Finite Element Analysis of Rail Vehicle Suspension Spring for Its Fatigue Life Improvement

Finite Element Analysis of Rail Vehicle Suspension Spring for Its Fatigue Life Improvement
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  Finite Element Analysis of Rail VehicleSuspension Spring for Its Fatigue LifeImprovement  M. A. Kumbhalkar, D. V. Bhope and A. V. Vanalkar 1 Introduction The paper represents a case study over an investigation for fatigue failure responseof primary inner suspension spring of a high-speed main line locomotive for goodshauling trains which has three motor on individual axle and is referred to as Co-Coframe assemblies, is main part of the locomotive. Total weight of the rail roadvehicle is supported by the bogie frames and provides a means for transmission of the tractive effort to the rails. To absorb and isolate the superstructure from theshocks is an important function of frame caused by variations in the trackbed andhence suspension system minimizes the transmission of these shocks to the loco-motive under frame [1].The helical spring is the simplest element which is found in many mechanicalsystems. It makes it conceivable to maintain a tension or a force in a suspensionsystem [2] of railway vehicle, to assimilate the shocks and to diminish the vibra-tions. Fatigue is the most well-known reason for failure in springs. Fatigue breakageby and large starts at the surface and the settled tensile stresses bring on additionaldevelopment of the created cracks and prompt premature failure of the springs. M. A. Kumbhalkar ( & )Department of Mechanical Engineering, JSPM Narhe Technical Campus,Pune, Maharashtra, Indiae-mail: manoj.kumbhalkar@rediffmail.comD. V. BhopeDepartment of Mechanical Engineering, Rajiv Gandhi College of Engineering,Research & Technology, Chandrapur, Maharashtra, Indiae-mail: dvbhope@rediffmail.comA. V. Vanalkar Department of Mechanical Engineering, KDK College of Engineering,Nagpur, Maharashtra, Indiae-mail: ©  Springer International Publishing AG, part of Springer Nature 2018K. Antony and J. P. Davim (eds.),  Advanced Manufacturing and Materials Science ,Lecture Notes on Multidisciplinary Industrial Engineering,  The helical suspension spring framework has a noteworthy signi fi cance on theoperation of rail road vehicle, considering the effect of curving and tracking [3].The suspension system of rail road vehicle has the main function to controlisolation and shock absorption between the bogie and frame [4]. The function of primary springs of middle axle of each frame is also to permit free movement inlateral direction. A primary suspension mounted between wheelbase and bogie withinclined damper at end axles and linkage to restrict lateral movement at middle axle.The middle axle has an assembly of concentric suspension spring of inner and outer opposite handed spring to acquire load without damper. This paper focuses onpremature fatigue failures of inner suspension spring due to dynamic effect. Thefailure region of middle axle primary inner suspension spring and arrangement for mounting on middle axle housing is shown in Fig. 1. 2 Fatigue Analysis The middle axle primary inner suspension spring is subjected to variable loads andhence the fatigue analysis approach is used to investigate the failure of the springusing  fi nite element method. A progression of forward and reverse loading por-trayed a fatigue; where plasticity is initiated in each cycle. The fatigue life of asuspension spring can be communicated as the number of loading cycles for theinitiation of crack and the number of cycles propagates that crack to failure [5].A computational model for fatigue examination of suspension spring has beenexhibited. A maximum and minimum load is often used for simulation of the cyclicloading in fatigue analyses on helical suspension spring [6].The actual crack starts at the cause which develops gradually over the fatiguezone, with a typical growth rate. The progression marks shows up which is becauseof the varieties in the load that brought about relating varieties in the crack growthrate. Eventually, the crack reaches the point where the remaining material getsoverstressed, and the overload zone results. The progression marks indicate how thecrack has developed and are just present in fractures where there have been gen-erous varieties