基于BP神经网络的T91钢蠕变行为预测研究

基于BP神经网络的理论,建立了多应力水平下T91钢蠕变速率预测模型.通过实验采集到了相关实验结果,利用建立的BP神经网络模型,对实验结果数据进行训练.结果表明:模拟结果与实测结果吻合良好,预测精度很高;采用BP神经网络法可为研究T91钢蠕变行为提供一条可行方法,根据该模型可改善材料的工艺.     

基于可靠度的Incoloy800H管材蠕变性能分析

结合蠕变特征量-温度参数模型,研究了Incoloy800H管材在600～1050℃下的蠕变行为,拟合得出材料稳态蠕变速率、蠕变断裂时间、蠕变第3阶段起始时间的可靠性方程,并建立了管材容许应力与服役温度、可靠度的关系.结果 表明,确定的蠕变特征量可靠性方程可以较好地预测Incoloy800H管材稳态蠕变速率、蠕变断裂时间...     

基于BP神经网络的电主轴热误差补偿模型

热误差是影响高精度数控机床加工精度的主要的误差因素.文章主要论述了利用BP神经网络来建立CX8075车铣复合加工中心电主轴热误差补偿模型的建模的过程,以两组不同的数据,分别进行的训练和预测,经过在软件MATLAB中的模拟测试,通过BP神经网络建立的电主轴热误差补偿模型具备了较高的拟合和预测精度.分析结果表明,电主轴的原始热误差值与模型计算的输出结果的值非常接近,最低补偿率可达90％以上,这代表运用该BP神经网络模型能够补偿大部分的热变形误差.     

Cu-Cr-Sn-Zn合金时效工艺人工神经网络建模

利用神经网络对Cu-Cr-Sn-Zn合金时效温度和时间与硬度和导电率样本集进行学习,建立了时效强化工艺BP神经网络模型.结果表明该BP神经网络具有良好的泛化能力,可以充分挖掘样本蕴含的领域知识,对材料性能进行有效预测和分析.     

基于遗传算法的神经网络在预测油管钢腐蚀速率中的应用

针对目前BP神经网络在实际应用中,网络结构难以确定以及网络极易陷入局部解问题,用遗传算法优化神经网络的连接权和网络结构,并在遗传进化过程中采取保留最佳个体的方法,建立基于遗传算法的BP网络模型,同时用一个实例说明该模型在预测油管钢腐蚀速率中的应用,实践证明神经网络预测结果与实验值吻合较好.最后通过现场实验数据检验了该神经网络的泛化能力，表明其预测结果与现场实验结果相近.     

基于BP神经网络的表面硬度预测模型

运用MATLAB中BP神经网络强大的数据预测功能,并结合VB编写的用户操作界面,建立了基于BP神经网络的表面硬度预测模型.对该模型进行训练和仿真后,其所得到的结果与实际测量值相差较小,能够达到模型预测的要求,有较好的工程实际意义.     

钢板水火加工温度场热源参数预报研究

本文以水火弯板加工过程中的燃气流量、火焰移动速度、加工时间和钢板厚度作为输入参数,热源热效率和热源半径作为输出结果,建立了一种可以预测水火弯板热源模型参数的BP神经网络方法.应用神经网络预测结果设定水火弯板数值模拟时钢板表面的热流载荷参数,基于ANSYS软件得到钢板水火弯板温度场数值计算结果.经应用实例验证,以BP神经网络输出为热源参数的水火弯板数值计算结果与试验测试结果基本一致,说明本文所建立的BP神经网络方法可以用来预测水火弯板温度场热源模型参数.     

Al-0.6Mg-0.4Si铝合金的蠕变变形行为及稳态蠕变本构模型的建立

采用蠕变拉伸实验研究了Al-0.6Mg-0.4Si铝合金在低于其屈服强度的应力和不同温度作用下的蠕变时效变形行为。建立了稳态蠕变速率与加载应力、实验温度之间关系的数值模型。结果表明,固溶态Al-0.6Mg-0.4Si铝合金第一阶段的蠕变速率随时间延长而不断降低。随着温度和应力的增大,蠕变曲线由第一阶段进入第二阶段的时间不断延迟,且第一阶段的蠕变量及总的蠕变量不断增大。随着蠕变时效温度和应力的提高,该合金的稳态蠕变速率逐渐增加。所建立的模型具有良好的拟合效果。     

MEA优化BP神经网络的电主轴热误差分析研究

针对磨齿机在磨削加工时,电主轴存在热致误差等问题,提出一种基于思维进化算法(MEA)优化BP神经网络建立磨齿机电主轴热误差预测模型的方法。通过测量磨齿机电主轴在加工过程中的温升与位移情况,利用思维进化算法优化BP神经网络算法在MATLAB软件中建立预测模型,并与未经过算法优化的BP神经网络建立的模型进行了对比。在电主轴X向热误差预测实验中,未经过算法优化的BP模型最低补偿率为84.85%,而经过思维进化算法优化BP模型最低补偿率为95.29%。结果表明:经过思维进化算法优化BP神经网络建立的热误差模型,在拟合和预测精度上要优于未经过算法优化的BP神经网络热误差模型。     

基于遗传神经网络的铣削力预测方法

铣削过程的复杂性和铣削力产生的多因素性使得铣削力预测模型很难建立.论文在遗传算法与BP网络模型相结合的基础上,利用遗传算法训练神经网络权重的方法,建立了铣削力预测的遗传神经网络模型.最后将神经网络预测结果与实验数据进行比较和误差分析,证明了该神经网络能够准确地预测铣削力的大小.     

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.     

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。     

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.     

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.     

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).     

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.