电动汽车差速器扭转冲击疲劳试验方法

针对电动汽车传动系的关键零部件差速器的实际受载情况,设计了基于液压伺服的电动汽车差速器扭转冲击疲劳试验系统。在此基础上,依照目前的试验技术条件,分析了差速器关键部件的应力集中部位,对加载波形、加载频率、加载幅值和加载频次进行了理论和载荷特征研究,构建了电动汽车差速器扭转冲击疲劳应变测试系统和测试方法,并对其进行了大量应变测试,对不同频率和不同幅值的测试数据进行了统计分析,结合分析结果和材料应力寿命(S-N)曲线,建立了完整的电动汽车差速器扭转冲击疲劳试验方法,并进行了试验验证。结果表明,差速器的疲劳破坏部位和形式与实车行驶时疲劳破坏部位和形式以及应力集中测点部位均一致。     

Fatigue behavior and statistical evaluation of the stress category for a steel-concrete composite bridge deck

The maintenance cost of bridges is rapidly increasing since many existing bridges are deteriorating or reaching their design life all over the world. Moreover, as many long-span bridges are under construction and planning in Korea, research and development on bridge decks with high load-resistance capacity as well as high fatigue strength has become a growing concern. This research gives experimental results of the fatigue behavior of a new-type of steel-concrete composite bridge deck being developed under such circumstances. The proposed composite bridge deck consists of corrugated steel plate, welded steel ribs, stud shear connectors, and reinforced concrete filler. Fatigue tests were conducted under a four-point bending test with four different stress ranges in constant amplitude. In order to determine the influence of the concrete filling, fatigue tests on partial steel specimens containing only plain corrugated steel plates were performed in advance. The partial steel specimens and the steel-concrete composite deck specimens both showed fatigue failure in the tension part concerning the fillet welding part between the corrugated steel plate and steel rib. Finally, the stress category of the fillet welding part of each specimen is evaluated based on a statistical approach of Albrecht’s probability model. The research concludes that the fatigue behavior of such steel-concrete composite decks under sagging moment can be estimated based on the classical S-N approach, focusing on steel components.     

碳纤维束疲劳损伤失效试验

为了解碳纤维束的疲劳特性及疲劳加载后剩余强度的变化, 为建立碳纤维复合材料疲劳性能的细观力学分析模型提供必要的基础数据, 研究设计了碳纤维束静载力学性能及疲劳特性试验方案, 并进行了试验。采用最小二乘法拟合得到了单束碳纤维的应力-寿命(S-N)曲线。对经过预疲劳的碳纤维束试验件进行了剩余强度试验, 采用最小二乘法拟合得到了碳纤维束疲劳加载剩余强度模型。试验结果表明: 试验所用碳纤维束的条件疲劳极限为静拉伸强度的80.47%; 碳纤维束经历一定循环次数的拉-拉疲劳可以提高其强度, 其剩余强度随着疲劳加载循环次数的增加先增加后减小。     

K节点应力集中系数的试验和数值研究方法

工程中常用的评价海洋平台中管节点疲劳寿命的方法是使用S-N曲线。当管节点承受疲劳载荷作用的时候,可以通过数值或者试验方法得到沿着焊缝处的热点应力幅的大小。然后通过S-N曲线,可以预测此节点在破坏前可以承受疲劳载荷的循环次数。应力幅的大小可以由应力集中系数这个参数来确定。对K型节点在承受基本载荷作用下的应力集中系数进行了数值和试验分析,得到了各种基本载荷作用下K节点沿着焊缝处应力分布情况和极值应力点的位置。     

天津盘山发电厂 600 MW 汽轮发电机异常工况轴系扭转疲劳损耗研究

介绍天津盘山发电厂将要安装的国产６００ＭＷ汽轮发电机在异常工况下轴系的疲劳损耗研究情况。     

Cr4、Cr5钢拉-拉疲劳性能研究

利用成组试验法对Cr4、Cr5型支承辊用钢的拉-拉疲劳性能进行了测定,并利用金相、XRD、SEM等手段对其组织进行分析。结果表明,当中值寿命为10~6时,Cr5钢的抗疲劳应力为659 MPa,Cr4钢抗疲劳应力为438 MPa．Cr5钢的抗疲劳性能优于Cr4钢。     

Flexural fatigue behavior of injection-molded composites based on poly(phenylene ether ketone)

Flexural fatigue tests were conducted on injection-molded short fiber composites, carbon fiber/poly(phenylene ether ketone) (PEK-C) and glass fiber/PEK-C (with addition of polyphenylene sulfide for improving adhesion between matrix and fibers), using four-point bending at stress ratio of 0.1. The fatigue behavior of these materials was presented. By comparing the S-N curves and analyzing the fracture surfaces of the two materials, the similarity and difference of the failure mechanisms in the two materials were discussed. It is shown that the flexural fatigue failure of the studied materials is governed by their respective tensile properties. The matrix yielding is main failure mechanism at high stress, while at lower stress the fatigue properties appear fiber and interface dominated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1857–1864, 1997     

南水北调中线京石段应急供水工程的建设管理

南水北调中线工程河北省渠段由冀豫交界处的漳河北始至冀京边界处的北拒马河中支南止,渠长462.36 km.京石段应急供水工程自石家庄古运河枢纽至北拒马河中支南.南水北调工程规模巨大,要到2010年才能全面实现通水.为确保2008年北京奥运会的顺利召开,国家决定先期建设南水北调京石段,自2007年暂将河北省岗南、黄壁庄4座水库的水引入北京.根据京石段的工程特点,其建设管理模式采用直管制、委托制、代建制,新型的建管模式必将推动水利建设项目管理的科学化、规范化、市场化进程.     

复合材料疲劳S-N曲线的建模

本文建立了复合材料疲劳寿命曲线的“有效缺陷模型”,阐明了模型中两个参数的物理意义。通过实验验证,说明该模型可以较好地预测复合材料的疲劳寿命。利用该模型,仅需较少的试验即可绘制出新材料的Ｓ－ Ｎ 曲线。     

基于构件S-N曲线的波纹管速度外压耦合加载下疲劳寿命研究

真空灭弧室用波纹管服役工况复杂,采用传统的理论计算方法和试验手段难以准确预测其疲劳寿命,一定程度上制约波纹管的设计与选用。本文利用数字图像相关技术,基于拉伸试验、疲劳试验,精细化获得了波纹管构件的S-N曲线,基于ANSYS有限元分析软件,建立波纹管弹塑性变形有限元模型,通过XTDIC验证了模型的准确性,结合nCode DesignLife对波纹管疲劳寿命进行了预测,并验证其准确性。研究了关键工艺参数(压力、位移、速度)对波纹管波峰、波谷等关键特征区域应力、应变和疲劳寿命的分布演变规律。研究表明：波纹管在只施加外压的工况下,波峰内壁处更容易产生疲劳损伤,位移载荷对波纹管应力应变分布影响更为显著,位移越大,波纹管更容易产生应力集中。在加载位移不变时,速度越大,波纹管等效应力越大,此时耦合0.2 MPa外压,抵消部分应力集中。在0.2 MPa外压下,当压缩速度由0.5 m/s增加到4 m/s,最大等效应力由378.89 MPa增加到424.27 MPa,疲劳寿命由49 540次减小到3 064次。