材料期刊网

CALCULATION OF 3-D TRANSIENT TEMPERATURE FIELD DURING LASER TRANSFORMATION HARDENING PROCESS

L. W Zhang , R.S. Wang , J. Th.M.De Hosson , Y.L. Xia and F. G. Wang 1) The State Key Lab. for Materials Modification by Laser , Ion and Electron Beams , Dalian University of Technology , Dalian 116023 , China 2) Department of Applied Physics , University of Groningen , The Netherlands

金属学报(英文版)

A three-dimensional transient heat transfer model for laser transformation hardening process has been developed in this paper. The finite size of the laser treated sample, the surface heat loss of the sample, the latent heat of phase transformation and the temperature dependence of thermal properties of materials were considered. The heat source was considered as a moving Gaussian heat flux with a constant velocity. Three-dimension unequally spatial grid explicit finite difference equations, alternating direction implicit finite difference equations and implicit finite difference equations were deduced respectively. Three programs to calculate the temperature field were developed using Fortran language. The transient temperature fields of C22, 42CrMo, C60 steel samples during laser transformation hardening process were calculated using these programs, and the widths and depths of laser transformation hardening zones were also predicted. C22, 42CrMo, C60 steel samples were treated by CO_2 laser,the widths and depths of laser transformation hardening zones of these samples were also measured experimentally. The calculated widths and depths of laser transformation hardening zones are in good agreement with the experimental results.

关键词: temperature field , null , null

CALCULATION OF RESIDUAL STRESS FIELD IN LASER TRANSFORMATION HARDENED MoCu NODULAR IRON

L. W. Zhang , J. Th.M.De Hosson , Y.L. Xia and F. G. Wang 1)The State Key Lab. for Materials Modification by Laser , Ion and Beams , Dalian University of Technology , Dalian 116023 , China 2)Department of Applied Physics , University of Froningen , The Netherlands

金属学报(英文版)

In this paper,a thermal elastic-plastic 2-D finite element model of stress generation during laser transformation hardening process was developed. In this model, the mechanical properties of the material, Young's modules E, Poisson's ratio v, yield limit s, and thermal expansion coefficient α, are all change with temperature. The equivalent expansion method was used to deal with the problem with phase transformation. Based on this model, a program to calculate the residual stress field was developed using FORTRAN language. The residual stress fields in CO2 laser transformation hardened MoCu nodular iron were calculated. The calculated results showed that in the transformation hardened zone, the residual stress state is compress,whereas adjacent to this zone the residual stress state is tensile, and there is a tensile stress peak close to the transformation hardened zone. To verify this model, the residual stress fields were measured using X-ray diffraction method. The calculated results of residual stress fields are in good agreement with the experimental results.

关键词: laser , null , null , null , null

Catalysis on nano-carbon materials: Going where to? Preface

Catalysis Today

This contribution to the special issue of Catalysis Today is dedicated to selected contributions presented at the Carbocat-IV (Carbon for Catalysis) Symposium held in Dalian (China) on November 7-10 (2010). The introduction first shortly overviews the main reasons for the interest on carbon materials for catalysis and the elements of novelty discussed on the contributions of this issue, and then provide a concise outline of the general trends and developments in this field to give a glimpse on the progresses in the field, and on the perspectives of this exciting area of catalysis. (C) 2012 Elsevier B. V. All rights reserved.

关键词: Nano-carbon;Catalysis on carbon;Nanostructured carbon-based materials;Carbon hierarchy;ordered mesoporous carbon;metal-free;nanostructured carbon;activated;carbon;oxidative dehydrogenation;heterogeneous catalysis;sustainable;energy;counter electrode;porous carbons;fuel-cells