共查询到20条相似文献,搜索用时 9 毫秒
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采用VK-9710型激光共聚焦显微镜对热浸镀铝球墨铸铁试样的三点弯曲失效过程进行原位观察,分析镀层和基体的裂纹萌生和扩展机理。结果表明:对于纯Al浸镀球墨铸铁,在拉应力作用下,铁铝合金镀层率先萌生裂纹,诱导临近基体中铁素体撕裂与石墨球剥离,裂纹近似垂直于拉应力方向并沿着临近石墨球最短途径扩展;压应力导致表面纯Al层剥离和铁铝合金层破碎,镀层失效对球墨铸铁基体基本无影响。对于Al-3.7Si-1.0RE浸镀球墨铸铁,拉应力作用下的失效机理与纯Al浸镀相似;压应力作用下纯Al层和铁铝合金层与基体脱开,表现为铁素体基体失效。 相似文献
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The engine crankshaft of a vehicle suddenly fractured, as the vehicle was running normally on a highway. The engine crankshaft was made from ductile cast iron. The failure cause was analyzed by chemical and metallographic examination, evaluation of mechanical properties, determination of depth of the quenched layer, measurement of distance between the quenched layer and the web, observation on the fracture surface as well as value determination of the fillet radius. The results showed that the failure mechanism of the crankshaft was fatigue fracture resulting from co-effect of bending and twisting, and the crack originated from the subsurface shrinkage in the unquenched layer of the crankshaft journal. Several aspects of the crankshaft were not up to the technical standards, such as distance between the quenched layer and the web, chemical composition, hardness and microstructure of the quenched layer, yield strength, and impact toughness. 相似文献
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An understanding of the kinetics of transformation during austenitization, cooling, and austempering of ductile iron is critical to achieving the desired microstructures and ultimately mechanical properties in austempered ductile iron (ADI). To this end, dilatometry experiments have been carried out to study the austenitization and cooling behavior of an unalloyed ductile iron. When a typical austenitization temperature of 900°C is used, unlike in steels, there is an initial expansion of the specimen, which levels off as the soaking time is increased. This occurs despite the fact that the temperature remains constant. This phenomenon, hitherto unreported, highlights the subtle differences between the austenitization of ductile irons and steels. The initial expansion is attributed to the increase in austenite lattice parameter, arising from the diffusion of carbon from the graphite nodules. The levelling off signals the saturation of austenite with carbon and can therefore be used as an indicator of the appropriate austenitization time. Studies of the cooling behavior of unalloyed ductile iron have also shown that the dilatometer can be used as a tool for determining the minimum cooling rates, which guarantee the formation of ausferrite during austempering. When ductile iron is appropriately heat-treated based on results from dilatometry studies, the mechanical properties obtained are typically superior and consistent. 相似文献
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随着空调能耗日益增加和节能技术的推广,免费供冷技术—冷却塔供冷技术的应用也越来越有前景。详细阐述了冷却塔供冷系统应用的原理及类型。在借鉴各文献及工程设计者的经验基础上,深入探讨了冷却塔供冷系统节能设计应该注意的问题。 相似文献
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分析了空调冷冻水系统两种泵制的特点;结合工程实例探讨了二级泵制使用率低的原因,对二级泵制的应用提出了建议。 相似文献
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对于单层面积大、内区房间多、冷负荷比较大的建筑,采用冷却塔免费供冷,既环保,又节能。本文以上海某集办公、酒店与商业为一体的玻璃幕墙建筑为研究对象,简要介绍了冷却塔免费供冷的原理与形式,通过对冷却塔免费供冷的分析与计算,确定了冷却塔过渡季节的供冷温度,并从空调机组送风温度、过渡季节冷负荷与夏季设计冷负荷之比、冷却塔供回水温差三个方面出发,研究其对冷却塔供水温度的影响,得出了一些有益的结论。 相似文献
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李安民 《理化检验(物理分册)》2013,(3):189-190,193
通过宏观检验、化学成分分析、非金属夹杂物检验、硬度测试以及金相检验等方法,对塔机提升系统输入齿轮失效的原因进行了分析。结果表明:该输入齿轮损坏属于接触疲劳失效,趋网状分布的铁素体降低了材料的硬度、耐磨性和疲劳寿命,是造成齿轮早期失效的主要原因。同时提出了预防控制措施。 相似文献
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针对广州工银大厦中央空调系统某品牌19XR离心式制冷机组,由于冷凝压力高使压缩机排气压力升高致主机运转容量受限制的故障现象,对其冷却水系统进行重新检查评估。通过调查综合分析发现原因,并对冷却塔实施有效改造,改进消音导风罩,在冷却塔内设置初步过滤。实践证明,改造后提高了堵塞故障监测及预报警,降低了机组故障率。 相似文献
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球墨铸铁机械性能的优化模型 总被引:1,自引:0,他引:1
通过对球墨铸铁机械性能影响因素的分析,指出在一定的生产条件下,球墨铸铁的机械性能主要取决于组织、成分。利用Matlab中的Neural Network Toolbox仿真环境和BP模型算法建立了球墨铸铁机械性能的优化模型,详细论述了模型结构的设计、数据处理、网络初始化、训练与仿真的过程。该方法对提高球墨铸铁的机械性能具有积极作用。 相似文献
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海水泵使用两个月即发生叶轮叶片断裂事故。采用化学成分分析、力学性能测试及金相检验等方法对其断裂原因进行了分析。结果表明:由于海水泵叶片本身存在大量的铸造孔洞及疏松等缺陷,在交变载荷的作用下产生裂纹失稳扩展直至产生疲劳断裂。建议提高海水泵叶轮部件铸造质量。 相似文献
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Pratesa Yudha Munir Badrul Najamuddin Suryadi 《Journal of Failure Analysis and Prevention》2019,19(2):431-437
Journal of Failure Analysis and Prevention - Commercial programs using finite element analysis (FEA) have been developed for casting design process. However, their applications have been limited... 相似文献
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通过分析不同因素对冷却塔冷却能力的影响,从运行过程中节约风机、水泵等能耗的观点出发,总结了利用冷却塔节能的各种实施方法。室外空气湿球温度,入口水温,及冷却水量的变化都将引起冷却塔冷却能力的变化。为了用户的最大限度节能,冷却塔的生产厂家在设计与制造过程中应多考虑冷却塔的自控功能,并且提供冷却塔在冬夏两种工况的热工参数。 相似文献