基于Murty准则的SiCp/Al复合材料热加工图研究

采用热模拟压缩试验对15%(体积分数)SiCp/Al复合材料在温度为623~773K、应变速率为0.001~10s^(-1)的热变形行为进行了研究,基于Murty准则建立了该材料的热加工图,并在此基础上建立了SiCp/Al复合材料临界失稳应变分布图。结果表明,随变形温度升高,SiCp/Al复合材料中的强化机制逐渐减弱,软化机制逐渐增强。基于临界失稳应变图可以确定出适合SiCp/Al复合材料加工的两个区域,分别为变形温度700~773K、应变速率0.001~0.01s^(-1)和变形温度740~773K、应变速率0.02~0.14s^(-1)。

微波组件自动测试系统研制

随着航天雷达技术的发展,微波组件的结构、功能变得日益复杂,给相应测试工作带来困难。针对微波组件参数测试困难的问题,设计了自动测试系统,提高了测试效率和测试精度。微波组件自动测试系统是针对于多通道微波组件测试做出的创新,通过微波测试转接机箱的设计兼容多型号微波测试组件测试,设计以FPGA为核心的数据采集及控制信号板卡完成测试组件所需控制信号输出及测试系统电源系统的实时监控。在微波组件自动测试系统中,以计算机为主控制器,将测试系统的各个部分相统一,自动测试软件的设计以及数据补偿的加入满足了测试速率、测试精度的高要求。

分布式能源系统常用储能技术综述

分布式能源系统具有灵活方便、高效可靠、排放低污染等特点,正逐步得到推广与发展。储能技术作为分布式能源系统的重要组成部分,占有举足轻重的地位。就分布式能源系统中常用的储热、蓄冷与储电技术进行介绍,并对技术的选取提出了建议。结合中国未来智能电网的建设规划,对分布式能源系统常用储能技术的发展前景进行了展望。

基于MRE与特征类的轴承故障诊断方法

针对滚动轴承振动信号难以提取的问题,为实现故障特征准确分类目的。通过多尺度极差熵(MRE)和EigenClas融合,提出了一种MRE-EigenClass分类方法来诊断轴承故障模式。首先,MRE从不同状态下轴承的振动信号提取20个尺度的特征向量,最后将提取到的特征向量输入到EigenClass分类器,得到分类结果。实验证明,提出的MRE与EigenClass算法能有效提取滚动轴承振动信号的特征,并且实现高精度分类。与其他故障识别的分类器相比,本方法具有更高的故障识别准确率,识别精度达到98.86%。

Micro-plasticity Constitutive Model Taking Account of Size Effects for Pure Aluminum by Microindentation

The macro-plasticity power function constitutive model （MPFCM）, the modified macro- plasticity power function constitutive model （MMPFCM） and the micro-plasticity constitutive model （MCM） taking the material intrinsic length were established to characterize the microindentation size effects of pure aluminum, respectively. The experimental results indicated MPFCM only determined precisely in the great indentation load. While a modified one named MMPFCM was subsequently established taking account of the parameters variation with the increase of indentation depth. The conventional dimensional analysis method was employed to determine the strength coefficient K and the strain hardening exponent n of this modified model. And then MCM taking account of size effects was proposed based on the Taylor dislocation model. The first- order steepest gradient descent method was adopted to obtain the material intrinsic length for the geometrically necessary dislocations. The parameters of MCM were identified by using the UMAT subroutine of ABAQUS software. The average absolute relative error of MCM is relatively lower than that of the macro-one. Although the precision of the modified one is also high, the applied scope is limited, only for the microindentation material. In addition, the intrinsic length 5.09 bun of pure aluminum is also obtained based on the strain gradient theory.

