Failure Analysis and Mechanical Performance Evaluation of a Cast Aluminum Hybrid-Iron Golf Club Hosel

This article details the failure analysis of a commercial golf club hybrid-iron that fractured through the hosel during normal use. The golf club hosel was manufactured from a cast aluminum alloy, and the optical analysis revealed casting pores up to 20% through the hosel thickness. Mechanical properties of the aluminum alloy were determined for material characterization and used to construct a finite element model to analyze the performance of the material under failure conditions. In addition, a full structural scale experiment was conducted to determine the failure strength.     

Failure Analysis of a Cracked Gasoline Engine Cylinder Head

This article presents a failure analysis on a gasoline engine cylinder head made of aluminum alloy, which has been used in passenger cars. During an endurance test, a crack initiated from the interior wall of a hole in the center of the cylinder head and then propagated through the thickness of the cylinder head. The metallurgical examinations are conducted in the crack origin zone. The results show that there are many casting pores due to poor quality of casting in the failed cylinder head which has certainly played a crucial role in initiating the crack. Finite element analysis of the cylinder head is performed to identify the stress components. Modeling of a bolt for the hole shows that the plastic stresses are occurred. Moreover, the lower strength of the material due to high assembly stress caused the failure in the cylinder head.     

铸造耐热铝合金在发动机上的应用研究与发展

主要综述了近年来铸造耐热铝合金在发动机上的研究现状和最新进展,列举了不同种类的铸造铝合金的高温性能,总结了提高铸造铝合金高温性能的几种方法,并展望了铸造耐热铝合金的发展趋势.     

Fracture Failure Analysis of Ductile Cast Iron Crankshaft in a Vehicle Engine

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.     

Injection Parameters Optimization and Artificial Aging of Automotive Die Cast Aluminum Alloy

High-pressure die castings are expected to be used in the near future as high-duty structural components in the automotive industry. The effects of die casting parameters and aging on the tensile properties of high-performance die cast aluminum alloy are therefore investigated in this work. Our results indicate that HPDC AlMg5Si2Mn specimens (formed under an injection pressure of 100 MPa, high-level fast-shot velocity, and speed transition point location 220 mm) possess good internal quality and superb tensile properties (351.1 MPa, 200.7 MPa, 13.77%). Sample density decreased along the die filling direction due to pressure loss. After 3 h aging at 250 °C, tensile strength and yield strength were significantly increased from 351.1 and 200.7 MPa to 380.5 and 246.9 MPa, respectively. Elongation decreased initially from 13.77 to 5.5% after 1 h aging and then recovered to 11.48%. In addition, the effect of cooling methods on mechanical properties was found to be insignificant.     

铝合金发动机缸盖的再制造技术研究

针对废旧汽车铝合金发动机缸盖的再制造需求,对发动机缸盖进行了失效分析,并研究了高速电弧喷涂Al-RE涂层的再制造工艺。实验结果显示,缸盖的失效主要表现为表面环形压痕和平面度超差,压痕区附近出现较多白色条状的Si相,硬度有所升高;高速电弧喷涂Al-RE涂层的组织致密,硬度略低于LM25TF铝合金基体,热压变形实验后涂层与铝合金基体结合良好,未出现裂纹和剥离。综合实验结果和典型零件的应用情况表明,高速电弧喷涂Al-RE涂层技术可实现铝合金缸盖的再制造。     

连续流变挤压技术在制备高性能铝材中的应用

目的探索铝材短流程制备工艺,制备出高性能铝合金材料。方法采用连续流变挤压成形技术制备Al-Ti-B晶粒细化剂与Al-Sc-Zr耐热铝合金导线;利用提出的连续流变挤压与累积连续挤压法,制备超细晶金属材料。结果采用连续流变挤压成形技术制备Al-Ti-B晶粒细化剂,其细化效果优于国外同类产品,且制备流程短、成本低;制备出的高性能的Al-Sc-Zr耐热铝合金导线,其抗拉强度、伸长率和导电率分别达到223 MPa、7.1%和60.5%IACS,并且可在230℃的温度下长期运行,相比于日本耐热铝合金导线,其抗拉强度、伸长率与导电率分别提高了39.4%,255%,0.83%;采用连续挤压技术制备的Al-Sc-Zr合金杆,经过累积连续挤压后,合金晶粒尺寸从100μm细化至800 nm,得到了超细晶Al-Sc-Zr合金。结论连续流变挤压技术制备铝材工艺流程短、产品性能优良,能连续高效制备铝合金超细晶材。     

