面向微观组织优化的锻造工艺预成形优化设计

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了锻造成形过程微观组织优化目标函数,并确定锻造成形预成形形状作为优化过程的设计变量,给出了优化设计的具体步骤,采用微观遗传算法和有限元模拟方法开发了锻造过程微观组织优化程序,并对典型的圆柱体镦粗进行了面向微观组织优化的预成形设计,取得了较好的效果.     

基于微观组织优化的锻造工艺预成形及毛坯形状优化设计

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了晶粒尺寸、锻件形状子目标函数以及无量纲化的总目标函数,确定了预成形形状作为优化过程的设计变量;给出了优化设计的具体步骤,采用微观遗传算法和有限元模拟方法开发了基于预成形设计的锻造过程微观组织优化程序;并对典型的圆柱体镦粗进行了面向微观组织优化的预成形设计,给出了能够获得具有良好微观组织的镦粗成形预成形模具型腔形状。通过分析不同高径比的初始毛坯形状对微观组织优化目标函数值的影响,给出了较为合理的初始毛坯形状高径比取值范围。     

基于有限元灵敏度分析的锻造成形微观组织优化设计

采用有限元、灵敏度分析与工程优化算法相结合的方法,以能充满型腔且少无飞边的终锻件的晶粒度分布均匀化为目标,以预成形形状为优化对象,对锻造成形过程的微观组织进行了优化设计。采用三次B样条函数描述预成形模具形状,并以B样条函数的控制点坐标为设计变量,给出了锻造过程微观组织演变的模型,建立了衡量锻件充型性能及微观组织分布均匀化的目标函数,推导了目标函数对设计变量的灵敏度,给出了优化设计步骤。并以一典型H型锻件为例,对锻件的微观组织进行了优化,取得了较好的结果。     

基于响应面法（RSM）的锻造预成形多目标优化设计

以航空发动机涡轮盘锻件为研究对象,应用响应面法(Response surfce Methodology,RSM)和有限元数值模拟(FEM)对锻造过程预成形设计的多目标优化问题进行了研究.首先以模具充填完整和提高锻件内变形均匀性为目标,建立了有限元数值模拟与响应面法相结合的二阶分析模型,并对优化结果进行了讨论.其次,在原优化设计的基础上以降低锻造过程的成形载荷为目标进行了预成形再设计.结果表明,应用响应面法可灵活有效的对难变形材料锻造预成形坯料形状进行多目标优化设计.     

面向微观组织优化的镦粗预成形优化设计及实验研究

采用微观遗传算法和有限元模拟方法开发了锻造过程微观组织优化程序,对圆柱体的镦粗成形进行了面向微观组织优化的预成形设计,取得了较好的优化效果.根据镦粗实例的预成形优化结果,进行了相应的实验研究,晶粒尺寸及其分布与优化结果比较吻合.     

300M高强钢起落架外筒锻件微观组织演变预测

飞机起落架外筒锻件形状复杂,利用数值模拟对其成形过程中的微观组织演变进行预测意义重大。以300M高强钢主起落架外筒锻件为研究对象,制定锻件的锻造工艺,将300M高强钢的微观组织模型写入DEFORM-3D软件,对材料热成形过程中的组织进行预测。结果表明,采用所制定的锻造工艺成形后的锻件晶粒尺寸较细小,并与实验结果进行了对比,吻合性较好,验证了该模拟的正确性。     

高筋薄腹板类锻件三维预成形设计及优化

高筋薄腹板类锻件通常具有较大的尺寸和较复杂的内腔,需要在锻造成形过程中进行合理的预成形设计。提出了一种三维预成形设计方法,以一个典型的高筋薄腹板类锻件为例,根据静电场与锻造速度场分布的相似性,用静电场等势面模拟获得其预锻形状;然后利用Deform-3D进行锻造模拟,对预锻形状进行验证和评估;最后通过构建神经网络,建立了毛坯尺寸、等势面电势值和等效应变差值、锻件填充率的映射关系,并结合遗传算法搜索最优解,实现了毛坯和预锻件的联合优化设计。结果表明,本方法可以快速而准确地设计出预成形件,可靠性较高。     

