a r t i c l e i n f o

Article history:Received 27 July 2012Received in revised form 5 November 2012Accepted 16 November 2012Available online 5 December 2012

Keywords:CouplingLongitudinal train modeling

a b s t r a c t

In addition, in some cases these must allow a rotation movement around of its own axis. Another requirement imposed tothe couplings lies in its ability to cushion the shocks received by the wagons. Operational safety of the wagon couplings de-pends primarily on their ability to resist at the tensile and compression dynamic forces generated by the propulsion or brak-ing of the train. The increase in tonnage and velocity simultaneously with changing the forces that acts on the couplings leadto a reduction of durability of wagon couplings due to the failure of some components [18]. On the other hand, the high

1350-6307/$ - see front matter 2012 Elsevier Ltd. All rights reserved.

Corresponding author.E-mail address: anghelcernescu@yahoo.com (A. Cernescu).

Engineering Failure Analysis 29 (2013) 93107

Contents lists available at SciVerse ScienceDirect

Engineering Failure Analysishttp://dx.doi.org/10.1016/j.engfailanal.2012.11.0091. Introduction

Railways wagons are some of the most important means for passengers and cargo transporting. The couplings bind therailway wagons together to form an entity named the train. In the longitudinal movement of the trains, the couplings havean important role in connecting adjacent wagons and the locomotive, while allowing the transmission of the locomotivetraction force on the axial direction. Besides the above condition the couplings must allow relative movements betweenwagons both in the vertical direction, produced by the each wagon suspensions and horizontally determined by the raceway.FEM and BEM analysisStress intensity factorsFatigue crack growth rateThe operation of passenger trains in different continents is still differentiated by differentwagon connections systems. The predominant wagon connection in North America andAustralia is the autocoupler system. The system of draw hooks and buffers is now rare.In Europe, draw hook and buffer systems are still in wide use. In particular, the majorityof passenger trains in Romania have wagons connected by draw hook and buffer systems.This paper presents an unusual situation for analysis of a damaged component of drawhook system and where has been lost the basic information about the causes of failure.Due to the lack of information, the analysis has a high degree of assumptions, being basedon failure scenarios. The broken component is a link plate made of forged steel. After aninitial examination of the fracture surface, was observed the existence of a structural defectin the material from which was initiated a fatigue crack. The analysis involves an experi-mental evaluation of the mechanical properties of the failed component material, followedby the modeling of the behavior of connection system according to the position where ismounted on the train. Based on the mode of fatigue crack propagation, correlated withthe loading level of the connection system, different scenarios have been made aboutthe time of propagation. Because important information about the failure causes was lost,the analysis was performed taking into account almost all factors that could inuence thefatigue crack propagation.This analysis came in completing the expertise done by specialists in Trafc Safety on the

Railways. 2012 Elsevier Ltd. All rights reserved.The analysis of a damaged component from the connection systemof the wagons

Anghel Cernescu , I. Dumitru, N. Faur, N. Branzei, R. BogdanMechanics and Strength of Materials Department, Politehnica University of Timisoara, Romania

journal homepage: www.elsevier .com/locate /engfai lanal

density of the micro-defects in the materials structure of the coupling systems components and poor quality of the surfaces,especially in critical areas, are also causes of fatigue damage of the coupling systems [5].

This paper presents a failure analysis of a wagon coupling from a passenger train with nine wagons and hauled by a dieselelectric locomotive. The coupling failure was caused by the fracture of a link plate due to the initiation and propagation of afatigue crack. The presented study consists of an analysis of the fracture surface and the mechanical properties of the linkmaterial, followed by an analysis of the wagon coupling loadings during the movement and a FEM and BEM analysis ofthe failed component. However, the study was hampered by the neglecting of the fracture surface, which leads to itsoxidation.

2. The wagons coupling system with screw and draw hook Description

In most passenger trains from the CFR Park (Rumanian Railways National Company) are used couplings with screw anddraw hook, Fig. 1.

The coupling system with screw and draw hook consists of two links mounted on the traction hook, two threaded nuts, ascrew and shackle. All parts of the coupling are made of quality carbon steel in enhanced condition (normalized). Also, these

The fracture was determined by the initiation and propagation of a fatigue crack, Fig. 3.