Failure Analysis of a Truck Diesel Engine Crankshaft Made from Spheroidal Cast Iron

A diesel engine crankshaft fractured in service after 13,656 km of operation. The fracture took place on the sixth, the fifth, and the fourth crankpins and the fracture surfaces have a 45° inclination with respect to the axial of crankshaft. The cracks of the sixth and the fifth crankpin are across the oil hole and a complete fracture took place at the sixth crankpin which bore the maximum torque load. On the fourth crankpin, crack is only through the thin wall side of oil hole. The results indicate that fatigue fracture is the dominant failure mechanism of the crankshaft. It was observed that the fatigue cracks in the crankpins initiated at machining dents present on the wall of oil hole. The appearance of the machining dents on the wall of oil hole suggests improper machining and these dents supplied the stress concentration site that was mainly responsible for the fatigue fracture of crankshaft.     

Failure Analysis of a Casting

Failure of a main steam strainer housing during hydraulic testing is attributed to hydrogen embrittlement associated with the welding procedure used to fit the housing to the hydraulic system. However, casting defects were also noted and recommendations to improve the quality of castings made.     

Influence of Processing Temperatures on Mechanical Properties and Microstructure of Squeeze Cast Aluminum Alloy Composites

The paper deals with the influence of melt and die temperatures on the squeeze cast silicon carbide particulate reinforced aluminum alloy composites. Samples were produced at the following constant melt and die temperatures: melt—750, 800, 850, and 900°C; die—250, 300, 350, and 400°C. During the specimen fabrication, pressure was maintained at 100 MPa. The results reveal significant influence of both melt and die temperatures on the mechanical properties. The optimum melt and die temperatures for the preparation of the composite are 850°C and 350 °C, respectively. Tensile and impact strengths, and hardness of composite samples prepared at this temperature combination are found to be better than those of samples prepared at other temperatures. Additionally, microstructures of samples prepared at this temperature combination display a relatively fine grain structure and the smallest degree of particle agglomeration which explain the dependence of mechanical properties on the melt and die temperatures.     

KV6汽车发动机铝合金缸体缸盖铸造质量改善

介绍了新引进的KV6汽车发动机铝合金缸体缸盖的铸造工艺特点和浇铸系统,针对试生产过程中发现的质量缺陷,利用质量控制工具对产品质量数据进行分析,通过排列图等方法快速地找出了影响产品质量的重点质量缺陷及这些缺陷易发生的部位,并提出了相应的解决方案,最后通过与采取了改进措施的生产数据的对比,表明本文采取的质量控制方法和措施可以有效地提高铸造产品质量.     

高铬铸铁热处理及其性能的研究

研究了高铬铸铁化学成分的控制范围、熔炼工艺、浇注工艺以及热处理工艺对其硬度；耐磨性和冲击性能的影响，并分析了该成分高铬铸铁经过不同热处理后的组织。结果表明，采用文中所述生产工艺和1040℃±10℃×6h特殊淬火液淬火＋275℃×6h或440℃×6h回火的热处理工艺，高铬铸铁硬度达60HRC以上，冲击韧性达10J／cm^2，其耐磨性是高铬铸铁Cr15的1．32倍、是高锰钢Mn13的1．95倍。     

The Role of Particles in Fatigue Crack Propagation of Aluminum Matrix Composites and Casting Aluminum Alloys

Fatigue crack propagation （FCP） behaviors were studied to understand the role of SiC particles in 10 wt pct SiCp/A2024 composites and Si particles in casting aluminum alloy A356. The results show that a few particles appeared on the fracture surfaces in SiCp/Al composites even at high △K region, which indicates that cracks propagated predominantly within the matrix avoiding SiC particles due to the high strength of the particles and the strong particle/matrix interface. In casting aluminum alloy, Si particle debonding was more prominent.Compared with SiCp/Al composite, the casting aluminum alloy exhibited lower FCP rates, but had a slight steeper slope in the Paris region. Crack deflection and branching were found to be more remarkable in the casting aluminum alloy than that in the SiCp/Al composites, which may be contributed to higher FCP resistance in casting aluminum alloy.     

