GM屈服准则求解锻压矩形坯

利用一种新的屈服准则求解锻压矩形坯,这种屈服准则是在π平面上取Tresca与双剪应力屈服轨迹间误差三角形的几何中线确定的屈服轨迹,从而建立了该轨迹在Haigh Westergaard应力空间上的应力方程,称此方程为几何中线屈服准则,或简称GM屈服准则。通过锻压实验,将GM屈服准则的解析解与Mises屈服准则的结果进行了比较,发现二者基本一致,并且GM屈服准则计算得到的压力与实测值误差仅为1.25%。     

Deduction of plastic work rate per unit volume for unified yield criterion and its application

A unified linear expression of plastic work rate per unit volume is deduced from the unified linear yield criterion and the associated flow rule. The expression is suitable for various linear yield loci in the error triangle between Tresca's and twin shear stress yield loci on the π-plane. It exhibits generalization in which the different value of criterion parameter b corresponds to a specific linear formula of plastic work rate per unit volume. Finally, with the unified linear expression of plastic work rate and upper-bound parallel velocity field the strip forging without bulge is successfully analyzed and an analytical result is also obtained. The comparison with traditional solutions shows that when b=1/(1+(√3)) the result is the same as the upper bound result by Mises' yield criterion, and it also is identical to that by slab method with m=1, σ0=0.     

应变速率矢量内积解三维锻压

将三维锻压的等效应变速率表示成二维的应变速率矢量,然后利用积分中值定理确定应变速率比值函数及该矢量的方向余弦,再对其内积进行逐项积分。将逐项积分结果求和,并得出三维锻压力的计算公式与鼓形测量公式的解析解,经纯铅锻压试验将锻压力的计算结果与实测结果比较表明,由该解析解计算的结果高于实测结果,优化后的误差缩小到不大于11.2%,说明此解仍属于上界解。     

Thermodynamic criterion for judging the symmetry of ternary systems and criterion applications

Based on previous significant and enlightening studies in the literature and on thermodynamic considerations, a thermodynamic criterion for identifying the symmetry of ternary systems (from energy-asymmetry) is now proposed after having been successfully tested on a large number of molten salt and alloy systems. After a systematic comparison was made of calculated phase diagrams and excess thermodynamic properties with experimentally measured ones, it can be concluded that in using geometric models to predict ternary thermodynamic properties from subbinary systems, the key point is to choose a reasonable symmetric or asymmetric model noting that in most cases the main source of error in prediction arises from misjudging the asymmetric component in the asymmetric geometric model. This is of great significance in improving the calculated accuracy when predicting the thermodynamic properties of a ternary solution phase from data for the subbinary systems.     

Inner-product of strain rate vector through direction cosine in coordinates for disk forging

1Introduction Since friction over the surface of disk forging lowers the velocity at the surface,causing the center y=0to move faster with a resultant bulge as shown in Fig.1(a).Therefore,this velocity gradient from the surface to the interior brings abou…     

直齿圆柱齿轮精锻工艺锻靠阶段的上限分析

本文利用上限法， 由有实验依据的上限流动模型， 建立了直齿圆柱齿轮精锻工艺锻靠阶段的动可容速度场， 获得了与实验结果吻合较好的上限解， 并利用该上限解分析了精锻时冲头直径、摩擦条件、凹模型式等因素对变形力的影响。研究结果表明： 采用活动凹模和终锻时开式模锻的精锻工艺方案，所需的单位流动压力约为屈服应力σｓ 的８７５ 倍；在齿根飞边区与上模或活动凹模间的摩擦磨损最严重； 改善模具的润滑条件， 可大幅度地降低变形力。     

Backward tracing simulation of precision forging process for blade based on 3D FEM

In order to obtain the desired final shape, the blade precision forging requires a reasonable preformed billet which can be obtained from a given final shape by using backward tracing scheme based on FEM. The key technologies of backward tracing scheme based on 3D rigid-viscoplastic FEM were explored, and some valid algorithms or methods were proposed. A velocity field was generated by combining the direct iterative method with Newton-Raphson iterative method, and then the initial velocity field of backward tracing simulation was achieved by reversing the direction of the velocity field. A new method, namely the tracking-fitting-revising method, was proposed and can be used to determinate the criterion of separating a node from die in the backward tracing simulation. The ceasing criterion of the backward tracing simulation is that all the boundary nodes are detached from dies. Based on the above key technologies, the 3D backward tracing simulation system for the blade precision forging was developed, and its feasibility and reliability were verified by forward loading simulation.     

