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Failure Analysis of Primary Suspension Spring of Rail Road Vehicle

Failure Analysis of Primary Suspension Spring of Rail Road Vehicle
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           1 3  Journal of Failure Analysis andPrevention  ISSN 1547-7029Volume 18Number 6 J Fail. Anal. and Preven. (2018)18:1447-1460DOI 10.1007/s11668-018-0542-1 Failure Analysis of Primary SuspensionSpring of Rail Road Vehicle M. A. Kumbhalkar, D. V. Bhope,A. V. Vanalkar & P. P. Chaoji           1 3 Your article is protected by copyright andall rights are held exclusively by ASMInternational. This e-offprint is for personaluse only and shall not be self-archived inelectronic repositories. If you wish to self-archive your article, please use the acceptedmanuscript version for posting on your ownwebsite. You may further deposit the acceptedmanuscript version in any repository,provided it is only made publicly available 12months after official publication or later andprovided acknowledgement is given to thesrcinal source of publication and a link isinserted to the published article on Springer'swebsite. The link must be accompanied bythe following text: "The final publication isavailable at”.  TECHNICAL ARTICLE—PEER-REVIEWED Failure Analysis of Primary Suspension Spring of Rail RoadVehicle M. A. Kumbhalkar  . D. V. Bhope  . A. V. Vanalkar  . P. P. Chaoji Submitted: 8 April 2018/in revised form: 26 August 2018/Published online: 1 October 2018   ASM International 2018 Abstract  WAG-9-type electric rail vehicle, of IndianRailways’ fleet used for goods train hauling and maintainedat Ajani, Nagpur Electric Loco Shed of central railway, hasa history of frequent failure of middle axle primary innersuspension spring. The study of failures revealed that thisspecific component fails at a very high rate. The failureinvestigation starts the experimental spectroscopy analysisto find chemical composition for different failed specimensof springs, and it is observed that all parameters are withinthe recommended range. Also the stiffness of primarymiddle axle and end axle suspension springs has beenchecked on spring testing machine to measure deflection of spring, and it is as per recommended values. Further staticstress analysis is carried out using analytical and finiteelement analysis for various phases of operation of railvehicle like straight track, curved track and also for tractiveeffort. The static stress analysis has not revealed the causeof failure, and hence the dynamic analysis is performed.For dynamic analysis, dynamic model of suspension sys-tem is considered and analyzed using analytical method,finite element method and using MATLAB Simulink model. The vibration response of actual suspension systemis also measured using FFT analyzer. It has been seen thatthe frequency of excitation and the natural frequency of thesystem are very close to each other which has resulted intosuspension vibration amplitude of 6–8 mm. Fatigue anal-ysis is carried out using finite element method toinvestigate the effect of dynamic loading on the failures of suspension spring. This analysis revealed that the middleaxle inner suspension spring has finite life and due to whichspring failure occurs earlier. Keywords  Indian Railway    Primary suspension spring   Vibration    Fatigue analysis    Spectroscopy analysis Introduction A rail road vehicle includes bogies, frame, suspensionelements, bushings, bearings, as well as other components.The bogies, such as the one shown in Fig. 1, also representcomplex systems that include frames and wheel sets thatcan have independent motions. The wheel sets, which canrotate freely about their own axes, are connected to theframe using primary suspensions, while the frame is con-nected to the car body using the secondary suspensions,safety chain and secondary dampers as shown in Fig. 1.The forces of dynamic interaction between the wheels andthe rails significantly influence the dynamics and stabilityof railroad vehicles due to friction between the rotatingwheels and the rails during motion. Clearly, a railroadvehicle system consists of a large number of interconnected M. A. Kumbhalkar ( & )Department of Mechanical Engineering, JSPM Narhe TechnicalCampus, Pune, Maharashtra, Indiae-mail: manoj.kumbhalkar@rediffmail.comD. V. BhopeDepartment of Mechanical Engineering, Rajiv Gandhi Collegeof Engineering, Research and Technology, Chandrapur,Maharashtra, Indiae-mail: dvbhope@rediffmail.comA. V. VanalkarDepartment of Mechanical Engineering, KDK College of Engineering, Nagpur, Maharashtra, Indiae-mail: P. ChaojiElectric Locomotive Workshop, Indian Railway, Bhusawal,Maharashtra, India  1 3 J Fail. Anal. and Preven. (2018) 18:1447–1460  components that experiences dependent/independentmotion. These components are connected by force ele-ments such as springs, dampers, and bushings as well as joints that impose restrictions on the motion of the system[1].The axle box is attached to each of the axle on which allthe primary springs are mounted. Each axle box has thesame space to mount the primary inner and outer spring,since middle axle contains both the spring assemblies. Theouter diameter of the end axle spring is larger, and theheight is lower than the middle axle outer spring inuncompressed state. The inner spring is mounted only inthe middle axle wheel set which has the compositeassembly of inner and outer spring. The free height of middle axle outer spring is 20 mm larger than the end axlespring and also