Analysis of a diesel generator crankshaft failure

This paper analyses a catastrophic crankshaft failure of a four-stroke 18 V diesel engine of a power plant for electrical generation when running at a nominal speed of 1500 rpm. The rated power of the engine was 1.5 MW, and before failure it had accumulated 20,000 h in service operating mainly at full load. The fracture occurred in the web between the 2nd journal and the 2nd crankpin. The mechanical properties of the crankshaft including tensile properties and surface hardness (HV₁) were evaluated. Fractographic studies show that fatigue is the dominant mechanism of crankshaft failure, where the beach marks can be clearly identified. A thin and very hard zone was discovered in the template surface close to the fracture initiation point, which suggests that this was the origin of the fatigue fracture. A finite element model of the crankshaft has predicted that the most heavily loaded areas match the fractured zone.     

Failure analysis of a cylinder sleeve from a turbocharged diesel engine

This work presents the conclusions of a failure analysis performed on a V12 Turbo Charged diesel engine cylinder sleeve. The failure analysis carried out established the most relevant factors that caused damage to the cylinder sleeve. An examination of the internal surface of the cylinder sleeve revealed an elevated number of cavities close to the top center area, which acted as stress concentrators reducing the resistance of the component, creating crack nucleation spots. Additionally there were internal differences in the microstructure of the component, which indicate that different cooling conditions occurred during its manufacture, providing a secondary failure mechanism, due to material fragility.     

Analysis of the error in measuring the specific fuel consumption of a dc diesel generator

Translated from Izmeritel'naya Tekhnika, No. 2, pp. 41–43, February, 1992.     

Failures of single cylinder diesel engines crank shafts

The single cylinder diesel engines are extensively used in agricultural areas for several purposes such as water pumping. In some cases, these engines are also used for driving some auxiliary agricultural vehicles. This imposes unexpected loads on the components of the engines resulting in the premature failures. In this study, two different failure cases of crankshafts of these engines are analyzed. Some characterization studies and fractographic analyses are carried out to asses the failure reason. However, the cranks have some miner design differences, both failures are occurred after a fatigue process. One of the failed cranks has important heat treatment error.     

Failure mode analysis of two crankshafts of a single cylinder diesel engine

This paper reports an investigation carried out on two damaged crankshafts of single cylinder diesel engines used in agricultural services for several purposes. Recurrent damages of these crankshafts type have happened after approximately 100 h in service. The root cause never was imputed to the manufacturer. The fatigue design and an accurate prediction of fatigue life are of primordial importance to insure the safety of these components and its reliability. This study firstly presents a short review on fatigue power shafts for supporting the failure mode analysis, which can lead to determine the root cause of failure. The material of these damaged crankshafts has the same chemical composition to others found where the same type of fracture occurred at least ten years ago. A finite element analysis was also carried out in order to find the critical zones where high stress concentrations are present. Results showed a clear failure by fatigue under low stress and high cyclic fatigue on crankpins.     

Catastrophic failure of a fan in a diesel engine cooler

The fan used to cool a diesel engine fractured catastrophically after approximately 100 h of operation. The fan failed at a spider, which was resistance spot welded to a shim placed between two circular spiders of 3 mm thickness. The detailed analysis of the fracture indicated that the premature failure of the fan was due to inadequate bonding between the sheets at the weld nugget. The fracture was initiated from the nugget-plate interface. The inadequate penetration and lack of fusion between the steel sheets during resistance spot welding led to poor weld strength and the fracture during operation. The propensity to crack initiation and failure was accentuated by improper cleaning of the surfaces prior to welding and to inadequate nugget-to-sheet edge distance.     

Failure analysis of cylinder clamping rods in diesel engines

This article discusses the failure of cylinder clamping rods in single cylinder diesel engines. The AISI 4140 hardened and tempered steel clamping rods were failing after 200–250 h of operation. The fatigue failures initiated at the root of the last thread on the clamping rod that was engaged in a blind hole in the cylinder block. The failures were caused by loose tolerances on the threads that resulted in a non-uniform distribution of load. The load was concentrated on the last threads to engage, thus causing fatigue crack nucleation at the thread root and propagation until the rod broke by overload. Changing the tolerance on the threads virtually eliminated the fatigue problem.     

