Experimental investigation of yaw damper performances: an improved and harmonised testing methodology developed within ModTrain EU project.

Transcription

1 Experimental investigation of yaw amper performances: an improve an harmonise testing methoology evelope within MoTrain EU project. 1 Stefano Bruni, 1 Paolo Belforte, Alessanro Cera, 3 Heiko Hartwig, Gianpaolo Mancini, 1 Laura Mazzola, 1: Politecnico i Milano, Milan, Italy; : Trenitalia, Florence, Italy; 3: Deutsche Bahn AG, Minen, Germany Abstract The paper presents some results from the activities performe in the Mobogie subproject (part of the Motrain research project), having as objective the stanarisation an moularisation of components an subsystems in the running gear. An important goal in this view is the stanarization of spare parts as well as the stanarization of interfaces of those spare parts. For instance, avantages can be achieve by railway operators in purchasing spare parts an minimize the sorts, so that ifferent suppliers for these parts are available on the market. In particular, the paper eals with stanarisation issues concerning yaw ampers, which at present still are non-interchangeable components for imensions, interfaces an performance specification. The paper tackles this problem by a twofol approach: from one sie, stanarization of geometrical interfaces an overall imensions is propose, but a proposal is brought forwar also concerning testing an qualification methos. In fact, geometric stanarization shall go along with the efinition of clear, stanarize an harmonise methos to quantify the performances of the component: only by this approach, a full interchangeability will be achieve, in the sense that changing from one component to another, besies ensuring geometric compatibility, will also ensure that the performances of the bogie subsystem are not moifie. 1. Introuction Dampers, an particularly yaw ampers, play an important role in the running behaviour of high spee trains. In the same time, yaw ampers are also among the bogie components that may suffer egraation, as the consequence of being subjecte to emaning working conitions an being expose to a harsh environment. Therefore, large maintenance costs are associate with the replacement of egrae yaw ampers. On account of its importance for vehicle performances an of the high maintenance costs relate, yaw ampers were ientifie in the Motrain project as one of the top-priority components for stanarisation an moularisation. MoTrain stans for Innovative Moular Vehicle Concepts for an Integrate European Railway System, an as Integrate Project it is the first of its kin in the area of joint European railway research. The project officially starte on February 1 st 004, with a total project uration of four years. MODTRAIN is efining an proving the necessary functional, electrical an mechanical interfaces an valiation proceures to eliver the range of interchangeable moules, which will form the basis for the next generation on intercity trains an universal locomotives. Rather surprisingly, until toay yaw ampers still are not an interchangeable component neither for imensions an geometric interfaces, nor for stanarise performances. Therefore, in the framework of the MoTrain European Fune Project, an in particular in the MoBogie subproject, a team compose by Railway Operators, vehicle integrators an research centres an acaemia starte an effective cooperation to enhance amper interchangeability. Yaw amper suppliers, although not irectly involve in the Motrain project, actively cooperate with this work an contribute to achieve its objectives. The approach followe was twofol: firstly the complete stanarisation of overall imension an fixing points was sought, to achieve complete geometrical interchangeability of the components. The secon stage of the work aime at the objectification of methos use for yaw amper testing an qualification: the objective of this part of the work is to ensure that a small number of performance inexes can be associate with the amper to specify in a clear, stanarize an harmonize way the performances of the component, with the aim of ensuring that the component will be interchangeable not only from the geometric point of view, but also in view of its influence on the overall performances of the running gear, clearly with main emphasis on vehicle running stability. 1

