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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. 相似文献
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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. 相似文献
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由于滚动轴承的工作环境复杂,所采集的信号中通常含有大量噪声,噪声的存在会影响故障诊断的结果.为了提高噪声数据的诊断精度,采用改进的小波阈值函数结合栈式自编码器(stacked auto-encoder,SAE)对强噪声环境下的轴承数据进行故障诊断.首先通过改进阈值函数对噪声数据进行去噪,其次用小波包变换提取去噪数据的小... 相似文献
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P. STARKE F. WALTHER D. EIFLER 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(11):1044-1051
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. 相似文献
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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. 相似文献
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湘钢SWRH82B/SAE1080质量分析与工艺控制 总被引:1,自引:0,他引:1
预应力钢丝、钢绞线用优质高碳盘条SWRH82B/SAE1080在拉拔过程中常出现脆性断裂现象.通过对中心缩孔和碳偏析、表面横裂纹、粗大珠光体或网状碳化物不良组织等引起断丝原因的分析,提出通过合理控制浇注温度、拉速、二冷强度、控轧控冷强度及拉拔工艺参数等措施,改进盘条实物质量,降低断丝率. 相似文献
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EPS系统的QoS机制 总被引:1,自引:0,他引:1
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。 相似文献