Deformation prediction of porcelain-enameled steels with strain history by press forming and high-temperature behavior of coating layer

Porcelain enamel coatings were widely applied for the protection of steel products because they offered high corrosion protection,resistance to heat and abrasion,high hardness,hygiene and ease of cleaning.The typical process to produce enameled steels is roughly divided into two stages:the first stage consists of a forming process to give the desired shape to a steel substrate,and the second stage consists of a firing process to bond enamel frits on the substrate.This firing process requires a high temperature above 800 °C,which may lead to austenitic transformation and severe thermal deformation of the steel substrate.The aim of this study is to develop a finite element analysis (FE analysis) technique to predict the mechanical and thermal deformations of the enameled steels during forming and any further enameling process,including firing.The FE analysis involves analyzing the strain history of the steel substrate,which comprises the stress and thickness distributions of the substrate and its deformed shape,and the high-temperature behavior of the enamel coating layer.The validity of the FE analysis is verified through the U-bending test and firing test with various numbers and positions of enamel coating layers on the substrate.The results reveal that the FE analysis results agree well with the experimental results with 8% error.

Au/CdTe纳米复合材料的静电作用制备及表征(英文)

将相反电荷的纳米Au和纳米CdTe通过静电作用得到纳米复合Au/CdTe粒子。在水溶液中分别用二甲氨基吡啶和巯基丙酸稳定纳米Au和CdTe粒子,使其表面分别带有正电荷与负电荷。Au/CdTe纳米复合材料的表面等离子体吸收光谱随着Au含量的增加而红移,表明纳米复合Au/CdTe粒子的长大是由于配位形成而引起的。纳米Au和纳米CdTe的比影响纳米复合Au/CdTe粒子的结构。复合纳米Au/CdTe粒子的尺寸和形状是影响金属/半导体纳米复合材料性能的重要参数。用小角X射线散射技术、透射电子显微镜、循环伏安法和X射线光电子能谱来表征纳米复合Au/CdTe粒子。

FEA technique of hot plate forming process using cell-typed die with cooling device

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG tank.Cell-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed die.Further,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA technique.The analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

Effects of elastic-plastic properties of materials on residual indentation impressions in nano-indentation using sharp indenter

One of the primary features of nano-indentation technique is that the contact area induced by an indenter is indirectly measured by a relationship between the penetration depth and the known geometry of the indenter.However,this indirect measurement occasionally leads to inaccurate properties of the indented material.The objective of this study is to investigate the effects of E/σr and the strain hardening exponents n of materials on the behaviors of pile-up and sink-in in nano-indentation and to predict n values of materials from the residual indentation impressions.The relations between the residual indentation profile and n value of the indented material were identified by dimensional analysis.Also,they were numerically formulated using FE analysis of nano-indentation for 140 different combinations of elastic-plastic parameters such as E,σy and n.The parameters of hrp/hm,herp/hm,Rr/hm and HO&P/Hreal were introduced as various dimensionless parameters to represent and quantify the residual indentation profile after indentation.They were subsequently characterized as dimensionless functions using n and E/σr values.Finally,the validity of these functions was verified through 3D FE analysis of nano-indentation for Al 6061-T6 and AISI 1010 materials.

采用气雾化Zn-22%Al粉末挤压制造微型螺旋齿轮(英文)

基于Zn-22%Al共析合金的超塑性,采用粉末挤压工艺制造微型螺旋齿轮,以减小成形压力和获得细小的显微组织。该螺旋齿轮的规格为:模数0.3,齿数1.2,螺旋角15°。将粉末压制坯通过烧结和固溶热处理进行致密化。致密化的坯料由层状和细晶状组织组成。在温度250°C,应变速率2.36×10-3和1.18×10-1s-1的条件下对坯料进行挤压,并对挤压成形的螺旋齿轮的力学性能进行测试。

High-damping and conducting epoxy nanocomposite using both zinc oxide particles and carbon nanofibers

In this study,high-damping and conducting epoxy nanocomposites were developed with carbon nanofibers as conducting materials,and zinc oxide particles as piezoelectric materials.The mechanical and electrical properties,electrical impedance,and loss factors were investigated by uniaxial tensile tests,voltage measurement,impedance measurement,and 3-point bending tests.Two percolation thresholds were found:the percolation threshold of resistivity due to the carbon nanofibers forming conductive networks in the matrix;and the impedance threshold due to the zinc oxide particles acting like electric barriers.A poling treatment of the high-damping and conducting epoxy nanocomposite was considered,and we found that poling treatment helped to make the networks more conductive and to generate voltage from ZnO particles.A high-damping and conducting epoxy nanocomposite with 3 wt%CNF and 10 wt%ZnO exhibited higher loss factor than those of others tested.