2 In this paper, the approach for the efinition of the stanarise geometrical interfaces will be escribe, proviing some selecte examples of its application (section ). Then the stanarisation of the amper performance efinition by laboratory tests will be reporte: firstly the outcome of the improve amper characterisation on the efinition of the vehicle critical spee will be reporte, by means of suitable multi-boy simulations (section 3.1). Then these eviences will be transferre in proposal for the change of actual testing methoology both for type test (section 3.) an serial test (section 3.3).. Stanarisation of geometrical interfaces an overall imensions. An important goal for the operators (SNCF, TI, DB AG) in the project Motrain is the stanarization of spare parts as well as the stanarization of interfaces of those spare parts. Avantages can be achieve in purchasing spare parts an minimize the sorts, so that ifferent suppliers for these parts are available on the market. This will carry the following important avantages: reuction in costs because of "economies of scale" resulting from partial or complete interchangeability an increase moularisation of the components; lower costs for the operation, maintenance an refurbishment of interface solutions base on the greater availability of moular equipments an interfaces. Moreover subsiiary benefits inclue improve staff flexibility, as various vehicle types are able to use moularise components an interfaces. In the framework of the project MOD-BOGIE, the requirements for hyraulic ampers were efine, interfaces escribe an etermine geometrical imensions establishe. Besies the System Integrators (Alstom, Bombarier, Siemens, Ansalo Brea) an the Operators, the componentmanufacturers were involve at this work too. These requirements shoul influence in the next step the rework of the European Norm EN 1380 Railway applications - suspension components Hyraulic Dampers. Beginning with the composition of the most important ampers for the high-spee-traffic in Europe, the imensions of the ampers were categorize an ivie in classes. Besies the geometrical imensions of the amper also the ifferent en mountings were taken into account on that occasion. For the amper imensions, the outsie iameter was efine in that way, that the most of toay use ampers can be covere by the stanar for the outsie iameter. Also the minimum-length of a amper was iscusse in the project. Different constructions, that require more or less space in each case, are available on the market. It was necessary to efine the minimum length of the amper, so that the amper with the biggest construction length fits in the available space. Table 1 contain the iameter-classes an the minimum-length of a stanar amper ( for primary or seconary suspension application) an for the yaw amper. These classes cover the most of the amper applications in the European high spee traffic. Size D1/D 85/75 105/90 10/110 L Stanar L Yaw Damper Table 1: Damper imensions.

3 Another important point has been the efinition of stanarize amper eyes. The most significant imensions are conense in the table. Size Eye Outsie Diameter Eye Axle to boy space Table : Damper eye imensions After stanarization of amper imensions, we concentrate on the en mountings examination. Here the three most important fortification types were examine altogether an size-classes were establishe. The recommene values are presente exemplary for two fortification-systems in table 3 an Size L L s Table 3: Damper En mounting form A Size 1 L Table 4: Damper En mounting form B 30 3,5 3

4 The stanarization of interfaces an geometrical imensions of ampers will leas to a better competitiveness of all involve partners in the MODBOGIE project - the component suppliers, system integrators an railway operators in Europe. 3. Stanarisation of type an serial tests Damper interchangeability oes not simply mean the component to be esigne accoring to stanarise interfaces an geometry, but also to be able to specify the performances of the components in such a clear way that interchanging components prouce by ifferent suppliers will not affect the performances of the bogie / vehicle system. Therefore, the process of component stanarisation has to eal also with the objectification of the measure of amper performances; besies ensuring component interchangeability, the improvement of testing proceures shall also lea to a more clear specification of target performances, allowing for a more clear interaction between the operator, the vehicle integrator an the manufacturer of the amper component. In the present European situation, a stanarise testing proceure is efine by EN1380, but the testing conitions (amplitue an frequency of eformation to which the amper shall be subjecte) are not agree an may be ifferent accoring to the vehicle integrator an operator involve an to the prouct consiere. Therefore, this section will focus on the stanarisation of testing proceures for yaw ampers, with the objective to propose a unifie proceure to perform type tests, so that the performances expecte by the amper can be clearly efine. This proceure was efine by a working group, forme within the Motrain/Mobogie project an being compose by representatives of operators (DB, SNCF, Trenitalia), vehicle integrators (Alstom Transport, Ansalo Brea, Bombarier, Siemens), amper manufacturers (Dispen, KONI, IsoComp, MSA,ZF Sachs AG) an by an acaemy (Politecnico i Milano). Furthermore, this section will resume the main finings of an investigation performe to unerstan the effect of amper flexibility on vehicle stability: the results of this analysis support the nee for a precise qualification of the amper not only in the working conition corresponing to large eformation at low frequency (where the viscous amping behaviour prevails), but also in the small eformation at high frequency conition, where internal eformability effects may become preominant. 3.1 Frequency epenent behaviour of oil ampers for railway applications Stanar EN1380, now in force in Europe, efines amper performance starting from the force vs. velocity iagram obtaine from tests carrie out at ifferent velocities, see figure 1. This iagram is obtaine by subjecting the amper to harmonic cycles of eformation, where the time-epenent variation of amper length (t) is efine by: () t = A ( πf t) = Acos( ω t) cos (1) where A is the amplitue of eformation, f is the frequency of the eformation cycle an ω is the corresponing angular frequency. The measure maximum force prouce by the amper as function of the maximum spee achieve in the cycle of eformation consiering ifferent combinations of amplitue an frequency allow to obtain a force vs. velocity iagram. From this iagram, two regions corresponing to ifferent amper behaviour are ientifie: at low rate of eformation, the amper force tens to increase linearly with the spee of eformation at higher eformation rates, a saturation effect takes place, an the amper force may eventually ten to become constant. This force vs. velocity iagram is use to efine the amping coefficient C (measure in Ns/m) which is meant to quantify the amper performance an is normally compute as the slope of the linear part of the iagram. 4

