FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA

S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper （SWT）Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis （FEA） of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life.

Identification of Axial Vibration Excitation Source in Vehicle Engine Crankshafts Using an Auto-regressive and Moving Average Model

Violent axial vibration of a vehicle engine crankshaft might lead to multiple defects to the engine.Much research on mechanism and control measures has been done on engines,such as using the dynamic stiffness matrix method,rayleigh differential method,and system matrix method.But the source of axial vibration has not been identified clearly because there are many excitation factors for the axial vibration of a crankshaft,such as coupled torsional-axial vibration and coupled bending-axial vibration,etc.In order to improve the calculation reliability and identify the excitation source of axial vibration of in vehicle engine crankshafts,this paper presents a method to identify the axial vibration excitation source of crankshafts for high speed diesel engines based on an auto-regressive and moving average（ARMA） model.Through determining initial moving average variables and measuring axial /bending/torsional vibrations of a crankshaft at the free-end of a 4-cylinder diesel engine,autoregressive spectrum analysis is applied to the measured vibration signal.The results show that the axial vibration of the crankshaft is mainly excited by coupled bending vibration at high speed.But at low speed,the axial vibration in some frequencies is excited primarily by torsional excitation.Through investigation of axial vibration source of engine crankshafts,calculation accuracy of vibration can be improved significantly.

Non-linear Torsional Vibration Characteristics of an Internal Combustion Engine Crankshaft Assembly

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.

Multi-body dynamic simulation research on the influence of piston engine crankshaft thrust bearings abrasion

Fault diagnosis studying on piston engine,crankshaft and gearbox is focused in this paper. The thrust bearing abrasion caused by axial movement of the crankshaft will affect the force of timing gears and oil pump gears,which will result in the fracture of gears,abnormal ignition,connecting rod cracking and collision of cylinder. Simulation based on CREO software is done to build three-dimensional models of crankshaft and gears of a WP10 diesel engine. The models are imported into ADAMS to complete multi-body dynamics simulations. The force analysis of gears in different kinds of axial movements is finished and variations rules of gear dynamic load is obtained. The presented results show that the crankshaft axial movement can cause overload and vibration on gears. Combined with the realistic case data,the fault feature through simulation research is validated and early warming parameters of gear fault are proposed.

The Applications of Measurement System for Crankshaft

This paper will introduce two types of multi-parameter co-measuring system and their application in the produc- tion.The first is crankshaft bent deformation measuring machine system.The second is the crankshaft pneumatic-electric measur- ing system.They have been used in final inspection procedure of automation line for crankshaft of automobie engine with good re- sults,the structure principle and soft clash technological process of the measurement system are presented.

Residual fatigue strength of 48MnV crankshaft based on safety factor

Residual fatigue strength of 48MnV crankshaft was studied and analyzed based on safety factor. Three different status crankshafts were used to the hop-up tests, which maintain new after 500h hop-up tests and after 1000h hop-up tests. Then, crankshafts were cut into unit cranks. The unit cranks were used to do endurance bending tests to get the residual fatigue strength. Finally, the results were analyzed based on safety factor. The results show that safety factor of crankshaft descends a little with the increase of the running time, and the residual safety factor is still much bigger than the endurable safety factor. Furthermore, after the crankshaft accomplishes a full life cycle, the residual fatigue strength of the crankshaft is enough to remanufacture and fulfill the next life cycle.

Fatigue life prediction of crankshaft repaired by twin arc spraying

This paper used Baumel Jr. and Seeger’s approach estimating fatigue parameters of 48MnV with 3Cr13 coatings. The fatigue life of the crankshaft of a six-cylinder engine, repaired by twin arc spraying 3cr13 deposits, is respectively calculated using different damage model such as S-N method, normal strain approaches, SWT-Bannantine approaches, shear strain approaches, and fatemi-Socie method based on dynamical simulation and FE analysis of crankshaft. The results indicate that the traditional calculation is conservative and that the life of crankshaft repaired by arc spraying is sufficient.

A Simplified Model for Vibration Analysis of Diesel Engine Crankshaft System

A spatial finite element model for vibration analysis of crankshaft system was proposed. The crankshaft body was simplified as spatial rigid frame by using beam elements based on Timoshenko beam theory. The main bearings in system were simplified as linear springs and dashpots. The natural frequencies of the crankshaft system of a four in-line cylinder engine were calculated and compared with the analytical and experimental values available in other publications. In order to simulate the motion of operating crankshaft system, the gas forces, rotating masses and reciprocating masses were considered, the crankshaft and main bearings were coupled in a rotating coordinate system, and a dynamic model for vibration analysis of crankshaft system was established. By applying the dynamic model, the influence of the mass and moment of inertia of front pulley on the behavior of crankshaft vibration was investigated.