94 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 9310734

Fig. 1. The coupling system with screw and draw hook: 1 the screw; 2 links; 3 shackle; 4 threaded nuts; 5 bolt.From the rst observations was established that the coupling was broken after about 5 years. Moreover, the coupling wasmounted on a wagon that in the period of 5 years has run about 1,354,150 km. Unfortunately there are no studies or doc-umentations that highlights the fatigue limit of this type of couplings. However, comparing the number of kilometers cov-ered by the wagon with the analysis performed by Cole and Sun [5] on the fatigue limit of couplings from the heavy haultrains was considered that the analyzed coupling failed before the operational use limit.

3. The evaluation of the mechanical properties of the link material

For the evaluation of the mechanical properties, material samples were taken from the remaining link and other threecouplings from the same lot with that was failed.

The experimental test results on the sampled material were compared with the mechanical properties of the materialspecied in the UIC 826 standard prescription, for the execution of the failed component (Table 1).

In Table 2 are given the results of chemical analysis performed on the sampled material, compared with the standard pre-scriptions. Tensile tests were performed on the sampled material, according to SR EN 100021, [10] and the results are givenin Table 3.

Considering that the coupling is subjected to dynamic loads during the train movement, it is necessary to determine thefracture impact energy of the material from which is made the broken component. In order, the resilience tests have been

12

5components are subjected to heat treatment of hardening and tempered to obtain the mechanical characteristics specied instandard prescription UIC 826 OR, [9], Table 1.

The components of the wagon coupling system are grouped into homogeneous lots composed of pieces from the sameproduction charge, to which has been applied the same heat treatment. Also, the couplings are grouped in lots of 200 pieces.All couplings from a lot are composed of components made from the same batch of the material.

The couplings are guaranteed for all defects imputable to manufacturing for a period of 2 years from the end of produc-tion (marked on parts).

During movement from Timisoara to Baia Mare, IR 1743 passenger train was stopped due to the failure of a coupling,Fig. 2. In this case, the failure not caused material damages, due to the dynamic breaking system of the wagons, but resultedin delayed trains on that route for an extended period.

The conclusion of the Railway Trafc Safety specialists was that the coupling failure was caused by the fracture of a link.

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 95Table 1The components of the coupling system according to UIC 826 OR standard.

The components Material The heat treatment The product standard Yield strength(MPa)

Ultimate tensilestrength (MPa)

ElongationA (%)performed on V-notch samples with cross-sectional dimensions of 10 10 mm, based on which was determined the Charpyimpact energy at the temperature of 24 C. The tests have been carried out according to SR EN ISO 1481, [11], Table 4.

After evaluation of the mechanical behavior of the sampled material it could make a rst observation on the failure anal-ysis of the coupling component. There is a difference between chemical composition and mechanical properties of the tested

The screw, 1 Fig. 1 41Cr4 Hardened and tempered SR EN 10083-1 560 800/950 1442CrMo4 650 900/1100 12

The link, 2 Fig. 1 41Cr4 Hardened and tempered SR EN 10083-1 560 800/950 14The shackle, 3 Fig. 1 42CrMo4 Hardened and tempered SR EN 10083-1 650 900/1100 12The threated nuts, 4 Fig. 1 42CrMo4 Hardened and tempered SR EN 10083-1 650 900/1100 12

41Cr4 Hardened and tempered SR EN 10083-1 560 800/950 14Bolt, 5 Fig. 1 41Cr4 Hardened and tempered SR EN 10083-1 560 800/950 14

42CrMo4 Hardened and tempered 650 900/1100 12

The broken link

Fig. 2. The failure of a wagon coupling from a passenger train.

Fatigue fracture surface

Unstable fracture surface

Fig. 3. The fracture surface of the link, due to the initiation and propagation of a fatigue crack.

Table 2The chemical composition of the sampled material.

Material C (%) Mn (%) Cr (%) S (%) P (%) Others (%)

The link material 0.286 0.596 0.118 0.0162 0.0701 Cu0.103 Fe98.3141Cr4 SR EN 10083-1/95 0.380.45 0.60.9 0.91.2 Max. 0.035 Max. 0.035 Si max. 0.4

Table 3The mechanical properties of the material.

