厚钢板对接焊缝残余应力的数值模拟

基于ABAQUS及其子程序DFLUX,采用热力间接耦合法,对不同厚度尺寸的Q345B厚钢板的对接焊缝进行了三维模拟分析,得到了焊接的温度场分布和最终焊接残余应力分布.结果表明：构件表面焊接残余应力大于中间面;表面纵向和横向残余应力都有一定的规律;对接焊缝沿纵向焊接残余应力随着板厚度的增加而增加,这种增加的趋势对厚度小于70 mm的钢板很明显,对70～80 mm的钢板不明显;而横向残余应力随钢板厚度的增加变化不显著.     

Numerical simulation of non-destructive testing of stainless steel composites plate by infrared thermography

The non-destructive testing (NDT) of debonding in stainless steel composites plate (SSCP) is performed by infrared thermography, finite element analysis (FEA) software ANSYS is taken as the simulative tool, and 2D simulative model has been set up to investigate effect of the thickness of coating and/or substrate on the detectibility of debonging in SSCPs. Two parameters, namely the maximum defect temperature difference and defect appearing index, are defined to evaluate the detectivity of defects, and their computational methods and formulas are given respectively. The preliminary changing tendency of the maximum defect temperature difference and defect appearing index with the thickness of coating and/or substrate is found by numerical simulation.     

Numerical simulation of macrosegregation during steel ingot solidification using continuum model

A continuum model is adopted to study the macrosegregation phenomena during solidification of large steel ingots. Evolution of temperature, melt velocity, and compositional concentration field during a 22 t steel ingot solidification are illustrated by using the finite volume method. Numerical results of temperature distribution are validated by experiments. The influence of local permeability relates to the friction that the melt experienced in mushy region is investigated. It is shown that the continuum model is able to predict the temperature field, and the variation of permeability obviously affects the melt flowing behavior and the final compositional distribution.     

Numerical simulation on temperature and stress fields in beryllium during cutting process

The temperature and stress fields in beryllium during high speed cutting process were studied by employing a thermo-mechanically coupled finite element method (FEM). The results show that the temperatures in beryllium increase only a little during the cutting process. Both of the residual stresses for along and normal to the cutting direction are tensile stresses in the surface of beryllium after cutting. The cutting force and thrust force are about 280 and −250 kN/m at the steady stage, respectively. The main effects of coolant on the cutting process are to decrease the friction coefficient and heat between the tool and the workpiece, so to reduce the temperature, but almost no effects are made for stress. This study is helpful to enhance the understanding for stress formation and optimize the process parameters of beryllium.     

钢-铝石墨半固态铸轧复合的数值模拟

铸轧区的温度分布直接影响着铸轧过程的稳定性和复合板材的质量.针对实验室复合板半固态铸轧试验的特点建立了数学模型,采用有限元法对钢-铝石墨半固态铸轧复合过程的热流耦合问题进行了数值模拟计算,分析了不同浇注温度和铸轧速度下熔池内温度场变化的情况.模拟结果表明,当浇注温度为620℃,铸轧速度在0.6～0.8 m/min的范围内可保证铸轧稳定进行,此结论与试验数据相吻合.该模型可以有效预测凝固前沿位置,为半固态铸轧复合工艺的进一步研究和钢-铝石墨复合板的数字化生产提供了依据.     

Numerical simulation of orthotropic steel deck bridges with two membrane layers systems

The finite element system CAPA-3D was utilized as the numerical simulation platform,two structural FE models of orthotropic steel bridge decks were set up,the static and dynamic FE simulations under different loading conditions were carried out,the special attention was given to identify the critical wheel load location,and the maximum tensile stress distribution and the variation of strain rate inside membrane layers.Simulation result shows that the FE models are capable of simulating the realistic behavior of orthotropic steel bridge.The distributions of strains and stresses inside the surfacing materials depend highly on wheel load level,wheel load frequency,wheel position,membrane bonding strength as well as the thicknesses and characteristics of surfacing layers.The maximum tensile stress of membrane layers is found around 0.4MPa,which coincides with the minimum requirement for the adhesive bonding strength of membrane material proposed by the standards NF P98-282and TP-BEL-B.The maximum membrane strain rate is found around 0.1,which is an important information that can be utilized for the characterization of membrane products.1tab,28figs,7refs.     