having difference of 9 mm in theirrespective outer diameters. The free height of middle axleprimary inner spring is 2 mm lesser than the free height of outer spring. It means that the total load of loco first acts onmiddle axle outer spring and then it acts over middle axleinner spring and after that it is distributed over the end axlesprings. The technical specifications of suspension springsets are given in Table 1.The problem identified in the suspension spring of WAG-9 locomotive is discussed as follows: •  The WAG-9 locomotive undergoes the minor mainte-nance with interval of 45 days, intermediatemaintenance with interval of 90 days and majormaintenance with the interval of 18 months or approx-imately 1,50,000 km whichever occurs earlier.Normally overall of complete suspension system comesunder major maintenance. •  It is reported by Electric Loco Shed, Ajni, Nagpur thatdue to the failure of middle axle primary innersuspension springs, WAG-9 locomotive is called back  Fig. 1  Primary and secondaryspring set assembly (Courtesy:Indian Railway) Table 1  Technical specifications of spring set (Courtesy: Indian Railway)Particulars UnitPrimary suspensionMiddle axle outer spring Middle axle inner spring End axle springFree length ( l f  ) mm 258.6 252.4 238.8Outer diameter (  D o ) mm 212 104 221Inner diameter (  D i ) mm 149 71 149Mean diameter (  D m ) mm 180.5 87.5 185Coil diameter ( d  ) mm 31.5 16.5 36No. of active coil ( n )  …  3.5 7.5 3Total no. of coil  …  5.0 9.0 4.5Pitch mm 64.65 31.5 68.22Helix angle Degree 8.15 9.10 8.062Modulus of rigidity ( G ) N/mm 2 78,500 78,500 78,500Stiffness ( k  ) N/mm 470 144 868Maximum tensile strength ( r u ) N/mm 2 1720 1720 1720Yield shear strength ( r  y ) N/mm 2 878 878 8781448 J Fail. Anal. and Preven. (2018) 18:1447–1460  1 3  to the loco shed within 90 days and it undergoes theunscheduled maintenance requiring the span of mini-mum 3 days, though only the middle axle primary innersuspension spring has failed. This has increased thedown time of WAG-9 locomotive. •  Hence based on the problem identified, the objective of this research work is to investigate the cause of frequentfailures of the middle axle primary inner suspensionspring and to suggest the necessary modifications toavoid their failures. It is also proposed to receive thefeedback from Electric Loco Shed after implementationof suggested modifications. Experimental Spectroscopic Analysis of SpringMaterial In the initial phase of investigation, it is felt necessary toensure the chemical composition of the failed springs of GBD make in accordance with the recommended chemicalcomposition of spring material [2]. As per the data pro-vided by loco shed, the spring material is chromiumvanadium (50CrV4) having the chemical composition asgiven in Table 2. An effort is made to determine thechemical composition of failed spring using spectrometerof make WAS, model Foundrymen to ensure that the failedsprings are having recommended chemical composition ornot.Total five failed spring specimens of different WAG-9locomotive are used for experimentation which has beenfailed in the gap of some instances. The surface of speci-mens is polished using emery paper of grade 80 and placedon flat base of spectrometer. The emitted ray from spec-trometer sparks on spring specimen, and it has provided theresults in the form of chemical composition in percentageas shown in Table 2. From the chemical composition of allspecimens revealed by the spectrometer, it is seen that thechemical composition of failed springs is well within therecommended range. This investigation revealed that thesprings are not failed due to improper material composi-tion. Hence, the cause of failure is observed to be differentthan this and hence it is felt necessary to extend the failureanalysis using other techniques. Experimental Determination of Stiffness of SuspensionSpring The recommended stiffness of suspension springs, i.e.,middle axle outer spring, middle axle inner spring and endaxle is given in Table 1 as 470, 144 and 860 N/mm,respectively. It is felt necessary to determine the stiffnessof all the suspension spring experimentally [3]. A springtesting machine of ENKAY make is used to determine thestiffness of GBD make springs. The load is varied from 100kgf (981 N) to 600 kgf (5886 N), and the deflection of spring is determined. This analysis is carried out on each of the five middle axle inner springs, middle axle outer springand end axle spring. The average deformations and averagestiffness as per loading are given in Table 2. The experi-mental setup is shown in Fig. 2. The average stiffness of middle axle inner spring, middle axle outer spring and endaxle spring is found out to be 145, 475, 870 N/mm which isin close agreement with the recommended stiffnesses of respective springs. This analysis has ensured that thesprings used in the suspension system are having the rec-ommended stiffnesses. This investigation ensured that the Table 2  spectrometer readings for failed middle axle innersuspension springLoco no. 31097 31087 31068 31072 31105C (0.47–0.55) 0.47 0.475 0.46 0.52 0.45Si (0.15–0.40) 0.24 0.15 0.20 0.35 0.18Mn (0.7–1.10) 0.90 0.74 0.81 0.93 0.82P (0.035 max.) 0.024 0.023 0.025 0.034 0.034S (0.019–0.035) 0.019 0.020 0.023 0.035 0.031Cr (0.9–1.2) 1.07 1.09 1.03 0.91 0.97V (0.1–0.2) 0.103 0.12 0.14 0.101 0.13 Fig. 2  Testing deflection of spring on spring testing machineJ Fail. Anal. and Preven. (2018) 18:1447–1460 1449  1 3
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