Material Yield strength (MPa) Ultimate tensile strength (MPa) Elongation (%)

The link material 539.12 895.5 9.641Cr4 SR EN 10083 1/95 560 800/950 14

96 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107Table 4The charpy impact energy of the material, according to SR EN ISO 148-1.

Material Charpy impact energy, CV (J)material and the materials prescribed in UIC standards for the execution of couplings connection. The chemical compositionindicate a Low Carbon Steel AISI 1025 and probably due to the heat treatment and/or that the component is made by forg-ing, the mechanical properties are higher than the usual AISI 1025 steel, cold drawn high temperature [12,13].

T = 24 CThe link material 61

Fig. 4. The fracture surface of the damaged component: (a) the striations which indicates the area damaged by fatigue crack propagation; (b) striations onthe failed surface 5 magnications.

4. The analysis of the fracture surface

The analysis of the fracture surface was difcult due to its oxidation and loss of some information about the fatigue crackpropagation. However, the fracture surface was carefully cleaned and examined with a Hirox optical microscope.

After initial examination, some striations were observed indicating the area from which the fatigue crack was initiated,Fig. 4a and b. Based on microscope examination it was observed that the fatigue crack initiation was caused by the existenceof a structural defect in material, very close to the lateral edge of the section, Fig. 5. The initial defect that formed the crack ison the type of a void resulted from casting of material. Normally this would be detected on ultrasound control. The defectsize was about 0.65 mm. For determining the size was measured the defect diameter in the plane of fracture section, Fig. 5(d = 0.73 mm), and computed the area Ad = 0.422 mm2. The defect size is given by the square root of the area in the plane offracture section.

Total area of the section: At = 14 40 = 560 mm2 The surface fracture by fatigue: Ac = 560 [(22 + 18) 14]/2 = 280 mm2 The critical crack size: ac =

pAc = 16.733 mm

Analyzing the fracture surface at 200 times magnication, it was possible highlighting in detail the striations, thus estab-lishing the distance between them in different areas of the fatigue fracture, Fig. 6.

Based on micrographic analysis, the fracture surface was divided into three regions, Fig. 7, for each region was estimated asize limit and an average distance between striations, such as:

Region I the limit of crack size was about 7.976 mm and the average distance was 2 103 mm; Region II the limit of crack size was about 13.468 mm and the average distance was 6 103 mm; Region III the limit of crack size was about 16.733 mm and the average distance was 5 102 mm;

of a train can be described by a system of differential equations. For the purposes of setting up the equations, modeling, and

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 97simulation, it is usually assumed that there is no lateral or vertical movement of the wagons.

14

22

40

18

The initial defect

d

Fig. 5. The initial defect location and size of fracture section (d the defect diameter in the plane of fracture section).At the same time, based on this analysis was done an estimation of the fatigue crack propagation curve, Fig. 8.

5. The modeling of the wagons coupling system and longitudinal train dynamics

To determine de loading level of the coupling on the move was made a longitudinal modeling of the train after a modelproposed by Colin, [5,14].

The longitudinal behavior of trains is a function of train control inputs from the locomotive, train brake inputs, tracktopography, track curvature, rolling stock and bogie characteristics, and wagon connection characteristics. Also, this behavior

98 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107Foracterithe coFor thveloci

Th

wheregravitis theCi (i

Inthe mthe analyzed case, the longitudinal dynamic behavior of the train was made tacking into account the technical char-stics of the wagons and the locomotive Table 5, and respectively the movement diagram of the train on the route thatupling failure occurred, Fig. 10. In the movement diagram is represented the locomotive velocity variation over time.e analysis performed was considered that a loading cycle is equivalent to an acceleration of the locomotive, when thety increases from 0 to 60 km/h. Thus, on the diagram were counted about 200 of such accelerations.erefore, the equations are:

m1a1 C1m1 m2 k1x1 x2 Ft=db Fr1 Fg1m2a2 C1m2 m1 C2m2 m3 k1x2 x1 k2x2 x3 Fr2 Fg2

m10a10 C9m10 m9 k9x10 x9 Fr9 Fg9

8>>>>>:

1

Ft/db is the traction and dynamic braking force of the locomotive; Fr is the amount of resistant forces, [14]; Fg is theational force caused by the runway slope; k is the proportionality factor of the coupling system; mi (i = 1,2 . . .10)wagon weight; ai (i = 1,2 . . .10) is the wagon acceleration; mi (i = 1,2 . . .10) is the wagon velocity;

= 1,2 . . .10) is Damping constant.Fig. 9 is outlined the train with those nine wagons, being indicated the position of each wagon by a reference point atoment t = 0 s.

