基于三维有限元动态模拟圆柱形表面腐蚀缺陷漏磁场

根据电磁场有限元分析的基础理论，对储罐底板圆柱形表面腐蚀缺陷，应用ANSYS三维有限元静态分析了圆柱形表面腐蚀缺陷漏磁场，得到了圆柱形表面腐蚀缺陷漏磁场的空间分布。在一定条件下，静态模拟的缺陷漏磁场受励磁结构中永磁铁磁场的影响较大，造成在永磁铁附近漏磁场分布的畸变。而动态模拟下得到的漏磁场只在缺陷附近有明显的变化，缺陷漏磁场受励磁结构中永磁铁磁场的影响很小，有利于对腐蚀缺陷的分析。     

交变漏磁检测中螺纹不同缺陷位置的识别方法研究

依据缺陷在螺纹区域的不同位置，将缺陷分为三类，分析了每类缺陷检测信号的特点，提出了识别判据，最后通过对膨胀螺钉上的该三类缺陷的检测，验证了识别模型的正确性。另外，对六角头螺栓结构根部缺陷的检测进行了试验研究，利用测量信号完成了缺陷的检测。     

添加稀土Er于熔剂中对铸态AZ91镁合金组织与性能的影响

研究了熔炼时在熔剂(42%MnCl2 53%LiCl 5?F2,质量分数,%)中添加稀土Er对铸态AZ91镁合金显微组织、力学性能、断口形貌以及腐蚀行为的影响。结果表明:在熔剂中添加稀土Er能够去除镁合金熔炼过程中产生的熔剂夹杂,净化镁合金熔体,提高铸态AZ91镁合金的拉伸性能和耐腐蚀性能;当熔剂中添加10%的稀土Er时,镁合金的抗拉强度σb和伸长率δ分别从156MPa和1.8%上升到最大值220MPa和4.1%;同时,镁合金在5%NaCl水溶液中的腐蚀速率从1.20mg/(cm2.d)下降到最小值0.15mg/(cm2.d);然而,随着稀土Er在熔剂中添加量的进一步提高,合金中开始有φ-(Al7ErMn5)和τ-(Al66.7Mg23.3Er10)等含有稀土Er的相生成,消耗了合金中的Al和Mn元素,改变了β-(Mg17Al12)相的形态;而且沿枝晶界附近分布的粗大φ-(Al7ErMn5)相降低了枝晶之间的结合力,使得合金的σb和δ下降;同时,部分网状的β-(Mg17Al12)相断裂,呈离散的块状,导致合金的腐蚀速率增加;熔剂中添加稀土Er不改变镁合金的断裂机理,断裂机制仍为准解理断裂。     

超宽板坯连铸机黏结漏钢原因及预防措施

分析了安钢第二炼轧厂超宽板坯连铸机黏结漏钢的原因,并采取了针对性的预防措施,黏结漏钢率大大降低.     

不平衡因子对药芯焊丝CO2气体保护焊焊缝金属韧度的影响

研究了由氮化物形成元素Al,Ti等控制的不平衡因子B对低合金药芯焊丝CO2气体保护焊缝金属韧度的作用.结果表明,在药芯具有氧化性的条件下,不平衡因子B对焊缝金属韧度的作用仍然明显.并且相比实心焊丝CO2气体保护焊而言,不平衡因子B的最佳值增大了.分析表明,药芯焊丝自身的氧化性是不平衡因子B增大的原因.在不平衡因子B由小增加到最佳值的过程中,焊缝金属组织由粒状贝氏体 板条铁素体逐渐向以夹杂物为核心的针状铁素体组织发展,由此其韧度逐渐改善;而当不平衡因子B超过最佳值较多时,过剩的氮化物形成元素进入铁素体固溶而导致脆化.     

