基于ANSYS的6110曲轴疲劳分析

曲轴主要承受交变的弯曲-扭转载荷和一定的冲击载荷,轴颈表面还受到磨损。主要失效方式是疲劳断裂和轴颈表面的严重磨损。因此对轴颈进行中频感应淬火强化处理,主要使圆角处产生残余压应力和淬硬层,来提高曲轴的疲劳强度和抗磨损能力。由于在线测量温度、组织、应力在当前技术条件下是不可能的,有必要借助计算机模拟技术的强大计算功能,进一步了解、改进淬火工艺,满足提高曲轴疲劳强度和耐磨性的要求。本文利用软件ANSYS建立6110钢曲轴的二维轴对称模型,利用其热固耦合功能对连杆轴颈感应淬火过程进行了模拟,计算了淬硬层厚度和淬火后的残余应力分布。然后利用ANSYS疲劳分析模块对淬火前和淬火后曲轴进行疲劳分析,计算结果表明：淬火使圆角产生的残余压应力确实显著提高了曲轴的疲劳强度,模拟可信。     

中频淬火曲轴磨削裂纹产生原因及对策

磨削表面烧伤是磨削过程的瞬时高温使工件金属表面产生一层很薄的氧化层,对于已淬硬件来说可能会造成表面磨削回火软化,严重的甚至产生裂纹,影响工件的耐磨性和使用寿命。以某型号发动机的球墨铸铁曲轴中频淬火后在磨削加工时轴颈表面产生裂纹现象为实例,分析轴颈表面由于磨削烧伤而产生裂纹的原因,并从热处理工艺及磨削工艺两个方面介绍了消除磨削裂纹的方法。     

汽车三柱槽壳断裂失效分析

为分析某车型的三柱槽壳在开发耐久试验过程中出现断裂失效的原因,对断裂失效件宏观断口的宏观形貌和微观形貌、金相组织、能谱元素、化学成分、硬度等进行了检测。结果表明:该断裂失效存在明显的疲劳断裂特征,可通过增加原材料的调质处理,芯部采用回火索氏体以保证柱杆的强韧性;样件表面热处理后,出现淬硬深度不均匀的现象,淬硬深度薄的区域容易出现应力集中,加剧了断裂,可通过改进热处理的淬火工艺、增加过渡圆弧半径等措施,减少应力集中。     

焊前和焊后淬回火对SDDVA钢堆焊层回火稳定性和抗热熔损性能的影响

对SDDVA钢进行钨极氩弧堆焊和淬回火处理,研究了焊前和焊后淬回火工艺对堆焊层回火稳定性和抗热熔损性能的影响。结果表明：2种工艺下堆焊层的组织均为回火马氏体,但是焊后淬回火工艺下堆焊层中析出了更多弥散分布的碳化物且组织更细小,马氏体组织更稳定;焊后淬回火工艺下堆焊层经600℃×48 h回火后的硬度降低幅度仅为10.2%,小于焊前淬回火工艺的30.4%;在700℃铝液熔损试验中,焊前淬回火工艺下堆焊层的熔损质量损失大于焊后淬回火工艺,界面层的厚度较大,堆焊层与铝液的反应更加剧烈;焊后淬回火工艺下堆焊层具有更优异的回火稳定性和抗热熔损性能。     

内燃机曲轴扭转疲劳强度试验研究与分析

通过对内燃机曲轴进行扭转疲劳试验研究,分析了影响曲轴扭转疲劳强度的因素以及导致曲轴扭转失效的原因,并提出了相应的改进措施。分析指出,随内燃机爆发压力的提高,曲轴所承受的扭矩会相应增大,由此导致的曲轴扭转疲劳失效不断增加。曲轴扭转失效位置主要在连杆颈油孔、曲柄臂和连杆颈下止点,失效原因涉及结构设计、原材料、机加工、热处理等多个因素。连杆颈油孔是扭转疲劳失效最常见部位,裂纹源一般在油孔内壁距轴颈表面约8～10 mm位置,轴颈表面感应淬火对扭转疲劳强度影响较大,表面感应淬火使曲轴的扭转疲劳强度降低约30%,油孔内壁抛磨可使轴颈表面淬火曲轴的扭转疲劳强度提高25%以上。     

淬火温度和回火工艺对4Cr5Mo2V钢高温耐磨性能的影响

将4Cr5Mo2V钢在1 000～1 090℃下淬火,并通过不同温度2次回火处理将相同淬火温度下试验钢的回火硬度分别调整至55,52 HRC,研究了淬火温度和回火工艺对显微组织、冲击韧性和高温(350℃)耐磨性能的影响。结果表明：回火硬度相同时,淬火温度过高或过低均会降低试验钢的韧性而加剧磨损表面材料剥落,从而降低耐磨性能;相同回火硬度下,1 030℃淬火条件下试验钢的韧性和高温耐磨性能最好,1 090℃淬火条件下最差;淬火温度相同时,较低温度回火试验钢因具有较高回火硬度,能够起到支撑表面氧化层的作用,其耐磨性能比较高温度回火时好;4Cr5Mo2V钢的推荐热处理工艺为1 030℃×30 min油淬+560℃×2 h×2次回火。     

