GH4169合金摩擦焊接过程的数值模拟研究
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摘要
GH4169高温合金广泛应用于航空航天、核工业等领域，这些高技术领域对部件之间的焊接质量要求很高，传统的熔焊已很难达到其质量要求，摩擦焊接作为先进的固态连接方法之一，已成为这些领域高温合金部件焊接的主要方法。由于高温合金的摩擦焊接技术主要用于航空航天等高技术领域，国外对相关技术实行了封锁，因此我们必须自主地对各种高温合金的摩擦焊接工艺进行系统深入的研究。传统上对摩擦焊接工艺的开发都是采用经验性“试错”的方法，这种方法的研制成本巨大，研究周期长，不适合我国社会经济发展的基本国情。为了降低成本和缩短研究周期，本文采用数值模拟结合少量实验的研究方法，探索了摩擦焊接过程中的物理参量的变化，以及工艺参数和工件的几何参数对摩擦焊接过程的影响规律，并建立了环形工件惯性摩擦焊的轴向缩短量神经网络预测系统。
采用弹塑性有限元法建立了惯性摩擦焊接过程的二维轴对称、热力耦合有限元计算模型，模型中采用库仑摩擦模型和剪切摩擦模型相结合的方法，成功地模拟了摩擦焊接过程中摩擦副的摩擦行为。以此为基础提出了惯性摩擦焊接过程中摩擦扭矩、工件转速、焊接能量和摩擦热流的计算方法。并且相应地编制了一系列计算子程序，耦合到有限元计算模型中，成功地实现了对GH4169合金大型环形件惯性摩擦焊接全过程的数值模拟。计算并分析了惯性摩擦焊接头的温度和应力分布、变形以及惯性摩擦焊接过程中的轴向缩短量、工件转速、摩擦扭矩和输入能量的变化情况，结合实验对上述计算结果进行了验证。
建立了连续驱动摩擦焊接过程的三维刚塑性有限元模型。该模型在摩擦焊接过程的数值模拟中引入了摩擦力，考虑了摩擦面上的环向摩擦力对接头应力分布及变形的影响，完成了两个GH4169高温合金棒材连续驱动摩擦焊接工艺过程的数值模拟。计算并实验验证了连续驱动摩擦焊接过程中接头的温度分布、变形情况和轴向缩短量；预测并分析了摩擦焊接头在高温变形阶段的变形速率、金属流动规律和接头裂纹缺陷的产生。
对连续驱动摩擦焊接过程的三维模型和二维轴对称模型的温度、变形、应力和轴向缩短量的计算结果作了对比研究。结果表明：由于三维模型引入了环向摩擦力对摩擦焊接过程温度和变形的影响，使其等效应力的计算结果更大，进而导致其接头变形量和轴向缩短量的计算结果也更大。通过进一步与实验结果比较发现：三维模型的计算结果更接近实验结果，三维模型能更好地模拟摩擦焊接过程。但是三维模型和二维轴对称模型的计算结果的这种差别并不大，几乎可以忽略，因此在摩擦焊接过程的数值模拟中，可以用二维轴对称模型代替三维模型。
应用所建立的摩擦焊接过程的有限元计算模型，研究了环形件惯性摩擦焊接过程中焊接工艺参数和工件的几何参数对轴向缩短量和焊接能量输入过程的影响，揭示出如下主要规律：(1)轴向缩短量随着初始转速、压力的增大，以及转动惯量的减小而增大，并且它对初始转速的变化最敏感，对压力次之，对转动惯量最不敏感；(2)在能量密度一定的条件下，环件的壁厚也会影响最终的轴向缩短量，壁厚越大，最终的轴向缩短量越小；(3)焊接工艺参数和焊件几何参数对摩擦焊初始阶段的能量输入影响不大，主要影响接头变形阶段的能量输入量以及输入率。一般压力的增大、惯量的减小以及壁厚的减小都会增加能量的输入率，而初始转速的增加只是增加了能量输入量，而不会改变输入率。这些规律对大型环形件摩擦焊接工艺的研制和优化有重要的指导意义。
利用建立的环件惯性摩擦焊有限元模型，对焊接过程塑性区的形成及扩展进行了数值模拟研究。得到了塑性区分布及扩展的规律：(1)环件惯性摩擦焊接过程中塑性区呈碟形分布；(2)摩擦焊初始阶段几乎没有塑性区产生，但塑性区一旦形成其扩展速度很快，到稳定摩擦阶段塑性区宽度达到一个稳定值，基本不再变化；(3)只有塑性区达到一定宽度时，接头才会发生轴向缩短，并且一般塑性区越宽，轴向缩短的速率越快。
基于经过实验验证的数值模拟计算结果，针对GH4169合金环形工件惯性摩擦焊过程的工艺参数和工件几何参数，运用改进的BP算法，建立了环形件惯性摩擦焊的轴向缩短量神经网络预测模型。采用训练后的模型进行惯性摩擦焊轴向缩短量的预测，得到了比较准确的预测结果。
GH4169 superalloy is widely used in high-tech fields, such as aerospace, nuclear industry and so on, which usually need excellent welding quality of superalloy parts. But the traditional fusion welding can't meet the demands. Friction welding, as one of the most advanced solid state welding, has been the main joining method of superalloy in high-tech fields. Because it is used in high-tech domain, the related technologies are blanked off in the oversea companies. So we must independently study the friction welding conditions for superalloy parts. Traditionally, new welding conditions were studied by the accumulated experience of trial and error approach, which was not suitable to the development level of our country's society and economy for it usually result in high cost and long lead-time. In order to reduce the cost and shorten the lead-time, the numerical simulation method was adopted to investigate the friction welding process, and then some experimental works were carried out to demonstrate and revise the numerical model, by which the evolutions of physical parameters during inertia friction welding were analyzed and the influence of technological parameters and geometrical parameters on the inertia friction welding process were explored. And then the ANN (artificial neural networks)prediction system of upset was also constructed for inertia friction welding of ring parts.
In this paper, a 2D axisymmetric thermal-mechanical coupled FE model of inertia friction welding process was developed using elastic-plastic FEM. In the model, a new method was adopted to treat the friction behavior of the work-pieces as Coulomb friction law. and shear friction law at different inertia friction welding stages, respectively. The calculating method of friction torque, rotating velocity of the work-piece, input energy and friction heat was proposed on the base of above friction model. By coupling the subroutines of friction, friction torque, rotating velocity, input energy and friction heat into the FE model, the inertia friction welding process of GH4169 superalloy ring parts was successfully simulated. The distribution of temperature, stress and deformation of the joint and the evolutions of upset, rotating velocity, friction torque and input energy were calculated and analyzed. The corresponding experiments were carried out to validate the calculated results.
