Hot ductility of simulated stainless-steel weld metals

Simulation of stainless-steel weld metals was performed using a Gleeble-1500 thermomechanical simulator. Two classes of materials were investigated, including both fully austenitic and austenitic-ferritic stainless steels. The niobium content varied within each class. The simulation comprised heating to melting point, melting for a short time, and cooling to a number of temperatures, at which point the samples were fractured under a tensile load. The hot ductility, in terms of reduction of area, was measured. Metallographic examinations were performed using both optical and electron microscopy. The hot ductilities of the austenitic-ferritic weld metals investigated were superior to those of fully austenitic weld metals of corresponding niobium content. The beneficial effects of ferrite were found to decrease with increasing niobium content. The effect of niobium on hot ductility was detrimental, i.e. an increase in niobium content resulted in a decrease in hot ductility which was attributed to the formation of (FeCrNi)₂Nb-, a low melting eutectic, along the austenitic grain boundaries. The criterion of hot ductility by simulation of the weld metals was also found to be reliable for evaluating susceptibility to solidification cracking.     

基于单片机的家庭报警系统设计

本文设计了一种基于AT89C2051芯片为CPU的家用报警系统,以烟雾探测器、门磁报警器、燃气体探测器等传感器为节点,当收集到异常信息后,由无线网络节点送至报警主机,通过主机报告给预留电话,从而完成了家庭报警系统的硬件组成、软件设计、数据采集与通信策略以及主程序设计,实现对家庭的非法入侵、火灾、燃气泄漏等事故的报警保护。     

对《网络创业实训》课程的探讨

针对各校对大学生创业实训进行讲授内容的不同,我们在结合本专业的基础上,开展了网络创业实训课程,在创业方向方面不再仅限于网店,而是可以进行多种模式的选择,同时在提高实践性方向,最终的成果也以创业企划书来全面衡量。     

Office Excel软件教学方法研究

本文主要对现阶段Office Excel软件教学中出现的问题进行深入研究,结合实际的教学经验,提出了以问题教学法、研究性教学法、项目教学法为主要方法的Office Excel软件教学方法。意在从教学方法的角度提高Office Excel软件教学质量,夯实学生的Office Excel软件基础。     

计算机硬盘坏磁道修复的思路与技巧

本文通过隐藏坏磁道分区的方法,着重介绍了硬盘坏磁道的修复技术及注意事项,同时还介绍了逻辑坏磁道、0磁道损坏的修复方法。     

实验室网络教学资源与人才培养创新理论的研究

实验室网络教学资源与人才培养创新理论的研究,要灵活多样,寻求多种途径,利用虚拟实验室及网络等现有资源,开展开放式实验实训和校外实训,利用远程教学,将实训教学与职业技能鉴定相结合,以网络资讯平台为基础,通过电视式校园媒体平台,以市场为导向的方针,规划人力资源,以就业为核心的现代化的传输手段,实现适应市场需求的各类人才的培养计划,努力建设一个以高校校园市场为基础的、完善的、能沟通企业、学校和学生的产、教、学信息平台。     

Application of a hybrid finite element method to determine stress intensity factors in unidirectional composites

In this paper a hybrid finite element method is applied in evaluation of the stress intensity factors K _I and K _II of unidirectional fiber reinforced composites. In order to satisfy the stress singularity at the crack tip a singular super-element based on a modified complementary energy principle is developed. The stress and displacement fields in the super-element are expressed in terms of polynomials of two complex variables ₁ and ₂ in the transformed -plane. The stiffness matrix of the super-element was determined by using a line integral along the boundary of the super-element. The displacement vector was expressed in terms of the element nodal displacement vector {q} and a properly selected shape function defined along the element boundary.Numerical results for K _I and K _II of glass-epoxy and graphite-epoxy unidirectional composites with cracks along the diameter of a circular cut out as well as elliptical cut outs were evaluated

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Résumé On applique, dans la présente étude, une méthode d'éléments finis hybrides à l'évaluation des facteurs d'intensité de contrainte K_I et K_II pour des composites renforcés de fibres unidirectionnelles. Pour tenir compte de la singularité de la contrainte à l'extrémité de la fissure, on développe un super élément singulier en se basant sur un principe modifié d'énergie complémentaire. Les champs de contraintes et de déplacements dans le super-élément sont exprimés sous forme polynormale de deux variables complexes ₁, et ₂ dans le plan de la transformée. La matrice de rigidité du super élément est, quant à elle, définie en utilisant une intégrale linéaire le long du contour de l'élément. Le vecteur de déplacement est exprimé par un vecteur (9) de déplacement nodal de l'élément, et par une fonction de forme appropriée, définie le long du contour de l'élément.On évalue les résultats numériques pour K_I et K_II, correspondant à des composites à fibres unidirection-nelles de types verre-epoxy et graphite-epoxy, oú des fissures se situeraient sur le diamètre de découpes circulaires et elliptiques

     

Enhanced Photoelectrochemical Performance of Hematite Photoanode by Decorating NiCoP Nanoparticles Through a Facile Spin Coating Method

Catalysis Letters - Hematite (α-Fe2O3) is a potential photoanode material for photoelectrochemical (PEC) water splitting, but its short hole diffusion length and low water oxidation kinetics...     

Low-Temperature Superplastic Deformation of Cold-Rolled Fe–5.6Mn–1.1Al–0.2C Steel

Metallurgical and Materials Transactions A - A cold-rolled low Al-added medium Mn steel was employed to investigate the low-temperature superplastic deformation at a relatively high initial strain...     

Effects of Ultrasonic Vibration on Material Flow and Thermal Cycles in Friction Stir Welding of Dissimilar Al/Mg Alloys

Comparative experiments are performed in friction stir welding (FSW) of dissimilar Al/Mg alloys with and without assistance of ultrasonic vibration. Metallographic characterization of the welds at transverse cross sections reveals that ultrasonic vibration induces differences in plastic material flow in two conditions. In FSW, the plastic material in the peripheral area of shoulder-affected zone (SAZ) tends to flow downward because of the weakening of the driving force of the shoulder, and a plastic material insulation layer is formed at the SAZ edge. When ultrasonic vibration is exerted, the stirred zone is divided into the inner and outer shear layers, the downward material flow trend of the inner shear layer disappears and tends to flow upward, and the onion-ring structure caused by the swirl motion is avoided in the pin-affected zone. By improving the flow behavior of plastic materials in the stirred zone, ultrasonic vibration reduces the heat generation, accelerates the heat dissipation in nugget zone and changes the thermal cycles, thus inhibiting the formation of intermetallic compound layers.