铸件中孔洞缺陷对疲劳性能影响的研究进展

孔洞类缺陷对铸造合金材料的疲劳性能影响很大,从疲劳裂纹的萌生到疲劳裂纹的扩展等各环节都会受到孔洞类缺陷特征因素(如孔洞尺寸、形貌特性、位置分布、体积分数等)的影响.本文分析了当前在这方面研究的成果及进展,认为有关孔洞类缺陷的疲劳模型尚不完善,复杂载荷下的疲劳行为以及铸造材料微观结构对疲劳性能影响的研究有待进一步深入研究...     

Failure Analysis of a Vehicle Engine Crankshaft

An investigation of a damaged crankshaft from a horizontal, six-cylinder, in-line diesel engine of a public bus was conducted after several failure cases were reported by the bus company. All crankshafts were made from forged and nitrided steel. Each crankshaft was sent for grinding, after a life of approximately 300,000 km of service, as requested by the engine manufacturer. After grinding and assembling in the engine, some crankshafts lasted barely 15,000 km before serious fractures took place. Few other crankshafts demonstrated higher lives. Several vital components were damaged as a result of crankshaft failures. It was then decided to send the crankshafts for laboratory investigation to determine the cause of failure. The depth of the nitrided layer near fracture locations in the crankshaft, particularly at the fillet region where cracks were initiated, was determined by scanning electron microscope (SEM) equipped with electron-dispersive X-ray analysis (EDAX). Microhardness gradient through the nitrided layer close to fracture, surface hardness, and macrohardness at the journals were all measured. Fractographic analysis indicated that fatigue was the dominant mechanism of failure of the crankshaft. The partial absence of the nitrided layer in the fillet region, due to over-grinding, caused a decrease in the fatigue strength which, in turn, led to crack initiation and propagation, and eventually premature fracture. Signs of crankshaft misalignment during installation were also suspected as a possible cause of failure. In order to prevent fillet fatigue failure, final grinding should be done carefully and the grinding amount must be controlled to avoid substantial removal of the nitrided layer. Crankshaft alignment during assembly and proper bearing selection should be done carefully.     

高锰钢的研究与应用进展

综述了高锰钢研究与应用的进展,重点介绍了高锰钢的成分设计、组织性能、铸造、热处理及车削加工的研究进展。     

Investigation of Failure in a Crankpin of a Motorcycle Engine

This study performs a failure analysis of a failed crankpin connecting the crank shaft with the piston rod in a motorcycle engine. The failed crankpin under examination is embedded in a 16NiCrMo12 alloy, a typical steel designed for carburizing treatment. The crankpin experiences a periodic compressive stress associated to the compression stroke featuring the cyclic movement of the piston rod imposed by the rotation of crank shaft. During the failure analysis, such mechanism has been associated to a pulsing fatigue phenomenon. The failure of the crankpin concerns the surface, which is affected by significant spalling phenomena causing the detachment of steel fragments, as the element is subjected to constant friction because of relative rotation. Since not all the produced crankpins undergo the observed damaging phenomena, the aim of the study is to identify the factors governing the failure phenomenon and to provide a working solution to the problem. The employed experimental techniques include microstructure analysis by means of optic microscopy and scanning electron microscopy, and hardness measurements. The combination of the obtained results has allowed us to identify the presence of large amounts of non-metallic inclusions underneath the surface as the cause of the damage.     

Investigation of Compressor Failure in a Military Turbojet Engine

During altitude maneuver loud bang sound was observed followed by rapid winding down of engine rotation and jet pipe temperature. Compressor casing top half was found severely ruptured and broken into many pieces. On viewing through the ruptured area compressor rotor blades were found sheared at the root. Systematic investigation revealed that the failure of compressor casing was due to sudden overload. Analyzing the possible reasons of sudden overload it could be concluded that the rupture of compressor casing was most probably due to surge during the maneuvers. Remedial measures are suggested to address such failures.     

高性能交易引擎ZCETE的设计与实现

针对大规模电子交易中存在的数据密集和事务集中引起交易引擎的性能下降问题,结合内存数据库和主动数据库技术,提出并实现了一个高性能交易引擎ZCETE。讨论了ZCETE中采用的主动响应机制、事务调度策略、数据组织方法、故障恢复措施等关键技术。将ZCETE应用于棉花交易,测试结果表明,在不产生事务延迟的条件下,交易事务的处理速率为1970TPS,平均响应时间为0．5ms,可满足大规模电子交易的需要。