变换气管道开裂原因分析

对水煤浆净化装置低温变换炉泄漏的出口管材质、裂纹进行宏观和微观的检测和分析，结果表明：焊接管是用φ720mm×18舢、板材沿轧制方向卷制而成，这种轧制方法使横焊缝具有极高的残余应力，大于AISI321奥氏体不锈钢在含有Cl^-水溶液中的应力腐蚀的临界应力，故相运行400d后发生Cl^-溶液中应力腐蚀，引起泄漏。同时对H2S的作用进行讨论，提出一些解决方案并应用于实际，取得成效。     

薄膜厚度的多探头计算机实时测控系统

阐述了用声阻抗法实时监测薄膜沉积的原理，介绍了一种使用个人计算机的实时测控系统。它可在真空镀膜的过程中对膜厚进行实时测量和控制，允许使用多个石英晶体探头，以适应多源共蒸发真空镀膜的需要。监测的过程和结果可以存储下来进行分析。为优化镀膜工艺提供了很大的方便。     

水压爆破拆除不等壁硫酸池

介绍了用水压爆破拆除中间有隔墙的不等壁池的设计与施工，采用多药包偏心布置，爆破效果良好。     

加氢换热器角焊缝密封接头焊接工艺参数优化

利用有限元软件ABAQUS,开发了一个顺次耦合的角焊缝焊接热应力计算程序,研究了加氢高压换热器板式焊接密封接头应力场的分布;以此数值模拟结果为基础,结合正交试验设计方法,分析了焊接电流、电弧电压、焊接速度及预热温度4个工艺参数对焊接残余应力场的影响,找到一组使焊接残余应力最小的最优焊接工艺参数.结果表明,焊接速度对焊接残余应力的影响最大,该角焊缝焊接残余应力的最高值集中在焊缝和热影响区附近.研究结果为优化加氢高压换热器板式焊接密封的焊接工艺,预防焊接密封接头的开裂失效提供了理论基础.

Abstract：

Using the finite element analysis software ABAQUS, a sequentially coupled fillet welding thermal-stress program was developed to calculate the stress distribution of plate sealing joint in the high pressure hydrogenation heat exchange. Based on the numerical solutions and the orthogonal method, the influence of four welding parameters including welding current, welding voltage, welding speed and preheating temperature on residual stress distribution was analyzed and a group of optimal welding parameters were obtained, which provided a reference for preventing the failure of fillet weld sealing joint in the high pressure hydrogenation heat exchange.     

Fatigue crack/residual stress field interactions and their implications for damage-tolerant design

Residual stress fields are now widely accepted to have significant influence on fatigue crack growth. Tensile stresses have detrimental effects on fatigue lives, whereas compressive residual stresses can be beneficial. Control of fatigue lives via residual stress is now established in many industrial applications, using techniques such as shot peening or cold expansion. However, knowledge of the processes that occur when a fatigue crack grows through a pre-existing stress field is far from complete. Although the residual stress field will clearly have an effect on crack growth, the crack will equally have an effect on the residual stress field. The determination of this effect is not trivial, and direct measurement may be the designer’s best safeguard. This article outlines the complementary effects that a growing fatigue crack and a residual stress field have on each other. Two types of residual stress field are considered: mechanically induced and thermally induced. The results are discussed in terms of the implications that residual stress interactions have for damage-tolerant-based design.     

Spacing of edge fractures in layered materials

Opening-mode fractures developed from a free surface in a layered material often terminate at the interface that divides the fractured layer and the underlying layer. They also display regular spacing that is of the same order of magnitude as the thickness of the fractured layer. We have investigated the stress distribution between two adjacent edge fractures as a function of the ratio of fracture spacing to thickness of the fractured layer using a two-layer elastic model with a fractured top layer. The results show that when the ratio of fracture spacing to the layer thickness changes from greater than to less than a critical value the normal stress acting perpendicular to the fractures near the free surface changes from tensile to compressive. This stress state transition precludes further infilling of fractures unless they are driven by mechanisms other than a pure extension, or there are flaws that significantly perturb the local stress field between the fractures. Hence, the critical fracture spacing to layer thickness ratio defines a lower limit for fractures driven by extension, which also defines the condition of fracture saturation. The critical value of the fracture spacing to layer thickness ratio is independent of the average strain of the fractured layer, and it increases with increasing ratio of Young's modulus of the fractured layer to that of the underlying layer. The critical value increases with increasing Poisson's ratio of the fractured layer, but it decreases with increasing Poisson's ratio of the underlying layer. For the case with the same elastic constants for the fractured layer and the underlying layer, the critical spacing to layer thickness ratio is about 3.1. Delamination between the fractured layer and the underlying layer makes the critical spacing to layer thickness ratio much greater. Infilling fractures grow more easily from flaws located near the bottom of the fractured layer than from those located near the free surface when the spacing to layer thickness ratio is less than the critical value. The propagation of an edge flaw between adjacent edge fractures is unstable, but for the flaw to propagate to the interface, its height has to be greater than a critical size, that decreases with increasing fracture spacing to layer thickness ratio. The propagation behavior of an internal flaw with its lower tip at the interface depends on the edge fracture spacing to layer thickness ratio. The propagation is unstable, when the fracture spacing to layer thickness ratio is greater than a critical value; stable, when the fracture spacing to layer thickness ratio is less than another critical value; and first unstable, then stable, and/or unstable again, when the fracture spacing to layer thickness ratio is between these two critical values.     

