硅藻土涂层气孔率对大口径球铁管外表面凹陷缺陷的影响

本文主要从涂层结构 ,即涂层气孔的种类、数量论述其对大口径球铁管外表面凹陷缺陷的影响。从涂料雾化液滴大小、金属型温度、喷嘴距金属型内表面距离、喷嘴移动速度、涂料中膨润土含量、金属型转速等工艺参数来控制涂层气孔率 ,保证涂层透气性 ,从而消除凹陷缺陷     

淬火工艺有限元模拟中弹塑性比例系数的计算方法

淬火过程是一个温度、相变、应力应变相互影响的材料非线性过程。根据淬火过程的特点,提出了一种新的计算弹塑性比例系数的方法,使用该方法可以求解过渡单元的弹塑性比。在模拟过程中,为了提高计算精度、减少计算时间,提出了两种加速弹塑性比例系数收敛的方法:弹性逼近法和插值方法。应用弹性逼近法和插值方法对无相变冷却过程和有相变冷却过程进行有限元模拟,将模拟所得应力变化曲线与实验结果相比较。结果表明,弹性逼近法和插值方法可以显著减少弹塑性比例系数的迭代次数,计算得到的应力值与实验结果吻合较好。     

Steam oxidation resistance of two-layered Ni-Cr and Al APS coating for USC boiler applications

Thermal spray of Ni-Cr and Al coatings was attempted on modified 9Cr-1Mo steel, to evaluate their steam oxidation resistance. Atmospheric plasma spray (APS) coatings of 50Ni-50Cr as undercoat and Al topcoat were attempted with the aim that the pores produced by 50Ni-50Cr undercoat can be filled with Al topcoat during the steam oxidation. The steam oxidized samples evinced the Ni and Cr diffusion towards the Al coating structure and changed the topcoat in to the Ni-Al intermetallics. Though the two-layered coating exhibited an excellent performance against the steam oxidation for the base steel substrate till 3000 h of test, the top layers of the coating underwent significant internal oxidation.     

火车轮预成形压缩比数值模拟

应用MARC／autoforge商用有限元软件,埘火车车轮预成形过程进行了热力耦合模拟,研究了车轮成形过程的应变分布。通过圆柱体自由镦粗,得到应变与压缩比的关系,应用拟合公式求出车轮断面的压缩比分布。     

A201铝合金针孔形成机制的探讨

本研究的目的为藉由完整的试验,找出铝合金中针孔与铝合金凝固期间热参数之间的关系,进而于铸造实际处理时,可为铸造方案设计及金属凝固提供参考。A201铝合金有127℃的凝固范围,适合作为研究对象;经由有系统的改变冒口大小,及平板铸件的长度及厚度,并浇注于两种不同的砂型中,通过变化铝合金凝固时的各种热参数,例如:局部凝固时间、冷却速率、液相前进速度及热梯度等,经计算针孔量,可得出热参数与针孔量间的关系。试验结果显示,A201铝合金的针孔量减少与补充参数值G/VSt1.10增大有一定的关系。     

Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure the density of coatings.     

流动条件下炔氧甲基季胺盐的缓蚀性能研究

利用交流阻抗(EIS)、线性极化、动电位极化和失重法，研究了炔氧甲基季胺盐对N80在常温CO2饱和的3％NaCl溶液中的电化学行为和缓蚀性能的影响．结果表明：空白溶液中N80的累计失重在4m／s以后急剧增大，即介质的临界流速为4～5m／s．动态下炔氧甲基季胺盐存在与静态下相同的浓度极值现象，流速低于5m／s时缓蚀剂的极值浓度与静态时相同，都为150mg／L，而流速高于5m／s后极值浓度有所增加．     

钢结构制造中焊接变形的控制方法

着重介绍了桥梁、建筑、船舶、压力容器等钢结构制造中经常遇到的一个比较棘手的问题--焊接变形的控制方法和解决方案.     

Effect of extrusion wheel angular velocity on continuous extrusion forming process of copper concave bus bar

The continuous extrusion forming process for producing large section copper concave bus bar under different extrusion wheel angular velocities was studied by three-dimensional finite element technology based on software DEFORM-3D. The rigid-viscoplastic constitutive equation was employed in the model. The numerical simulation results show that the deformation body flow velocity in the die orifice increases gradually with the increase of the extrusion wheel angular velocity. But slippage between the rod and extrusion wheel occurs when the extrusion wheel angular velocity is high. The effective stress near the die orifice enhances gradually with increasing extrusion wheel angular velocity. High stress is concentrated in adjacent regions of the flash gap. The effective strain gradient is greater near the abutment than that near the die orifice. The effective strain of the product increases gradually with increasing extrusion wheel angular velocity. In the deformation process, the deformation body temperature increases remarkably due to friction and deformation. So the cooling is necessary in the region of the die and tools.     

基于EEMD能量比和GG聚类的滚动轴承故障诊断

针对滚动轴承故障特征提取困难导致故障类型难以辨识的问题,提出基于集合经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)和GG(Gath-Geva,GG)聚类的轴承故障诊断方法。首先,使用EEMD分解方法对轴承的振动信号进行分解,结合相关系数原则提取含有主要故障信息的4个固有模态函数(IMF)分量,计算其能量百分比作为特征值,再用GG聚类对特征值进行聚类分析。通过仿真验证了GG聚类的优越性,然后采用文中提出的GG聚类方法与FCM聚类、GK聚类对轴承故障数据的聚类效果进行对比分析,验证了文中所提方法在滚动轴承故障识别中的可行性。