船用柴油机气缸套几何误差在线测量技术研究

设计一套船用柴油机气缸套几何误差在线测量系统,分析机床定位误差、传感器安装及测量误差对缸套表面各被测点坐标计算准确度的影响,建立测量误差计算数学模型。基于非线性规划方法建立缸套直线度误差、圆度误差、圆柱度误差的评定数学模型,通过与现有测量数据及误差评定模型的对比分析,表明该模型评定准确度较高。搭建在线测量原型系统,并进行测量实验,实验数据表明该系统具有结构简单、检测准确度及检测效率高等特点。     

Analysis of a crack in a disclinated cylinder

In this paper, the stress intensity factors and the opening displacement of a crack loaded by a negative wedge disclination in an isotropic cylinder are numerically determined. The disclination axis coincides with the long axis of the cylinder, and one end of the crack coincides with the disclination location. The cylinder may also be subjected to equal and opposite line loads on its surface. An exact formulation leads to a pair of decoupled singular integral equations of the Cauchy type. Numerical solutions show that if the cylinder represents a grain in a polycrystal, (i) unstable submicroscopic cracks 10^-5 to 10^-1 times the grain size and stable microscopic cracks of the order of the grain size, are predicted, (ii) the submicroscopic crack length to grain size ratio decreases, while the microscopic crack length to grain size ratio increases, as the grain size increases, (iii) significant differences exist, even in the case of the submicroscopic cracks, between the predictions of the exact theory and the approximate theory which ignores stress redistribution, and (iv) the opening displacement is independent of the elastic constants and the crack profile is wedge-shaped.     

Proportional hazards analysis of diesel engine failure data

Canadian Pacific Rail's diesel engines undergo scheduled major overhaul at intervals of approximately four years. Between these overhauls the condition of an engine is monitored by a series of physical tests and spectroanalysis carried out on samples of lubricating oil. At present the results of these tests are interpreted by the combination of skilled oil-analyst technicians and an expert system. The success rate of this is over 70 per cent, where success is defined to mean that the oil-analyst/expert system recommends that the engine should be scheduled for maintenance and it does indeed subsequently show evidence of an imminent failure. The purpose of the paper is to report on an examination of the method of proportional hazards modelling to determine whether or not PHM could improve on the accuracy of the oil-analyst/expert system in determining the risk of failure of a diesel engine.     

Concerning numerical simulation of the failure of a magnetic-fluid seal with a rotary outer profiled cylinder

The behavior of a circular magnetic fluid seal in the narrow gap between an immovable shaft and a rotary hyperbolic concentrator of the magnetic fluid flow surrounding it is studied. The range of the dimensionless rotation parameter within which the seal is stable is determined. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 105–110, January–February, 1996.     

The concrete cylinder: stress analysis and failure modes

The rationale for using the circular cylindrical specimen for determining the tensile strength of concrete is reviewed, and the stress fields and fracture modes associated with the familiar splitting test and a pressurized cylinder test are discussed. Special attention is paid to contradictory reports and unresolved issues in the literature as to exactly how the fracture of a concrete cylinder develops and progresses under increasing load.The effect of a macrocrack on the stress field within a cylinder is introduced as a means of understanding the progressive fracture of a cylindrical specimen. In particular, it is argued that, while the idealized stress field in an unflawed cylinder may explain how and where the first macrocrack develops in a cylindrical specimen, it is the stress field modified by the presence of the macrocrack that must be considered to understand subsequent behavior. This point of view enables us to take a unified view of a variety of different observations about the indirect tensile mode of failure.The axial tensile failure of a concrete cylinder loaded by radial pressure is also considered in the context of classical elastic stress analysis. Whereas this failure mode has been described as paradoxical in the literature, we demonstrate that the induced tensile stress field is indeed of sufficient magnitude to explain the axial failure under radial pressure by an elementary strength of materials argument.