A 3D rigid viscoplastic FE model of continuous drive friction welding was established with torsional friction in the friction interface being introduced into the calculation of stress and deformation. The model simulated two continuous drive friction-welding cases of GH4169 superalloy rod by performing coupled thermal and mechanical analyses. The temperature distribution, deformation and upset of the joint were calculated and validated by the experiments. Also, the deformation rate, the material flow and the possibility of defect occurrence in the joint were predicted and analyzed.
The comparative study was carried out on the calculated results of temperature, deformation, stress, and upset by 3D model and 2D model, respectively. The results show that it is because of the introduction of trosional friction that the calculated equivalent stress of 3D model is larger, which lead to heavier deformation and bigger upset of the joint. Further comparison between the calculated and the experimental results show that the calculated results of 3D model fit the experimental results better and the 3D model can more accurately simulate the friction welding process. However there is only slight difference of calculated results between 3D model and 2D model, so the 3D model can be replaced by 2D model in the simulation of friction welding process.
Applying the FE model of inertia friction welding, the influence of technological parameters and geometrical parameter of ring parts on the evolutions of upset and input energy was studied during inertia friction welding process. Several regulations were discovered: (1) increasing initial rotating velocity, increasing pressure or decreasing rotating inertia will produce an increase in upset, which is found to be most sensitive to initial rotating velocity, next to pressure, and most insensitive to rotating inertia. (2) Even keeping the input energy density constant in the inertia friction welding of different ring parts, the thickness of the ring parts has a significant influence on the upset, which will decrease with the ring thickness increasing. (3) At the initial stage of inertia friction welding, the technological parameters and geometrical parameters of ring parts have little influence on the input energy, while at the deformation period there is a significant influence both on quantity of input energy and energy input rate. With increasing of the pressure or decreasing of rotating inertia and ring thickness, the energy input rate will increase. At the same time if increasing the initial rotating velocity, only the quantity of input energy is enhanced, and the energy input rate nearly keep constant. All the above regulations have an important instruction in the optimization and investigation of friction welding parameters.
Using the FE model of inertia friction welding, numerical simulations were carried out on the formation and extension of the plastic zone in the joint during entire inertia friction welding process. Several regulations were found: (1) the plastic zone covered in the joint as the shape of disk. (2) At the initial stage of inertia friction welding, the plastic zone is confined to a very thin layer. Then once the plastic zone begins to be produced, it will spread rapidly into the bulk of the work-piece material till the steady equilibrium stage of friction welding, when the plastic zone almost keep a constant thickness. (3) Only when the plastic zone extends to a critical thickness, the axial shortening of the joint can be produced. And wider the thickness of plastic zone, faster the upset rate happens.