形位误差包容评定的快速优化算法与实现

对形位误差评定理论及应用进行了研究,在建立形位误差评定的几何模型的基础上,分析了形位误差包容评定的特征,并建立了包容性拟合的线性规划数学模型;以最小条件和极差极小化理论作为形位误差评定的判别准则,实现了利用修正单纯形法对形位误差数学规划模型的优化求解.以圆度为例,通过对实际测量数据的误差评定,结果表明该方法具有收敛速度快、评定精度高、计算稳定等优点.该方法在实际工程中对其它形位误差的评定中也取得了较好的效果,体现了较好的通用性和实用性.     

Hot forging process design and parameters determination of magnesium alloy AZ31B spur bevel gear

Magnesium alloys have relatively low workability at room temperatures due to hexagonal crystal structure. In general, the forging process of magnesium alloys is considered to be very difficult because of the poor flowability and the sensitivity to the temperature and strain rate. Taken spur bevel gear as an example, the hot forging process of the complicated shape parts of magnesium alloy AZ31B was investigated by means of finite element (FE) simulations combined with experiments. After the two-stage hot forming process (preforming operation without gear shape and finish forging operation) was determined, the influence of various shapes of preform dies on the hot forging process was discussed by the commercial finite element analysis software Marc, and the optimum preform die shape was obtained. According to the numerical simulation results, the hot forging experiments of magnesium alloy AZ31B spur bevel gear were successfully conducted. By comparison between experimental load–stroke curves and the calculated ones, it shows that the calculated results are consistent with the experimental ones.     

Analysis of three-dimensional upset forging of arbitrarily-shaped prismatic blocks

The present study is concerned with upset forging of arbitrarily-shaped prismatic blocks which is characterized by three-dimensional deformation with sidewise spread and bulging along thickness. A kinematically admissible velocity field to incorporate the three-dimensional deformation is proposed. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets and commercially pure copper billets at room temperature for different frictional conditions and geometrical shapes such as clover and rounded rectangles. The theoretical predictions both in the forging load and the deformed configuration are shown to be in good agreement with the experimental results. Therefore, the proposed method of analysis in this work can be used for the prediction of forging load and deformation in upset forging of arbitrarily-shaped prismatic blocks.     

Influence and prediction of hot deformation parameters on microstructure of Ti—15—3 alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉ 15 3(Ｔｉ 15Ｖ 3Ｃｒ 3Ｓｎ 3Ａｌ)ａｌｌｏｙｉｓａｎｅｗｍｅｔａｓｔａｂｌｅβ ｔｙｐｅｔｉｔａｎｉｕｍｃｈａｒａｃｔｅｒｉｚｅｄｂｙｉｍｐｒｏｖｅｄｈｉｇｈｓｐｅｃｉｆｉｃｓｔｒｅｎｇｔｈａｎｄｃｏｌｄｆｏｒｍａｂｉｌｉｔ     

Preform Design for Large-Sized Frame Forging of Ti-Alloy Based on 3-D Electrostatic Field Simulation and Geometric Transformation

Large-sized frame forging of Ti-alloy is an important forced component of aircraft. The frame forging has complicated shape which leads to great difficulties in deformation. Some defects may be produced during the forming process such as un-filling or overlapping. Preform design is an effective method for producing qualified forging. In this article, a new method based on 3-D electrostatic field simulation is proposed to design preform of a large-sized frame forging of Ti-alloy and a geometric transformation method is introduced to obtain the preform dimension. In order to select more suitable preform of large-sized frame forging, FEM software Deform-3D is employed to simulate the isothermal forming process of designed preform. Deformation uniformity index ψ is introduced as a criterion to judge the forging quality and the most appropriate preform is obtained by virtual orthogonal test design.     

用MATLAB研微波渗硼扩散问题

用MATLAB的偏微分方程（PDE）工具箱求解钢在微波渗硼过程中的扩散偏微分方程，计算了渗硼层厚度。仿真结果与实测数据相比表明，用MATLAB的PDE工具箱求解微波渗硼过程中的扩散偏微分方程具有较高的精度，计算出的渗硼层厚度与实测的相比，计算误差小于4．05％。     

Analysis of upset forging of cylindrical billets considering the dissimilar frictional conditions at two flat die surfaces

An upper-bound method is applied to the determination of forging load and deformed bulge profile during upset forging of cylindrical billets. A simple kinematically admissible velocity field which takes into account the dissimilar frictional conditions as well as the same frictional conditions at the top and bottom die surfaces is proposed for upset forging of cylindrical billets. From the proposed velocity field the upper-bound load and the deformed profile are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for several frictional conditions. The theoretical predictions both in the forging load and the deformed profile are in good agreement with the experimental results.     

