Kriterien des Betriebsfestigkeitsnachweises für die Festlegung der Versuchslaufzeit bei der Substitution von Stahl- durch Aluminiumbauteile am Beispiel von Nutzfahrzeugrädern

The experimental structural durability proof bases on a damage equivalent shortening of the design spectrum into a test spectrum with reduced length taking statistics founded safety factors into account. Historically, test spectra were first derived for steel parts using Woehler-lines for steel; the damage equivalence was calculated by applying the Palmgren-Miner rule with the modification according to Haibach. When aluminium parts were introduced later, the question arose, whether test spectra developed for steel parts could be applied without modifications for their durability proof. Caused by different slopes of aluminium before and after the knee-point, the test spectra derived for steel wheels result for aluminium components a lower cumulated damage in comparison to the design spectra. This fact requires a longer test duration for aluminium components when test spectra or proving grounds developed for steel components are used. By the example of steel and aluminium wheels for commercial vehicles with comparable fatigue critical areas, the material dependent features regarding the required test life for the structural durability proof of aluminium parts are demonstrated.     

Diffusionslöten von Aluminium mittels PVD applizierter Lotzusatzwerkstoffe

Diffusion brazing of aluminium by PVD applied filler metals Diffusion brazing of aluminium and aluminium alloys precoated with filler metal components enables fluxless wetting and obtains braze joints of high strength at moderate brazing temperatures. Previously deposited components of filler metals on the base materials as thin film, using Arc‐PVD‐process lead during a subsequently diffusion brazing process to the formation of a local liquid phase (transient liquid phase). The liquid phase is formed from the deposited thin film material and the base material and is solidified isotherm due to diffusion procedures. In doing so braze joints of higher melting point than brazing temperature can be realised. In this work, vacuum brazing of the two systems, Al‐Cu and Al‐Cu‐Si have been investigated. Cu and Al‐Cu‐Si were deposited on the base material using Arc‐PVD‐process. The base materials were pure aluminum and EN‐AW6060. Metallographic and scanning electron microscope analyses proved that the braze seam area after the completed diffusion brazing process shows similar structure and composition as the base material.     

Low density steel 1·2C–1·5Cr–5Al designed for bearings

Abstract

A novel alloy design, designated as 1·2C–1·5Cr–5Al, has been proposed with high aluminium(～5 wt-%) and more carbon(～1·2 wt-%) addition into the classical 1C–1·5Cr bearing steel for lowering density and improving performance simultaneously, which is approximate 8 wt-% lighter than convention. In order to understand preliminarily the suitability of the novel alloy for bearing application, the martensite starting temperature and hardness, related to microstructure evolution and mechanical properties, respectively, after partial austenitisation treatment with undissolved carbides have been investigated carefully. The martensite starting temperature is comparable with conventional 1C–1·5Cr alloy. The hardness of 860±3 HV20 achieved is much higher than convention.     

钢包铜复合线的制备研究

介绍了3种钢包铜复合导电柱的复合坯制备方法，探索了3种复合坯的制备工艺（1）液固相复合法；（2）直接装配法：（3）特殊装配法，对制备出的钢包铜复合导电柱复合界面组织致密性、界面结合状态及密封性能的影响。试验表明：前两种工艺制备的复合线材其结合面有局部结合不紧密，在界面未形成冶金结合状态，致使复合界面经氦检漏有漏气现象；第三种工艺制备的钢包铜复合线经气密性等综合性能试验，达到了使用要求。     

3Cr13钢耐磨盘裂纹产生原因分析

通过化学成分分析、金相检验和断口分析等方法对3Cr13钢耐磨盘产生裂纹的原因进行了分析。结果表明:该裂纹是锻造过程中产生的,是由锻造工艺执行不当和受环境温度影响而引起的终锻温度过低,以及变形作用力和变形量过大所致。     

复合材料Co2（OH）4-x(C10H17O2)x·zH2O的差热分析与磁特性

将有机手性配体3,7-二甲基-6-辛烯酸(C10H18O2)嫁接到无机层状羟基醋酸钴中,合成出新型的有机-无机杂化材料,并对这些杂化材料通过元素和热重分析,研究了有机配体在无机层间的交换过程,并在此基础上讨论了合成出的这些杂化材料的磁性特性。     

Microstructure – A Dominating Parameter for Chip Forming During High Speed Milling

High speed milling experiments with cutting speeds of up to 7000 m/min have been performed on an aluminium alloy (AlZnMgCu1.5, AA 7075) and a steel (40CrMnMo7). Both materials were heat treated to produce a variety of microstructures in order to investigate the influence of microstructure on segmentation during chip formation. In case of the aluminium alloy it has been shown that chip formation is governed by the precipitation state, but not by the hardness of the material. In contrast, hardness can be used for a qualitative prediction of chip shape of the steel. In all cases, the chip formation mechanisms remain essentially unaffected by cutting speed, i.e. no transition from continuous to segmented chips occurred.     

基于热加工图的锻造斗齿用钢热加工工艺参数

目的制定一种锻造斗齿用新型低合金耐磨钢的热加工工艺参数。方法采用Gleeble-1500D热模拟试验机对实验钢进行高温压缩,在变形温度为1173~1473 K,应变速率为0.01~10 s~(-1)条件下,压缩变形60%,得到其真应力-真应变曲线。依据压缩实验数据,基于动态材料模型,建立材料的热加工图,分析实验钢在不同热变形条件下的变形特点。结果该锻造斗齿用低合金耐磨钢在不同应变下的热加工图呈现相近特征,能量耗散系数η随变形温度的升高而增大,随着应变速率的减小而减小;当应变值大于等于0.3时,在变形温度为1173~1440 K,应变速率为0.32~10 s~(-1)范围内,热加工失稳区域随着变形温度的升高而减小,随着应变速率的减小而减小。结论该锻造斗齿用低合金耐磨钢适宜的热加工工艺参数范围:变形温度为1185~1373K,应变速率为0.01~2 s~(-1);最优参数范围:变形温度为1330~1340 K,应变速率为0.2~0.5 s~(-1)。     

无铺装层钢箱梁日照温度场分析

针对我国桥涵设计规范未给出无铺装层钢箱梁日照温度梯度和采用实测方法确定其温度梯度工作量大的不足,根据热传导和有限元基本原理,应用ANSYS建立了江东大桥自锚式悬索桥一段无铺装层钢箱梁三维模型,求解了其温度梯度,并经现场实桥测试,实测值与计算值吻合较好.对钢箱梁日照温度场影响因素进行参数敏感性分析,发现吸收率对温度场计算...     

稳态温度场下轴对称梯度功能材料的热应力分析

本文基于热弹性理论及计算数学方法，对轴对称梯度功能材料内部各点的热应力进行了理论分析。提出了稳态温度场下，环状截面梯度功能柱体的温度分布与热应力计算公式。