挤压型材拉弯回弹预测与补偿方法研究

发布时间：2018-06-07 21:53

本文选题：拉弯 + 成形极限　；参考：《西北工业大学》2016年博士论文

【摘要】：拉弯成形工艺能成形屈服比高的弯曲零件且加工精度高、回弹小,在航空、航天、武器装备、汽车等交通工具的构件制造中广泛应用。随着新材料的引入、新工艺的提出,以及高端装备大运力、低能耗和长寿命的要求不断提高,新形势下的拉弯成形面临以下难题:高性能材料,如高强铝锂合金和钛合金挤压型材室温变形抗力大、成形极限低,导致冷拉弯回弹大,成形过程型材极易断裂;新淬火态铝合金析出硬化,导致回弹随时效时间变化,成形质量不稳定;热拉弯成形能有效的攻克高强度材料冷拉弯成形难题,然而,其多场耦合机理和工艺控制方法有待研究。本文围绕挤压型材拉弯回弹预测与补偿难题,采用解析、模拟和试验相结合的方法,针对材料参数、工艺参数和温度条件的回弹影响,建立了拉弯回弹力学基础模型、加载过程有限元仿真模型、多场耦合的拉弯回弹预测模型以及多因素耦合的响应面模型,在此基础上,建立了回弹补偿算法,实现拉弯成形的回弹稳定控制。研究内容和创新性成果如下:1)从回弹产生的内因出发,针对型材材料性能、弯曲半径和截面尺寸多变的特点,提出了材料参数影响的型材拉弯回弹预测基础模型。首先,建立了应变、应变率、温度、时效时间相关的统一材料本构模型,用于表征材料应变硬化、时效硬化、应变率硬化和高温软化行为;然后,基于虚功原理,考虑截面中性层移动和摩擦影响,运用变分法求解截面位移函数,建立了型材拉弯回弹力学模型;最后,通过试验验证了模型的精度,在此基础上建立了材料性能和几何参数耦合的拉弯回弹响应面模型,显式的表达弹性模量、硬化指数、屈服强度、截面尺寸、弯曲半径和角度等参数耦合影响的回弹率变化规律。上述方法解决了新型铝锂合金型材拉弯回弹难以预测的难题,为工艺参数的影响建模和回弹补偿提供了基础模型。2)针对位移控制拉弯加载过程面临的材料、几何和边界条件非线性难题,提出了工艺参数影响的型材拉弯加载过程建模方法。首先,基于上述回弹预测基础模型,考虑预拉伸、弯曲和补拉伸三个阶段的加载过程,建立了位移控制拉弯回弹力学模型;然后,针对位移控制型材拉弯复杂加载过程,引入连接单元的夹钳轨迹建模方法,提出了一般引导线外形的轨迹算法,进而建立了位移控制拉弯的有限元模型,仿真回弹;最后,针对新型铝锂合金和铝合金型材拉弯成形试验对模型进行了验证,在此基础上建立了预拉应变、补拉应变和摩擦系数耦合的回弹响应面模型。上述方法改善了位移控制拉弯轨迹控制方法在成形模拟过程中截面畸变的问题,同时适用于一般引导线外形的拉弯回弹仿真。3)针对电热转台式拉弯过程面临的多工序、多场耦合复杂难题,提出了温度条件影响的电热拉弯多场耦合建模方法。首先,基于热力学和弹塑性力学原理,建立了电热拉弯回弹力学模型,揭示了型材电热拉弯多场耦合的回弹机理;然后,建立了电热拉弯成形的顺序耦合有限元模型,包括电热传导分析和热应力分析,仿真其温度分布和回弹变形。最后,通过Ti-6Al-4V钛合金电热拉弯成形试验对模型进行了验证,在此基础上,针对型材初始加热温度、补拉伸时间间隔和初始模具温度等重要影响参数,建立了工艺参数和温度条件多因素耦合的热拉弯回弹响应面模型。上述方法改善了电-热-力完全耦合模拟好耗时长,计算成本高的问题,同时保证了热拉弯回弹预测精度。4)针对材料参数、工艺参数和温度条件影响的拉弯回弹补偿难题,提出了多因素耦合影响的型材拉弯回弹补偿方法。首先,提出了型材拉弯三种断裂模式的极限解析模型和拉弯断裂仿真建模方法,预测极限弯曲半径,指导回弹补偿。然后,针对回弹的材料参数、工艺参数和温度条件的复杂影响,建立了拉弯回弹补偿算法和可补偿性分析方法,提出了工艺和温度补偿的回弹稳定控制方法。最后,针对铝合金型材拉弯的工程实例,进行模具回弹修正设计,试验验证了回弹补偿方法。上述方法解决了新淬火拉弯回弹随时间变化的补偿问题,同时保证了补偿精度。全文以挤压型材拉弯成形为研究对象,成功解决了其回弹预测、回弹补偿与回弹稳定控制技术难题。研究成果应用于ARJ21和C919客机机身框缘类零件精确制造。
[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.
【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG306

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