Dynamic Characteristics of the Crankshaft System with Coupling Effect

The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional and axial vibration, the actuating force applied on the piston, the actuating torque and force applied on the propeller is included. The governing equations of the model denote a strong nonlinear and non autonomous system. By numeric simulation, the dynamic response of the system to initial displacement and initial speed, variable moment of inertia, the pressure applied on the piston by combustion gas, the torque and the axial force applied on the propeller by fluid is researched respectively. According to the research results, the variable moment of inertia and coupling effect between torsional and axial vibration are the fundamental reason for nonlinear vibration. Different actuating factors can not only result in different frequency components of the response, but make the same frequency component have different vibration amplitude. The dynamic behavior of the system is not influenced obviously by the actuating torque and force applied on the propeller. There is obvious difference in sensitivity of the dynamic response in the different direction to the same actuating factor.

Production of 48MnV-C non-heat treatment crankshaft steel by means of converter plus continuous casting and hot-rolling process

48MnV-C non-heat treatment crankshaft steel is specially used for making crankshafts of Cummings C engines.It mainly adopts the technology of V—N micro-alloying,at present,it has been successfully used in making crankshaft of heavy duty truck engines.BX STEEL made trial production by means of converter→secondary metallurgy(RH + LF)→rectangular slab caster→hot rolling process,and studied the T[O],T[N],[H]and non-metal inclusion in 48MnV - C steel under continuous casting process condition,the actual grain size and the slab quality.All the chemical compositions and test results met the needs of Cummings Crankshaft Steel Standard.In order to ensure the mechanical properties of the non-heat treatment steel,a certain amount of nitrogen is added to it,also a small amount of sulfur is added to improve the cutting property of the steel.This process route can make full use of the de-hydrogen function of RH,and during RH treatment,rough adjustment of alloy elements may be made while the adjustment of Nitride Manganese nitrogen pick up and adjusting Mn,as well as Ca treatment and S content adjustment may be done during LF treatment so as to ensure the requirement of high nitrogen,low hydrogen,low oxygen content in 48MnV-C steel.Magnetic marks are defects shown in magnetic powder testing after the steel was used to make finished crankshafts.The 48MnV - C non-heat treatment crankshaft steel produced by means of the above-mentioned process route has not only relatively high robust performance which meets the needs of truck crankshaft safety,but also high qualification rate and basically no "magnetic marks" are found after being made into finished crankshafts,which meets the crankshaft standard.Therefore,this steel has been widely used in domestic crankshaft industry.

Impact of Material on Crankshaft Torsional Vibrations

In this study, it shows how the main indicators of torsional vibrations of the crankshaft change when its materials change. In the study, the crankshaft of diesel engine with four cylinders in line was taken, in which the material is changing from steel to cast iron, due to the technological possibilities of production. For study of torsional vibration of crankshaft system, the construction of equivalent reduced scheme is carried. Reduced inertia moments of discs are determined for each crank of crankshaft, by receiving the impact of piston group and rod mass. Reduced rigidities of crank are determined by experimental method. The results show that the rigidity of crank for the same crankshaft varies up to 6%, while the change between crankshafts goes up 10%. At the end, frequency and vibration forms are calculated using Tole-Holxer method. From calculations, it results that the frequencies are 19% smaller, while the vibration forms varies slightly. In this case, the change of the materials leads to the first frequency in the area of engine rotations and it can worsen the level of torsional vibration, therefore, it should check the resonance areas and vibration amplitude.

Effect of Lightening Hole on Dynamic Characteristics and Fatigue Life of Diesel Engine Crankshaft

As the core components of diesel engine,the structure and dynamic characteristics of the crankshaft has a vital role on engine performance. To Process the lightening hole with properly size in a certain location can reduce the weight of the crankshaft so as to,improve the dynamic characteristics and the connecting rod load of the crankshaft. Using finite element method and using three-dimensional software to model,the structural static and dynamic analysis theory to are gotten the performance and fatigue life analysis of crankshaft which have lightening hole with appropriate size. In this paper,to select the lightening hole for 25 mm size to analyze and compare the results with no hole of crankshaft analysis data can get that lightening hole can improve the crankshaft strength and the fatigue life of some location of the crankshaft.

Mechanical properties of vanadium-alloyed austempered ductile iron for crankshaft applications

