叶片磨床的几何误差建模与精度分配优化

基于多体系统理论和坐标变换方法,构建某叶片数控磨床的几何误差模型。在此基础上,建立其精度分配优化目标函数,使用MATLAB遗传算法对各误差参数进行优化。优化后大多数经验设计变量值得到不同程度的放大,磨床的制造成本得以降低,且优化值均满足预定加工精度,有效地平衡了磨床的加工精度和经济性能。     

数控成形槽专用磨床的设计与研究

介绍了1种磨削汽车螺杆类零件的专用数控磨床。重点分析了磨削加工中的技术方案以及数控成形槽专用磨床设计中的关键技术。根据数控成形槽专用磨床的特点,制定了研究开发的技术路线。通过对磨削加工对象的主要技术指标分析,提出了设计的新思路,优化了磨床的设计布局。数控成形槽专用磨床的成功设计经验,为磨床设计人员在进行方案设计时提供借鉴。     

导轨安装面精铣代磨工艺可行性研究

介绍了采用数控龙门铣代替导轨磨床对磨床床身导轨进行加工的工艺可行性研究,分析了磨床导轨的设计精度和加工工艺流程,详细介绍了在磨削试验的基础上对磨床床身导轨面经采用数控龙门铣铣削后的精度检查的方法,并作了铣削和磨削的精度对比,通过改变切削参数的试验,达到了设计图纸的要求。研究结果表明,采用数控龙门铣替代导轨磨对磨床床身导轨表面的加工方法可行,可以推广应用。     

基于FMECA与FTA的数控磨床数控系统可靠性分析

数控系统是数控磨床的关键子系统之一，其可靠性水平决定数控磨床整体质量。采集某系列数控磨床的故障数据，对数控系统进行可靠性分析。采用故障模式和影响性分析法，求出数控系统对整机的危害度；利用故障树分析法进行分析，求出最小割集，确定造成数控系统故障的直接原因。针对故障原因，提出改善措施，以提高数控磨床整体可靠性。研究结果能够为数控磨床的设计和制造提供参考。     

数控磨床头架系统的FMECA和FTA可靠性分析

鉴于目前国产数控磨床可靠性较低,以某机床厂生产的某系列数控磨床为研究对象,进行可靠性分析。经过现场采集的故障数据分析可知头架系统是该系列数控磨床发生故障率最高的系统,并对头架系统故障数据进行了FMECA和FTA可靠性分析。通过对头架系统的FMECA分析计算出头架系统对数控磨床的危害度为0.003344169。通过对头架系统的FTA可靠性分析确定了头架系统的最小割集和发生故障原因。为提高数控磨床的可靠性,经过故障数据的分析提出了几点可靠性提升方案,对提高国产数控磨床可靠性具有重要意义。     

基于机器人的偏心轴磨床加工系统改造研究

针对目前偏心轴加工过程中存在的夹具调整复杂、加工效率低下等问题进行研究,提出了利用三菱机器人对偏心轴数控磨床加工系统进行改造的方法。采用康奈斯3D视觉系统代替传统的装夹方式,设计出针对性的机器人控制程序,解决偏心轴数控磨床自动上下料、偏心距自动调整、机器人与数控磨床通讯等难题,实现偏心轴加工过程的全自动化柔性控制,极大地提高了偏心轴零件的加工精度与加工效率。     

数控外圆磨床床身的有限元分析与优化

利用solidworks软件建立了数控外圆磨床床身的三维模型,并在simulation软件模块中对其进行了静力学和模态的有限元分析,根据分析结果对床身的壁厚、掏沙孔型等不合理结构进行修改。结果表明,磨床床身经有限元分析和优化后,床身的最大应力可以降低22．27％,床身的质量可以减少9．14％,solidworks分析软件为设计出性能优良、成本低廉的床身提供了理论支持。     

高精度随动数控凸轮轴磨床砂轮架模态分析

利用SolidWorks软件建立了JKM8330高精度随动数控凸轮轴磨床砂轮架的三维模型,导入ABAQUS有限元分析软件,采用弹簧阻尼单元模拟轴承弹性支承的方法,建立了砂轮架的动力学分析有限元模型。通过分析计算,获得了砂轮架的前9阶振型和模态频率,并深入研究了不同轴承弹性支承刚度对砂轮架模态频率的影响规律。结果表明:可以通过调整轴承弹性支承刚度较好地控制砂轮架的模态频率,进而可以减小砂轮架的振动,从而保证机床磨削加工精度及可靠性。研究结果为高精度随动数控凸轮轴磨床的结构优化设计提供了参考。     