TC25G钛合金高温变形组织演变及强塑性研究

对比研究了网篮组织TC25G钛合金棒材在不同变形量下的组织演变及其550℃热暴露和蠕变性能变化。结果表明:随变形量的增加,合金热暴露后拉伸塑性逐渐增加,而高温抗蠕变性逐渐减弱,2种性能在变形量100%时达到良好匹配,均可满足工程应用要求。变形量的增加对应显微组织中片层α相的球化过程,在片层α相充分球化前,显微组织中多层级结构的界面强化效应使得合金具有良好的高温抗蠕变性;而α相充分球化后,以等轴组织为主的显微组织使得合金具有较好的塑性。随变形量的增加,热暴露后拉伸断口韧窝尺寸逐渐变得细小均匀,且韧窝深度增加,表明合金热暴露后塑性提升。纳米显微硬度测试结果表明,合金中初生α相的显微硬度高于β转变组织,通过固溶温度调整合金中α相的含量和分布,可提升抗蠕变性,但其效果不及变形量的调控显著;为获得最佳的高温强塑性匹配,可通过控制片层α相球化程度来实现。

Forming Limit Stress Diagram Prediction of Aluminum Alloy 5052 Based on GTN Model Parameters Determined by In Situ Tensile Test

The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-based diagram （FLSD） has been adopted to predict the fracture limit of aluminum alloy （AA） 5052-O1 sheet. Nakazima test is simulated by plastic constitutive formula derived from the modified Gurson-Tvergaard-Needleman （GTN） model. An in situ tensile test with scanning electron microscope （SEM） is proposed to determine the parameters in GTN model. The damage evolution is observed and recorded, and the parameters of GTN model are identified through counting void fraction at three damage stages of AA5052-O 1. According to the experimental results, the original void volume fraction, the volume fraction of potential nucleated voids, the critical void volume fraction, the void volume fraction at the final failure of material are assigned as 0.002 918, 0.024 9, 0.030 103, 0.048 54, respectively. The stress and strain are obtained at the last loading step before crack. FLSD and FLD of AA5052-O 1 are plotted. Compared with the experimental Nakazima test and uniaxial tensile test, the predicted results show a good agreement. The parameters determined by in situ tensile test can be applied to the research of the forming limit for ductile metals.

Optimization of structural parameters for elliptical cross-section spiral equal-channel extrusion dies based on grey theory

The elliptical cross-section spiral equal-channel extrusion （ECSEE） process is simulated by using Deform-3D finite element software. The ratio m of major-axis to minor-axis length for ellipse-cross-section, the torsion angle u, the round-ellipse cross-section transitional channel L1, the elliptical rotation cross-section transitional channel L2 and the ellipse-round cross-section transitional channel L3 are destined for the extrusion process parameters. The average effective strain eave on cross-section of blank, the deformation uniformity coefficient a and the value of maximum damage dmax are chosen to be the optimize indexes, and the virtual orthogonal experiment of L16 （45） is designed. The correlation degree of the process factors affecting eave, a and dmax is analyzed by the numerical simulation results using the weights and grey association model. The process parameters are optimized by introducing the grey situation decision theory and the ECSEE optimal combination of process parameters is obtained： u of 120 , m of 1.55, L1 of 7 mm, L2 of 10 mm, and L3 of 10 mm. Simulation and experimental results show that the material can be refined with the optimized structural parameters of die. Therefore, the optimization results are satisfactory.

航空航天大型环锻件智能产线管控与集成技术

现阶段我国航空航天大型环件锻造生产线大多处于小批量、多品种的生产模式,面临着设计周期长、成形质量不稳定、能耗高、效率低等问题。针对以上问题,提出一种多级闭环协同运行的锻造智能管控平台,以环锻件热加工生产线中的先进成形装备、柔性物流设备和在线检测设备的互联互通为基础,在对生产过程数据的全面采集和集成的前提下,进一步构建环形锻件工艺智能设计系统、多目标优化动态调度系统、质量检测与稳健控制系统及实时反馈调控的智能管控集成平台,建立各级系统间的集成方式与优化关系,形成工业网络环境下环锻件成形工艺设计、生产组织、过程控制和质量检测协同运行与管控体系,并在此基础上分析了航空航天大型环锻件智能化生产应展开的研究内容。