基于桁梁实桥试验的钢管混凝土界面传力机制

为分析钢管混凝土桁梁桥的承载性能和钢-混凝土组合作用机理,进行了桁梁上、下弦钢管混凝土界面传力行为实桥试验和全桥板壳-实体有限元参数分析;以主跨71 m的简支半穿式钢桁梁桥为依托,沿其上、下弦杆节间长度范围内共布设102个应变测点,测试并分析了加载车作用下钢管轴向应变分布和钢-混凝土界面传力特征;采用ABAQUS软件建立了试验桥板壳-实体有限元模型,经实测挠度与应变数据验证模型的可靠性后,进行了界面连接状态、界面抗剪刚度、钢管厚度、管内混凝土强度等对钢管混凝土界面传力性能的参数影响分析。分析结果表明：钢管轴向应变分布规律可反映钢管混凝土界面传力的基本特征;钢管混凝土桁架上、下弦杆节点区域均出现界面剪力不均匀分布现象,钢-混凝土界面有效传力范围内钢管轴向应变呈负指数函数分布,其他区域钢管轴向应变保持不变;完全脱黏的钢管混凝土桁架弦杆的钢管轴向应变在节点一定范围内呈二次抛物线函数分布;钢管轴向应变因界面连接状态所表现出的不同应变分布规律和剪力传递长度可用于评价钢管混凝土组合作用强弱和界面工作状态;桁架弦杆的剪力传递长度随钢管厚度和管内混凝土强度的增加而增大,钢管厚度的影响更显著;在钢管混凝土桁架弦杆内设置抗剪连接件可缩短剪力传递长度。     

Finite element simulation of rod and wire continuous rolling

This paper discusses the application of several techniques involved in the development of the 3D finite element (FE) models of rod and wire continuous rolling process. The FE models are implemented into the FE-program MSC.Marc and used to investigate the thermal and mechanical behavior of billet during the rolling process. All nonlinear equations included in the models are solved by the static and dynamic procedures, respectively. Data transfer technique is proposed to keep the continuity of simulation results. And the computational time of static procedure is significantly reduced by using a rigid pushing body. In all models, the constant time step method and the auto time step method are respectively used to define time step for the solution of equations. Simulation results of the models with different time step methods are compared. And comparison between calculated values and measured ones of the temperature at the surface of billet shows the validity of the FE models.     

Influence of soaking temperature on microstructure of multi-pass compression deformation for low carbon steels

The influence of soaking temperature on microstructure of high temperature multi-pass compression deformation for two low carbon steels (steel A: w _C = 0.032% and w _Mn = 0.25%; steel B: w _C = 0.165% and w _Mn = 0.38%) is studied on the thermal-mechanical simulator in order to rationalize the hot-rolling schedule of low-carbon steel and to promote the low-temperature heating technology. The results show that the microstructures of steel A are almost not affected by reducing soaking temperature, but the acicular ferrite forms in steel B when the soaking temperature is reduced from 1 200 to 1 170°C, due to its smaller initial austenite grain size according to recrystallization kinetics theory.     

土工格栅处治填挖交界路基数值模拟与现场试验

考虑地基与路基的压缩变形与填挖交界处的相互作用, 应用分析软件ANSYS建立了路基变形有限元模型, 模拟了格栅竖向间距与挖方段铺设长度对土工格栅加筋纵向处治填挖交界路基的影响规律, 并通过现场修筑不同方案的试验路段和沉降跟踪观测, 研究了土工格栅铺设层数对填挖交界路基差异沉降的影响。分析结果表明: 土工格栅的竖向铺设间距在0.8~1.0m时, 路基不均匀沉降较小, 路面产生竖向位移的变化较缓慢, 建议土工格栅铺设的竖向间距以不大于1.0m为宜; 改变锚固端格栅铺设长度对路面竖向沉降的影响很小, 从经济角度考虑, 挖方段土工格栅的最小锚固长度选取2m;在路基96区和94区底各铺设一层土工格栅可以有效降低路基差异沉降。     

船舶航行的数值模拟

应用数学模型研究船舶在航道中的航行条件 ,可以经济、快速了解水利工程兴建后 ,其对船舶航行的影响 .介绍了船舶航行数学模拟的方法、方程等 .并将其用于某河段的航迹线模拟 ,得到了较好的结果     

机车车辆动态模拟和台架试验

分析了动态模拟技术, 包括实物模拟、计算机模拟和混合模拟, 在机车车辆研制过程中的重要作用, 给出了模拟技术和对象以及研究内容之间的相互关系。通过计算机模拟对机车车辆方案进行仿真分析来优化结构和悬挂参数, 用实物模拟或混合模拟研究零部件服役性能, 采用全尺寸试验台架对机车车辆样机进行运行模拟, 以确定其运行性能。给出了计算机模拟的步骤、实物模拟应遵循的相似原则和混合模拟的实施方法, 探讨了机车车辆台架试验方法和试验分类, 以及台架试验的应用情况, 介绍了牵引动力国家重点实验室研制的机车车辆整车滚动振动试验台和综合参数测定试验台的主要技术指标和功能。     

