外花键冷滚打成形力解析方法

为确定外花键冷滚打的力能参数,分析了冷滚打金属变形区的特点,在一次冷滚打过程中,变形区参数和位置随滚打轮的移动不断变化,接触弧和压下量都很小,在冷滚打初始阶段存在不完整变形区。提出了计算冷滚打单位压力和变形力的解析方法,将一次冷滚打过程离散为无限多个复杂断面的冷滚轧过程,给出了冷滚打单位压力和变形力的解析公式,确定了冷滚打单位压力值及其分布特征。为验证解析方法,建立冷滚打有限元模型并计算了冷滚打成形力,改造卧式铣床进行冷滚打实验,测量了冷滚打成形力。将解析公式预测结果与仿真和实测结果进行对比,结果表明:冷滚打径向力最大值误差分别约为7%和4%,冷滚打径向力变化曲线基本相符,但一次冷滚打过程时间略短。解析方法正确地预测了冷滚打变形力的大小和变化过程。     

冷滚打成形对花键组织与性能的影响

通过显微观察等测试手段,对花键在冷滚打加工时形成的纤维组织、齿形表层硬度分布等进行了研究;分析了冷滚打成形过程中,等轴晶被拉伸形成金属纤维的过程以及齿形表层硬化的原因.试验表明:花键冷滚打加工使工件内部晶粒破碎、细化并拉伸形成了与花键齿形一致的金属纤维组织,冷滚打的冷作硬化使花键齿表层硬度及抗冲击能力有较大提高;高应力在改善花键齿形表面质量的同时,也可能导致高变形抗力,使滚打轮过早失效.     

20钢花键冷滚打成形表层物理力学性能优化

为了实现对20钢花键冷滚打成形表层物理力学性能的合理控制,以冷滚打转速、进给量和滚打轮圆角半径为试验参数,进行了冷滚打成形正交试验,分别测量花键分度圆处的表层加工硬化程度和残余应力,采用田口理论信噪比权衡各加工参数对花键表层物理力学性能的影响程度;运用熵权理论与田口过程能力指数设置各评价指标的权重,建立花键表层物理力学性能的改进田口过程能力指数优化模型,使用广义简约梯度法对模型进行优化,将得到的最优加工工艺参数组合通过冷滚打成形试验进行验证,并对其表层微观组织形貌进行观察和分析。结果表明:进给量对冷滚打花键表层物理力学性能影响程度最大,滚打轮圆角半径次之,冷滚打转速最小;花键表层物理力学性能最优加工参数组合为冷滚打转速1581 r·mm-1,进给量42 mm·min-1,滚打轮圆角半径2 mm;所对应的花键表层物理力学性能最优值为:表层加工硬化程度148. 92%,表层残余应力-85. 83 MPa。     

冷滚打成形表层残余应力模型建立

为提高冷滚打成形工件的表面性能,实现对冷滚打成形过程中残余应力的控制,以渐开线花键为研究对象,采用轮廓法测量冷滚打成形花键齿廓不同位置的残余应力,依据实验结果采用响应曲面法建立冷滚打成形花键齿廓齿根处、分度圆处和齿顶处的残余压应力峰值和残余压应力层深与冷滚打成形参数的关系模型,对比分析了实验结果与模型的预测结果。研究表明所建立的残余压应力峰值模型的最大预测误差为3.3%,残余压应力层深模型的最大预测误差为6.1%,预测结果具有较高的可信度,可以进行不同冷滚打成形参数的齿廓空间残余应力和残余压应力层深度的预测。     

花键冷滚打表面粗糙度灰色预测模型

为了改善花键冷滚打表面粗糙度,提高花键冷滚打表面质量。根据花键冷滚打成形原理,以花键冷滚打表面粗糙度作为主要影响因素,滚打轮转速和工件进给量作为变量,进行花键冷滚打试验,利用花键冷滚打试验结果构建花键冷滚打表面粗糙灰色预测模型,对比分析表面粗糙度试验值与预测值,运用后验差比值和小误差概率验证构建的花键冷滚打表面粗糙度预测模型。研究表明:计算得到后验差比值为0.367,小误差概率大于0.95。将计算得到的后验差比值和小误差概率与灰色预测模型精度表进行对照,验证了所构建预测模型的正确性与可行性。     

