Compacted graphite iron-A material solution for modern diesel engine cylinder blocks and heads

The demands for improved fuel economy,performance and emissions continue to pose challenges for engine designers and the materials they choose. This is particularly true for modern diesel engines,where the primary path to achieving improved engine performance and emissions is to increase the Peak Firing Pressure in the combustion chamber. The resulting increase in thermal and mechanical loading has required a change from conventional grey cast iron to Compacted Graphite Iron (CGI) in order to satisfy durability requirements without increasing the size or the weight of the engines. With at least 75% higher tensile strength,45% higher stiffness and approximately double the fatigue strength of conventional grey cast iron,CGI satisfies durability requirements and also provides the dimensional stability required to meet emissions legislation throughout the life of the engine. Currently,there are no CGI diesel engines running on the roads in North America. This is set to change considerably as new commercial vehicle and pick-up SUV diesel engines are launched with CGI cylinder blocks in 2008 and 2009. These initial programs will provide over 2 million CGI diesel engines when ramped to mature volume,potentially accounting for 10%-15% of the North American passenger vehicle fleet within the next four years.

Application of complex inoculants in improving the processability of grey cast iron for cylinder blocks

Effect of several complex inoculants on mechanical properties, process-ability and sensibility of grey cast iron used in cylinder block were investigated. The experimental results showed that the grey cast iron treated with 60%FeSi75+40%RE complex inoculants has tensile strength consistently at about 295 MPa along with good hardness and improved metallurgy quality. While the grey cast iron inoculated with 20%FeSi75+80%Sr compound inoculants has the best process-ability, the lowest cross-section sensibility and the least microhardness difference. The wear amount of the drill increases correspondingly with the increase of the microhardness difference of matrix structure, indicating the great effect of homogeneousness of matrix structure in the grey cast iron on the machinability of the grey cast iron.

Cavitation of a Submerged Jet at the Spherical Valve Plate/Cylinder Block Interface for Axial Piston Pump

The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate,resulting in special cavitation phenomenon on the spherical port plate pair.In order to study cavitation characteristics of spherical port plate pair,a dynamic CFD model of the piston pump including turbulence model,cavitation model and fluid compressibility is established.A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh,which makes up for the lack of research on the meshing of the spherical oil film.In this paper,using CFD simulation tools,from the perspectives of pressure field,velocity field and gas volume fraction change,a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out.The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point.The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface.These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair.The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate,but also cause strong impact and denudation on the lower surface of the cylinder body.Finally,the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.

Quantitative models for microstructure and thermal conductivity of vermicular graphite cast iron cylinder block based on cooling rate

The relationships of cooling rate with microstructure and thermal conductivity of vermicular graphite cast iron(VGI) cylinder block were studied, which are important for design and optimization of the casting process of VGI cylinder blocks. Cooling rates at different positions in the cylinder block were calculated based on the cooling curves recorded with a solidification simulation software. The metallographic structure and thermal conductivity were observed and measured using optical microscopy(OM), scanning electrical microscopy(SEM) and laser flash diffusivity apparatus, respectively. The effects of the cooling rate on the vermicularity, total and average areas of all graphite particles, and the pearlite fraction in the VGI cylinder block were investigated. It is found that the vermicularity changes in parabola trend with the increase of cooling rate. The total area of graphite particles and the cooling rate at eutectoid stage can be used to predict pearlite fraction well. Moreover, it is found that the thermal conductivity at room temperature is determined by the average area of graphite particles and pearlite fraction when the range of vermicularity is from 80% to 93%. Finally, the quantitative models are established to calculate the vermicularity, pearlite fraction, and thermal conductivity of the VGI cylinder block.

Finite Element Analysis of Fretting Behavior Between an Engine Cylinder Block and a Main Bearing Cap

The finite element analysis of the fretting behavior between a cylinder block and a main bearing cap is presented. The stresses, relative fretting slip, frettin g friction work parameter W and crack initiation location parameter Gon the fretting contact surface of the cylinder block are obtained and analyzed. It shows that the fretting fatigue problem of the cylinder block can be quantitat ively explained by WorG. The effects of pretightening force, friction factor and material combination of the cylinder block and the main bearing cap are studied. The computational results indicate that the fretting fatigue of the cylinder block can be allayed by increasing the elastic modulus of the cylinder block, but not by changing the other two factors.

