Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

Variable-based Ramberg-Osgood constitutive model of power spinning bushing

The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.

Effects of material properties on power spinning process of parts with transverse inner rib

Material properties of blank have a great effect on power spinning process of aluminum alloy parts with transverse inner rib.By using finite element(FE) and Taguchi method,the effects and significance of five key material parameters,namely,anisotropic index in thickness direction,yield strength,hardening exponent,strengthening factor and elastic modulus on the formability of inner rib,tendency of wall fracture and degree of inhomogeneous deformation of finished spun parts were obtained.The achievements provide an important guide for selecting reasonable spinning material,and are very significant for the optimum design and precision control of power spinning process of parts with transverse inner rib.

Optimization of Processing Parameters of Power Spinning for Bushing Based on Neural Network and Genetic Algorithms

A neural network model of key process parameters and forming quality is developed based on training samples which are obtained from the orthogonal experiment and the finite element numerical simulation. Optimization of the process parameters is conducted using the genetic algorithm (GA). The experimental results have shown that a surface model of the neural network can describe the nonlinear implicit relationship between the parameters of the power spinning process:the wall margin and amount of expansion. It has been found that the process of determining spinning technological parameters can be accelerated using the optimization method developed based on the BP neural network and the genetic algorithm used for the process parameters of power spinning formation. It is undoubtedly beneficial towards engineering applications.

A high performance fast-Fourier-transform spectrum analyzer for measuring spin noise spectrums

A high performance fast-Fourier-transform (FFT) spectrum analyzer, which is developed for measure spin noise spectrums, is presented in this paper. The analyzer is implemented with a field-programmable-gate-arrays (FPGA) chip for data and command management. An analog-to-digital-convertor chip is integrated for analog signal acquisition. In order to meet the various requirements of measuring different types of spin noise spectrums, multiple operating modes are designed and realized using the reprogrammable FPGA logic resources. The FFT function is fully managed by the programmable resource inside the FPGA chip. A 1 GSa/s sampling rate and a 100 percent data coverage ratio with non-dead-time are obtained. 30534 FFT spectrums can be acquired per second, and the spectrums can be on-board accumulated and averaged. Digital filters, multi-stage reconfigurable data reconstruction modules, and frequency down conversion modules are also implemented in the FPGA to provide flexible real-time data processing capacity, thus the noise floor and signals aliasing can be suppressed effectively. An efficiency comparison between the FPGA-based FFT spectrum analyzer and the software-based FFT is demonstrated, and the high performance FFT spectrum analyzer has a significant advantage in obtaining high resolution spin noise spectrums with enhanced efficiency.

Dynamic Economic Dispatch for Wind Power System Considering System Security and Spinning Reserve

In this paper, dynamic economic dispatch model is proposed for power systems with bulk wind power integration. The wind turbine generators are assumed to partially undertake the spinning reserve for the thermal generator. A double-layer optimization model is proposed. The outer layer use the differential evolution to search for the power output of thermal generators, and the inner layer use the primal-dual interior point method to solve the OPF of the established output state. Finally, the impact of spinning reserve with wind power on power system operating is validated.

Key Problems of Cold Power Spinning of Ti-15-3 Alloy

The key problems of cold power spinning of Ti-15-3 alloy are studied. Reasonable billet preparation methods are presented to improve crystal structure and avoid crack of billet. Influences of original wall thickness, reduction rate and feed rate on expanding in diameter are analyzed and some methods to prevent expanding in diameter are given.

Finite element modeling of power spinning of thin-walled shell with hoop inner rib

A 3D elasto-plastic finite element(FE)model of power spinning of thin-walled aluminum alloy shell with hoop inner rib was established under software ABAQUS.Key technologies were dealt with reasonably.The reliability of the FE model was verified theoretically and experimentally.The forming process was simulated and studied.The distribution of the thickness and stress,and the variations of spinning force were obtained.The workpiece springback was analyzed with ABAQUS/Standard.The results show that the FE model considering elastic deformation can not only be used to analyze the workpiece springback in the complex spinning process,but also serve as a significant guide to study the local deformation mechanism and choose the reasonable parameters.

Study of Mechanical Model During Power Spinning Simulation of Cylindrical Workpiece

Whether the proposed mechanical model fits in the nature of technology is the key to solving the problems during three dimensional simulation of power spinning. The study of mechanical model includes: the definition of the contour of contact zone and processing the velocity and frictional force boundary conditions on contact zone. The movement locus of roller surface is a spiral cone and contact zone between roller and workpiece is a part of cone surface of roller. So the contour of the contact zone is intersected by roller cone surface, spiral cone surface and cylindrical surfaces. In this paper, a solution to defining the contour and applying space restriction of the contact zone was proposed. Considering the sudden change in the direction of foctional force on the contact zone during power spinning, an inverse tangential frictional model was adopted to solve the problem. So a new mechanical model comes into being and the 3 - D FEM simulation results prove it to be right.

