Modeling Wear in Cylinder Liners

We present and discuss a stochastic model describing the wear process of cylinder liners in a marine diesel engine. The model is based on a stochastic differential equation, and Bayesian inference is illustrated. Corrosive action and measurement error, both quite negligible, are modeled with a Wiener process whereas a jump process is used to describe the contribution of soot particles to the wear process. The model can be used to forecast the wear process and, consequently, plan condition‐based maintenance activities. In the paper, we provide a critical illustration of the mathematical and computational aspects of the model. We propose a strategy that, implemented for simulated and real data, allows for stable parameter estimation and forecasts. Copyright © 2016 John Wiley & Sons, Ltd.     

Failure Analysis of Mill Shaft Roll

A strip mill roll shaft failure was investigated. The investigation revealed that the fatigue strength of the shaft had been compromised by a combination of several factors that included: inadequate fillet radius size, the use of dissimilar filler materials to rebuild the shaft surface, the presence of slag inclusions at the weld/alloy interface, and machining defects on the shaft surface. Such failures have occurred repeatedly, and this paper presents a case study investigating the cause of the problem and discusses possible remedial measures to prevent similar occurrences.     

一种测量球磨机衬板受力的方案

为了测量球磨机衬板所受到的载荷施加的力,分析衬板的受力情况,根据衬板的受力特点提出一套测量方案,该方案包括一台测量装置和对该装置输出信号的处理方法。在此测量方案中,测量装置的铰链杠杆结构将衬板受到载荷所施加的力等效可分解成3个分力,再采用传感器测量出分力作用在测量装置上引起的负载梁应变,通过相关的计算,得出这3个分力的大小,进而得到衬板的受力的大小。     

卧式行星磨粉磨过程的无因次量及数学模型分析

以卧式行星磨为研究对象,从选出的9个参变量中利用量纲分析法导出6个表征粉磨过程的无因次准数,利用决定性、非决定性无因次准数之间的关系,建立粉磨产量、粉磨能耗2个数学模型,并利用多重线性回归分析正交试验结果得到数学模型。结果表明,模型的相关系数大于0.8,且实测值与模型理论预测值的相对误差约为15%,证明了数学模型的正确性。     

卧式行星磨筒内研磨过程的动力学相似分析

为了研究卧式行星磨筒内研磨体的运动规律,通过相对运动方程理论求解出研磨体的脱壁分离条件、脱落轨迹方程及研磨体的抛落时间等运动学规律。结果表明:卧式行星球磨机磨筒内研磨体的相对运动与传统球磨机内研磨体的运动完全运动相似和动力学相似;行星因子为z时,相似球磨机的直径是行星磨磨筒直径的z1/4倍;运用相似原理证明了行星球磨机相对于普通球磨机的节能率为(1.29z3/8-1)/(1.29z3/8)。     

球磨机变速器开裂的失效分析

某矿山球磨机变速器圆锥齿轮使用10 d即发生开裂失效,为此,用直读光谱仪、拉伸试验机、维氏硬度计、金相显微镜、扫描电镜研究了球磨机齿轮的化学成分、力学性能、金相组织及断口形貌.结果表明:齿轮的金相、硬度、成分均符合技术要求,断口的裂纹源位于断口内部,裂纹源处有较多的O、Al、Ca、Na等夹杂物,这些夹杂物硬度较高,割裂...     

碱性介质中旋塞阀磨损失效分析

采用金相显微镜和扫描电镜对在碱性介质中发生泄漏的不锈钢旋塞阀进行了宏微观形貌和金相组织分析;并采用光电直读光谱仪、EDS、红外碳硫分析仪和NHO 分析仪对旋塞阀材质和表面沉积物进行了系统的表征分析.结果表明旋塞阀的失效模式为腐蚀磨损和磨粒磨损.阀门塞子材质与设计规定不符以及塞子材料抗腐蚀性能降低是旋塞阀泄漏的主要原因.提出了解决问题的相应对策,为防止类似事故的再次发生提供了技术依据.     

热轧机轧辊失效分析及对策

Cr-Ni-Mo无限冷硬Ⅳ材料轧辊在使用中出现了工作层剥落和炸裂的现象,经现场取样分析,并在实验室进行了系列温度的时效工艺试验和耐磨性试验的基础上确定了该材料热处理条件与性能之间的关系.无限冷硬Ⅳ材料轧辊经过(425±5)℃去应力处理后,可以得到最佳性能配合和使用效果.使轧制带钢的宽度增加了10%以上,即解决了生产中的轧辊质量问题,又为用户增加产品规格提供了条件,具有推广价值.     

气流磨尾尘的超细粉碎

用气流磨加工碳化硅磨料时,约有5%-15%的物料变成了尾尘.这部分碳化硅微粉由于粒度分布范围很宽,无法直接利用.本实验研究对气流磨碳化硅尾尘用搅拌磨粉碎进行了探讨.实验研究了不同研磨时间粉尘的纯度变化;分散剂对粒度变化的影响以及不同研磨时间,微粉的粒度、粒度分布的变化关系,实验结果证明气流磨尾尘经过搅拌磨研磨可以得到分布窄、单峰的理想微细粉体;随着研磨时间的增加,粉体纯度下降;磷酸盐水分散剂可以促进研磨的进程.     