Tribological Properties of Cylinder Block/Valve Plate Interface of Axial Piston Pump on the Tribometer

The tribological properties of cylinder block/valve plate is an important consideration in the design of axial piston pump.The effect of materials and heat treatment on friction and wear properties has been studied in depth.Engi-neering experiences show that the speed and load also affect the tribological properties,but these have not been systematically analyzed.The purpose of this paper is to evaluate the tribological properties of the commonly used materials(CuPb1 5Sn5 and 38CrMoAl/42CrMo)for cylinder block/valve plate with different heat treatment and con-tact pressure at different speed.During the test,tribometer is used to simulate the contact pattern between the valve plate/cylinder block in axial piston pump,the friction coefficient,wear rate and surface topography are analyzed to evaluate the tribological properties of different types of friction samples at different speed.Results indicate that:(1)contact surface of the samples at 1800 r/min is more prone to adhesive wear than those at 500 r/min;(2)in the terms of wear resistance,quench-tempered and nitrided 38CrMoAl(38CrMoAl QTN for short)is better than quench-tem-pered and nitrided 42CrMo,although they are all commonly used materials in the axial piston pump;(3)2.5 MPa is the critical contact pressure of the interface between valve plate made of 38CrMoAl QTN and cylinder block made of CuPb1 5Sn5 on the tribometer,which implies the pressure bearing area at the bottom of the cylinder block should be carefully designed;(4)the valve plate/cylinder block made of 38CrMoAl QTN/CuPb15Sn5 exhibits good tribological properties in a real axial piston pump.This research is useful for the failure analysis and structural optimization design of the valve plates/cylinder block.

航空活塞发动机气缸体多物理场耦合磨损机理研究

航空活塞发动机气缸体表面摩擦失效是滑动摩擦应力场、气缸体表面温度场和循环多变功率载荷耦合作用的结果。统计分析了航空活塞发动机在多种工况环境下的摩擦磨损润滑状态,绘制了航空活塞发动机气缸体载荷功率谱。通过多变工况确定多物理场加载参数方案,在SRM-4摩擦试验机上给定功率、温度、载荷和滑油量拟耦合摩擦环境测试废旧气缸体。通过检测气缸体表面状态参数,检验拟废旧气缸体摩擦前后的表面状态。通过拟耦合研究了气缸体应力场、温度场、载荷功率变化对气缸体摩擦系数的影响。结果表明:气缸体表面摩擦系数随温度的增加呈指数增加;低温段(92℃)和中温段(145℃)时,摩擦系数对载荷在35~38N时的变化较为敏感,摩擦系数随载荷的增加而增加,磨损形式以疲劳磨损、疲劳点蚀为主;大于38 N后,载荷对摩擦系数的影响较小;高温段(198℃),载荷对摩擦系数的影响程度减小,温度是主要影响因素,摩擦形式由磨粒磨损(两体/三体磨损)转变为粘着磨损。摩擦系数随频率的变化相对较小。

基于熵值法的铝合金缸体低压铸造工艺多目标优化

基于有限元软件ProCAST构建某型铝合金缸体的有限元模型,设计L16(44)正交试验方案,探究了浇注温度、模具预热温度、充型时间、保压压力四个工艺参数对凝固时间和缩松体积的影响。采用熵值法分别计算两个评价指标的权重,将凝固时间与缩松体积转化为综合评分值进行单目标优化。通过极差分析与方差分析,得到了各参数对综合评分的影响程度为:浇注温度(A)>模具预热温度(B)>保压压力(D)>充型时间(C),确定了最优的工艺参数为A1B2C1D3。对比原工艺参数方案和优选工艺参数方案发现:凝固时间缩短了20.35%,缩松体积下降了2.96%。经生产试验,缸体铸件外观质量良好,无明显铸造缺陷,验证了最佳工艺参数的合理性。

基于切削仿真的缸体进排气面铣削优化

针对缸体进排气面凸台铣削余量大、刀具耐用度低的技术问题,运用切削仿真技术对铣削参数进行分析。在确保切削负载、切削温度的前提下,通过优化加工程序提升加工效率和刀具耐用度。

非道路柴油机缸筒芯的快速改型工艺

在柴油机缸体新产品的开发过程中,往往使用模具造型(芯)、无模数字化精密成形技术切削成形、喷墨3D打印成形等方法先制造砂型,再将金属液浇注入砂型中形成铸件,但是上述制备砂型的方法有的造型周期长、有的砂型制造成本高。因此,本文研究了一种快速改型方法,将原有砂型改造成为可以再次用于缸体新产品生产的新砂型,使缸体新产品开发过程中砂型制造成本降低39.2%,具有较好的推广应用价值。

缸体铸件切削性能差异的原因分析

为查明相同的切削条件下,切削不同厂家的缸体铸件相同部位所用刀具寿命相差1倍左右的原因,从2种缸体铸件顶面相同部位取样进行了化学成分分析、金相组织分析以及夹杂物的形貌和组成分析,找出了引起切削性能差异的原因,并提出了相应的改进措施为:(1)降低Cr的加入量,严格控制原材料中的w(Ti)和w(V)量,避免形成硬质点而加快刀具磨损;(2)合理设计孕育处理工艺,避免产生D型、E型石墨以及过冷铁素体基体;(3)适当提高w(Mn)和w(S)量,避免由于生成MnS与TiC共生夹杂物而恶化切削性能。