5 Figure 1: Typical shape of the force vs. velocity iagram for a yaw amper However, it may occur that this proceure leas to ambiguous results in terms of amping coefficient calculation which, especially in the case of yaw ampers, may not correspon to the real behaviour of the component uring service. Inee, the maximum spee of eformation V is efine as the prouct of the amplitue of eformation times the circular frequency: V ( ) = ωa = max & () an hence the same spee can be obtaine in ifferent working conitions, e.g. large eformation amplitue at low frequency or small eformation amplitue at high frequency. Figure a shows then the results of a more etaile investigation, where ifferent amplitues of eformation were consiere, ranging from 1 to 1.5mm. It is observe that for the same value of the spee of eformation, the force measure in a conition corresponing to large amplitue an low frequency is always higher than the force measure at small amplitue an higher frequency. This can be explaine with the internal amper flexibility playing a more important role, in case of low amplitue, in efining the real performance of the amper [1], []. As will be shown in subsection 3., the effect of amper flexibility ten to become more an more important with increasing frequency. The situation can be even more far from the simplifie analysis propose by the present stanars (an represente in figure 1) if we consier that the force prouce by the amper is not an ieal viscous amping force, which means is not opposite to the spee of eformation. Therefore, to obtain a realistic measure of the actual amping effect, the total measure force has to be ecompose into a amping component F opposite to the spee of eformation an an elastic component F e opposite to the eformation of the amper. Figure b shows the tren with eformation spee of the single amping component of the measure force, for ifferent amplitues of eformation: in this case the sensitivity to an increase of frequency is even more evient, since in the lowest amplitue case (A=1mm), corresponing to the higher values of frequency, the amping force is not increasing monotonically with spee, but instea reaches a maximum an then ecreases its value. Since the total force generate by the amper is monotonically increasing with spee (Fig. a), this shows that for increasing frequency the elastic component of the force generate by the amper tens to become preominant with respect to the amping component. This effect becomes particularly important for yaw ampers, which are esigne to increase energy issipation to prevent the hunting instability of the bogie, typically occurring at moerate amplitue of eformation (in the range 1-3mm) but with quite high frequency (typically 4-8Hz, see e.g. []). 5

6 (a) Figure : Measure frequency epenent behavior of a yaw amper a) Maximum force vs. spee, b) amping component of the force vs. spee Accoring to the above mentione analysis, a ifferent metho is neee proviing the amper performances, taking into account frequency epenent behaviour an where for the elastic an amping component of the force generate by the amper. If a linear behaviour can be assume for the amper, the elastic force component can be efine as proportional to amper eformation whereas the amping force component is proportional to the spee of eformation & : F = F + F = k + c & (3) e eq where k eq an c eq are efine as the equivalent stiffness an equivalent amping of the amper uner consieration. Taking the Fourier transform of eq. (3), the frequency response function H(jω) between amper eformation an force can be efine: eq ( k + jωc ) ( jω) H ( jω) ( jω) (b) F( jω) = (4) eq eq = consiering equations (3) an (4), some remarks can be one: - the force generate by a (linear) amper is the sum of an elastic an amping components, which are efine respectively by the equivalent stiffness k eq an equivalent amping c eq parameters - only the amping component of the force is effective in generating energy issipation, whereas the elastic component will only prouce an aitional loa on the carboy an bogie frame, without affecting the amper performance in terms of energy issipation. - the amper behaviour is completely efine by the equivalent amping c eq an equivalent stiffness k eq parameters, which can be compute respectively as the real part of the frequency response function H(jω) an as the imaginary part of H(jω) ivie by the angular frequency ω. Figure 3 represents the equivalent amping an equivalent stiffness values measure uring the test whose results in terms of force velocity iagrams were reporte in figure. For any given amplitue of eformation, the equivalent stiffness has an increasing tren with frequency, whereas the equivalent amping is monotonically ecreasing with frequency. It is hence confirme that for the real amper the elastic force component becomes preominant for increasing frequency, as pointe out before. It is also observe that in the frequency range 4-7Hz corresponing to hunting instability the equivalent amping can be as low as 0% of its value at low frequency, an the equivalent stiffness can be 6 times larger than at low frequency. Hence, it is confirme that measuring the amping properties at low frequency of eformation an large stroke is not appropriate to efine the actual behaviour of the component when mounte into a vehicle unergoing hunting oscillation. 6