Based on the validated simulation results by the above model, an improved BP algorithm was used to construct the ANN prediction system of the upset according to technological parameters and geometrical parameter of the ring parts during inertia friction welding process. The upset was predicted using the trained ANN system, and perfect results were obtained.
采用弹塑性有限元法建立了惯性摩擦焊接过程的二维轴对称、热力耦合有限元计算模型，模型中采用库仑摩擦模型和剪切摩擦模型相结合的方法，成功地模拟了摩擦焊接过程中摩擦副的摩擦行为。以此为基础提出了惯性摩擦焊接过程中摩擦扭矩、工件转速、焊接能量和摩擦热流的计算方法。并且相应地编制了一系列计算子程序，耦合到有限元计算模型中，成功地实现了对GH4169合金大型环形件惯性摩擦焊接全过程的数值模拟。计算并分析了惯性摩擦焊接头的温度和应力分布、变形以及惯性摩擦焊接过程中的轴向缩短量、工件转速、摩擦扭矩和输入能量的变化情况，结合实验对上述计算结果进行了验证。
建立了连续驱动摩擦焊接过程的三维刚塑性有限元模型。该模型在摩擦焊接过程的数值模拟中引入了摩擦力，考虑了摩擦面上的环向摩擦力对接头应力分布及变形的影响，完成了两个GH4169高温合金棒材连续驱动摩擦焊接工艺过程的数值模拟。计算并实验验证了连续驱动摩擦焊接过程中接头的温度分布、变形情况和轴向缩短量；预测并分析了摩擦焊接头在高温变形阶段的变形速率、金属流动规律和接头裂纹缺陷的产生。
对连续驱动摩擦焊接过程的三维模型和二维轴对称模型的温度、变形、应力和轴向缩短量的计算结果作了对比研究。结果表明：由于三维模型引入了环向摩擦力对摩擦焊接过程温度和变形的影响，使其等效应力的计算结果更大，进而导致其接头变形量和轴向缩短量的计算结果也更大。通过进一步与实验结果比较发现：三维模型的计算结果更接近实验结果，三维模型能更好地模拟摩擦焊接过程。但是三维模型和二维轴对称模型的计算结果的这种差别并不大，几乎可以忽略，因此在摩擦焊接过程的数值模拟中，可以用二维轴对称模型代替三维模型。
应用所建立的摩擦焊接过程的有限元计算模型，研究了环形件惯性摩擦焊接过程中焊接工艺参数和工件的几何参数对轴向缩短量和焊接能量输入过程的影响，揭示出如下主要规律：(1)轴向缩短量随着初始转速、压力的增大，以及转动惯量的减小而增大，并且它对初始转速的变化最敏感，对压力次之，对转动惯量最不敏感；(2)在能量密度一定的条件下，环件的壁厚也会影响最终的轴向缩短量，壁厚越大，最终的轴向缩短量越小；(3)焊接工艺参数和焊件几何参数对摩擦焊初始阶段的能量输入影响不大，主要影响接头变形阶段的能量输入量以及输入率。一般压力的增大、惯量的减小以及壁厚的减小都会增加能量的输入率，而初始转速的增加只是增加了能量输入量，而不会改变输入率。这些规律对大型环形件摩擦焊接工艺的研制和优化有重要的指导意义。
利用建立的环件惯性摩擦焊有限元模型，对焊接过程塑性区的形成及扩展进行了数值模拟研究。得到了塑性区分布及扩展的规律：(1)环件惯性摩擦焊接过程中塑性区呈碟形分布；(2)摩擦焊初始阶段几乎没有塑性区产生，但塑性区一旦形成其扩展速度很快，到稳定摩擦阶段塑性区宽度达到一个稳定值，基本不再变化；(3)只有塑性区达到一定宽度时，接头才会发生轴向缩短，并且一般塑性区越宽，轴向缩短的速率越快。
基于经过实验验证的数值模拟计算结果，针对GH4169合金环形工件惯性摩擦焊过程的工艺参数和工件几何参数，运用改进的BP算法，建立了环形件惯性摩擦焊的轴向缩短量神经网络预测模型。采用训练后的模型进行惯性摩擦焊轴向缩短量的预测，得到了比较准确的预测结果。
GH4169 superalloy is widely used in high-tech fields, such as aerospace, nuclear industry and so on, which usually need excellent welding quality of superalloy parts. But the traditional fusion welding can't meet the demands. Friction welding, as one of the most advanced solid state welding, has been the main joining method of superalloy in high-tech fields. Because it is used in high-tech domain, the related technologies are blanked off in the oversea companies. So we must independently study the friction welding conditions for superalloy parts. Traditionally, new welding conditions were studied by the accumulated experience of trial and error approach, which was not suitable to the development level of our country's society and economy for it usually result in high cost and long lead-time. In order to reduce the cost and shorten the lead-time, the numerical simulation method was adopted to investigate the friction welding process, and then some experimental works were carried out to demonstrate and revise the numerical model, by which the evolutions of physical parameters during inertia friction welding were analyzed and the influence of technological parameters and geometrical parameters on the inertia friction welding process were explored. And then the ANN (artificial neural networks)prediction system of upset was also constructed for inertia friction welding of ring parts.