聚丙烯挤出机螺杆轴断裂失效分析

某聚丙烯挤出机在运行中发生螺杆轴断裂,采用断口宏观分析、扫描电镜观察、化学成分分析、显微组织检验、力学性能测试等方法对断裂轴开展失效分析。结果表明:螺杆轴的断裂为扭转疲劳断裂,裂纹起源于花键根部;螺杆轴的疲劳强度低、花键槽根部应力集中、材料内部微孔聚集、材料组织不均匀等原因共同导致螺杆轴发生早期疲劳断裂;建议采取改进热处理工艺、提高安装精度、检查表面缺陷等措施。     

大型洗衣机电机转子皮带轮轴失效分析

本文系对某洗涤机械厂大型洗衣机皮带轮轴的失效分析总结。大量征象表明皮带轮轴断裂原因为辅助轴安装偏心,出现弯曲应力,轴颈截面突变,表面刀痕形成应力集中,_钢材存在冶金缺陷以及未经调质处理,疲劳强度低等因素所造成的应力疲劳断裂,改进后成批生产使用至令已五年半,尚未发现皮带轮轴断裂。     

基于ANSYS的6110曲轴疲劳分析

对曲轴轴颈进行中频感应淬火,使圆角处产生残余压应力和淬硬层,以提高曲轴的疲劳强度和抗磨损能力.因在线测量温度、组织、应力在当前技术条件下是不可能的,需借助计算机模拟技术来了解、改进淬火工艺,满足提高曲轴疲劳强度和耐磨性的要求.本文利用ANSYS软件对连杆轴颈感应淬火过程进行模拟.计算了淬硬层厚度和淬火后的残余应力分布,并利用ANSYS疲劳分析模块对淬火前和淬火后曲轴进行疲劳分析,结果可信.     

基于ANSYS的611O曲轴疲劳分析

对曲轴轴颈进行中频感应淬火，使圆角处产生残余压应力和淬硬层，以提高曲轴的疲劳强度和抗磨损能力。因在线测量温度、组织、应力在当前技术条件下是不可能的，需借助计算机模拟技术来了解、改进淬火工艺，满足提高曲轴疲劳强度和耐磨性的要求。本文利用ANSYS软件对连杆轴颈感应淬火过程进行模拟，计算了淬硬层厚度和淬火后的残余应力分布，并利用ANSYS疲劳分析模块对淬火前和淬火后曲轴进行疲劳分析，结果可信。     

Misaligned journal effects in liquid hydrostatic non-recessed journal bearings

The performance characteristics of a capillary-compensated hole-entry hybrid misaligned journal bearing have been studied theoretically. The journal of the bearing is allowed to tilt on an axial plane containing the load vector and on a plane perpendicular to an axial plane containing the load vector. The journal misalignment has been accounted for by defining a pair of misalignment parameters σ and δ. The finite element method has been used to solve Reynold's equation governing the lubricant flow field in the clearance space of the journal bearing. Static and dynamic performance characteristics are presented for the different representative values of the journal misalignment parameters for both hydrostatic and hybrid modes of operation of the bearing. The bearing performance characteristics are also compared for the two hole-entry bearing configurations so as to facilitate the selection of a suitable bearing configuration by the designer. The study suggests that the journal misalignment significantly affects the performance of the hole-entry journal bearing, and for a more accurate prediction of the bearing performance it must be considered in the analysis.     

Experimental study of journal bearings with undulating journal surface

A journal bearing test rig was designed and constructed to test the behaviour of journals with wavy surfaces, the circumferential undulations being varied both in amplitude and in number. Results show that wavy journal surfaces may well enhance the load carrying capacity of a bearing. Moreover, surface undulations are shown to move the journal centre locus closer to the load line, ie cause a lower attitude angle. These effects are found to be more pronounced with larger wave amplitudes, and with higher numbers of waves around the journal circumference. In general, friction is found to be reduced with increase in surface wave amplitude.Good agreement is shown to exist between test results and a computer aided analysis conducted by the authors to predict wavy journals performance¹. It has been established that a wavy journal surface may, under certain conditions, display higher load capacity, lower friction and permit safer running of journal than bearings with perfectly smooth surfaces.     