EFFECTS OF AXIAL PRESSURE DROP ON THE LENGTH-AVERAGED PERMEATE FLUX IN CROSSFLOW MICROFILTRATION

A hydrodynamic model is presented which predicts the dependence of the steady-state, length-averaged permeate flux on the longitudinal pressure drop during crossflow microfiltration in both flat slit and tubular channels. The integral approach described by Romero and Davis (1988) has been extended to predict the axial variation of the transmembrane pressure drop along with that of permeate flux and cake layer thickness. The mechanism of shear-induced diffusion is employed in the analysis, which is restricted to particles with diameters of approximately 0.5-20μm (Davis, 1992), but the procedures may be extended to other particle transport mechanisms. The model predictions have been compared to the corresponding values calculated using a constant transmembrane pressure drop set equal to the arithmetic mean of those at the channel entrance and exit. The simulation results show the axial pressure drop to have the most significant effect on the average, steady-state permeate flux predictions for long, tubular channels with small critical lengths, operating under membrane resistance limited conditions and low transmembrane pressures. Neglecting the axial pressure drop, under typical operating conditions, results in as much as a 50% overestimation of the length-averaged, steady-state permeate flux.     

钛合金活性剂氩弧焊研究进展(1)

钛合金氩弧焊时加卤化物等活性剂焊接(A-TIG焊)不仅气孔明显减少,而且熔深可成倍增加,焊接接头力学性能也有所改善.由于焊接热输入可大大降低,因此会改善焊接接头组织和减少应力变形.厚板焊接时可大幅度提高生产率.文中介绍了A-TIG焊活性剂及形态、活性剂对焊缝熔深/熔宽比及焊接质量的影响、深熔机理及焊缝成形问题,并对一些问题进行了评论.     

不锈钢活性激光焊工艺研究

以不锈钢SUS304作为试验对象,分别研究了焊接速度、散焦离焦量、激光功率和保护气体等工艺参数以及活性剂和活性元素硫对不锈钢YAG激光焊焊缝成形的影响.试验结果表明,各焊缝表面成形良好,焊接速度和激光功率能明显影响焊缝成形,散焦离焦量和保护气体种类对YAG激光焊焊缝成形的影响较小.与硫含量较低的情况相比,活性剂和活性元素硫含量较高的情况下均能使得焊缝熔宽发生明显收缩,随着热输入量增加,活性剂增加熔深的效果也越明显,表明活性剂对熔深的影响效果与焊接过程的热输入量有密切联系.     

Experiment and simulation study of 3D magnetic field sensing for magnetic flux leakage defect characterisation

Magnetic flux leakage (MFL) testing is widely used to detect and characterise defects in pipelines, rail tracks and other structures. The measurement of the two field components perpendicular to the test surface and parallel to the applied field in MFL systems is well established. However, it is rarely effective when the shapes of the specimens and defects with respect to the applied field are arbitrary. In order to overcome the pitfalls of traditional MFL measurement, measurement of the three-dimensional (3D) magnetic field is proposed. The study is undertaken using extensive finite element analysis (FEA) focussing on the 3D distribution of magnetic fields for defect characterisation and employing a high sensitivity 3-axis magnetic field sensor in experimental study. Several MFL tests were undertaken on steel samples, including a section of rail track. The experimental and FEA test results show that data from not only the x- and z-axes but also y-axis can give comprehensive positional information about defects in terms of shape and orientation, being especially advantageous where the defect is aligned close to parallel to the applied field. The work concludes that 3D magnetic field sensing could be used to improve the defect characterisation capabilities of existing MFL systems, especially where defects have irregular geometries.     

活性剂对镁合金交流A-TIG焊的影响

分别以单质Te,Ti和Si,氧化物SiO2,TiO2和V2O5,卤化物MnCl2,CdCl2和ZnF2作为表面活性剂进行了镁合金交流A-TIG焊,研究了活性剂对焊缝成形和组织的影响规律.Te粉,ZnF2和CdCl2都能明显增加熔深,其中Te粉使熔深达到传统TIG焊的1.6倍,焊缝深宽比达到0.43.Ti粉对焊缝熔深熔宽几乎没有影响.V2O5,SiO2,TiO2,MnCl2和Si粉都使得焊缝熔深熔宽减小.在三种明显增加熔深的活性剂中,Te粉和ZnF2都使得焊缝组织晶粒细化,而CdCl2使得焊缝组织晶粒略有粗化.结果表明,活性剂增加镁合金ATIG焊熔深主要与活性剂粒子和电子复合导致电弧收缩有关.