数控装置可靠性预计方法的研究

为了能够准确有效地评估现有数控装置的可靠性,对当前高可靠性数控装置的可靠度能够有一个定量的分析,因此对目前某型号数控装置进行了研究,运用工程上常用的评分方法对该装置的可靠性进行了分配,并且引入了国家军用标准GJB/Z299C《电子设备可靠性手册》常用的元器件计数法对该装置进行了可靠性模型建立和可靠性的详细预计,定量地预测其可靠性水平,评价装置是否能达到要求的可靠性指标,并且能够找出系统薄弱环节,及时改进设计。实验表明,该方法具有实用性,能够利用此方法来对数控装置的可靠性进行分配和预计,而且评价出的可靠性水平可以指导该数控装置的可靠性测试与试验。     

MTS1600 500六轴数控砂带磨床构建及磨削仿真验证

MTS1600-500六轴数控砂带磨床是用于叶片磨削抛光的精密加工高端数控机床,该磨床磨削加工的工件主要以宽弦空心风扇叶片为主,空心叶片的制造工艺复杂,成本昂贵.磨削加工处于叶片加工关键步骤中的最后一步,这就要求在实际磨削加工前进行虚拟仿真磨削.该磨床可实现六轴联动,机床结构复杂,不存在现有仿真环境.为解决此问题,以UG为平台构建MTS1600-500六轴数控砂带磨床的几何模型并装配,在VERICUT中搭建该磨床磨削加工仿真环境.以某型号宽弦空心风扇叶片为仿真加工对象,对该磨床建模仿真环境进行验证,最后通过实际磨床的磨削加工验证了所建模型与仿真环境的正确性.该磨床的虚拟仿真环境可实现磨削加工过程的动态仿真,加工效率得以提升,也为后续加装在机测量模块奠定基础.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Microstructure and Mechanical Properties of X80 Pipeline Steel Joints by Friction Stir Welding Under Various Cooling Conditions

X80 pipeline steel plates were friction stir welded(FSW) under air, water, liquid CO_2 + water, and liquid CO_2 cooling conditions, producing defect-free welds. The microstructural evolution and mechanical properties of these FSW joints were studied. Coarse granular bainite was observed in the nugget zone(NZ) under air cooling, and lath bainite and lath martensite increased signifi cantly as the cooling medium temperature reduced. In particular, under the liquid CO_2 cooling condition, a dual phase structure of lath martensite and fi ne ferrite appeared in the NZ. Compared to the case under air cooling, a strong shear texture was identifi ed in the NZs under other rapid cooling conditions, because the partial deformation at elevated temperature was retained through higher cooling rates. Under liquid CO_2 cooling, the highest transverse tensile strength and elongation of the joint reached 92% and 82% of those of the basal metal(BM), respectively, due to the weak tempering softening. A maximum impact energy of up to 93% of that of the BM was obtained in the NZ under liquid CO_2 cooling, which was attributed to the operation of the dual phase of lath martensite and fi ne ferrite.     

INDUSTRY NEWS

China Securities News reported on March 21, 2014： Guangdong Hongtu Wuhan Die Casting Co., Ltd. （Wuhan Hongtu）, a wholly owned subsidiary of Guangdong Hongtu Technology （Holdings） Co., Ltd., held a groundbreaking ceremony recently. With the registered capital of 50 million Yuan, Wuhan Hongtu has a total land area of 100,000 square meters and a plant construction area of 72,000 square meters. It is expected to have a production capacity of about 30,000 tonnes of aluminum castings annually after it is put into production.     

Microstructure,Mechanical Properties and Corrosion Behavior of Extruded Mg–Zn–Ag Alloys with Single-Phase Structure

Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag(wt%,x=0.2,0.5 and0.8)alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.     

Growth Morphologies of a Binary Alloy with Low Anisotropy in Directional Solidification

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.