Analyse of warm surface rolling on the grooved steel axle

Warm surface rolling is a working process between room temperature and re-crystallization temperature. With warm surface rolling of steel grade 45 grooved axle, its fatigue lifespan was measured by the endurance bending test. The influence of surface rolling reduction on the axle fatigue life period was experimentally studied at different surface rolling temperatures. The experimental results show that the fatigue life of the steel axles can be significantly improved by the warm surface rolling process. The optimum rolling reductions for the maximum fatigue life at different warm surface rolling temperatures were explored. The microstructures of the steel axles were analyzed. The surface strength improved by refining grains after the warm surface rolling was calculated by the Hall-Petch model. These research achievements could be also valuable to the relevant works.     

Numerical simulation of fluid flow caused by buoyancy forces during vacuum arc remelting process

The metallurgical structure and composition of ingots which depend critically on the fluid motion within the molten pool during the vacuum arc remelting (VAR) process have important effect on the subsequent mechanical processes like forging, rolling and welding. In order to determine the fluid motion of molten pool, a 2D finite element model is established using ANSYS10.0 software, combined with the turbulent fluid flow and heat transfer. The fluid motion caused by thermo buoyancy forces is investigated at different VAR processes in the present study. The results indicate that the fluid flows symmetrically along the axis of the molten pool and clockwisely along the circle at the right pool’s profile. It is also shown that the maximum velocity increases with increasing melting rate and a direct proportional relationship exists.     

关于钢筋剥肋滚压连接的探讨

着重论述了钢筋剥肋滚压连接与其他连接方式的比较,阐述了接头质量、成本、施工速度及施工环境各方面的优势。     

Numerical simulation of thermal and iron ore reduction conditions in pre-reduction shaft furnace based on reducing gas composition and temperature

Based on the principles of mass, momentum and heat transfers between the reducing gas and the iron ore solid, a two-dimensional mathematical model for above two phases is established to study the influences of reducing gas composition on thermal and reduction conditions in pre-reduction shaft furnace with the temperature ranging from 1 023 to 1 223K. Due to the strong endothermic effect of iron ore reduction participated by hydrogen (H₂), increasing the ratio of carbon monoxide (CO) to H₂ enlarges high temperature zone under present calculation conditions, thus improves reduction efficiency inside the furnace. In addition, replacing of the reducing gas with an appropriate proportion of nitrogen (N₂) featuring the same temperature has a potential to reduce fuel consumption by as much as 6.5% while the products of similar quality are yielded.     

覆土波纹钢板桥涵自振特性试验及分析

依托等跨度的低弧拱和高弧拱两种线形的覆土波纹钢板桥涵模型,分阶段测试从裸拱状态到覆土回填务实完毕整个过程的结构自振特性变化.试验分析结果表明：随覆土高度的增加,结构自振频率逐渐下降;在覆土回填至拱顶以前,结构自振频率下降缓慢,覆土高过拱顶以后,结构的自振频率下降较快;覆土回填夯实结束后,两种线形结构的自振频率十分接近.此类结构的自振特性受回填土影响显著,埋置较深时,结构的振动性态趋向于与周围土层结合成一个整体系统.     

泡漩水数值模拟研究

笔者针对泡漩水所具有的三维性、自由表面、强紊动性的特点,采用三维K-ε模型,引入通度概念处理不规则边界,用VOF法追踪自由表面,并对突嘴深槽组合地形产生的泡漩水流场进行了数值计算,计算结果与实测资料吻合良好.     

发动机泄漏辅助制动数值模拟

为了研究发动机泄漏辅助制动系统的工作过程, 应用计算流体力学软件Fluent建立了发动机泄漏辅助制动系统的数值模拟计算模型, 利用压力曲线对模型进行了验证, 计算了发动机泄漏制动时的缸内压力和流场分布情况。发现: 发动机泄漏辅助制动系统工作时, 排气门预开间隙大, 则缸内所能达到的压力峰值小, 得到的制动功率小。在压缩过程开始阶段与膨胀过程中, 出现了气体由排气道倒流入气缸中的现象, 且转速低, 排气门开度大时, 倒流现象出现得早。分析结果表明: 适当选择排气门预开间隙, 可以提高发动机泄漏辅助制动系统的制动功率。