Review on modified and novel techniques of severe plastic deformation

This review highlights very recent achievements and new developments of severe plastic deformation(SPD) technology for producing bulk ultrafine-grain(UFG) and even nanocrystalline(nc) materials.These numerous modified and novel SPD methods include cyclic forward-backward extrusion,axi-symmetric forward spiral extrusion,vortex extrusion,simple shear extrusion,planar twist extrusion,tubular channel angular pressing,cone-cone method,high-pressure tube twisting,tube channel pressing and elliptical cross-section spiral equal-channel extrusion.According to classification,these new methods are categorized into the extension of equal-channel angle pressing(ECAP),high-pressure torsion(HPT),twist extrusion(TE) and constrained groove pressing(CGP),respectively.The principles of various new SPD technologies are described in detail.In addition,the microstructure revolution characteristics and mechanical properties of materials produced by SPD process,as well as the applications of SPD techniques to UFG materials,are also reported.Furthermore,this article reviews recent progresses in determining the refinement and/or deformation mechanisms,e.g.dislocation deformation mechanism,twin deformation mechanism and grain boundary sliding and torsional deformation mechanism,and further orientation of SPD technology.

Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

By using instrumental micro-indentation technique, the microhardness and Young＇s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester （MCT）. The micro-indentation experiments were performed with different max- imum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young＇s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions （maximum load and loading speed） and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increas- ing. During the analysis, the effect of loading conditions on Young＇s modulus and microhardness were explained. Besides, the elastic-plastic properties of matrix were analyzed. The validity of cal- culated results was identified by finite element simulation. And the simulation results had been pre- liminarily analyzed from statistical aspect.

Description of shape characteristics through Fourier and wavelet analysis

In this paper, Fourier and Wavelet transformation were adopted to analyze shape char- acteristics, with twelve simple shapes and two types of second phases from real microstructure mor- phology. According to the results of Fast Fourier transformation （FFT）, the Fourier descriptors can be used to characterize the shape from the aspects of the first eight Normalization amplitudes, the number of the largest amplitudes to inverse reconstruction, similarity of shapes and profile roughness. And the Diepenbroek Roughness was rewritten by Normalization amplitudes of FFT results. Moreover, Sum Square of Relative Errors （SSRE） of Wavelet transformation （WT） signal sequence, including approximation signals and detail signals, was introduced to evaluate the simi- larity and relative orientation among shapes. As a complement to FFT results, the WT results can retain more detailed information of shapes including their orientations. Besides, the geometric sig- natures of the second phases were extracted by image processing and then were analyzed by means of FFT and WT.

山东枣庄15岁以下儿童乙型肝炎流行特征(2010-2017年)

目的了解2010-2017年枣庄市15岁以下人群乙型肝炎的流行特征,为进一步控制疫情,制定适合的防治策略提供依据。方法采用描述流行病学方法,对国家法定传染病信息报告系统和山东省儿童乙型肝炎监测系统中枣庄市2010-2017年15岁以下乙型肝炎病例的监测数据进行分析。结果2010-2017年枣庄市15岁以下儿童乙型肝炎发病率分别为1.56/10万、0.86/10万、1.00/10万、1.64/10万、2.05/10万、2.10/10万、0.74/10万和1.68/10万,年平均发病率为1.34/10万;男性和女性发病率分别为1.80/10万和0.82/10万。14岁和13岁儿童发病率分别为2.94/10万和2.48/10万,高于其他年龄儿童发病率。乙型肝炎发病率居于前两位的是薛城区和山亭区,年龄标化后发病率分别为2.10/10万和1.88/10万。结论2010-2017年枣庄市15岁以下儿童乙型肝炎发病率处于较低水平,但大龄儿童和男孩值得重点关注,特别是在薛城区和山亭区。