7 (a) (b) Figure 3: Damper behaviour a) Equivalent amping versus frequency, b) Equivalent stiffness versus frequency In orer to complete this section, the case of a amper showing a markely non-linear behaviour has finally to be consiere. It has to be pointe out that the same amper can show either a linear or non linear behaviour epening on the amplitue an frequency of eformation to which it is subjecte. As an example, figure 4 shows the ifferent behaviour of the same amper alreay consiere in figures an 3 for two ifferent testing conitions: figure 4a shows the force vs. eformation hysteresis cycle measure for A=1mm an f=1hz, whereas in figure 4b the same hysteresis cycle is represente for A=5mm an f=4hz. It is observe that in the first case the cycle has an elliptic shape, which is the result of a harmonic variation of amper eformation combine with a harmonic variation of the total force F, which correspons to the linear force-eformation relationship represente by equation (3). In the secon case, the shape of the cycle is far from elliptic, which shows that the force generate by the amper when subjecte to a harmonic cycle of eformation is far from having a harmonic tren with time, an hence emonstrates that the force-eformation relationship is not represente by (3), but instea by a non-linear relationship where a harmonic input (eformation ) besies proucing a synchronous response of the amper (having the same circular frequencies ω) also gives rise to super-harmonic components, characterise in this case by o multiples 3 ω, 5 ω, of the frequency of eformation. (a) (b) Figure 4: Force-isplacement iagrams a) Linear behaviour, b) Non-linear behaviour In case of non-linear amper behaviour, the efinition of the equivalent stiffness an equivalent amping parameters accoring to equation (4) can still be retaine, provie that the value of the frequency response function H(jω) corresponing to the frequency of the eformation cycle is use. This correspons to approximating the actual force prouce by the amper with its funamental component, synchronous to the eformation. It coul however be questionable whether taking the C eq parameter accoring to eq. (3) also in the case of a non-ellyptical hysteresis cycle is an aequate way of representing the actual issipative behaviour of the amper. 7

8 A secon way to procee in this case is to efine C eq as the amping coefficient of a linear viscous amper that woul prouce the same energy issipation as measure from the non-elliptic hysteresis cycle. Since the energy issipate in one cycle by an ieal linear viscous amper with amping constant c is: E v π c A (5) = ω in this secon approach, the equivalent amping C eq is efine as: E C eq = (6) π ω A where E is the energy issipate by the real amper in one cycle of eformation, represente by the area of the hysteresis cycle, which can be compute accoring to: E = T 0 F( t) & ( t) t (7) In figure 4, the values of E compute accoring to equation (7) are reporte for the elliptic an nonelliptic hysteresis cycles. Furthermore, for the same two cycles the values of C eq compute accoring to equation (3) (enote as metho 1 ) an accoring to equation (6) (enote as metho ) are compare: it is observe that the two methos of calculation provie very close values (within 1% ifference) not only in the case of elliptic cycle (linear behaviour of the amper), but also in the case of non-elliptic cycle (non-linear behaviour). 3. Effect of amper behaviour on vehicle running behaviour. In subsection 3.1 it was shown that the internal flexibility of the yaw amper has a strong influence on the energy issipation process, so that the elastic force component generate by the amper becomes increasingly important at higher frequency, whereas the amping force component becomes relatively less important. In this subsection, it will be shown, by means of multi-boy simulation, that the internal flexibility of the amper has also a critical influence on the running stability. In orer to account for the frequency epenant behaviour escribe in 3.1 into multi-boy simulations, a problem has to be solve, since the equivalent amping an equivalent stiffness parameters escribing the amper behaviour are efine as function of frequency, whereas multiboy simulations have to be performe in time omain, since multi-boy moels have to account for non-linear effects in wheel-rail contact to ensure appropriate accuracy of their results. A practical but very satisfactory way to solve this problem is represente by aopting the so-calle Maxwell moel for the yaw amper. This is compose by a spring in series with a viscous ashpot, both having frequency-inepenent (i.e. constant) parameters, see figure 5a. By choosing appropriate values for the stiffness K an viscous amping C parameters of the Maxwell moel (which, accoring to EN1380 are calle hereafter ynamic stiffness an ynamic amping respectively), the measure trens of the equivalent stiffness an amping parameters measure for the real amper can be interpolate with reasonable accuracy. To ientifie these parameters, the frequency response function (FRF) for the Maxwell moel H M ( jω) is easily obtaine in the form: H M C ω 1 ( ) K jω = K + jω C (8) C ω Cω K K By fitting the analytical expression (8) of the FRF to expression (4) where the FRF of the real amper is expresse as function of the equivalent amping (C ) an equivalent stiffness (K ) parameters, it is possible to fin the values of the Maxwell moel parameters K an C which provie the best-fit (e.g. in the least-square sense) of the measure FRF. As an example, Table 5 reports the results of parameter ientification for the amper consiere in section

