Microstructure and Properties of ZL101 Alloy Affected by Substrate Movement Speed of a Novel Semisolid Continuous Micro Fused-Casting for Metal Process

A novel semisolid continuous Micro Fused-Casting additive manufacturing technology for producing a ZL101 alloy strip was developed, Micro Fused-Casting means that the semisolid metal slurry was pressed out from the outlet of bottom of crucible to the movable plate. The degree of sub-cooling was easily provided by movement of substrate in the micro fused-casting area. Under the aid of 3 D manufacturing software, the ZL101 alloy strip was solidified and formed layer by layer. The microstructure and properties of ZL101 semisolid slurry were improved by the cooling conditions. The results showed that the ZL101 alloy strip samples fabricated by Micro Fused-Casting had uniform structures and good performances with the substrate movement speed at 20 mm/s and the temperature at 590 ℃, the ultimate tensile strength and elongation of the ZL101 alloy strip reached 242.59 MPa and 7.71%, while the average Vickers hardness was 82.55 HV.

Vibration test of micro machined gyroscope based on high speed photography and SURF

Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.

A High Speed Autofocusing System for Micro System Applications

In this paper,we present a high speed autofocus system for micro system applications and design a look-up-table based autofocusing algorithm for applications when a target object is always visible,e.g.,manufacturing parts with alignment fiducials.We perform an evaluation of 24 focus measures to verify that which focus measure is the best for the look-up-table based method.From the evaluation,we find that the Chebyshev moments-based focus measure（CHEB） is the most suitable.Furthermore,we also develop a look-up-table based autofocus system that uses CHEB as the focus measure.In training phase,we offline construct a table from training images of an object that are captured at several lens distances.Each entry of table consists of focus measure computed from image and lens distance.In working phase,given an input image,the algorithm first computes the focus measure and then finds the best match focus measure from the table and looks up the corresponding lens position for moving it into the in-focus position.Our algorithm can perform autofocusing within only 2 steps of lens moving.The experiment shows that the system can perform high speed autofocusing of micro objects.

Increasing the Efficiency of Grid Tied Micro Wind Turbines in Low Wind Speed Regimes

Major problem with grid tied micro wind turbine is synchronization and wind variability. Due to this problem the stability of available grid gets reduced. The stability can be achieved by output power control of the turbine. Major part of many countries like India, the annual mean wind speed is not high. The rated wind speed of turbine remain around 11 m/s and cut in is around 3.5 m/s. Due to this problem we aimed to develop a sustainable wind energy system that can provide stable power supply even at the locations of low wind speed of 2 - 4 m/s. To address this issue, a momentary impulse or external torque to the rotor by external motor is one of the good options to maintain the momentum of blades and thus provide stability for sufficient time. Various theoretical calculations and experiments are conducted on the above method. This would increase the output power and also the efficiency of wind turbine. We show that Return-On-Investment will be high as compared with other grid connected turbines. Our proposed concept in the present study, if implemented properly, can help the installation of number of wind turbines even at domestic level. It also makes the consumers energy independent and promotes the use of wind as a source of energy and may enter as a rooftop energy supply system similar to solar.

Simulation of Fluid Flow, Heat Transfer and Micro-Segregation in Twin-roll Strip Casting of Stainless Steel

In twin-roll strip casting process, metal flow and temperature distribution in the molten pool directly affect the stability of the process and the quality of products. In this paper, a 3D coupled thermal-flow fenite element modeling （FEM） simulation for twin-roll strip casting of stainless steel was performed. Influences of the pouring temperature and casting speed on the temperature fields were obtained from the numerical simulation. The micro-segregation of the solutes during the strip casting process of stainless steel was also simulated. A developed micro-segregation model was used to calculate the micro-segregation of solutes in twin-roll casting of stainless steel. The relationship between the solidus fraction in solidification and temperature was given, which was used to determine the LIT （liquid impermeable temperature）, ZST （zero strength temperature） and ZDT （zero ductility temperature） in the period of non-equilibrium solidification. The effect of temperature on the micro-segregation was discussed. According to the computational results, the solidification completion temperature in the twin-roll strip casting of stainless steel was then determined, which can provide a basis for controlling the location of solidification completion temperature and analysing the crack of the casting strip.