Fig. 6. Micrographic analysis of the fracture surface.

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 99Region I

Region II To solve the movement equations of the train, was needed to determine the proportionality constant of the coupling sys-tem, k.

The wagon coupling system with screw and hitch can take loading only at the traction phase, while at compression, re-sulted from the braking or decelerations, the loading is taken by the dampers mounted on the wagons.

The wagon couplings can be described by a resort type model, Fig. 11, in which the loading force of the coupling is a func-tion of the displacement, Dx, between two adjacent wagons:

Region III

Fig. 7. Dividing the surface fracture by fatigue in three regions.

Fig. 8. The fatigue crack propagation curve.

Table 5Technical characteristics of the train vehicles.

Technical characteristics The locomotive Wagon

Type of vehicle LDE 3000 HP Corail AVA-200The weight of vehicle 120 t 41 tThe weight per axle 20.5 t 16 tThe length of vehicles 24,500 mm 19,000 mmThe maximum starting force 350 kN The maximum continuous traction force 238 kN The maximum velocity 140 km/h 140 km/h

K2; C2

v1

Fr1 Fg1

Ft/b Fr2Fg2

m1m3 m2m9m10

9500

19000

29250 147750

167500 190000

24500

x1

750 x2

v2

Fig. 9. Schematization of the train with nine wagons (units: mm).

FcFt

FcFt

k1

k2

k3k3

k4

k4

k4

k4

k5 k5

k5 k5

1

3

2

45

Fig. 11. Rheological model of the wagon coupling connection: 1 the shackle; 2 the screw; 3 the link; 4 elastic element; 5 the dampers.

Fig. 10. The movement diagram of the train: at the moment t = 0 s, the locomotive speed is 0 km/h, after 60 s the speed increases to 30 km/h, at t = 120 s thelocomotive speed is 45 km/h and so on.

100 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107

whereIn

pling

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 101f Dx k Dx 2k is the proportionality factor for a perfect resort.

some cases k can have a nonlinear dependence of Dx. Some other authors take into account in the expression of cou-forces and the damping inuence, [5]:

f Dm C Dm 3

Fig. 12. The tensile test on a link of the coupling.

Fig. 13. The tensile tests on the screw nuts shackle assembly.

Fig. 14. The forcedeformation curves of tested components.

Fig. 15. Case I the coupling forces corresponding to acceleration from 0 to 60 km/h in 180 s.

Fig. 16. Case II the coupling forces corresponding to acceleration from 0 to 60 km/h in 240 s.

Fig. 17. The boundary conditions of the coupling.

102 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107

For traction:

D de1 de2 de3 4de1 k1F The deformation of the shacklede2 k2F The deformation of the screw

de3 k3 F2 The deformation of the link

kF k1F k2F k3 F2k k1 k2 k32

5

For determining the proportionality constant of the coupling, k, tensile tests were performed on a coupling from the samelot as that the link was failure. The tensile tests were performed on a testing machine of 1000 kN, model VEB Werkstoffprufmaschinen, Leipzig. Due to excessive length of the coupling, there have been performed tensile tests on the link, Fig. 12 andseparately on the screwnutsshackle assembly, Fig. 13.

On the each test performed was applied a traction force of up to 100 kN recording the corresponding elongations of thecomponents, Fig. 14.