基于动态子结构的三维焊接残余应力变形数值模拟

焊接残余应力和变形三维弹塑性有限元模拟由于是高度非线性的热力耦合过程而计算非常耗时.为提高计算效率,采用动态子结构方法来计算焊接残余应力和变形.考虑焊接过程中只有焊缝和热影响区的小部分区域在焊接热源作用下呈现高度非线性,而其余区域受热源的影响小,将整个模型的三维弹塑性计算问题处理为窄小的焊缝和热影响区为局部非线性弹塑性区,其余大部分非焊接区域作弹性子结构的计算问题;且随焊接热源的移动,子结构不断变化.结果表明,动态子结构方法能显著提高计算效率,并能保证焊缝和热影响区的残余应力分布与全模型计算结果接近.     

局部加载拉应力对平板焊接残余应力场的影响

采用有限元模拟技术,观察在局部加载条件下平板焊接残余应力场的应力分布,比较平板构件焊接过程中拉伸与焊后拉伸在降低应力方面的不同效果.发现在局部加载条件下焊接过程中拉伸比焊后拉伸可更好地减小焊接残余应力,且当外加载荷低于材料的屈服强度时,载荷越大,残余应力的降低越明显.用200 MPa外截拉伸时,焊后拉伸残余应力最大值由常规焊条件下的235 MPa降至130 MPa,焊接过程中拉伸残余应力最大值可降至50 MPa.结果表明,通过局部加载减小焊接残余应力是可行的.     

Improvement of the film thickness by modification of the hydroxymethylbenzene SAM with tetraethoxysilane and octanediol for protection of iron from corrosion in 0.5 M NaCl

For enhancing the protective efficiency, P of a film prepared by modification of a p-hydroxymethylbenzene HOC₆H₄ (HOMB) self-assembled monolayer (SAM) adsorbed on iron by the formation of a covalent bond, an increase in the film thickness, d was attempted. The HOMB SAM was modified with tetraethoxysilane (C₂H₅O)₄Si (TES), 1,8-octanediol HO(CH₂)₈OH (C₈DO), 1,2-bis(triethoxysilyl)ethane (C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃ (BTESE) and alkyltriethoxysilane C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18). The P value of the film was determined by polarization measurement of a covered iron electrode in an aerated 0.5 M NaCl solution after immersion in the solution for 1.5–72 h of the immersion time, t. High values of P, more than 82% were obtained for the films of HOMB SAM modified with TES, C₈DO and C_nTES and with TES, C₈DO, BTESE and C_nTES in the range of t up to 72 h. The highest value was 93.2%, for the film of HOMB SAM modified with TES, C₈DO, BTESE and C₁₈TES, of which d was 4.7 nm. The film of HOMB SAM modified with TES, C₈DO and C₈TES was characterized by contact angle measurement, X-ray photoelectron spectroscopy and FTIR reflection spectroscopy.     

Validation of mobile LiDAR surveying for measuring pavement layer thicknesses and volumes

Mobile LiDAR surveying is currently one of the most popular topics in road inspections. This non-destructive technology is suitable for collecting infrastructure inspection data related to 3D geometry and radiometry. Ground penetrating radar (GPR) is traditionally used to measure pavement thickness, though this technique requires reference data (cores) when surveying in a ground-coupled configuration.Within this work, a new alternative method to GPR has been studied for determining pavement layer thicknesses and volumes. We analyze the performance of mobile LiDAR technology in this scope and test its accuracy compared to the results obtained with a ground-coupled 2.3-GHz GPR antenna. The findings presented here are based on field data collected from the Ourense–Celanova highway, in Northwestern Galicia. The results showed the potential of the Lynx Mobile Mapper to obtain the designed pavement thickness of newly constructed roadways with errors that are always less than 1.5 cm.