Micro pore and throat characteristics and origin of tight sandstone reservoirs: A case study of the Triassic Chang 6 and Chang 8 members in Longdong area, Ordos Basin, NW China

The microstructure differences of the Triassic Chang 6 and Chang 8 members tight reservoirs in the Longdong area of Ordos Basin were compared by means of cast thin sections, scanning electron microscope, X-ray diffraction, and constant rate mercury injection. Their pore evolution models were established, and the effects of main diagenesis on densification were examined. The throat is the main factor controlling the physical properties of the Chang 6 and Chang 8 members reservoirs: The lower the permeability, the smaller and the more concentrated the throat radius and the larger the proportion of the throats in the effective storage space. There are several obvious differences between Chang 6 and Chang 8 members:(1) with the increase of permeability, the contribution of the relative large throats to the permeability in the Chang 8 member reservoir is more than that in the Chang 6 member reservoir;(2) the control effect on pore-throat ratio of the nano-throats in the Chang 6 member reservoir is more significant. The sedimentary action determines the primary pore structure of the Chang 6 and Chang 8 members sand bodies, and the diagenesis is the main factor controlling the densification of the reservoirs. Because of the difference in rock fabrics and the chlorite content of Chang 6 and Chang 8, the strong compaction resulted in less porosity reduction(17%) of the Chang 81 reservoir with larger buried depth and larger ground temperature than the Chang 63 reservoir(19%). The siliceous, calcareous and clay minerals cement filling the pores and blocking the pore throat, which is the key factor causing the big differences between the reservoir permeability of Chang 6 and Chang 8 members.

On Propagation of Rayleigh Type Surface Wave in a Micropolar Piezoelectric Medium

In the present paper, the governing equations of a linear transversely isotropic micropolar piezoelectric medium are specialized for x-z plane after using symmetry relations in constitutive coefficients. These equations are solved for the general surface wave solutions in the medium. Following radiation conditions in the half-space, the particular solutions are obtained, which satisfy the appropriate boundary conditions at the stress-free surface of the half-space. A secular equation for Rayleigh type surface wave is obtained. An iteration method is applied to compute the non-dimensional wave speed of the Rayleigh surface wave for specific material parameters. The effects of piezoelectricity, non-dimensional frequency and non-dimensional material constant, charge free surface and electrically shorted surface are shown graphically on the wave speed of Rayleigh wave.

压缩空气储能系统的微机电控制技术

结合当前能源需求的大背景,综述了压缩空气储能系统的微机电控制技术研究情况。首先详细阐述了压缩空气储能系统的内部运行逻辑,包括运行方式和相关机械结构。在此基础上,从转速和储能电机两个角度,探讨储能系统的微机电控制技术的最近研究进展。最后列举了当前较为常用的控制优化技术,可为后续研究提供一定的理论借鉴和思考。

织构化盘式摩擦副性能及优化设计研究

为探索提高盘式摩擦副抗摩擦磨损性能的有效途径,以斜盘柱塞泵配流副为研究对象,综合运用仿真分析及试验研究方法对比分析了面积织构率和截深形状相同条件下,椭圆开口和圆形开口离散凹坑微织构及沟槽形微织构配流副的摩擦因数随织构形貌、转速和压力的变化规律。研究结果表明:摩擦因数随转速的增大而显著降低,随压力的增大而降低,椭圆开口离散凹坑微织构为三种微织构中提高配流副性能最优者。对椭圆开口离散凹坑微织构进行多目标参数优化,得出的最优参数为:椭圆开口长轴半径为452μm、短半轴为187μm、径向中心距为0.7 mm。试验结果表明,优化后的织构在不同工况下较优化前摩擦因数和磨损量均有不同程度的降低。

微速差双转子信号分离方法精度研究

针对提取频率相近信号特征的经典算法Zoom-FFT(ZFFT)在分离差频1 Hz以内的微速差信号时,需要足够的数据长度才能达到良好的信号分离效果的问题,为了在不增加数据长度的基础上提高信号频率分辨率,在ZFFT算法的基础上产生了ZFFT+FT算法。通过LabVIEW软件仿真试验研究了该算法对频率差1 Hz和0.5 Hz的微速差信号提取精度,并与chirp Z transform(CZT)算法、ZFFT算法以及FFT算法的提取精度作了对比,通过提取结果的相对误差及方差来衡量提取精度。在同轴微速差双转子试验台进行现场试验,利用FFT对微速差信号28 s数据集的提取结果与CZT,ZFFT及ZFFT+FT算法对4 s数据集的提取结果作对比,ZFFT+FT与FFT算法的提取结果最大相差0.56 μm,验证了ZFFT+FT的实时性和精确性。结果表明,ZFFT+FT算法能够实时精准提取频率差1 Hz以内的微速差信号。研究结果可为旋转机械微速差信号的提取提供参考。

THEORY DEPOSITION MODEL AND INFLUENCING FACTORS DURING PROCESS OF PREPARING MICRO-LAYER LAMINATE BY EBPVD

This paper briefly introduces the characteristics of electron beam physical vapor depo-sition (EBPVD) technique and the whole process of preparing micro--layer compositelaminate. And several major influencing factors are presented and discussed. It wasfound that residual gas pressure should be low enough to guarantee the unobstructedtransporfation of vapor steam and electron beam; the evaporation method and evapo-ration speed are up to the different vapor pressure deficit of compositions of raw mate-rials; and the substrate temperature could have great influence on the microstructureof the micro--layer laminates.