The proportionality constant of the coupling was determined by the following relations:

k1 k2 DFDu 116;250 N=mm 6

DF

6. The

Acc

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 103Fig. 18. The normal stress distribution in the damaged component for the force of 350,000 N.eformations and a force of 850 kN without cracks or fracture.nent dnumerical analysis of the damaged component

ording to UIC 826 OR standard prescription the coupling must withstand to traction force of 350 kN without perma-k3 Du 62;500 N=mm 7

k k1 k2 k32 147;500 N=mm 8

Du the elongation of the componentsAfter were set up all parameters needed to solve the equations, were determined the coupling forces for two cases, when

the locomotive accelerates from 0 to 60 km/h, Figs. 15 and 16.

Considering this, a FEM analysis was performed to determine the stress and strain state of the damaged component forthe cases were the coupling would be loaded with 350,000 N forces but also with maximum values of the calculated forcesfor the rst ve couplings in the train.

For numerical analysis was made a geometrical model of the coupling, that was imported into ANSYS Workbench soft-ware version 11, [15]. The model was meshed in tetrahedral nite elements type Solid. Regarding the boundary conditions,was applied a cylindrical support on the bolt which does not allow axial and radial displacement, instead allow the rotationof the assembly. On the contact surface between shackle and hook was applied a pressure corresponding to the calculatedforces, Fig. 17.

In Figs. 1820 are given the normal stress and respectively strain distributions on cross section of the damagedcomponent.

The FEM analysis results show that both the stress and strain states are in the acceptable limits of strength in stiff-ness of the coupling link material, for the force of 350,000 N. At the same time, it can be seen that the area with max-imum concentration of the normal stress is the lateral edge of the cross section of the link, from where the crackinitiated, Fig. 20.

Fig. 19. The normal stress distribution in the damaged component for the force of 350,000 N.

104 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107Fig. 20. The normal stress distribution on cross section of the damaged component for the force of 350,000 N.

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 105Fig. 21. The maximum values of the normal stress on the cross sectional of the damaged component, for the rst ve couplings in the train.Alsspond

Basversiofatigureachi

Forfactor

Inrespecof the

whereIt s

couplio, in Fig. 21 are the maximum values of the normal stress on the cross sectional of the damaged component, corre-ing to the maximum values of the calculated forces in the case I for the rst ve couplings in the train.ed on the coupling forces, determined analytically in case I, was performed a BEM analysis, using Franc 3D softwaren 3.2, [16]. For this analysis was considered a semi-elliptical initial crack with size of 0.65 mm, in the place where thee crack initiated. For different values of the coupling forces, the initial crack size was extended over several steps untilng the unstable state, Figs. 22 and 23.each of extension step were determined the surface crack, the crack front length and respectively the stress intensitys on the crack front (KI, KII and KIII), [17].Fig. 24 is represented the equivalent stress intensity factor depending of the crack size, for the force of 350,000 N andtively 222,859 N. The second value considered represents the maximum calculated force, in Case I, for the coupling 9train.

Keq K2I K2II

K2III1 m

s9

m = 0.3 is Poissons ratiohould be noted that in all the performed simulations the force applied on the link is half of the force which load theng.

Fig. 22. The initial crack extension.

Fig. 23. The crack opening displacement corresponding to the unstable crack extension.

Fig. 24. The variation of the equivalent stress intensity factor function of crack size for two loading forces of the coupling.

Fig. 25. The crack propagation curves corresponding to the rst ve couplings from the train and that estimated on the fracture section.

106 A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107

Using the fatigue crack growth module in Franc 3D, was estimated the propagation curve of the crack function of thenumber of cycles, for the maximum value of the coupling forces. Based on the calculated forces in Case I, has been denedloading spectra with R = 0 and the maximum forces corresponding to the rst ve couplings of the train. The propagationconstants were set from the Refs. [18] and [19], (C = 1.515 1014 and n = 3.7).

The propagation curves determined analytical were compared with that estimated from the analysis of the fracture sec-tion. In Fig. 25 are shown the curves of fatigue crack propagation determined analytically for the rst ve couplings from thetrain and that estimated on the fracture section. It can be observed that the nal stage of the crack propagation, before break-ing, is quite close to the crack propagation curve determined for the third coupling from the train. Thus, it can be said that theloading level of the damaged link before breaking, was similar to the loading level of the coupling 3.

