, the stress and strain distribution uniformity of the forming part first increases and then decreases, the gap is too large, the forming area is wrinkled, the width of the sheet is 1200mm, and the working conditions of the 10 clamps are on the sheet. The forming effect is the best when the gap of the clamp is 1/9 of its width. The forming force according to the reasonable amplitude can improve the forming quality of the forming mass.4. in the high flexible stretch forming. The method of surface defect is studied with spherical and saddle parts as the research object. The method of finite element numerical simulation and tensile test are used to compare the influence of the conventional arrangement, the inclined staggered arrangement and the parallel interlaced multi point die on the forming result. The interlaced multi point die can effectively restrain the indentation defect, improve the surface quality and forming precision of the forming parts, and better than the conventional multi point die forming..5. studies the influence of the form of the basic body ball on the forming result, and derives the geometric strip tangent to the ball head and the sheet material, and builds the drawing based on the multi point die of the swinging ball head. The finite element model is used to analyze the influence of the swinging ball head on the forming result by combining the finite element numerical simulation with the tensile test. The analysis shows that when the radius of the ball head is less than the critical radius of the tangent, the forming quality is higher and the radius of the ball head is larger than the critical radius when the radius of the ball head is increased, with the ball head half the radius, with the ball head half the head. The shape of the swinging ball head die instead of the fixed ball head can effectively restrain the surface indentation of the forming parts, reduce the springback and improve the forming quality. The forming effect of the multi point die with swinging ball is superior to that of the conventional multi point die.6.. The friction coefficient of different friction contact pairs under dry friction and oil lubrication is tested. The effect of friction conditions between sheet and die is studied by finite element numerical simulation. Multi point die and elastic cushion, elastic cushion and elastic cushion are studied by the combination of finite element numerical simulation and tensile forming test. The effect of the combination of friction conditions on the forming results is shown. The results show that the forming effect of the forming part is better in the dry friction between the sheet and the die, but the stress and strain of the transition zone are large. The method of oil lubrication can effectively reduce the stress of the transition zone and should be changed; in the presence of multiple contact pairs, the contact pairs can be kept between each contact pair. For dry friction, the forming effect of the effective forming area is better. When oil lubrication is used between the elastic cushion and the elastic cushion, the forming effect is poor.7.. The effect of the elastic cushion on the high flexible stretch forming is studied by the spherical parts. The finite element numerical simulation method is used to analyze the thickness of the elastic cushion, the hardness and the number of layers on the surface quality and forming error of the forming parts. The results show that the thickness of the elastic cushion increases, the surface quality of the forming part increases, but the forming error increases; the greater the hardness of the elastic pad, the higher the surface quality and the forming precision of the forming parts; the elastic cushion with the same thickness increases with the number of layers, the surface quality of the forming parts. And the forming precision is reduced, but the rebound amount is reduced at the same time; it is simpler to use the section method to judge the sheet material. The error compensation can be realized quickly by the mould surface correction method of multi point die.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG306

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