考虑粗糙度的复合微织构轴承动力特性分析

为了提高滑动轴承旋转摩擦副的动力学性能和优化轴承结构,综合考虑表面粗糙度和复合微织构等因素,建立轴承转子系统的动力学特性计算模型,从理论上研究了考虑表面粗糙度时的复合微织构轴承的稳定性。针对圆形复合矩形微织构轴承,计算了不同粗糙度下轴承的油膜压力和临界速度,分析了不同复合微织构深度下的轴承刚度系数、阻尼系数及临界速度。研究结果表明:复合微织构轴承可以获得更大的临界速度,提高轴承的稳定性;复合微织构轴承的稳定性随织构深度的增大先增大后减小,在圆形和矩形织构无量纲深度分别为0.2和0.3附近稳定性最佳;相较于不考虑粗糙度时,采用均方根偏差为0.209μm时的考虑粗糙度的复合微织构轴承稳定性更佳,但最佳织构深度有所减小。

400 km/h高铁隧道联通式缓冲结构对微气压波的影响

随着高速列车运行速度的提升,隧道口微气压波幅值剧增,强烈的爆破噪声同时影响着周边环境和附近居民的正常生活。本文研究由平行导坑与横通道组成的联通式缓冲结构对400 km/h高铁隧道微气压波的缓解作用。首先,进行400 km/h动模型试验,验证数值模拟方法的准确性;其次,基于RNG k-ε湍流模型和滑移网格技术分析联通式缓冲结构位置距隧道入口的距离D与联通式缓冲结构长度L对微气压波的影响。研究结果表明:随着D增加,微气压波的缓解率逐渐增大,在D=25 m时达到最优,微气压波幅值减少34.4%;随着L增加,微气压波幅值缓慢增加;当L=30 m时,隧道口20 m处的微气压波幅值为91 Pa,缓解率为37.1%。联通式缓冲结构与既有350 km/h高铁线路上的断面扩大开孔型缓冲结构组合,可将隧道口20 m处微气压波幅值减小至47.3 Pa,降幅达67.3%。联通式缓冲结构合理利用了修建隧道时遗留的平行导坑,可在保障施工成本几乎不变的前提下,显著缓解微气压波,保护隧道周边环境。

微转速差双转子系统对自动液力变速器车型怠速抽动的影响研究

为分析液力变矩器与曲轴组成的微转速差双转子系统对自动液力变速器(AT)车型怠速抽动的影响,通过对双转子系统动不平衡耦合激励力进行希尔伯特变换(Hilbert Transform),揭示出部件拍振是导致有规律怠速抽动的根本原因,其抽动激励幅值最大值为激励力之和,抽动间隔频率为激励力频率之差。建立包括发动机、变速器、悬置等系统的机械系统动力学自动分析(ADAMS)模型并进行仿真,结果表明,动力总成垂向刚体模态频率与激励频率越接近,液压悬置垂向一阶动刚度越大,振动幅值越大。因此,可通过动力总成Z向模态频率与曲轴动不平衡激励频率间的避频设计、降低液压悬置垂向动刚度、提高悬置系统的隔振性能等方式改善怠速抽动。

多线切割保公差工艺对烧结钕铁硼永磁体表面质量的影响

采用多线切割保公差工艺切割烧结钕铁硼永磁体,利用SJ-410粗糙度仪、JMS-6010LA型扫描电子显微镜对微观形貌及表面粗糙度R_(a)进行表征。结果表明:随着进给速度增高和线速度的降低,金刚石磨粒压入深度减小,微观形貌由深犁沟、凹坑、破损变为浅犁沟、浅凹坑和破碎,材料去除机理由塑性去除变为塑性变形。粗糙度R_(a)随着进给速度和线速度的增高而减小;进给速度和线速度对法向载荷呈相反作用,在不同工艺参数下的材料去除方式中,塑性变形和塑性去除占据主导作用,进给速度10 mm/h和线速度1190 m/min的粗糙度最低,表面质量最优。切割时间只与进给速度有关,线弓随着进给速度增加,随线速度降低。