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Résumé On examine les motivations d'utiliser une éprouvette à section cylindrique pour déterminer la résistance à la traction du béton, et on discute des champs de contraintes et des modes de rupture correspondant à l'essai classique de séparation et à l'essai sur cylindres soumis à pression. Les rapports de caractère contradictoire, et les données non résolues figurant dans la littérature, sont examinés en particulier en ce qui regarde la maniére exacte selon laquelle se développe et progresse sous charges croissantes une rupture dans un cylindre en béton.Un moyen de comprendre la rupture progressive d'une éprouvette cylindrique est d'introduire l'effet d'une microfissure sur le champ de contraintes dans un cylindre. En particulier, on avance que si un champ de contraintes idéal dans un cylindre sans défauts peut expliquer comment et où la première microfissure se développe dans une éprouvette cylindrique, c'est le champ de contraintes modifié par la présence des microfissures qui est à prendre en considération pour comprendre le comportement subséquent.Cette opinion permet aux auteurs d'adopter une vision globale d'une série d'observations diverses sur un mode de rupture par contraintes indirectes.On considère également le cas de la rupture par contraintes axiales d'un cylindre de béton sollicité par une pression radiale, dans le cadre d'une analyse classique des contraintes élastiques.Bien que ce mode de rupture ait été décrit dans la littérature comme paradoxal, on démontre que l'amplitude du champ de contraintes de traction induites est bien suffisante pour expliquer la rupture axiale sous pression radiale, en recourant à une explication basée sur la résistance élémentaire des matériaux.

     

Stress and failure analysis of the crankshaft of diesel engine

In this work the failure analysis of the crankshaft of diesel engine was performed. Visual examination of the crankshaft fracture showed that beach marks, typical for fatigue failure were observed. Additional observations of the crack initiation zone indicated that crack origin was not covered by material defects or corrosion products. Performed hardness test of the fractured crank pin showed that large HRC values were observed in central part of the pin only. On the corner of cylindrical pin surface where the crack origin was located the hardness of material was much smaller. In order to explain the reason of premature crankshaft damage, the finite element method was utilized. The results of nonlinear static analysis showed that during work of the engine with maximum power the high stress area was located in crack initiation zone. Based on results of performed investigations it was concluded that the main reason of premature fatigue failure was high-cycle fatigue of the material in external zone of the crank pin where the small structural radius was designed. In final part of the work the recommendations for increase of the fatigue life of analyzed crankshaft were formulated.     

Analysis of fatigue failure on the keyway of the reduction gear input shaft connecting a diesel engine caused by torsional vibration

The vibratory torque of a diesel engine caused by the reciprocating motion of the mass and gas pressure force of a cylinder is one of the main causes of the failure of the driving shaft of the diesel engine and the connecting shaft to the reduction gear. Because high cycle torsional fatigue can occur in the reduction gear shaft connecting the engine under vibratory torsional stress, the US Navy restricts it under the MIL G 17859D(SH) standard and suggests a procedure for evaluating the safety of the shaft for the reduction gear. In this study, the structural safety of the reduction gear input shaft in which fatigue failure occurs in typical naval vessels is investigated in accordance with the VDI 3822 RCA (root cause analysis) procedure based on the MIL G 17859D(SH) standard. When evaluating the safety factor in accordance with the MIL G 17859D(SH) standard, the alternating bending moment from the lateral vibration and the stress concentration factor under static load are considered. In addition, an improved design is suggested by CAE to satisfy the safety factor suggested by the MIL G 17859D(SH) standard.     

一起氧压机烧缸事故的分析

20 0 2年 7月 6日 ,新疆陆美工贸公司氧气厂 2号 2 1 67/1 5 0型氧压机三级缸发生着火燃烧事故。该氧压机是苏州制氧机厂产品 ,产品代号为 0 3 2 8,已连续运行 9年余。1　事故经过2 0 0 2年 7月 6日 9时 40分 ,我厂三台氧压机均在正常运行 ,其中两台是杭氧产 0 3 45A氧压机 ,一台为苏氧产 0 3 2 8氧压机。据现场操作人员回忆 ,氧压机三级排气压力在 1 1～1 2MPa之间 ,突然 2号氧压机发出“轰”的一声闷响 ,随之该氧压机中间体以上、活塞杆密封器以下被一团火焰包围 ,并向四周喷射火苗 ,火舌长达 2 5米以上 ,机体上部冷却水箱的冷却水也…