Internal void closure during the forging of large cast ingots using a simulation approach

Large cast ingots often contain defects or undesirable microstructural features, such as voids and zones related to casting. Some of these features can remain after hot open die forging, which is an important process for converting large cast ingots into wrought components. During the initial cogging and deformation steps prior to the detailed open-die-forging operations, any internal voids should be eliminated. The present work focuses on the closure of internal voids during open die forging so as to produce a sound component. Hot compression tests were conducted to obtain the flow strength of the cast microstructure at different temperatures and strain rates. The measured flow strength data together with other appropriate material properties were used to simulate the forging steps for a large cast ingot. The numerical simulations for the forging deformation and for the internal void behavior were performed using DEFORM-3D™. Actual defects were measured in commercial ingots with an X-ray scanner. The simulation results for the void deformation behavior are compared with voids measured before and after forging. Through the comparison of experimental results and numerical simulation, a criterion for void closure is proposed. The criterion is that a local effective strain value of 0.6 or greater must be achieved for void closure during forging. Such a criterion can be used in conjunction with simulations to insure that a sound component is produced during the hot open die forging of large cast ingots.     

Solution for slab forging with bulge between two parallel platens by strain rate vector inner-product integration and series expansion

1INTRODUCTIONSlab forging with bulge between two parallelplatens is shown in Fig.1.Friction over the sur-face decreases the velocityvxat the surface,andcauses the centery=0to move faster with a result-ant bulge as shown in Fig.1(a).Therefore,thisvelocity gradient from the surface to the interiorintroduces a shear strain rateε.xy.Fig.1Slab forging with bulge betweentwo parallel platensIt is the bulge that make the forging more dif-ficult to be analytically solved[1].However,nu-merical m…     

Forging preform design with shape complexity control in simulating backward deformation

This paper presents a preform design method which employs an alternative boundary node release criterion in the finite element simulation of backward deformation of forging processes. The method makes use of the shape complexity factor which provides an effective measure of forging difficulty. The objective is to release die contacting nodes in a sequence which will minimize the geometric complexity throughout the backward deformation simulation. This is done by calculating the effect of releasing each of a select group of boundary element nodes at each finite element solution step. The particular detached node which results in the minimum shape complexity factor will be released for the current step. This process continues for each backward step until the last few nodes remain in contact. This design method is demonstrated through the simulated forging of an integrated blade and rotor turbine disk blank. A preform shape developed by this method is compared with an empirically designed preform. Performance parameters for comparison include die fill, flash volume, effective strain variance, frictional power and die load. Comparing the results of the forward simulations indicates improved performance of the preform design using FEM based backward deformation method over that of the empirical design.     

直齿圆柱齿轮精锻力的上限解

利用上限法，由有实验根据的变形流动模式设计了直齿圆柱齿轮精锻终了时的动可容速度场，获得了实验结果吻合较好的上限解，表明所建立的动可容速度场是可行的．     

锻造机双缸液压同步控制系统建模及仿真

为了提高锻造机双缸液压同步控制的精度,以便保证锻造成形的质量,简化锻造机双缸液压同步电液伺服控制系统模型,推导同步控制系统模型,得到控制目标方程。使用单神经元PID控制算法和交叉耦合算法作为锻造机双缸液压同步控制算法,通过仿真,分别得到并对比了使用常规模糊PID控制算法与模糊-单神经元PID控制算法作用下的锻造机左右液压缸的位置跟踪误差、相对同步控制误差以及液压缸的速度和压力跟踪误差。结果表明,相比于常规模糊PID控制算法,模糊-单神经元PID控制算法下的系统能够更快速地收敛,说明模糊-单神经元PID控制算法使得锻造机双缸液压同步电液伺服控制系统具有更强的鲁棒性。实验结果与仿真结果的变化规律一致,两者之间的误差小于10%,验证了提出的锻造机双缸液压同步控制方法的可行性。     

压缩矩形坯的应变矢量分析解法

提出了将能量泛函应变张量表示为应变矢量点积,而不采用不等式放大被积函数的直接积分法,进而使被积函数转换为可积的线性组合函数,并得到平面变形锻压矩形坯能量泛函的解析解。该解经实验与能量法、上界法及滑移线法解析结果及实测结果进行了比较,表明应变矢量分析结果低于数值结果和上界结果,与压力机实测指示的压力值误差为1.6%。