结合数值模拟与物理实验的叶片锻造预成形拓扑优化设计研究

利用所提出的拓扑优化方法,对复杂形状叶片锻造的预成形形状进行了优化设计。详细给出了该方法在三维模式下的优化策略、优化目标、单元增删准则、几何模型处理等关键技术。以合理精简毛坯、提高模腔充填性为综合优化目标,利用自行开发的优化程序,经过十余次的优化迭代,获得了理论上的优化结果。研制了叶片锻造模具,对优化后的预成形件进行了锻造成形实验;利用激光测量设备采集了叶片锻件型面的几何数据,并与数值模拟结果进行了比对。对预成形件制备工艺的可行性进行了详细讨论。结果表明:基于拓扑优化方法所获得的叶片预成形设计结果较为理想。     

锻造过程优化设计目标的研究

本文以锻造过程为研究对象，对锻造过程优化设计常用的目标函数进行了分析与综合，给出了包括材料消耗、终锻力、变形能、锻件质量等研究指标的目标函数，并对锻造过程的多目标优化设计的目标函数的组合形式进行了研究，提出了一个同时以获得净形锻造和变形均匀锻件为目标的多目标优化设计的目标函数的表示形式，最后给出了一个以实现净形锻造为优化设计目标的预成形模具形状优化设计的实例。     

核电封头-过渡锥体一体化成形全工艺过程多尺度模拟

SA508-3钢由于其优良的力学和理化性能而被广泛应用于核电大型锻件的制造。为了控制锻件的形状,并掌握大型锻件成形过程中开裂破坏和微观组织的演化规律。将SA508-3钢的流动应力模型、热成形开裂模型及微观组织演变模型通过软件二次开发与DEFORM-3D集成,建立了热锻成形多尺度模拟系统,并通过实验验证了该系统模拟的准确性。运用该多尺度模拟系统对核电封头-过渡锥体一体化成形进行了全工艺过程模拟,并对锻件形状、开裂趋势和微观组织演化进行了预测和分析。结果表明,锻件的形状得到了良好的控制;锻件在锻造过程中不会发生开裂;温度和应变是影响晶粒尺寸变化的主要因素。     

单工序锻造过程预制坯多目标优化设计的研究

针对单工序锻造在终锻之前一般都需要以镦粗进行预制坯的实际情况，以刚粘塑性有限元为工具，以获得形状和变形均匀性都较好的终锻件为优化设计目标，以镦粗的压下量为优化设计变量，采用黄金分割法对其预制坯工艺进行了多目标优化设计的研究。并对一轴对称锻件的镦粗压下量进行了优化设计，优化取得了明显的效果。     

Microstructure optimization in design of forging processes

A new approach based on sensitivity analysis for optimizing the microstructure development during the forging processes is proposed in this work. The analytical sensitivities of the recrystallization volume fraction and dynamically recrystalized grain size with respect to the design variables are derived. The mean grain size in each finite element is introduced so that the complex recrystallization mechanics, such as no recrystallization, partial recrystallization and complete recrystallization are all considered. The objective is to minimize a function describing the variance of mean grain size and the average value of mean grain size in the whole final product. Two constraints are imposed on die underfill and excessive material waste. Two different kinds of design variables are considered, including state parameter (initial shape of billet) and process parameter (die velocity). The optimization scheme is demonstrated with the design of a turbine disk made of Waspaloy in non-isothermal forging process. The optimal initial shape of billet and the die velocity are obtained.     

