本文選題：拉彎 + 成形極限　； 參考：《西北工業(yè)大學》2016年博士論文

【摘要】：拉彎成形工藝能成形屈服比高的彎曲零件且加工精度高、回彈小,在航空、航天、武器裝備、汽車等交通工具的構件制造中廣泛應用。隨著新材料的引入、新工藝的提出,以及高端裝備大運力、低能耗和長壽命的要求不斷提高,新形勢下的拉彎成形面臨以下難題:高性能材料,如高強鋁鋰合金和鈦合金擠壓型材室溫變形抗力大、成形極限低,導致冷拉彎回彈大,成形過程型材極易斷裂;新淬火態(tài)鋁合金析出硬化,導致回彈隨時效時間變化,成形質量不穩(wěn)定;熱拉彎成形能有效的攻克高強度材料冷拉彎成形難題,然而,其多場耦合機理和工藝控制方法有待研究。本文圍繞擠壓型材拉彎回彈預測與補償難題,采用解析、模擬和試驗相結合的方法,針對材料參數(shù)、工藝參數(shù)和溫度條件的回彈影響,建立了拉彎回彈力學基礎模型、加載過程有限元仿真模型、多場耦合的拉彎回彈預測模型以及多因素耦合的響應面模型,在此基礎上,建立了回彈補償算法,實現(xiàn)拉彎成形的回彈穩(wěn)定控制。研究內容和創(chuàng)新性成果如下:1)從回彈產生的內因出發(fā),針對型材材料性能、彎曲半徑和截面尺寸多變的特點,提出了材料參數(shù)影響的型材拉彎回彈預測基礎模型。首先,建立了應變、應變率、溫度、時效時間相關的統(tǒng)一材料本構模型,用于表征材料應變硬化、時效硬化、應變率硬化和高溫軟化行為;然后,基于虛功原理,考慮截面中性層移動和摩擦影響,運用變分法求解截面位移函數(shù),建立了型材拉彎回彈力學模型;最后,通過試驗驗證了模型的精度,在此基礎上建立了材料性能和幾何參數(shù)耦合的拉彎回彈響應面模型,顯式的表達彈性模量、硬化指數(shù)、屈服強度、截面尺寸、彎曲半徑和角度等參數(shù)耦合影響的回彈率變化規(guī)律。上述方法解決了新型鋁鋰合金型材拉彎回彈難以預測的難題,為工藝參數(shù)的影響建模和回彈補償提供了基礎模型。2)針對位移控制拉彎加載過程面臨的材料、幾何和邊界條件非線性難題,提出了工藝參數(shù)影響的型材拉彎加載過程建模方法。首先,基于上述回彈預測基礎模型,考慮預拉伸、彎曲和補拉伸三個階段的加載過程,建立了位移控制拉彎回彈力學模型;然后,針對位移控制型材拉彎復雜加載過程,引入連接單元的夾鉗軌跡建模方法,提出了一般引導線外形的軌跡算法,進而建立了位移控制拉彎的有限元模型,仿真回彈;最后,針對新型鋁鋰合金和鋁合金型材拉彎成形試驗對模型進行了驗證,在此基礎上建立了預拉應變、補拉應變和摩擦系數(shù)耦合的回彈響應面模型。上述方法改善了位移控制拉彎軌跡控制方法在成形模擬過程中截面畸變的問題,同時適用于一般引導線外形的拉彎回彈仿真。3)針對電熱轉臺式拉彎過程面臨的多工序、多場耦合復雜難題,提出了溫度條件影響的電熱拉彎多場耦合建模方法。首先,基于熱力學和彈塑性力學原理,建立了電熱拉彎回彈力學模型,揭示了型材電熱拉彎多場耦合的回彈機理;然后,建立了電熱拉彎成形的順序耦合有限元模型,包括電熱傳導分析和熱應力分析,仿真其溫度分布和回彈變形。最后,通過Ti-6Al-4V鈦合金電熱拉彎成形試驗對模型進行了驗證,在此基礎上,針對型材初始加熱溫度、補拉伸時間間隔和初始模具溫度等重要影響參數(shù),建立了工藝參數(shù)和溫度條件多因素耦合的熱拉彎回彈響應面模型。上述方法改善了電-熱-力完全耦合模擬好耗時長,計算成本高的問題,同時保證了熱拉彎回彈預測精度。4)針對材料參數(shù)、工藝參數(shù)和溫度條件影響的拉彎回彈補償難題,提出了多因素耦合影響的型材拉彎回彈補償方法。首先,提出了型材拉彎三種斷裂模式的極限解析模型和拉彎斷裂仿真建模方法,預測極限彎曲半徑,指導回彈補償。然后,針對回彈的材料參數(shù)、工藝參數(shù)和溫度條件的復雜影響,建立了拉彎回彈補償算法和可補償性分析方法,提出了工藝和溫度補償?shù)幕貜椃�(wěn)定控制方法。最后,針對鋁合金型材拉彎的工程實例,進行模具回彈修正設計,試驗驗證了回彈補償方法。上述方法解決了新淬火拉彎回彈隨時間變化的補償問題,同時保證了補償精度。全文以擠壓型材拉彎成形為研究對象,成功解決了其回彈預測、回彈補償與回彈穩(wěn)定控制技術難題。研究成果應用于ARJ21和C919客機機身框緣類零件精確制造。
[Abstract]:Bending forming process can form curved parts with high yield ratio, with high precision and small resilience. It is widely used in the component manufacturing of transportation tools such as aviation, space, weaponry and automobile. With the introduction of new materials, new technology, high end equipment and large capacity, low energy consumption and long life requirements, the new situation is drawn. Bending forming faces the following difficult problems: high performance materials, such as high strength aluminum lithium alloy and titanium alloy extruded profiles, have large deformation resistance at room temperature and low forming limit, resulting in large cold drawing bending and forming process. The new Quenched Aluminum alloy is precipitated and hardened, resulting in the change of springback at any time and the unstable forming quality; the hot drawing bending can be effective. In this paper, the multi field coupling mechanism and the process control method need to be studied. In this paper, the combined method of analysis, simulation and test is used to solve the problem of prediction and compensation of stretch bending springback of extruded profiles. The bending resilience is established according to the impact of material parameters, process parameters and temperature conditions. The basic model, the loading process finite element simulation model, the multi field coupled stretch bending resilience prediction model and the multi factor coupling response surface model, based on this, the resilience compensation algorithm is established to realize the rebound stabilization control of the bending forming. The research content and the innovative results are as follows: 1) from the internal cause of the springback, the material is aimed at the profile material. The material properties, bending radius and cross section size are changeable, and a basic model for prediction of stretch bending springback is proposed. First, a unified material constitutive model is established for strain, strain rate, temperature and aging time, which is used to characterize strain hardening, aging hardening, strain rate hardening and high temperature softening behavior. On the basis of the principle of virtual work, considering the movement of the neutral layer and the influence of friction, the section displacement function is solved by the variational method. The tensile bending mechanical model of the section is established. Finally, the accuracy of the model is verified by the