基于数据合成与机器学习的6DM气缸体复杂铸件缺陷预测

在汽车核心零部件制造等关键领域,复杂铸件出现缺陷的后果尤为严重,因此对复杂铸件进行缺陷预测并提高其生产质量刻不容缓。本文针对实际铸造过程中采集到的6DM气缸体复杂铸件生产数据中气孔、砂眼等缺陷类别的数据量严重不平衡问题,对基于数据合成与机器学习的6DM气缸体复杂铸件缺陷预测进行研究,梳理了人工神经网络与复杂铸件缺陷预测的研究现状,结合企业现场生产情况,开展了需求分析,获取6DM气缸体复杂铸件生产数据。并基于SMOTE(synthetic minority oversampling technique)算法,创建了合成数据集,采用合成数据集作为训练模型的数据集,预测准确率达到99.37%。结果表明,构建的复杂铸件缺陷预测模型能够准确预测复杂铸件缺陷。

改善下缸体压铸件缩孔缺陷的模具优化设计

介绍了一款铝合金下缸体压铸件的结构特点及缺陷形式,运用“鱼骨图”对下缸体局部缩孔缺陷进行分析。采用局部挤压技术对铸件局部厚大处进行增压补缩,同时加大缺陷部位的型腔冷却,采用“分水盘”结构改变冷却水道进出口位置,避免与挤压油缸的干涉。通过以上措施有效地提高了下缸体的内部和外观质量,大幅提高产品的合格率。

基于结构优化方法的某柴油机缸体研究

缸体是发动机中质量最大的部分,在很大程度上影响着发动机的重量,因此,对其减重显得尤为重要。本文以某柴油机缸体为例,提出一种将扑优化方法和形状优化方法相结合的两级优化方法对缸体进行优化,寻找缸体加强筋部位最佳材料分布,去除冗余材料;进行形状优化寻求最合理的加强筋形状。最终优化结果使缸体最大应力降低10.6%,实现缸体减重3%,达到了本次优化目的。同时本研究也可为发动机其它零部件结构优化、轻量化提供一定的理论依据。

中国现代早期砖拱壳历史遗产之建造组织方式研究——1958年重建工大型空心砌块筒拱厂房设计建造一体化实验回顾

揭示节约“三材”约束条件下,重庆建筑工程学院师生探索设计、施工一体化的快速施工方式,是教学与生产实践结合的一次有益尝试。基于历史文献研究、三维图式、口述采访的工作方法,从设计过程、施工组织、机械工具、人员协调等多方面回顾了1958年重建工师生使用大型空心砌块筒拱技术承建江陵厂厂房的史实。它是新中国早期砖薄壳结构谱系中的重要类型,对当下的建造教学也具有参考价值。

Performance optimization for high speed axial piston pump considering cylinder block tilt

Increasing the rotating speed is considered as an efficient approach to upgrade the power-to-weight ratio in an axial piston pump,but penalized by more leakage and more severe wear resulting from the adverse cylinder block tilt.Previous studies mainly focused on the bearing characteristic of the valve plate/cylinder block pair,but the spline coupling also plays a key role in the undesired cylinder block tilt,which has been little studied.A theoretical model for the rotating assembly is presented to investigate the effect of the spline coupling length on the cylinder block tilt and the performance of the valve plate/cylinder block pair.A typical high-speed axial piston pump with the displacement of 5.2 mL/r at 10000 r/min was studied by simulation and experiment.It shows that the optimal spline coupling length is one value increased by 2 mm from the original,bringing a remarkable leakage reduction under the high-speed condition by decreasing the cylinder block tilting angle.The experiment result matches well with the simulation.The influences of the spline coupling on the cylinder block tilt and the leakage were demonstrated.

一种V型气缸体缸孔夹渣缺陷的原因分析及工艺优化

简要介绍了一种V型干式缸套气缸体铸造工艺,针对缸孔加工后发现的夹渣缺陷进行了分析。通过优化排气溢流系统、提高浇注温度、增强滤渣排渣结构、增加毛坯局部补贴等措施,最终大幅降低缸孔夹渣缺陷率,解决了夹渣问题。

铸件修补技术在灰铸铁气缸体上的应用

介绍了铸件缺陷修补技术,包括铸件粘胶修理、铸件热焊补、冷焊补等修复工艺,通过生产实例验证了各种修复技术的适用铸件和适用缺陷,并对公司1~11月份修复的铸件进行经济效益统计,结果显示降成本效果明显。最后指出:气缸体的缺陷及所处的部位不同,如果采用单一的焊接或粘接法进行修复处理,会降低修复质量,甚至导致缺陷扩大和延伸,因此,在修复缺陷时应灵活运用上述补焊方法,才能取得满意的修复效果。

缸盖-缸垫-机体联合仿真在某产品开发中的应用

缸盖和机体组件作为发动机的本体支撑件,工作过程中承受复杂的机械载荷和热负荷,其可靠性直接决定了发动机的使用寿命。因此针对缸盖和机体在产品设计开发中需要进行详尽的评估验证,保证结构设计的合理性与可靠性。本文介绍了产品设计阶段针对缸盖、机体设计与缸垫联合仿真的评估方法,结合某产品开发过程对该仿真方法进行了详细阐述。根据产品后续试验结果,对仿真计算结果进行了对标验证,确认了联合仿真方法的合理性和有效性。