A. Cernescu et al. / Engineering Failure Analysis 29 (2013) 93107 107[7] Mousavi ZN, Dehghani S, Pouranvari K. Failure analysis of automatic coupler SA-3 in railway carriages. Eng Fail Anal 2007;14:90312.[8] Daunys M, Putnaite D, Bazaras Z. Determination of lifetime for railway carriages automatic coupler SA-3. Mechanika 2005;2(52).[9] prEN 14033-1, Railway applications. Track. Technical requirements for railbound construction and maintenance machines. Part I. Running of railbound

machines UIC 826 OR Screw couplings; 2003.[10] SR EN 10002-1, Metallic materials. Tensile testing. Part 1: Method of test at ambient temperature; 2002.[11] SR EN ISO 148-1, Metallic materials Charpy pendulum impact test Part 1: Test method; 2011.[12] Infante V, Branco C, Brito A, Morgado T. A failure analysis study of cast steel railway couplings used for coal transportation. Eng Fail Anal

2003;10:47589.[13] Daunys M, Putnaite D, Bazaras Z. Principles for modeling technological processes investigation into strength and durability of automatic coupler SA-3

in railway carriages. Transport 2009;24(2):8392.[14] Cole C. Longitudinal train dynamics. Handbook of Railway Vehicle Dynamics 2006:23977 [chapter 9].[15] ANSYS Workbench version 11.[16] Franc3D - .[17] Kocak M, Webster S, Janosch J, et al. FITNET FFS procedure fracture, fatigue, creep, corrosion 2008;vol. I.[18] NASGRO v. 4.0 Manual - .[19] Stephens RI et al. Constant and variable amplitude fatigue behavior of eight steels. J Test Eval 1979;7(2):6881.7. Conclusions

The failure of the link was done by the presence of a structural defect which cause the initiation of a fatigue crack. The material of the analyzed link is different from that is specied in UIC 826 standard prescription. The loading force of the damaged coupling was estimated at about 229 kN and the propagation curve estimated on thefracture section is closed to that calculated for the coupling No. 3.

Based on the estimation of total number of cycles for propagation of the crack (about 6474 cycles), the number of cyclesduring one travel (about 200 cycles or accelerations) and the number of the travels per day (1/day), was calculated a prop-agation period of about 1 month. It was concluded that the wagons connection couplings have not been veried in the lastmonth before breaking. Probably, if had been made a visual inspection, the fracture of the link would have been avoided.

The higher degree of loading of the coupling systems, associated with additional shocks and the possible structuraldefects shows the need of initiation of a program to verify these systems and also an improvement of the testing meth-odology of the couplings.

Acknowledgments

This work was supported by the strategic Grant POSDRU/89/1.5/S/57649, Project ID-57649 (PERFORM-ERA), co-nancedby the European Social Fund-Investing in People, within the Sectoral Operational Programme Human Resources Develop-ment 20072013. Also, the authors wish to thank of Mr. Colin Cole.

References

[1] Dailydka S, Lingaitis LP, Myamlin S, Prichodko V. Modeling the interaction between railway wheel and rail. Transport 2008;23(3):2369.[2] Bazaras Z, Sapragonas J, Vasauskas V. Evaluation of the strength anisotropy for railway wheels. J Vibroeng 2008;10(3):31624.[3] Boelen R, Cowin A, Donnelly R. Ore-car coupler performance requirements for the new century. In: Proceedings on Railway Engineering, Darwin:

26.126.7; 2004.[4] Boelen R, Curcio P, Cowin A, Donnelly R. Ore-car coupler performance at BHP-Biliton iron ore. Eng Fail Anal 2004;11(2):22134.[5] Cole C, Sun Y. Simulated comparisons of wagon coupler systems in heavy haul trains. Proc. IMechE, vol. 220, Part F: J. Rail and Rapid Transit.[6] Infante V, Duarte P, Branco C. Failure analysis of railway coupling joint. Eng Fail Anal 2007;14:117584.

The analysis of a damaged component from the connection system of the wagons1 Introduction2 The wagons coupling system with screw and draw hook Description3 The evaluation of the mechanical properties of the link material4 The analysis of the fracture surface5 The modeling of the wagons coupling system and longitudinal train dynamics6 The numerical analysis of the damaged component7 ConclusionsAcknowledgmentsReferences