异形花键截面钢丝辊模拉拔模拟研究

利用Deform-3D软件对异形花键截面钢丝的辊模拉拔工艺过程进行模拟研究。对预成形阶段的辊拉模外齿圆角与内齿圆角进行了参数优化,获得了最佳工艺参数组合,即外齿圆角半径R_1为0.5 mm,内齿圆角半径R_2为0.5 mm。为保证最终产品尺寸,选定整形阶段外齿圆角半径R_1为0.4 mm,内齿圆角半径R_2为0.4 mm。根据最优组合参数进行了模拟仿真与实验验证。模拟结果表明,工件上的圆角均能填充饱满。实验结果表明,零件表面齿形处成形质量较好,外齿与内齿处圆角填充完整。实验结果与模拟结果基本一致,获得了符合产品尺寸的制件。模拟和实验结果有助于研究异形花键截面钢丝辊模拉拔过程的宏观变形,为精密异形丝的成形过程提供了理论指导。     

凸锥夹层板辊式成形工艺研究

基于MSC.Marc有限元软件对凸锥夹层板的辊式成形过程进行了数值模拟,以夹层凸锥辊式成形后壁厚最大减薄率为成形性评价指标,研究了各主要结构参数对成形的影响。结果表明:凸模圆角半径R1、凸模转角半径R2以及摩擦系数μ对凸锥夹层板的壁厚最大减薄率影响较大,并给出了其影响规律和成形目标零件的参数建议取值。基于分析结果,设计了用于辊式成形的试验机,并进行了凸锥夹层板辊式成形实验,验证结果表明针对凸锥形夹层板辊式成形工艺的可行性,但仍存在凸锥点阵间纵向过桥位置起皱、板料纵横向翘曲、板边不齐、凸锥曲面卸载畸变等成形质量问题。     

平顶链链板卷圆冲压成形模具的设计与仿真北大核心CSCD

为提高平顶链链板卷圆工序的成形精度,根据工艺要求设计了一套平顶链链板卷圆冲压成形模具,该模具的上、下模均采用拼接式结构,上、下模间设有校孔装置,对该模具的关键参数进行了初步设计。利用Abaqus软件对链板的卷圆成形过程进行仿真,分析链板所受的等效应力及其成形精度,并根据仿真结果,对模具的关键参数进行修正。仿真结果表明:工件所受的最大等效应力位于链板左右两侧形成的卷圆处,符合链板卷圆成形的实际受力情况;且当卷圆销孔上模的圆角半径为6.12 mm、铰孔上模的圆角半径为6.35 mm、销孔下模的圆角半径为6.14 mm、铰孔下模的圆角半径为6.28 mm时,仿真后的链板的成形精度高。最后,制作模具样机并进行卷圆冲压成形实验。结果表明,卷圆冲压成形后工件的合格率达到98%。     

预成形毛坯过渡圆角半径对气门终锻成形过程的影响

采用数值模拟与实验相结合的方法,对气门毛坯的楔横轧-模锻工艺过程进行研究,依据气门毛坯楔横轧成形工艺及终锻成形工艺的要求设计了不同过渡圆角半径的预成形毛坯,采用有限元软件进行数值模拟。分析其成形工艺过程中坯料的金属流动规律、不同过渡圆角半径的坯料所需最大成形载荷,并研究成形过程中坯料与凹模的接触情况。研究结果表明,与锻件过渡圆角相比,毛坯圆角半径与锻件圆角半径越接近,综合效果越好;当毛坯圆角半径过小时,所需的成形载荷也较小,但毛坯过渡圆角处的氧化皮难以清除,且会出现较浅的挤压痕迹;当毛坯圆角半径过大时,成形载荷也越大,产生严重的挤压痕迹,使模具产生严重的磨损,从而降低模具的使用寿命。     

基于微观遗传算法优化法兰滑套成形工艺

基于DEFORM-3D平台,采用拉丁超立方抽样设计,以法兰滑套预成形坯料角度、圆角半径、底面半径为设计变量,将挤压成形最大载荷、凹模累积磨损量作为优化目标,设计了试验表,并对试验表中的每组数据进行数值仿真,最终得出每组数据对应的最大载荷、凹模累积磨损量。应用MATLAB软件编写微观遗传算法程序,对目标设计变量进行优化,得出坯料角度为29°,圆角半径为14.5 mm,底面半径为82 mm时为最佳优化条件。将优化后的坯料进行数值仿真并进行工业试制,经与原生产工艺进行对比发现,法兰滑套挤压成形的最大载荷从614 k N降低到496 k N,凹模寿命从3000件提高到4000件。     