Sensitivity analysis based preform die shape design for net-shape forging

A sensitivity analysis method for preform die shape design in net-shape forging processes is developed in this paper using the rigid viscoplastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of B-spline are used as the design variables. The optimization problem is to minimize the zone where the realized and desired final forging shapes do not coincide. The sensitivities of the objective function, nodal coordinates and nodal velocities with respect to the design variables are developed in detail. A procedure for computing the sensitivities of history-dependent functions is presented. The remeshing procedure and the interpolation/transfer of the history-dependent parameters, such as effective strain, are stated. The procedures of sensitivity analysis based preform die design are also described. In addition, a method for the adjustment of the volume loss resulting from the finite element analysis is given in order to make the workpiece volume consistent in each optimization iteration. The method developed in this paper is used to design the preform die shape of H-shaped forging processes, including plane strain and axisymmetric deformations. The results show that a flashless forging with a complete die fill is realized using the optimized preform die shape.     

基于有限元法的正反向模拟技术在链轨节锻造中的应用

锻造过程的预成形设计是提高锻造质量和降低产品成本的一个极其重要的方面，基于刚一粘塑性有限元法的正反向模拟技术能够从最终的锻件形状直接得出坯料的预成形形状，通过改善设计制坯操作来减少作为飞边的材料浪费。中介绍了覆带链轨节锻造的常规工艺，说明了目前覆带链轨节锻造中存在的问题，阐述了有限元法、预成形设计思想和正反向模拟技术以及它们在覆带链轨节锻造中的应用。     

Preform optimization for hot forging processes using an adaptive amount of flash based on the cross section shape complexity

In multistage hot forging processes, the preform shape is the parameter mainly influencing the final forging result. Nevertheless, the design of multistage hot forging processes is still a trial and error process and therefore time consuming. The quality of developed forging sequences strongly depends on the engineer’s experience. To overcome these obstacles this paper presents an algorithm for solving the multi-objective optimization problem in designing preforms. Cross wedge rolled preforms were chosen as subject of investigation. An evolutionary algorithm is introduced to optimize the preform shape taking into account the mass distribution of the final part, the preform volume and the shape complexity. A crucial factor in preform optimization for hot forging processes is the amount of flash. Therefore an equation for improving the amount of flash is derived. The developed algorithm is tested using two connecting rods with different shape complexities as demonstration parts.     

Sensitivity analysis based preform die shape design using the finite element method

This paper uses a finite element-based sensitivity analysis method to design the preform die shape for metal forming processes. The sensitivity analysis was developed using the rigid visco-plastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of the B-spline are used as the design variables. The optimization problem is to minimize the difference between the realized and the desired final forging shapes. The sensitivity analysis includes the sensitivities of the objective function, nodal coordinates, and nodal velocities with respect to the design variables. The remeshing procedure and the interpolation/transfer of the history/dependent parameters are considered. An adjustment of the volume loss resulting from the finite element analysis is used to make the workpiece volume consistent in each optimization iteration and improve the optimization convergence. In addition, a technique for dealing with fold-over defects during the forming simulation is employed in order to continue the optimization procedures of the preform die shape design. The method developed in this paper is used to design the preform die shape for both plane strain and axisymmetric deformations with shaped cavities. The analysis shows that satisfactory final forging shapes are obtained using the optimized preform die shapes.     

Microstructure Modeling of a Ni-Fe-Based Superalloy During the Rotary Forging Process

The microstructure evolution of Ni-Fe superalloys has a great influence on the mechanical behavior during service conditions. The rotary forging process offers an alternative to conventional bulk forming processes where the parts can be rotary forged with a fraction of the force commonly needed by conventional forging techniques. In this investigation, a numerical modeling of microstructure evolution for design and optimization of the hot forging operations has been used to manufacture a heat-resistant nickel-based superalloy. An Avrami model was implemented into finite element commercial platform DEFORM 3D to evaluate the average grain size and recrystallization during the rotary forging process. The simulations were carried out considering three initial temperatures, 980, 1000, and 1050 °C, to obtain the microstructure behavior after rotary forging. The final average grain size of one case was validated by comparing with results of previous experimental work of disk forging operation. This investigation was aimed to explore the influence of the rotary forging process on microstructure evolution in order to obtain a homogenous and refined grain size in the final component.