基于改进灰色关联度的液压系统可靠性模型优选方法

针对目前以假设检验等方法进行模型优选区分度和准确性不高的问题,提出了基于斜率相似和中值相近的灰色关联度模型优选方法,研究了该优选方法的算法。根据采集的数控磨床液压系统的可靠性数据,分别用5种概率密度函数对液压系统进行了建模,并利用所提模型优选方法对5种分布模型进行了拟合优度检验,结果显示液压系统最适合于伽马分布。与相关系数法、传统灰色关联度法、K-S检验等方法进行模型优选相比,基于改进灰色关联度的模型优选方法的区分度分别提高了86.42%、67.27%、2.59%,且准确性很高,优选效果良好。所述的模型优选方法可以用于可靠性模型的优选,也可以为其他曲线拟合的优选提供参考。     

基于混合威布尔分布的数控折弯机可靠性评估

在收集国产WEHK 110/3100型数控折弯机故障数据的基础上,选用两参数混合威布尔模型进行数据建模,采用最大期望值(EM)算法进行参数估计,通过拟合优度检验确定,机床故障过程服从混合威布尔分布,最后通过计算获得该型机床的可靠性指标。结果表明,机床可靠性指标与企业实际运行非常契合,可作为该型机床可靠性水平的参考,为国内关于数控折弯机的可靠性评估提供了一种新方法。     

高档数控装备多层贝叶斯可靠性评估模型研究

为实现少量故障数据样本下五轴联动数控机床精确的可靠性评估,通过对贝叶斯估计方法进行研究,设计实现数控机床可靠性建模。该方法首先设定威布尔模型参数服从伽玛分布,为解决无先验信息问题,引入两层贝叶斯方法。为解决积分求解后验分布计算困难问题,使用MCMC方法计算模型参数估计值,最终建立起威布尔模型。引用某机床一年的历史故障数据,使用所设计方法与最小二乘法实现建模,用拟合优度检验将两个方法结果进行比较判断出所设计方法具有可行性。最后依据建立的可靠性模型对机床进行可靠性评估。     

基于故障关联度的数控系统可靠性建模北大核心

为了研究高可靠长寿命高档数控系统可靠性,提高数控系统可靠性模型的拟合效果,提出一种基于故障关联度的数控系统可靠性建模方法。首先,基于关联规则,利用FP-Growth算法挖掘频繁项集,通过对故障数据的挖掘建立一个既满足最小支持度又满足最小置信度的关联规则;其次,提出基于故障关联度的数控系统建模方法并给出故障关联因子的计算公式,通过故障关联因子对Weibull分布模型进行优化,建立改进模型,并与Weibull分布模型进行了对比。结果表明,改进模型的均方误差远小于Weibull分布模型,且在超过400 h之后改进模型与故障数据的拟合效果优于Weibull分布模型,该模型完善了数控系统可靠性评估方法,提高了数控系统的故障预测能力。     

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。     

基于遗传算法的数控磨床可靠性优化分配技术研究

可靠性设计是保证产品质量的重要环节,可靠性分配是可靠性设计的主要内容,可靠性指标分配受到成本的制约。数控磨床是精密制造系统中最后一个加工设备,其可靠性的高低对加工质量和生产效率有重要影响。为了确保数控磨床在一定的系统可靠性水平下成本最低,提出了可靠性优化分配技术。建立了数控磨床的可靠性优化分配模型,利用遗传算法对数控磨床的各个子系统进行可可靠性指标分配,并将分配后的成本与现有数控磨床的成本进行了比较,结果表明:总成本可以降低3.7%,优化效果明显;该方法可以应用在数控磨床的可靠性设计中,也可以为其他类似机电产品的可靠性设计提供参考。     

基于GA与RBF神经网络的工程陶瓷点磨削表面硬度数值模拟

基于RBF神经网络理论,对工程陶瓷点磨削表面硬度HV与切削速度vc、进给速度f、切削深度ap、倾斜角α、和偏转角β五个工艺参数的关系进行了单因素数值拟合,并以拟合优度对拟合结果进行了检验,检验结果表明模型具有较高可信度。基于遗传优化算法,对点磨削表面硬度关于五个工艺参数的多元模型进行了优化建模,设计了正交实验对模型进行检验,最大误差在10%以内,表明模型具有较高的可靠性。     

面向最小维修的数控机床可靠性评估

为了解决数控机床最小维修的可靠性评估问题,提出了基于幂律过程的可靠性评估方法,建立了基于幂律过程的故障数据模型。对故障数据进行趋势检验和更新过程检验,验证了幂律过程应用的前提条件成立。提出CBT与CLT的分步检验方法对评估涉及的多台机床的同质性进行了验证。用极大似然估计法和Fisher信息矩阵法给出了模型参数的点估计与区间估计,并给出了机床可靠性指标的点估计和基于Delta法的区间估计。应用Cramér-von Mises法对模型进行拟合优度检验。实例分析表明:幂律过程能够反映出数控机床的瞬时与累积可靠性特性,提出的CBTCLT分步检验方法能够有效地对多台机床同质性做出判断,得到的结果更符合实际。     

基于生命周期的数控车床寿命分布模型及控制

针对国产数控机床故障频繁的问题,提出了建立基于生命周期的寿命分布模型,并揭示了故障机理和规律.选择国产和进口相同类型的数控车床,由同一机床用户进行现场跟踪试验.通过对故障时间信息进行拟合优度检验等建模分析,得出两类寿命分布模型:发达国家机床运行于故障率近似恒定的偶然故障期;而国产机床寿命模型包含浴盆曲线左侧面,首先运行于高故障率的早期故障期,然后过渡到偶然故障期.由此揭示了造成国内外机床可靠性差距的原因,提出了消除早期故障的方法,采用该方法可显著提高国产机床的可靠性水平.     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

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。     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.