发动机托架后安装板翻边成形拐角区域的开裂研究

从调整首次拉延圆角、增设工艺凸包和增加工艺切口圆角3个方面,利用Autoform有限元分析软件,研究了发动机托架后安装板成形质量的变化规律。分析了首次拉延圆角r_0与二次拉延圆角r_1的比值对缺陷和料厚的影响规律,随着首次拉延圆角r_0值的增加,最终成形工件的料厚呈现先增加再减小的趋势,越靠近r_0=0.75r_1(即k=0.75),材厚越大。当r_0=r_1时,增设工艺凸包对破裂缺陷具有一定的改善作用;当r_0=0.75r_1时,增设工艺凸包对缺陷和料厚的改善作用很小。随着工艺切口圆角r_(切口)的增大,能够有效减小应力集中系数,FLD中对应于原始破裂位置的点已完全进入安全区域,且距离成形极限曲线越来越远,料厚呈现增大趋势,对缺陷的改善效果明显。     

含硼高强钢带热辊压成形回弹的数值模拟

针对采用含硼高强钢带制造槽形件的回弹与应用问题,设计了一种新的六辊式热辊压成形装置。以2.2mm厚的含硼高强钢带为原料,设定奥氏体化温度为900、910、920℃,穿带速度为750 mm/s,运用ANSYS有限元软件模拟计算了其热辊压成形回弹情况。结果表明,奥氏体化温度对板料热辊压成形回弹影响显著。塑性变形区主要发生在圆角半径较小的圆角处,随着板料成形前奥氏体化温度的升高,板料回弹量呈现减小趋势。900℃奥氏体化温度对应的板料回弹角为8.7°,塑性应变在0.11左右,最大等效应力为589.1 MPa;910℃奥氏体化温度对应的回弹角为7.9°,应变在0.15左右,最大等效应力为584.2 MPa;920℃奥氏体化温度对应的板料回弹角为6.5°,应变在0.16左右,最大等效应力为574.0 MPa。     

电池包纵梁辊冲成形仿真分析与实验验证

提出某QP1180超高强钢制的电池包纵梁辊冲成形方案,以解决该超高强钢梁类零件台阶结构特征的成形问题。为了成形此类具有典型变高度特征的电池包纵梁,考虑到辊冲成形独特的运动方式,避免在零件成形过程中出现模具与板料碰撞的缺陷,提出了具有新型结构的辊冲模具,通过数值仿真的方法,对零件在辊冲成形过程中的应力分布情况以及机架的工作载荷进行了分析,判断了工艺方案的可行性;进而基于仿真结果对模具进行优化迭代,确定了最终模具的补偿参数,将仿真结果的角度偏差控制在±1°以内;最后,开展辊冲成形的实验与试样制备,试制零件的尺寸偏差在±1 mm以内。     

凸模圆角半径对钢板冲压成形的影响

圆角半径的确定一直是冲压件工艺设计的关键技术,本文采用实验与理论模型相结合的手段,研究了凸模圆角半径对钢板冲压成形的影响。结果表明：冲压成形中的开裂位置和凸模圆角大小有关;圆角处的减薄率基本上与相对圆角半径R／t成反比;极限成形高度随凸模圆角半径的增大而增大。     

复杂覆盖件均匀成形的动态调控

将压边力、拉深筋高度、凸筋圆角半径和凹筋圆角半径作为自变量,以正交试验为设计方案,模拟右托架覆盖件成形,获得成形质量目标破裂、起皱和厚度最大变薄率的数据。运用层次分析法计算多目标质量的权重,运用灰色系统理论计算每个细分成形过程的多目标质量的关联系数与关联度,获得该覆盖件拉深过程优化的压边力、拉深筋阻力工艺参数的最佳动态匹配。进一步运用动态调控的工艺参数组合进行有限元模拟验证,仿真结果表明成形质量明显提高。     

面向零件形状的计算机图形库的开发

论述了CAD技术中参数化设计的三种建模方法，重点介绍了基于特征的参数化建模原理。在此基础上，分析机械设计中的机构结构，归纳出其零件的几何特征构成。设计了机构CAD图形库，并提出了该图形库生成步骤和人机交互界面。     

FeCrAIW电弧喷涂层组织的致密化研究

采用激光辐照对FeCrAlW电弧喷涂层的组织进行致密化处理,借助扫描电镜和X衍射对涂层的组织进行了分析.测试了涂层的显微硬度.结果表明:涂层组织致密度提高,孔隙率明显降低.随着激光扫描速度的增加,涂层的显微硬度降低.在较低的扫描速度下,涂层与基体之间形成互熔区,涂层与基体之间产生良好的冶金结合.     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.     

试论洋务派教师聘任的思想

洋务派在洋务学堂的办学活动中,为了解决西学专业学科的教学困难,采用了聘请外籍教师的应急措施.他们以真才实学,合同制管理作为主导思想,并认为这种解决师资的途径只是权宜之计,并非久远.从客观上看,洋务派的教师聘任思想有深刻的历史影响.