X70管线钢焊接性分析

针对管道建设中日益广泛采用的X70管线钢，分析了其碳当量与冷、热裂纹敏感性问题，探讨了防止X70管线钢产生冷裂纹的工艺措施，计算了不同板厚X70管线钢的预热温度，为实际的管道建设提供了理论依据与工程指导。     

Oblique Y-groove cracking test of the welding cold cracking susceptibility of domestic X-70 pipeline steel

“Gas Transmitting From West to East Project“ is significant.it should ensure the welding quality and safety of pipeline.The task is very arduous to guarantee the quality of the projcet in the condition of long line.complex weather and geolgy features.in this paper,the welding cold cracking susceptibility of domestic X-70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline,was studied by means of oblique Ygroove cracking test.The crack ration of surface and section was tested under the conditions of different welding materials and preheat temperature.The thickness of plate stell was 14.7mm and 10.3mm.The results reveal that X-70 pipeline steel has good crack resistance.The research has important value for the construction of large-scale pipeline engineering and the application of domestic X-70 pipeline steel.     

Finite element analysis of tailored sheet forming processes considering laser welding zone

The finite element formulation for predicting strain distributions and weld line movements in the forming processes of tailored sheet metals is developed. The material properties of the welding zone such as strength coefficient, work-hardening exponent, and plastic anisotropic parameter are analytically obtained from those of base metals based on the tensile tests. The welding zone is modelled with the several, narrow finite elements called by weld elements. To verify the finite element formulation for tailored blanks, the forming processes of autobody door inner panel section and hemispherical dome are simulated. FEM predictions are compared and showed good agreements with experimental measurements.     

A study of tailored blank welding between mild steel sheet and zn-coated steel sheet by CO2 laser beam

Research was conducted on tailored blank welding between mild steel sheet and Zn-coated steel sheet using CO₂ laser beam. The materials used in this study were low carbon steel sheets with a thickness of 1.2 mm and Zn-coated steel sheet with the same thickness and 6.3 μm Zn coating. Experiments were conducted by applying the Taguchi method to obtain optimum conditions for the application of this tailored blank laser welding method in practical manufacturing processes. Optical microscopy, XRD, SEM and TEM analysis were performed to observe the microstructures and to determine the structures of welded zone. In addition, mechanical properties were measured by the microhardness test, tensile test and Erichsen test to evaluate the formability of the welded specimen. There was no trapped Zn in the fusion zone, and the phases of this region consisted of polygonal ferrite, quasi-polygonal ferrite, banitic ferrite and martensite. The elongation value of welded specimen was more than 80% of the value in substrate metal, and the LDH value was more than 90% of the value in substrate metal.     

Banding formation and eutectic lamellar growth in directional solidified Ni50Al20Fe30 alloy

Banding formation and eutectic lamellar growth in a directionally solidified Ni₅₀Al₂₀Fe₃₀ alloy were investigated. It was found that the banding area consists of two layers. The first layer is a γ layer, while the subsequent one is a γ layer. The composition of various phases around the banding area changes with the solidification process. The banding is formed by two steps process and caused by factors such as the fractions during the sample growth process. It was found that the band was found at relatively low growth rate. Therefore. this study indicates that increasing the growth rate is an effective method to eliminate the band formation. Eutectic lamellae nucleate and grow again after the banding formation. During the initial transition lamellar growth, the relationship between the square lamellar spacing, γ₂, and the distance from, the banding, d, can be described by the following equation: γ₂ = K [1-exp(A.d)] where K and A are constant.     

HSn70-1B铜管在碱性NaCl溶液中的腐蚀行为

利用表面分析技术和电化学方法研究了HSn70- 1B 铜管在碱性NaCl溶液中的腐蚀行为.在自腐蚀状态下，HSn70-1B铜管表面生成以Cu2 O为主的表面膜；在阳极极化电位下表面CuCl的生成反应为一级反应，电极表面形成CuCl膜 后，存在极限电流密度；电化学阻抗频谱(EIS)有2个容抗弧，随Cl-含量的增加，容抗弧 逐渐收缩，弥散性增大.     

基于粗糙集的软件项目风险管理研究

软件项目的复杂性导致软件风险涉及的数据具有很大的不确定性和模糊性。由此基于粗糙集理论,分析了软件项目风险管理的历史数据:利用等价类和分辨矩阵等概念提出软件项目风险分析系统,在此基础上给出了两个风险因子的相关性系数以及不可分辨矩阵的计算方法。此项工作能为风险控制提供策略,有助于发现风险管理活动中的薄弱环节,达到改进过程的目的。     

稀有类分类算法的研究

稀有类的分类问题在商业、金融、电信、科学研究等诸多的领域都有着广泛的应用,但是由于其难区分性、多态性、稀有性等主要的特征,使其传统的分类方法对于稀有类的分类来说,并没有良好的效果。因此对于稀有类分类问题的研究是具有理论及其实践意义的。将稀有类的现有分类算法分别进行了阐述,而且引入了专用于稀有类分类算法的评估标准。