This study focused on the development of austempered ductile iron(ADI)with desirable combination of mechanical properties for crankshaft applications by the combined effect of vanadium(V)alloying and an optimized heat treatment process.The produced unalloyed GGG60,0.15%V-alloyed GGG60(V-15),and 0.30%V-alloyed GGG60 samples were subjected to austenitizing at 900℃for 1 h and subsequent austempering processes at 250,300,and 350℃for 15,30,60,90,and 180 min.As a result of these austempering processes,different bainitic structures were obtained,which led to the formation of diverse combinations of mechanical properties.The mechanical properties of the austempered samples were tested comprehensively,and the results were correlated with their microstructures and the stability of the retained austenite phases.From the microstructural observations,the V-alloyed samples exhibited a finer microstructure and a more acicular ferrite phase than unalloyed samples.The V addition delayed the coarsening of the acicular ferrite structures and considerably contributed to the improvement of the mechanical properties of GGG60.Moreover,the X-ray diffraction results revealed that the retained austenite volume and the carbon enrichment of austenite phases in ADI samples were remarkably affected by the addition of vanadium.The increase in volume fraction of retained austenite and its carbon content provided favorable ductility and toughness to V-15,as confirmed by the elongation and impact test results.Consequently,the dual-phase ausferrite microstructure of V-15 that was austempered at 300℃for 60 min exhibited high strength with substantial ductility and toughness for crankshaft applications.

基于改进YOLOv8曲轴表面缺陷检测算法

针对曲轴表面小目标缺陷检测难度大、缺陷背景复杂和检测速度慢等问题,提出一种改进曲轴表面缺陷检测的算法RB-YOLOv8。首先,用RepViT模块取代了传统的C2f模块,有助于减少网络的计算负担并加快其运行速度;接着,通过优化双向特征融合模块BiFPN及增加小目标检测层,改善小目标缺陷识别的能力;然后,利用BiFormer注意力机制强化模型的抗干扰能力和解决缺陷背景复杂的难题,提高检测准确率;最后,使用MPDIoU损失函数调整,从而进一步提升检测的精准度。实验结果表明,所提出的算法的检测精度可以达到98.4%,模型大小缩减为2.797 MB,同时使每秒帧数(FPS)达到了169 f/s,成功地实现了对曲轴表面的缺陷检测。

基于改进粒子群的曲轴件数控加工刀具轨迹自动优化方法

针对曲轴件加工质检合格率较低、加工过切量较大的问题,提出基于改进粒子群的曲轴件数控加工刀具轨迹自动优化方法。先以刀具轨迹长度最小为目标建立轨迹优化目标函数,设定相应的约束条件,再通过改进粒子群惯性权重参数更新方法及增加压缩因子,实现对粒子群算法的改进,最后利用改进粒子群对最优轨迹求解,自动优化基于改进粒子群的曲轴件数控加工刀具轨迹。实验证明,该方法可对曲轴件数控加工刀具轨迹进行优化,且其应用后曲轴件加工质检合格率得到有效提升,加工过切量得到有效控制,具有良好的优化效果。

大型往复式压缩机曲轴深度裂纹焊接修复

某企业一台大型往复式压缩机在检修时发现曲轴产生深度裂纹缺陷。对曲轴最危险截面进行强度校核,对曲轴材料焊接工艺进行抗裂性试验,对焊接方法进行比较与工艺分析,最终采用常温下手工氩弧焊的方法来恢复曲轴原有功能。

基于线激光的压缩机曲轴圆度和平面度测量

目前人工使用千分表测量空调压缩机曲轴圆度和平面度时存在易伤工件表面、效率低和不能精确评定等问题。针对上述问题,设计了一套基于线激光位移传感器的空调压缩机曲轴圆度和平面度非接触式测量系统。首先,通过测量标准量棒,提出一种系统误差的标定方法;其次,基于线激光采样数据,开发了一种曲轴横截面圆度测点的提取算法,并将系统误差用于测点补偿,实现曲轴圆度测量;接着根据曲轴平面测点间的斜率分离出轮廓线,通过均匀下采样方法获取精简点云数据并采用最小二乘法实现曲轴平面度测量;最后,基于上述方法开展了曲轴圆度和平面度的测量实验。实验结果表明:该测量系统的圆度测量精度<4μm,平面度测量精度<2μm,圆度重复度测量误差<0.8μm,平面度重复度测量误差<0.3μm,满足曲轴圆度和平面度快速准确的测量需求。

曲轴综合测量机几何误差建模及敏感性分析

为提高曲轴综合测量机测量精度,针对其几何误差元素多,逐一进行补偿工作量大、过程繁琐等问题,基于多体系统理论和齐次坐标变换建立曲轴综合测量机的几何误差模型,采用Sobol敏感性分析方法进行分析,识别出对测量精度影响较大的关键几何误差项。通过对曲轴综合测量机随动测板不同位置处的误差元素敏感性系数进行分析计算,从21项几何误差中识别出10项对曲轴综合测量机测量精度影响较大的关键项,为合理经济地提高曲轴综合测量机测量精度提供依据。

曲轴开裂原因

采用宏观观察、化学成分分析、力学性能测试、微观分析等方法对某开裂曲轴进行分析。结果表明:曲轴在服役时发生润滑不良,使其与铜合金轴瓦之间相互摩擦,铜合金在摩擦高温的影响下发生异种金属渗入现象,曲轴表面形成较多填充有铜合金的微裂纹,这些裂纹成为疲劳源,最终导致曲轴疲劳开裂。