Failure Analysis of a Cylindrical Roller Bearing from a Rolling Mill

Premature failure of a cylindrical roller bearing of a gear box input shaft from a hot strip mill has been investigated. The pins of the cylindrical rollers of the bearing broke from the welded joints at their ends on the cage ring. Investigations were carried out on the failed roller pin and the welded joint. The investigation consists of visual observation, chemical analysis, characterization of macro- and microstructures, measurement of hardness profile, fractography, and energy dispersive spectroscopy (EDS). The fracture surface of the roller pins exhibits beach marks. Scanning electron microscopy (SEM) of the fracture surfaces reveals striations suggesting fatigue failure. The measured hardness profile along the welded joint shows very high hardness due to the presence of untempered martensite at the fusion boundary as revealed by the microstructural examination. Analyses of the results infer that the roller pins failed by the initiation of fatigue cracks from the welded joint because of the presence of untempered martensite originated due to improper welding process.     

炉卷轧机工作辊磨损预测

以国内某厂3500炉卷轧机为研究对象,分析了炉卷轧机工作辊磨损产生的原因,采用现场在线磨损计算模型进行了离线模拟计算;利用现有磨床测试轧辊磨损曲线,对理论计算与实测数据的进行了比较。同时,回归出在线板形控制的磨损计算模型参数,修正后的计算结果符合轧辊磨损的一般规律,可用于轧辊磨损在线预报。     

搅拌磨制备超细粉体粉磨工艺的研究

通过模型实验 ,系统地研究了矿浆浓度、搅拌器转速、球料比、研磨介质种类及尺寸等主要操作参数对搅拌磨粉磨效果的影响规律 ,并分析了产生这种影响的原因     

矿物粉体搅拌磨湿法超细磨矿中研磨介质的行为与作用

利用工业湿式搅拌磨 ,以煅烧高岭土为原料 ,研究了磨矿介质各行为———介质种类、介质尺寸配比和介质物料比等对矿物粉体湿法超细磨矿的影响。在优化研磨介质等条件的基础上 ,进行了模拟生产状态的连续磨矿试验 ,实现了磨矿产品小于 2 μm的颗粒质量分数大于 90 %的预期结果。     

Failure Analysis of Wear Block of Crush Deck Used in Sinter Plant

Failure analysis of wear block used in the crush deck of a Sinter Plant was carried out. Crush deck acts as a platform to transfer the hot sinter cake from sinter machine to crushing unit. Hot sinter cake with a temperature around 800 °C falls on the crush deck from the discharging end of rotating sinter machine. This investigation consists of visual observation, chemical analysis, characterization of microstructures, energy dispersive spectroscopy, and measurement of hardness. Analysis revealed that this is an iron-based material with Cr–Ni alloying with higher hardness and lower toughness, which was due to improper microstructure. Microstructure revealed a large number of primary carbides along with needle-shaped carbides, which drastically reduce the toughness of the material. Application point of view the wear block should have optimum combination of toughness and wear resistance at elevated temperature; however, analyses showed the actual wear block had with higher wear resistance and lower toughness. This was reflected in the undesirable microstructure observed during metallographic study. It was thus concluded that the component failed before a proper life cycle was achieved due to poor material properties. Based on the failure analysis suitable heat treatment process was recommended. Metallurgical study carried out on the suggested material, showed significant improvements in material property. Trial of recommended wear block was taken at the plant level and life of the recommended material improved twice than that of previous one.     

Root Cause Failure Analysis of Pinch Roll Bearing at Hot Strip Mill

Journal of Failure Analysis and Prevention - Bearings are one of the most widely used and highly stressed engineering components. If properly manufactured, mounted, operated and maintained, they...     

环缝磨研磨介质的配比及其对研磨效率和微粉粒度分布的影响

研究了一种可以制备超细粉体的新型磨机-环缝磨中研磨介质球配比.首先利用均一球形颗粒填充结构理论计算了介质球不同粒径的体积配比,利用最密填充理论计算了介质球的粒径大小的配比,求出了环缝磨研磨介质的优化配比.通过实验分析了不同介质球体积和粒径的配比对研磨效率和微粉粒度分布的影响,从而得出采用几何学的级配填充达到最密填充时的介质球配比能达到较好的研磨效果的结论.     

Tribological Failure Analysis and Suitability of Grease Lubrication for Sugarcane Crushing Mill Journal Bearings

Journal of Failure Analysis and Prevention - Influence of tribological performance parameters like speed, eccentricity ratio, load and frictional torque on the performance of sugarcane mill heavily...     

Kinetics of Alumina Ultrafine Grinding in a Planetary Ball Mill

A novel design of the planetary mill using two motor drives instead of the customary single drive is shown here. The grinding of alumina powder to micron sizes is achieved in a matter of 20 minutes. A factorial design of experiments on the mill delineated the key variables for achieving product quality. Furthermore, the time evolution of product size distribution is analyzed with the selection-breakage type model also known as population balance model.     

Wear Failure of Rigid Magnetic Recording Disks

A pin-on-disk apparatus was used to study the tribological failure of rigid disk drives, which can be described as lightly, lubricated non-metallic (mostly, ceramic-on-ceramic) sliding systems operating at low loads. The wear models proposed to explain the degradation of the disk magnetic coating, which is deposited on a metallic substrate, can be grouped into two categories; gradual abrasive or adhesive wear processes or sudden fatigue-type failures. In this paper experimental results are reported to eliminate the latter possibility, and an analytical model based on the adhesive wearof alumina particles is derived. This model, which was experimentally verified, expresses the disk life as a function of the mechanical and physical properties of disk and head materials, and the geometry of the pin-medium interface.