基于ABAQUS的丝杠冷滚打变形力仿真

丝杠冷滚打成形是一种新型的绿色近净塑性成形技术,其中的变形力是冷滚打成形过程中一个非常重要的因素,不仅关系到材料的应力和应变,还是设备设计、验算工具强度、制定合理工艺制度的重要依据.基于仿真进行丝杠冷滚打变形力的研究,介绍丝杠冷滚打的原理,讨论基于 ABAQUS的有限元模型的建立,在此基础上进行了丝杠单次滚打正应力、切应力的仿真,进而获得了变形力及其分力随时间的变化情况,为后续研究奠定了基础.     

冷敲花键相邻齿槽之间成形影响的分析

在分析花键冷敲成形原理的基础上,采用ABAQUS/Explicit算法对花键冷敲相邻齿槽成形过程进行了有限元模拟仿真,研究了工件经过不同敲打次数后两个相邻齿槽的应力、应变分布规律。在自行研制的LQ200型冷敲设备上加工花键轴,利用光学显微镜研究冷敲花键不同成形区的显微组织形貌,以及不同成形区的影响层深度。结果表明:冷敲成形属于局部表层成形,敲打齿槽在敲击时应力波扩散到了相邻齿槽,应力波对相邻齿槽齿顶、齿侧、齿根的影响依次减小,敲打齿槽在敲击时对相邻齿槽的应变影响很小;齿顶成形区分度圆以上均为影响区,相比齿侧、齿根成形区,齿顶影响区范围最大;齿侧成形区的影响区深度大约为1 mm;齿根成形区的影响区深度大约为600μm。     

高速冷滚打成形硬化程度预测模型建立

为提高冷滚打成形工件的表面质量,改进冷滚打成形工艺,以渐开线花键为研究对象,进行了高速冷滚打成形工件的显微硬度试验,并对实验得到的数据进行了数理统计分析,根据冷滚打加工参数对工件齿廓不同位置表面硬化程度的影响关系,采用曲面响应法建立了成形花键齿廓不同位置表面硬化程度随滚打轮转速和工件进给量变化的多元回归模型,并对模型进行了显著性检验及方差分析,通过试验数据与预测模型的对比分析,证明了该模型在滚打条件相近的情况下,能够对齿廓不用位置的表面硬化程度起到精确的经验预测作用。     

花键冷滚打和铣削加工的金属组织变形研究

本文针对冷滚打花键和铣削花键加工工艺特点,从微观组织分析角度,对两种加工方法得到工件金相组织和硬度分布进行分析比较.试验表明:铣削加工过程中,金属表面组织被切断,内部组织没有发生变化,对力学性能也没有影响;而冷滚打加工后的花键金属组织未被切断,晶粒破碎和细化,位错密度增加,最终被拉成条形纤维组织.相对于铣削,冷滚打加工改善了加工表面金属组织,硬度和强度有较大提高.从而为冷滚打花键成形技术的进一步研究奠定了基础.     

冷滚打花键表层性能熵权-灰色理论优化研究

为提高花键冷滚打成形表面性能,研究冷滚打加工参数对表层性能的影响程度,筛选影响冷滚打花键表层性能最优的冷滚打工艺参数,以渐开线花键为研究对象,以冷滚打转速和进给速度为主要工艺参数,将熵权理论与灰色理论相互结合,对花键齿面分度圆处的表面粗糙度、残余应力和硬化程度进行关联分析研究。结果表明:花键表面粗糙度和硬化程度随进给速度的增加而增大,随冷滚打转速的增加而减小;花键残余应力随进给速度的增加而减小,随冷滚打转速的增加而增大;进给速度对冷滚打花键表层性能影响较大;冷滚打花键表层性能最优的冷滚打工艺参数为冷滚打转速1428 r·min~(-1)和进给速度42 mm·min~(-1)。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.