本文選題：多點成形　切入點：鋁型材　出處：《大連理工大學》2015年博士論文

【摘要】：鋁型材三維彎曲成形零件能夠提供輕量化的車身結構,良好的空氣動力學性能,以及更加安全舒適的乘坐空間等,越來越受到人們的關注。然而,由于型材三維彎曲成形的復雜性和成形件形狀難于控制,鋁型材的三維彎曲成形加工工藝制約了其快速發(fā)展。 為了實現(xiàn)復雜截面型材的快速、精確、以及柔性的三維彎曲成形技術,同時為了滿足我國高鐵列車車頭制造過程中對三維彎曲結構件的緊迫需求,本文提出了一種新型的柔性三維拉彎成形工藝。新工藝采用離散化多點模具柔性成形方法,開發(fā)了多組聯(lián)動離散化的單元體模塊及多自由度的三維拉彎機械臂,并研制了成形裝備。基于變形疊加理論,將鋁型材三維變形分解為水平和垂直兩個平面內的變形分量,分步實現(xiàn)了鋁型材復雜三維空間構型的成形工藝。通過解析計算、數(shù)值仿真與實驗相結合的方法,對柔性三維拉彎成形工藝、裝備、單元體調形技術及成形件的形狀控制進行了研究,分述如下。 采用自動化的調形方法,設計開發(fā)了配套的單元體串行水平調形與并行垂直調形機構。建立了調形控制系統(tǒng)的框架,設計了水平方向(DSP2812搭配步進電機)與垂直方向(STC89C52搭配直流電機)的調形控制單元,采用主從通信的方式編寫了控制程序。自動化的調形方式較傳統(tǒng)的人工調形方式提高效率60%以上。采用液壓動力單元替換垂直方向上的直流電機調形控制單元,開發(fā)了一種水平拉彎與垂直壓彎相結合的三維彎曲成形新方法,實現(xiàn)了型材更為復雜的W形狀三維拉彎成形。 另外,文中還建立了描述三維彎曲成形件形狀的數(shù)學模型,確定了成形過程中控制成形件形狀相關工藝參數(shù)的計算方法,包括單元體的調形參數(shù)和夾鉗的運動軌跡。建立了一套三維拉彎成形零件回彈的評價方法,開發(fā)了配套的檢測工具。將原有的二維拉彎成形力學解析模型擴展至三維,對成形后零件軸向上的主應力狀態(tài)進行了討論和分析,推導了計算三維彎曲回彈的解析計算公式。將實驗、解析計算、仿真的結果進行了對比,三者的回彈結果基本吻合,證明解析計算模型與仿真模型均取得了較為滿意的回彈預測結果,實驗結果表明三維拉彎成形過程中,垂直方向的彎曲會減小水平方向上的回彈變形,且垂直方向上變形的幅度越大,水平方向上回彈減少的越多。 最后,本文對回彈補償?shù)姆椒ㄟM行了研究,提出了一種多點模具包絡面修正直接補償?shù)姆椒�。通過有限元仿真的方法對高鐵列車車頭骨架成形件的模面進行了優(yōu)化,成形件輪廓度誤差由1.01%降至0.06%。優(yōu)化后的模面實際實驗測得的輪廓度誤差為0.05%,實現(xiàn)了柔性三維拉彎成形零件的精確成形。目前,該工藝及裝備已實現(xiàn)產(chǎn)業(yè)化的生產(chǎn)。
[Abstract]:Three-dimensional bending forming parts of aluminum profile can provide lightweight body structure, good aerodynamic performance, and more and more safe and comfortable ride space, etc., which has attracted more and more attention.However, because of the complexity of profile 3D bending forming and the difficulty of controlling the shape of forming parts, the rapid development of aluminum profile is restricted by the 3D bending forming process.In order to realize the rapid, accurate and flexible three-dimensional bending forming technology of the complex section profile, and to meet the urgent need of the three-dimensional bending structure in the manufacturing process of the high speed train front in China,In this paper, a new flexible three-dimensional bending process is proposed.In the new process, the discrete multi-point die flexible forming method is used to develop the unit body module of multi-group linkage discretization and the three-dimensional bending machine arm with multiple degrees of freedom, and the forming equipment is developed.Based on the theory of deformation superposition, the three-dimensional deformation of aluminum profile is decomposed into two deformation components in horizontal and vertical plane, and the forming process of complex three-dimensional spatial configuration of aluminum profile is realized step by step.By means of analytical calculation, numerical simulation and experiment, the flexible three-dimensional bending process, equipment, unit body shape adjusting technology and shape control of forming parts are studied, which are described as follows.The serial horizontal and parallel vertical tweaking mechanism of the unit body is designed and developed by the automatic adjusting method.In this paper, the frame of the profile control system is set up, and the adjusting control unit of horizontal direction DSP2812 with stepping motor and vertical direction STC89C52) is designed. The control program is compiled by master-slave communication.The efficiency of automatic tweaking is more than 60% higher than that of traditional manual tweaking.A new 3D bending forming method combining horizontal tension bending and vertical bending is developed by replacing DC motor profile control unit in vertical direction with hydraulic power unit.In addition, a mathematical model is established to describe the shape of three dimensional bending parts, and the calculation method for controlling the shape related process parameters of the forming part is determined, including the adjusting parameters of the element body and the motion track of the clamp.A set of springback evaluation method for three-dimensional bending forming parts is established, and a set of testing tools are developed.The original analytical model of two-dimensional tensile bending forming is extended to three dimensions. The principal stress state of the formed parts is discussed and analyzed. The analytical formula for calculating the three dimensional bending springback is derived.The results of experiment, analytical calculation and simulation are compared. The springback results of the three models are basically consistent. It is proved that both the analytical model and the simulation model have achieved satisfactory springback prediction results, and the experimental results show that in the process of three-dimensional bending, the results show that,The bending in the vertical direction will reduce the springback deformation in the horizontal direction, and the larger the amplitude of the deformation in the vertical direction, the more the springback will be reduced in the horizontal direction.Finally, the method of springback compensation is studied in this paper, and a direct compensation method for multi-point die envelope correction is proposed.By means of finite element simulation, the die surface of the forming part of the head frame of the high-speed train is optimized, and the contour error of the formed part is reduced from 1.01% to 0.06%.The contour error measured by the optimized die surface is 0. 05. The precise forming of the flexible three dimensional bending parts is realized.At present, the process and equipment has been industrialized production.
【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG306

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