in the component stress as the crack develops over the piece [7]. The Fig. 1  Photographs of failed primary inner spring and arrangement of middle axle suspensionspring near middle wheel40 M. A. Kumbhalkar et al.  schematic representation of fatigue fracture surface showing crack srcin and itsprogression is shown in Fig. 2.This section discusses the  fi nite element analysis of helical suspension spring of rail vehicle using a numerical tool ANSYS to  fi nd its fatigue life. Analytically, theforces acting on suspension springs and shear stresses induced are calculated for static condition and continued to fatigue analysis for displacement variation of 6 – 8 mm as per the observation of rubbing marks over dampers. Fatigue analysis hasbeen carried in ANSYS considering the load ratio, ultimate and endurance shear limit for chrome vanadium material.It is observed that the spring gets de fl ected at some instances as observed fromrubbing marks over the end axle dampers as shown in Fig. 3. Because of this theadditional force acts over the spring. But the band of polished surface on thedamper indicates that, there is the displacement of the spring in the range of 6 – 8 mm which may cause the fatigue failure of spring. The maximum and minimumload corresponding to the additional de fl ection of 6 – 8 mm is given Table 1.The basic S-N curve for fatigue analysis of suspension spring can be plotted for fully-reversed stress cycle for its alternating stress values. The typical loadingcondition with mean stress is shown in Fig. 4.The accompanying conditions are utilized to characterize a stress cycle with bothalternating and mean stress. The stress range is the mathematical contrast betweenthe maximum and minimum shear stress in a cycle: The shear stress amplitude isone-half of the stress extend: The mean shear stress is the arithmetical mean of themaximum and minimum shear stress in the cycle [8]: D s ¼ s max  s min  s a  ¼ D s 2 ¼ s max  s min 2 s m  ¼ s max þ s min 2 (a) Fatigue fracture with benchmark(b) Fatigue crack initiation and propagation Fig. 2  Schematic representation of fatigue fracture surfaceFinite Element Analysis of Rail Vehicle Suspension  …  41  Fig. 3  Rubbing and polishing marks over end axle damper  Table 1  Parameters for fatigue analysis of inner suspension springParticulars Symbol andunit Inner suspension springFor 6 mmde fl ectionFor 7 mmde fl ectionFor 8 mmde fl ectionMinimumde fl ection d min  (mm) 64.6 64.6 64.6Minimum load F min  (N) 9351.46 9351.46 9351.46Maximumde fl ection d max  (mm) 70.6 71.6 72.6Maximum load F max  (N) 10,219.62 10,364.37 10,509.13Mean load F m   (N) 9784.54 9857.92 9930.29Alternating load F a   (N) 434.08 506.46 578.83Wahl ’ s factor K 1.29 1.29 1.29Mean shear stress  s m   (N/mm 2 ) 626.46 630.77 634.72Variable shear stress s a   (N/mm 2 ) 27.79 32.42 37.06Stress ratio R 0.92 0.90 0.89Equivalent shear stress s eq  (N/mm 2 ) 688.07 702.66 717.8942 M. A. Kumbhalkar et al.  Two proportions that are regularly characterized for the portrayal of mean shear stress are the shear stress ratio R and the amplitude ratio A [8]:  R ¼ s min s max  A ¼ s a s m ¼ 1   R 1 þ  R This method de fi ne various curves to connect the endurance limit on the alter-nating stress axis to the yield shear strength, S ys , ultimate shear strength S us , or truefracture shear stress S fs  on the mean stress axis. A Soderberg criteria given below ismainly used for ductile material for S-N curve [3, 8]. FS  : s m S   ys þ FS  : K   f   : s a S  es ¼ 1where K fs  is fatigue shear stress concentration factor and  s eq  is equivalent toallowable stress S ys  /FS [8]. S   ys : K   f   : s a S  es þ s m  ¼ S   ys FS S   ys : K   f   : s a S  es þ s m  ¼ s eq 3 Finite Element Analysis for Fatigue Life of SuspensionSpring FE analysis of inner suspension spring has been carried out to  fi nd its fatigue life inANSYS 12.0 with the help of 3-D, 10-node SOLID 187 element [9, 10]. A stress ratio is given as input for fatigue analysis in ANSYS and it is given in Table 1.Stress-Life (S-N) curve with low cycle and high cycle fatigue life has to be pro-vided in material property of spring material. Hence S-N curve has been plotted for  Fig. 4  Typical cyclic loading parametersFinite Element Analysis of Rail Vehicle Suspension  …  43
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