单位生产成本与加工精度的多工序车削优化

切削参数优化对于加工质量、生产效率、加工成本、产品利润具有非常重要的意义.数控加工过程中,单位生产成本和加工精度很大程度上决定了零件加工成本的高低和加工质量的好坏.建立以单位生产成本与加工精度为双目标的多工序车削优化模型进行切削参数优化选择十分必要.多工序车削模型同时充分考虑了粗精的刀具耐用度、切削功率、切削进给力、稳定切削区域、刀具表面切削温度及精车表面粗糙度等实际约束条件.运用高斯变异和多项式变异的NSGA-Ⅱ算法对多工序车削模型进行比较优化计算,优化实例表明多项式变异的NSGA-Ⅱ算法获得了更好的加工精度、单位生产成本的Pareto最优解集以及相应的粗精切削参数.用多项式变异的NSGA-Ⅱ算法得到的优化粗精切削参数进行切削试验,得到与NSGA-Ⅱ算法优化的加工精度、单位生产成本基本相符,为多工序车削切削参数优化提供了实践指导.     

变双曲圆弧齿线齿轮切削仿真及参数优化

变双曲圆弧齿线圆柱齿轮（VH-CATT）是一种将圆弧齿线运用于齿轮齿线上的新型齿轮。由于缺少专用的加工机床,导致加工时其切削参数的调整较为复杂。为解决这个问题,根据其啮合原理及加工过程,利用ABAQUS对其切削加工过程进行模拟仿真;利用得到的数据,根据正交试验方法建立切削力的预测模型。利用鲸鱼算法,建立以加工效率与较小切削力为目标的函数优化模型,并通过加权求和法与归一化处理将它转化为单目标函数优化模型,通过鲸鱼算法得到优化后的切削参数。结果表明：所提出的单目标函数优化模型能够很好地对切削参数进行选定优化,以得到更好的加工效果;优化后的切削参数为主轴转速n=189.3 r/min,每齿进给量fz=0.046 mm,切削深度ap=1.89 mm。     

基于模糊综合评判粗加工过程中铣刀的优选

针对粗加工过程中铣刀选型的多因素性,在分析机床加工特点的基础上,结合已有刀具选型方法,提出一种基于层次分析的模糊综合评判的方法,构建刀具模糊评判模型。通过综合考虑铣刀选型因素,建立以切削效率、加工时间以及加工成本作为优化目标的铣刀选型模型。结合具体加工实例对以上方法进行验证,表明基于层次分析的模糊综合评判方法在铣刀选型系统中有较好的作用,判断结果能够实现粗铣加工过程中刀具的优选。     

数控铣削参数模糊正交优化及实验研究

为了充分考虑数控铣削加工参数优化中的不确定性问题,运用模糊正交优化法研究铣削加工中满足高材料去除率和大刀具耐用度要求的切削参数优化。通过正交试验,获得不同切削用量下的刀具耐用度,并以模糊数学方法建立刀具耐用度和材料去除率隶属函数,计算模糊综合评价隶属度。结果表明:优化结果与模糊综合评价直观分析结果是一致的。     

基于动态材料模型和正交试验的直锥齿轮优化研究

基于动态材料模型的加工图技术被广泛用于设计和优化材料热加工工艺中。为了提高直齿锥齿轮的综合力学性能,基于Deform软件材料数据库建立了20GrMnTi钢的热加工图。分析了变行温度和应变速率对材料微观组织结构和性能的影响,确定了直齿锥齿轮热精密锻造工艺的参数范围。并以成形载荷、模具磨损为优化目标,选择锻造温度、模具运动速度、连皮厚度和飞边槽高度为优化变量,采用正交试验设计进行有限元数值模拟及其多目标优化分析。结果能为实际生产提供参考。     

基于神经网络和粒子群算法的切削参数现场实时优化

为了使金属切削加工中，能实现切削参数的实时优化，保证产品质量和设备效率，提出了一种新的切削参数最优化方法，引入加工时间、加工精度、加工成本三个目标控制量，建立了多目标非线性规划模型。并用惩罚函数法将多目标非线性约束规划问题转换成无约束非线性单目标规划问题。通过对神经网络和粒子群算法的有机结合，并充分利用了粒子群算法和BP网络各自具有的优点，对模型进行了求解。数值试验表明该方法能较好地解决切削参数的优化问题。     

复杂薄壁零件数控加工变形误差控制补偿技术研究

高性能航空发动机整体叶盘、大小叶片转子、离心叶轮、叶片等零件广泛采用钛合金薄壁结构。加工过程中的切削力、残余应力将产生零件加工变形及加工误差。本文重点讨论了薄壁零件加工过程中的切削力建模和工件加工表层残余应力的分布规律,提出了对叶盘零件加工变形误差的补偿方案。通过建立精确的切削力、残余应力预报模型,对切削加工过程进行力学仿真,优化切削参数、补偿刀位轨迹,进而实现薄壁结构叶盘零件的精密数控加工。     

基于自适应控制技术的铣削参数优化

采用BP神经网络算法应用于铣齿功率建模能较准确地预测铣齿功率大小,进而运用STATISTICA的正交设计优化试验数据对滚齿机进行再制造,通过在主轴箱加设传感器实现了机床振动稳定性的的在线监控,分析各个切削状态下主轴箱振动同铣削功率的关系,进行优化切削参数,实现了数控系统与在线监控技术的自适应闭环监控.完成了4m大型滚齿机向高速铣齿机床SKX-4000的智能化再制造.结果表明,采用的控制策略能适应强力铣削的工况变化,稳定地控制加工过程,达到保护机床、刀具和提高加工效率的目的.     

基于模糊综合评判高速钢立铣刀切削用量优化选择

针对高速钢立铣刀铣削过程中切削用量选择的模糊性,在分析高速钢立铣刀加工特点的基础上,结合现有铣刀切削用量选择方法,提出一种基于加权平均模型的模糊综合评判方法。通过综合考虑影响铣刀切削用量选择的因素,建立以单个工序加工时间、加工成本以及刀具耐用度为目标优化模型。结合具体加工对象分析表明:基于加权平均模型的模糊综合评判方法,能够实现高速钢立铣刀在铣削过程中切削用量的优化,评判结果准确、适用。     

基于支持向量机的钛合金铣削加工参数优化

针对钛合金材料在加工过程中受铣削力影响易于产生变形而影响加工效果,属难加工材料,为了保证加工质量,提高生产效率及降低加工成本,其切削加工参数的合理选择非常关键;对钛合金铣削加工进行有限元数值计算,结合试验设计方法构建了基于支持向量机的切削力预测模型,提出了一种基于支持向量机和遗传算法的优化方法,对钛合金铣削工艺参数进行了优化;结果表明,该方法准确、高效、可行,为钛合金加工工艺参数优化提供一种新的思路,具有良好的推广价值。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.