目的 基于全量流动理论,研究管材弯曲成形过程中的外侧破裂和内侧起皱,分析其产生的原因及控制方法.方法 采用理论解析方法,建立了管材弯曲变形应力、应变计算公式,推导管材外侧破裂和内侧起皱发生的判据,并试验验证了预测公式的可靠性.结果 基于推导的应力、应变计算公式,依据临界许用变形程度,建立了管材外侧破裂判据;采用能量准则,提出了管材弯曲过程起皱发生公式,确定了起皱失稳计算公式的各个边界参数.结论 试验与理论结果表明,构建的最小壁厚下许用R/r(弯曲半径与管材平均半径的比值)计算公式、基于起皱失稳计算的许用R/r(弯曲半径与管材平均半径的比值)计算公式均有较高精度,可用于指导弯管工艺参数设计与优化.

目的 获得一种低成本钛合金Ti12LC准确的相变点.方法 采用差热分析法和连续升温金相法,对钛合金的相变温度进行了测定.首先通过差热分析,初步确定了该钛合金相变温度范围,接着采用连续升温金相法,进一步精确分析钛合金的相变点.通过分析DSC曲线中的吸热、放热现象,对该合金的相变温度范围进行研究,再通过试样淬火后的金相分析,研究 α 相和 β 相的数量及分布.结果 确定了Ti12LC钛合金的相变温度在880～890℃之间,而连续升温淬火金相法测得Ti12LC钛合金的相变温度为885℃.结论 由于淬火温度间隔小,两种分析方法下,该相变温度的测定较为准确.

目的 获得Ti12LC钛合金适用的固溶处理工艺.方法 开展固溶时效工艺试验,研究不同固溶温度及冷却方式对合金微观组织及力学性能的影响.结果 随着固溶温度的升高,初生α相含量有所减少,而β转变组织含量则显著增加,合金的抗拉强度也显著上升,而伸长率则有所下降,固溶温度越接近相变点,性能的变化则越敏感.在900℃固溶时,温度已在相变点以上,获得的组织为粗大的魏氏组织,表现出较高的强度但同时的塑性降低明显.结论 该合金的最佳固溶工艺为820～860℃保温,空冷至室温.

The hot pressure deformation tests were carried out by using Gleeble-2000 simulator at the temperature of 950°C ~ 1150 °C and strain rate of 0.001s -1 ~ 1s -1 for a kind of high strength construction steel 34CrNiMo6 for Crankshafts and the curve of its flow stress were obtained. By studied the data, the flow stress constitutive equation, hot deforming active energy and the Z parameter were obtained. The curve of flow stress of 34CrNiMo6 steel indicated that the flow stress was increased with the decrease of temperature or increase of the strain rate. During the deformation, temperature and strain rate take important effect on dynamic recrystallization and dynamic recovery. It was propitious to dynamic recrystallization with raising temperature or reducing strain rate, and also made for the refinement of grain.

The paper aims to solve the issue of low dimensional accuracy caused by axial flow in upsetting & extrusion process of crankshaft. A finite element model was established according to simulation on the whole flow of heating, forming and cooling of blanks based on kinematics of upsetting & extrusion process device, thermodynamics of forming process, constitutive model of crankshaft material, geometric model, etc. to analyze causes of axial deviation. Based on simulation analysis of finite element, billet volume and flash thickness were the keys for axial flow in upsetting & extrusion forming. The abnormal axial flow might be controlled by optimizing the geometrical shape of blanks for step shaft. Experimental results show that the axial flow of the crankshaft is controlled effectively. The length deviation of single crank shaft is controlled within the range of ±1 mm and the qualified rate of crankshaft forging is up to 90%.

目的 通过对新型镁合金材料Mg-5Gd-4Y-0.3Zr进行力学性能实验和成形工艺数值模拟分析,对镁合金机匣成形工艺进行设计优化和开发参考.方法 采用Gleeble-3500热模拟试验机,得到该镁合金材料在不同温度、不同应变速率下对应的真应力数据,并建立材料模型,应用在有限元模拟分析中.结果 经优化后的工艺方案能得到充型饱满、无质量缺陷的镁合金机匣锻件,并通过工艺实验,验证了该设计方案的可行性.结论 采用可分凹模模锻成形,能够锻造出外形美观、强度达标的轻质镁合金机匣.