In this paper, a 2D axisymmetric thermal-mechanical coupled FE model of inertia friction welding process was developed using elastic-plastic FEM. In the model, a new method was adopted to treat the friction behavior of the work-pieces as Coulomb friction law. and shear friction law at different inertia friction welding stages, respectively. The calculating method of friction torque, rotating velocity of the work-piece, input energy and friction heat was proposed on the base of above friction model. By coupling the subroutines of friction, friction torque, rotating velocity, input energy and friction heat into the FE model, the inertia friction welding process of GH4169 superalloy ring parts was successfully simulated. The distribution of temperature, stress and deformation of the joint and the evolutions of upset, rotating velocity, friction torque and input energy were calculated and analyzed. The corresponding experiments were carried out to validate the calculated results.
A 3D rigid viscoplastic FE model of continuous drive friction welding was established with torsional friction in the friction interface being introduced into the calculation of stress and deformation. The model simulated two continuous drive friction-welding cases of GH4169 superalloy rod by performing coupled thermal and mechanical analyses. The temperature distribution, deformation and upset of the joint were calculated and validated by the experiments. Also, the deformation rate, the material flow and the possibility of defect occurrence in the joint were predicted and analyzed.
The comparative study was carried out on the calculated results of temperature, deformation, stress, and upset by 3D model and 2D model, respectively. The results show that it is because of the introduction of trosional friction that the calculated equivalent stress of 3D model is larger, which lead to heavier deformation and bigger upset of the joint. Further comparison between the calculated and the experimental results show that the calculated results of 3D model fit the experimental results better and the 3D model can more accurately simulate the friction welding process. However there is only slight difference of calculated results between 3D model and 2D model, so the 3D model can be replaced by 2D model in the simulation of friction welding process.
Applying the FE model of inertia friction welding, the influence of technological parameters and geometrical parameter of ring parts on the evolutions of upset and input energy was studied during inertia friction welding process. Several regulations were discovered: (1) increasing initial rotating velocity, increasing pressure or decreasing rotating inertia will produce an increase in upset, which is found to be most sensitive to initial rotating velocity, next to pressure, and most insensitive to rotating inertia. (2) Even keeping the input energy density constant in the inertia friction welding of different ring parts, the thickness of the ring parts has a significant influence on the upset, which will decrease with the ring thickness increasing. (3) At the initial stage of inertia friction welding, the technological parameters and geometrical parameters of ring parts have little influence on the input energy, while at the deformation period there is a significant influence both on quantity of input energy and energy input rate. With increasing of the pressure or decreasing of rotating inertia and ring thickness, the energy input rate will increase. At the same time if increasing the initial rotating velocity, only the quantity of input energy is enhanced, and the energy input rate nearly keep constant. All the above regulations have an important instruction in the optimization and investigation of friction welding parameters.
Using the FE model of inertia friction welding, numerical simulations were carried out on the formation and extension of the plastic zone in the joint during entire inertia friction welding process. Several regulations were found: (1) the plastic zone covered in the joint as the shape of disk. (2) At the initial stage of inertia friction welding, the plastic zone is confined to a very thin layer. Then once the plastic zone begins to be produced, it will spread rapidly into the bulk of the work-piece material till the steady equilibrium stage of friction welding, when the plastic zone almost keep a constant thickness. (3) Only when the plastic zone extends to a critical thickness, the axial shortening of the joint can be produced. And wider the thickness of plastic zone, faster the upset rate happens.
Based on the validated simulation results by the above model, an improved BP algorithm was used to construct the ANN prediction system of the upset according to technological parameters and geometrical parameter of the ring parts during inertia friction welding process. The upset was predicted using the trained ANN system, and perfect results were obtained.
引文
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