OBTAINING THE CRITICAL DRAW RATIO OF DRAW RESONANCE IN MELT SPINNING FOR POWER LAW POLYMER FLUIDS

A direct difference method has been developed for Non-Newtonian power law fluids to solve the simultaneous non-linear partial differential equations of melt spinning, and to determine the critical draw ratio for draw resonance. The results show that for shear thin fluids, the logarithm of the critical draw ratio has a well defined linear relationship with the power index for isothermal and uniform tension melt spinning. When the power index approaches zero, the critical draw ratio points at unity, indicating no melt spinning can be processed stably for such fluids. For shear thick fluids, the critical draw ratio increases in a more rapid way with increasing the power index.

兼具求解速度与隐私性的复杂供热管网等值简化模型

电热能源系统模型维度高将会导致求解难度较大。为此,提出一种兼具求解速度与隐私性的复杂供热管网等值简化模型。首先,基于热网拓扑结构特点,提出可对供热管网进行灵活化简的供热管网拓扑简化方法,并根据简化后的管道结构和参数建立复杂供热管网等值简化模型。其次,充分考虑热电联产(combined heat and power,CHP)机组以热定电模式和热网热惯性对旋转备用容量的影响,建立了系统旋转备用模型。基于此,建立了考虑旋转备用约束的电热能源系统调度模型。最后,采用信息间隙决策理论(information gap decision theory, IGDT)处理系统成本与风电不确定度之间的关系。算例结果分析了供热管网拓扑简化方法在不同简化程度下的简化效果,验证了所提模型适用于电热能源系统优化调度,有效地减少优化模型的求解时间。

退火温度对旋压激光熔覆涂层性能及残余应力的影响

采用激光熔覆技术在27SiMn钢上制备铁基合金熔覆层,并采用强力旋压技术对其进行加工,通过剧烈的塑性变形来改善熔覆层的表面性能。而通过强力旋压工艺制备的熔覆层筒型件通常需要进行热处理以消除较大的残余应力,同时也会对熔覆层的耐磨性产生影响。在350、450、550℃退火2 h后,对其残余应力、显微硬度、耐磨性进行测定。结果表明,热处理后,熔覆层中残余应力明显降低,在试验参数范围内熔覆层表层硬度随温度的升高而出现一定的下降。350℃去应力退火后,其耐磨性能最佳;450℃去应力退火后次之,均优于未热处理熔覆层耐磨性;550℃的耐磨性出现一定的降低。

考虑源荷不确定性和N-1安全约束的电力系统优化调度

大规模风电并网增加了系统运行的不确定因素,文章利用快速可调资源平抑风电和负荷波动引发的功率不平衡,并考虑备用调用过程减少对系统潮流的影响。首先分析了风电和负荷预测误差的概率分布模型;然后,建立含N-1网络安全机会约束和旋转备用机会约束的电力系统优化调度模型,以系统调度总成本最小为目标优化机组出力;最后,基于起作用整数变量的识别方法的Benders分解法处理N-1网络安全约束,提高求解效率。利用修正的IEEE30节点系统,验证了所提模型能够保障系统备用可用性、经济性和安全性,充分挖掘抽水蓄能的快速可调能力。

ZnO/Spiro-MeOTAD异质结自驱动光电探测器的制备及性能(特邀)

ZnO具有高稳定性、低成本、宽带隙等优点,被广泛用于光电探测器但响应速度较慢,采用Zn(TFSI)2和CNT∶TiO_(2)作为混合掺杂剂来代替Li-TFSI,以提高Spiro-MeOTAD的稳定性及光电性能,采用旋涂法制备了ZnO/Spiro-MeOTAD异质结构筑光电探测器。ZnO/Spiro-MeOTAD光电探测器在250~600 nm波长范围内,具有良好的自驱动特性。在0 V条件下,ZnO/Spiro-MeOTAD器件在368 nm的入射光照射下具有最高的光电性能,响应度为27.34 mA W^(-1),比探测率为3.62×10^(11)Jones,开关比为2029,上升/下降时间分别为0.71 s/0.55 s,相较于ZnO的光电性能(响应度为17.74 mA·W^(-1),比探测率为5.11×10^(10)Jones,开关比为63.6,上升/下降时间为11.76 s/1.49 s)分别提升提高了1.5倍、7倍、32倍。ZnO/Spiro-MeOTAD器件在550 nm处仍具有明显响应,响应度和比探测率分别为2.48 mA·W^(-1)和3.32×10^(10)Jones,对比ZnO器件提高了248倍和940倍。不同放置时间(1个月)和预处理温度(0~140℃)下光电流的变化,验证了Spiro-MeOTAD加入构筑p-n异质结,不仅可以显著提升ZnO基光电探测器的响应度、开关比和响应速度,同时使得探测器具有良好的稳定性,可以应用于较高温度工作环境。