目的 基于实测的流动应力曲线,构建可用于热成形模拟的34Cr2Ni2Mo合金结构钢高精度本构方程.方法 采用热模拟试验测试该材料的流动应力曲线,在动态再结晶的条件下,构建了基于物理机制的热本构方程,通过曲线拟合获得了本构方程参数.结果 热模拟试验测试的流动应力曲线具有明显的动态再结晶现象,构建的本构方程包括流动应力、屈服/饱和川临界/稳态应力、发生50％再结晶的时间等内变量计算方程,在参数拟合后对其误差分析表明,本构方程计算的流动应力偏差控制在±15MPa以内.结论 34Cr2Ni2Mo合金结构钢本构方程能够较为准确的描述该钢在热成形过程的流动应力变化特征,具有较强的数值稳定性和外延拓展性.

The aim of this study was to investigate the hammer forging process of connecting rod of one high-power-den-sity engine. The classical process design method was employed to design the hammer forging process, and the finite element method was used to analyze the process. By using numerical simulation, the filled effect was analyzed, the geometrical evo-lution of preform and defect were shown in numerical simulation results, and the geometry of preform and hammer process were optimized. Experimental work verified the accuracy of numerical simulation results. The obtained forging of connecting rod has homogeneous microstructure without any defects, which can satisfy all the technical requirements.

Crankshaft is one of the most important parts in the engine of vehicle.The feasibility of the process of full fiber forging of the crankshaft was analyzed.The status of the metal flow and the distribution of deformation were simulated.On this basis,process test of the full fiber forging of the crankshaft was carried on.Finally,qualified crankshaft forging was trial-produced.The results indicate that the full fiber forging crankshaft is quite doable,which can apply to the large marine crankshaft and the vehicular crankshaft.

Taking at the planetary bevel gears as an object,the characteristics of closed precision forging were studied.And the formability of the part was analyzed.The whole course of closed forming gears was numerically simulated.The results show that:when forging finishes,each part of cavity is filled completely,without corner collapse,fold and crack.And taking the lower die as an example,the status of die stress was also studied.The results of the simulation were proved by the technology test,and the high precision and quality forging were obtained.The utilization of the material was greatly reduced.

Recent research achievements both in domestic and abroad about W-Cu composite were analyzed and the application,preparation and densification technology,and the research progress and application of W-Cu compo-sites with high performance shaped charge liner.The prospect of preparation method and application development was discussed.

Dynamic shear experiment of TC11 at high strain rates(700～2 100 s-1) was carried out by torsional split Hopkinson bar.The behavior of dynamic shear,microstructure and properties of TC11 alloy were investigated by optical microscope,microhardness instrument,stereoscan electron microscope and transmission electron microscope.The results show that the sensitivity of adiabatic shear increases with increase of strain rate.Adiabatic shear band consists of elongated microstructures located in transition areas and equiaxed grains with fine grain size of intermediate position.Adiabatic shear band is about 10 μm and characterized by shearing deformation streamline.The microhardness value of shear bands is higher than that of matrix body.This can be attributed to strain rate strengthening and interacting between strain strengthening and thermal softening.

The design of precision forging process of a steel forge piece with non-machined surface was studied by the combined method of numerical analysis and process experiments. The study results were shown as follows, high-precision material model is key part of process design, numerical analysis results were consistent with the results of process experiments, numerical analysis results provided the reference for the forging process design, trial production of small lot size was carried out and showed the forging process satisfied the design requirements.

According to the production requirements of high quality and low cost for car cup class piston product, the ro bust design of warm and cold compound forming parameters based on multiple response surface methodology is given in this paper. The quadratic satisfaction function and quality loss function model based on signal-to-noise ratio are constructed, and the optimum process parameter combination combined with orthogonal test is that the warm forming temperature is （795±5） ℃, the billet deformation ratio through warm forging is 0.45, the cold extrusion punch working zone dimension is 2.5 mm, and the cold extrusion punch fillet dimension is 7 mm. The small batch test assessment shows that the piston product quality stability control ability is very strong through using the optimum warm and cold compound forming parameters, and the engineering production capacity of piston product is got completely.