Growth characteristics and kinetics of niobium carbide coating obtained on AISI 52100 by thermal-reactive diffusion technique

Niobium carbide coating was produced by thermal-reactive diffusion technique on AISI 52100 steel in salt bath at 1 123 K, 1 173 K, and 1 223 K for 1, 2, 4, and 6 hours. The salt consisted of borax, sodium fl uoride, boron carbide, and niobium pentoxide. The presence of NbC phase on the steel surface was confi rmed by X-ray diffraction analysis. Microscopic observation showed that niobium carbide coating formed on the substrate was smooth and compact. There was a distinct and fl at interface between the coating and substrate. The micro-hardness of niobium carbide coating was 2892±145HV. The thickness of coating ranged from 1.6 μm to 14μm. The forming kinetics of niobium carbide coating was revealed. Moreover, a contour diagram derived from experimental data was graphed for correct selection of process parameters. Some mathematical equations were built for predicting the coating thickness with predetermined processing temperature and time. The results showed that these mathematical equations are very practical as well as the kinetics equation.     

基于CAN总线的柴油发动机参数自动监测系统

开发了一种CAN总线和SAE J1939协议的柴油发动机运行参数自动监测系统,设计了微控制器与CAN总线连接电路、上位机通信电路设计和电源电路,实现了发动机参数的实时采集和监控,提高了发动运行的安全性.     

热处理工艺对SAE4140钢板组织和性能的影响

通过光学显微镜和力学性能等测试手段,对比分析了正火+回火与淬火+回火热处理工艺下SAE4140钢板的组织及力学性能变化,为制定代替原调质工艺提供理论指导。结果表明,13mm厚SAE4140钢板在850℃正火,540℃～560℃区间进行回火得到的NT态钢板性能与QT态钢板相近,并且批量生产效果良好。     

电动公交客车CAN总线网络通信结构的设计

为了研究电动公交客车上CAN总线网络节点信息的实时性及可靠性问题,依据CAN总线网络通讯协议技术的特点,研究并设计了一种电动公交客车的CAN总线网络通讯结构,并给出了适用于电动公交客车的SAE J1939应用层协议及汽车CAN总线网络的硬件接口模块,软件模块采用了基于优先权竞争的模式,通过CAN总线网络和基于优先权模式的方法,实现了实时采集、分析、处理电动公交客车的各个数据节点的信息和数据.最后,在路况测试中通过对实际数据的采集,验证了电动公交客车CAN总线网络通讯结构的硬件、软件模块设计合理,具有实际的学术价值和应用前景.     

车载双路CAN总线冗余网关的设计

为了使现有车载网关的实时性、稳定性和可靠性得到进一步的提高,基于双核16位单片机MC9S12XDP512设计了车载双路CAN总线冗余网关方案.在设计中采用了双路CAN总线冗余备份方案,并且还采用了嵌入式系统设计的双核技术,开启了单片机内的协处理器XGATE来处理各种中断,使主处理器集中进行数据的处理工作.该设计方案简单易行、便于实现,且通用性强,也有利于开发和维护.     

一种基于BOA-SAE-EELM的光伏阵列故障诊断方法

光伏阵列非线性输出的特性以及最大功率点跟踪算法,会影响光伏阵列保护设备的工作.为了正确辨识光伏阵列的运行状态,本研究提出一种基于贝叶斯优化算法(BOA)、堆栈自动编码器(SAE)以及集成极限学习机(EELM)相结合的故障诊断方法.首先,将光伏阵列的时序波形进行标准化处理;接着,使用SAE对标准化后的时序波形进行特征自动...     

Fatigue assessment and fatigue life calculation of quenched and tempered SAE 4140 steel based on stress–strain hysteresis, temperature and electrical resistance measurements

In this paper, mechanical stress–strain-hysteresis, temperature and electrical resistance measurements are performed for the detailed characterization of the fatigue behaviour of quenched and tempered SAE 4140 steel used for many applications in the automotive industry. Stress-controlled load increase and constant amplitude tests (CATs) were carried out at ambient temperature on servo-hydraulic testing systems. The applied measurement methods depend on deformation-induced changes of the microstructure in the bulk material and represent the actual fatigue state. The plastic strain amplitude, the change in temperature and the change in electrical resistance can be equally used for an assessment of baseline fatigue properties in generalized cyclic deformation curves as well as in generalized Morrow and Coffin–Manson curves. On the basis of comprehensive experimental fatigue data, the physically based fatigue life calculation method ‘PHYBAL’ based on the generalized Basquin equation was developed. S–N (Woehler) curves calculated with ‘PHYBAL’ using data from only three fatigue tests agree very well with the conventionally determined ones.     

Influence of hydrogen content and microstructure on the fatigue behaviour of steel SAE 52100 in the VHCF regime

The fatigue life of the bearing steel 52100 (100Cr6) in bainite and martensite conditions was investigated up to 2 × 10⁹ cycles. The tests were performed under cycling tension (R = 0.1) and tension–compression (R = −1) on a piezo-electric ultrasonic testing equipment. The specimens are designed with a cylindrical part in the highly stressed centre. Due to grinding, compressive residual stresses are found at the surface, hence crack initiation solely occurs subsurface. Prior testing half of the specimens was charged with hydrogen. The hydrogen content varies from 0.6 as initial condition to 3 ppm after charging. The increased hydrogen content decreased the endurance limit to nearly half of the value of uncharged conditions and crack initiation changed: Conditions with low hydrogen content failed from chromium carbides, titanium nitrides or slag agglomerations. Conditions with 3 ppm hydrogen failed from slag agglomerations, often in combination with aluminium magnesium oxides, and manganese sulphides. Next to the inclusions a fine granular area (FGA) could be observed in some cases, and nearly all fractured surfaces showed a fisheye surrounded by an Optically Bright Zone (OBZ) with the crack initiating inclusion in its centre. Furthermore, selected specimens where analysed using secondary ion mass spectroscopy in a time of flight setup (ToF-SIMS) to ascertain the local hydrogen content. From the results it is assumed that hydrogen accumulates in the cavity at inclusions or bonds to the inclusion if it contains silicon.     

EPS系统的QoS机制

为了适应未来10年移动通信技术的发展，给用户不断增强的数据业务需求提供更好支持，3GPP组织启动了长期演进计划（LTE）与系统框架演进（SAE）研究项目。针对未来数据业务具有高速、突发性的特征，演进的分组系统（EPS）对服务质量（QoS）机制进行了诸多改进与增强，通过引入默认承载、聚合资源调度等概念，真正实现了用户的“永远在线”，提高了业务的数据速率，进而最终提升了用户体验。同时，针对未来UTRAN与E-UTRAN网络之间的互操作场景，设计了EPS的QoS等级标识（QCI）参数与通用移动通信系统（UMTS）QoS参数之间的合理映射。     

基于SAE J1939协议的发动机总线数据模拟器开发

为测试仪表性能,针对具有CAN总线接口的汽车仪表,开发了基于SAEJ1939协议的发动机总线数据模拟器。该系统采用USBCAN-Ⅱ作为发动机总线数据模拟器和仪表间的硬件接口．用C#语言开发设计发动机总线数据模拟器。该系统能够作为一个虚拟节点模拟发动机向总线网络发送发动机参数报文和故障报文．从而对总线网络上的另一节点仪表进行测试,检验仪表的性能。此外,该模拟器还能实现数据帧信息显示、虚拟仪表显示、帧回放等多项功能。实验结果表明,该系统能够稳定发送报文至仪表并在仪表上实时显示,可以代替真实的发动机完成测试工作．开发周期和成本至少降低了10％。