取向型微沟槽高速球铣加工制备方法及其减摩性能研究

探究直接利用高速球铣加工工艺制备取向型表面微沟槽织构的方法,并对该类型表面微织构的减摩性能进行研究.鉴于高速球铣加工工艺走刀路径灵活可变、表面材料残留几何尺寸与分布形态具备可控性的特点,利用Matlab仿真对高速球铣加工表面形貌进行预测,通过高速球铣加工试验验证仿真结果,并基于流体动压润滑理论,结合Fluent流体仿真分析与高速环-块摩擦磨损试验,对该类型表面微织构的减摩性能进行分析.当切削参数选用径向切深明显大于每齿进给量的组合时,高速球铣加工表面残留材料能够形成明显的微沟槽形貌,且微沟槽特征的取向可由球头铣刀的走刀路径进行控制;微沟槽承载能力与其取向密切相关,随着微沟槽取向角由90°减小至20°,负压区与正压区范围呈现扩大趋势,油膜内逆流效应逐渐减弱,动压效应逐渐增强,微沟槽承载能力提高了20.64%,表面摩擦系数由0.02845降低至0.02165;然而,当取向角过小时,负压区与正压区的范围过小,不能形成有效的收敛楔,微沟槽承载能力下降,表面摩擦系数上升.通过高速球铣加工工艺能够实现取向型表面微沟槽织构的可控制备,且该类表面的减摩性能与取向角α密切相关,在本文研究范围内,取向角为20°时表现出最小的摩擦系数与最高的油膜承载力.本文研究结果可为表面织构造型方法提供一种新思路,能够为满足零件表面的减摩需求提供很好的解决方法.

高速铁路声屏障宽频穿孔吸声降噪结构

采用传递矩阵法对高铁声屏障的多层微穿孔结构的吸声进行计算。对给定空腔深度,适当增加具有不同声阻抗的微穿孔板可改善吸声性能。经遗传算法得到具有优化参数的4层和5层微穿孔结构可显著拓宽吸声频带,提高整个频带的吸声系数,在200~3150 Hz频率范围内的平均吸声系数分别为0.70和0.80,吸声频带涵盖250~350 km⋅h^(-1)高速铁路主要噪声频率范围。5层结构在400~4000 Hz频率范围内吸声系数可达0.8。

山区输电线路跳线风偏状态方程及临界风速研究

为研究山区微地形中的竖向风速对跳线风偏的影响,基于刚性直棒法对导线、跳线及绝缘子串增加竖向风荷载分析,确定跳线处最大风偏位移值作为风偏指标,建立风荷载作用前后跳线静力平衡平面的几何变换关系,提出了考虑竖向风速影响的跳线风偏状态方程。建立半径5 km的地形模型,包含跳线风偏事故地点与微气象站点,采用数值模拟方法将微气象站点风速推演到事故地点风速,获得了考虑微地形影响的跳线风偏闪络事故风速。将事故线路参数及竖向风速代入跳线风偏状态方程,得到跳线风偏临界水平风速,通过与事故风速进行比较验证了跳线风偏状态方程的可靠性。最后根据风偏状态方程分析竖向风速的变化对跳线风偏临界水平风速的影响。结果表明:随着竖向风速的增大,跳线风偏临界水平风速线性减小,当风攻角为20°时临界水平风速可降低16%。考虑竖向风速影响的跳线风偏临界水平风速取值较为安全,建议在山区输电线路跳线设计过程中加以考虑。

微型燃汽轮机发电系统柔性协调控制策略

在微型燃汽轮机发电系统中,转速稳定对于微型燃气轮机的效率、运行安全十分重要,而负荷变化对燃气轮机转速稳定有很大影响。为此,提出了一种针对负荷变化的微型燃汽轮机发电系统柔性协调控制策略。策略将负荷变化引起的转速波动由燃气轮机和变流器共同控制,构成“机-电”协调控制。结果表明,在加快功率动态响应的同时,保障了控制策略的准确性,避免微型燃气轮机系统达到温度限制而转速失稳。

基于ABAQUS的微织构刀具切削钛合金仿真研究

构建无织构刀具和呈微凹坑、平行槽、垂直槽、斜向槽形貌的微织构刀具模型,并利用有限元分析软件ABAQUS研究了微织构刀具对钛合金车削过程的影响。通过分析不同形貌微织构刀具在切削过程中的切削力、摩擦系数、切削温度和工件表面残余应力,确定了较优的微织构形貌;研究了切削速度对微织构刀具切削钛合金性能的影响。结果表明,微织构刀具能有效降低切削力、摩擦系数和切削温度,使工件表面残余应力由拉应力转变为压应力,其中垂直槽微织构刀具能最有效地改善切削质量;随着切削速度的提高,切削力和切削温度增大,摩擦系数减小,工件表面残余应力由压应力向拉应力转变并有增大的趋势。