基于FFT的风力发电机转子谐波分析方法研究

为了准确测量风力发电机运行中转子的谐波电流参数,本文提出了一种基于汉宁窗的FFT风力发电机转子谐波参数测量方法。该方法对一个采样周期内电压电流数据的加窗FFT结果进行多项式变换,得到新的频谱序列,依据变换后的新频谱数据提取基波谐波参数。将其用于风力发电机转子谐波测量,并与横河功率分析仪测量参数进行对比,结果表明,该方法能够有效测量风力发电机转子谐波参数,与功率分析仪测量结果相比误差不超过1.5%,为谐波参数计算提供一种新方法。

基于Spin的Rdt2.2及其改进的形式化分析

用Promela语言对滑动窗口协议中的Rdt2.2模型进行了描述,通过Spin对该描述进行了形式化分析验证,并发现存在一个死锁。进而对该协议进行改进,采用添加定时器的方法解决了死锁问题,通过这种形式化验证增加了协议的正确性和可靠性。

大尺寸电力电容器杂散电感提取方法研究

变流器换流回路存在的杂散电感对于功率半导体器件的影响巨大,然而准确提取大尺寸电力电容器的杂散电感难度较大。目前,对电力电容器杂散电感标准的提取方法为放电法,但是该方法不适用于包含多谐振频率的电容器。由于积分法提取母排杂散电感的精度高,故将积分法推广到提取大尺寸电力电容器杂散电感,明确误差校正过程,将积分法结果作为准确结果。积分法虽然精度高,但是会占用大量试验资源,并存在高压安全风险,效率较低。因此,文章提出了一种基于阻抗分析仪的杂散电感提取方法,详细介绍了测试工装和阻抗补偿方法。将阻抗分析仪测量结果与积分法测量结果进行对比,其误差小于7.3%,证明了基于阻抗分析仪提取方法的准确性,并且该方法不存在高压试验风险,测量便捷、复用性强、效率高。

核能发电用主设备封头锻件制造技术的选择与应用

基于实际研发制造业绩,重点介绍了反应堆压力壳封头、蒸汽发生器封头、稳压器封头、补水箱封头等多种典型核电主设备封头锻件的制造技术及应用情况,讲述了热拉伸成形工艺、胎模旋压全仿形锻造工艺、胎模旋压与热拉伸复合成形工艺、胎模旋压半仿形锻造与气割修刨组合成形工艺、拉伸成形与管嘴翻边复合成形工艺等典型工艺的优缺点,总结了封头制造技术的选用原则,为核电封头制造的质量稳定性和标准化生产提供依据。

ANALYSIS OF MECHANICS IN BALL SPINNING OF THIN-WALLED TUBE

Ball spinning is applied to manufacturing thin-walled tube with high precision and high mechanical properties. On the basis of plastic mechanics, by simplifying ball spinning of thin-walled tube as plane strain problem, slab method is used for the purpose of calculating the contact deformation pressure. The spinning force components, the torsional moment, the deformation power and the deformation work are calculated further as well. The influence of the two important process parameters such as the feed ratio and the ball diameter on the spinning force components is analyzed in order to further control the spinning force components by regulating the two process variables during the ball spinning process. The stress and strain state in deformable zone as well as mechanics boundary conditions in ball spinning are obtained. The effect of the three spinning force components on the formability of the spun part is analyzed and validated through the ball spinning experiments. The theoretical and experimental results show that the radial spinning component plays a significant role in ball spinning of thin-walled tube, and the mechanics situation in backward ball spinning contributes to enhancing the plasticity of the metal material, but that in forward ball spinning contributes to advancing the axial flow of the metal material.

Application of BPANN in spinning deformation of thin-walled tubular parts with longitudinal inner ribs

Back-propagation artificial neural network (BPANN) is used in ball backward spinning in order to form thin-walled tubular parts with longitudinal inner ribs. By selecting the process parameters which have a great influence on the height of inner ribs as well as fish scale on the surface of the spun part, a BPANN of 3-8-1 structure is established for predicting the height of inner rib and recognizing the fish scale defect. Experiments data have proved that the average relative error between the measured value and the predicted value of the height of inner rib is not more than 5%. It is evident that BPANN can not only predict the height of inner ribs of the spun part accurately, but recognize and prevent the occurrence of the quality defect of fish scale successfully, and combining BPANN with the ball backward spinning is essential to obtain the desired spun part.