experiment. On this basis, the response surface model of the tensile bending elastic response surface coupled with the material properties and the geometric parameters is established, and the elastic modulus is expressed explicitly. The hardening exponent, yield strength, section size, bending radius and angle and other parameters influence the change of the rebound rate. The above method solves the difficult problem of predicting the springback of the new type Al Li alloy profile, and provides a basic model.2 for the influence modeling and rebound compensation of the process parameters. Material, geometry and boundary condition nonlinear problem, the modeling method of stretch bending loading process is proposed. First, based on the above model of rebound prediction, the loading process of three stages of pretension, bending and reinforcement is considered, and the displacement control pull bending elastic model is established. Then, the displacement control profile is drawn. In the bending complex loading process, the clamping path modeling method of the connecting element is introduced, and the trajectory algorithm of the general guide line is proposed. Then the finite element model of the displacement control and stretch bending is established, and the rebound is simulated. Finally, the model of the new type Al Li alloy and aluminum alloy profile drawing test is verified. On this basis, the pretest is established. The springback response surface model is coupled with tension strain, tension strain and friction coefficient. The above method improves the problem of the cross section distortion in the forming simulation process of the displacement control, and is suitable for the drawing and rebound simulation.3 of the general guide line shape. A multi field coupling modeling method of electrothermal tension bending is proposed with the influence of temperature conditions. First, based on the principle of thermodynamics and elastoplastic mechanics, an electrothermal stretch bending resilience model is established, and the rebound mechanism of the multi field coupling of the electric heating and bending is revealed. Then, the sequential coupling finite element model of the electrothermal bending forming is established, including the electric heating transmission. The temperature distribution and the springback deformation are simulated by the analysis of the thermal stress and the thermal stress. Finally, the model is verified by the Ti-6Al-4V titanium alloy electrothermal tension bending test. On this basis, the factors such as the initial heating temperature, the time interval of the filling and the initial die temperature and the other important parameters are established, and the process parameters and the temperature conditions are established. The above method improves the long time, high calculation cost of the full coupling simulation of electric thermal force and the high calculation cost, at the same time, it ensures the precision.4 of the rebound prediction accuracy of the hot pull bending. First, the limit analytic model of three fracture modes and the bending fracture simulation modeling method are put forward. The limit bending radius is predicted and the rebound compensation is instructed. Then, the compensation algorithm and compensable analysis are established for the resilience compensation algorithm and the complex effect of the material parameters, process parameters and temperature conditions of the springback. Method, the resilience stability control method of process and temperature compensation is put forward. Finally, according to the engineering example of drawing bending of aluminum alloy section, the correction design of die springback is carried out, and the method of resilience compensation is verified by the test. The above method solves the compensation problem of the time variation of the new quench springball and ensures the compensation precision. The full text is squeezed in the full text. As the research object, the springback prediction, rebound compensation and springback stability control are solved successfully. The research results are applied to the precise manufacturing of frame rim parts of ARJ21 and C919 airframe.
【學位授予單位】：西北工業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG306

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