Performance characteristics of hydrostatic journal bearings with journal rotation by a finite element method

Theoretical studies have been made of a capillary-compensated hydrostatic oil journal bearing supporting a rotating spindle, using a finite element method. Performance data are developed for a four-pocket bearing of $\text{L}\text{D}\text{= 1.0}$. Stiffness and load capacity curves for two significant directions of the line of centres are given for various design parameters and eccentricity ratios. The effects of rotation and the feeding system on the stiffness, load capacity, flow and attitude angle are discussed.     

The effects of journal lobing on the performance of a hydrodynamic plain journal bearing

Accurately ground journals nominally of 44.25 mm diameter and 63.5 mm wide were produced. One was cylindrical and the others had three, four, five, six, nine or twelve equispaced lobes, 0.025 mm high, on their peripheries. Each journal was fitted into a cylindrical lead-bronze bearing liner with a radial working clearance of 0.05 mm and operated at speeds of up to 1000 rev min^?1 and at bearing loads of up to 10 kN whilst the oil pressure was maintained at or just above atmospheric pressure.The test results indicated that when a comparison is made between the lobed journals and the cylindrical journal (1) there are no significant differences in the load-carrying capacity of the bearing and (2) in the higher portion of the loading range the boundary lubrication conditions are improved when using three- or four-lobed journals whilst the presence of lobes on the other journals produces only a slightly adverse effect,It was concluded that the effect of lobing, which often occurs accidentally during the manufacture of plain cylindrical journals, is not detrimental to the performance of the bearing when operated within the range of speeds and loads used.     

Tensile stress in journal bearings

The precise pressure distribution in the range of negative pressure of journal bearings was measured dynamically by a semiconductor pressure transducer fitted in the journal. Characteristics of the pressure distribution in the range of negative pressure were investigated and tensile stress was detected. A special apparatus was constructed to investigate the characteristics of tensile stress generation in lubricating oils. Currently available mineral oils of low viscosity, within a short standing time, were in a condition under which tensile stress could be generated.     

Experimental investigation of hybrid journal bearings

Experimental pressure distribution measurements in hybrid journal bearings are presented and the influence of inertia forces in the recess outlets and pressure generation in the pockets for high rotating speeds are shown. These results are in good agreement with the theoretical results given by an established model.     

Comparative tribological evaluation of journal bearings

Performance of sliding bearings with reeled bimetallic bushes of three different bronzes was compared with the performance of solid bushes of aluminium alloy with a view to replacing aluminium bushes in gear pumps by reeled bimetallics. a set of tribological selection criteria was proposed and comparative investigations were carried out.     

Lubrication of finite porous journal bearings

An analytical solution is attempted for a finite porous bearing, press-fitted into the housing and working with a full film of lubricant. The pressure distribution is determined by a simultaneous solution of Reynolds equation for the film and the Laplace equation for the bearing material while maintaining the continuity of pressure at the film-bearing interface.The pressure in the bearing material and film are taken in series form so that all the boundary conditions are satisfied. Using a suitably truncated series, the modified Reynolds equation is then solved by the Galerkin method. It is shown that two dimensionless parameters—(1) the permeability parameter and (2) the thickness to breadth ratio ($\text{H}\text{b}$)—adequately describe the operation of these bearings. Numerical calculations for all the bearing characteristics were carried out by digital computer. The results are tabulated so that designers can interpolate values required.The results indicate the progressive reduction in Sommerfeld number with permeability parameter; the dimensionless coefficient of friction and the attitude angle progressively increase with permeability parameter.     

Oil whip-induced wear in journal bearings

This paper investigates the effect of oil whirl and oil whip in fluid film radial bearings due to possible metallic contact. The degree of metallic contact and thereby wear and tear between rotating shafts and bearing bushes is assessed by measuring electric currents through the oil film. The current as well as the voltage varied in accordance with the contact ratio between the shaft and bush in the fluid film radial bearing. The gauge signal thus indicates the degree of metallic contact based on the thickness of the oil film in the load zone. Some experimental results are provided to illustrate that at low normalised loads involving oil whirl and oil whip, no electric current is detected, while high levels of electric current are registered at high load levels when no oil whirl or oil whip occurred. It is therefore concluded that at low loads, oil whirl and oil whip have little influence on wear and tear in a journal bearing.     

Acoustical properties of hydrodynamic journal bearings

Results of theoretical investigations on acoustical properties of hydrodynamic journal bearings are presented. Nonlinear analysis including rotor imbalance is performed for a rotor-bearing system in order to obtain acoustical properties of the bearing. Furthermore, a cavitation algorithm, implementing the Jakobsson–Floberg–Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties are investigated through frequency analysis of pressure fluctuation calculated from the nonlinear analysis. Results show that the acoustical frequency spectra of the fluid film are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that super-harmonics are predominant at the neighborhood of the fluid film reformation and rupture regions.