9 C Dynamic amping 543 [Ns/mm] K Dynamic stiffness 1658 [N/mm] Table 5: Maxwell moel parameters for a teste amper Clearly, the C parameter represents the equivalent amping of the real amper at very low frequencies, an the K parameter accounts for the effect of internal amper flexibility. In orer to investigate the influence of this latter parameter on vehicle stability, two stability analyses were performe by multi-boy simulation, consiering the same vehicle but using ifferent moels for the yaw ampers: case1 : in this case, each yaw amper in the vehicle was moelle using a Maxwell Moel using the parameters liste in table 5 case: same moel neglecting the effect of internal amper flexibility. This correspons to setting an infinite value for the K parameter of the Maxwell moel, an hence to using a simple viscous ashpot C to moel the yaw amper Figure 5b shows the tren with frequency of the equivalent amping parameter for the two moels of the yaw amper: in case 1, this was obtaine by applying the efinition of C eq to the expression (8) of the Maxwell moel FRF, whereas in case, on account of the infinite stiffness of the amper, the equivalent amping is equal to C, regarless the frequency consiere. It is possible to see that in case 1 the Maxwell Moel fits well the tren with frequency of the equivalent amping, whereas in case a large over-estimation of the amping performances is introuce, especially at high frequencies as those corresponing to the frequency of amper eformation when the vehicle unergoes hunting motion. The assessment of the critical spee was performe accoring to the proceure escribe in [3, 4], by means of a MB coe suitable for reproucing the railway vehicle running behaviour [], an the critical spee values obtaine in the two cases were significantly ifferent, since in case 1 the instability threshol was 30 km/h approximately, whereas in case it was higher than 40 km/h. These results point out the critical influence of the internal amper flexibility on vehicle stability an emonstrate that the efinition of a moel for the yaw amper to be use for stability calculation has to be base on a complete experimental characterisation of the amper, to be performe uner the same ranges of amplitue an frequency of eformation the amper unergoes uring hunting motion of the vehicle. Furthermore, appropriate techniques like those introuce in this subsection are require to extract from experimental tests appropriate values for the mathematical moel of the amper to be use in multi-boy simulations. (a) Figure 5: Damper ynamic characteristics a) Maxwell Moel, b) Equivalent amping versus frequency (b) 9

10 3.3 Proposal for improve tests. Base on the analysis presente in the sections 3.1 an 3., a proposal to integrate EN regulations regaring yaw amper testing methos an post-processing,was elaborate by the Mobogie team in cooperation with component suppliers. In this section the escription of the main moifications propose to the stanar are reporte. First of all, a istinction is propose between serial tests an type tests. Serial tests aim at ensuring the quality of components at the en of the manufacturing process, an hence has to be simple, fast an as low-expensive as possible. On the other han, type tests are meant to allow the qualification of the component in view of a particular application an hence they have to emonstrate that the amper meets the corresponing performance requirements; furthermore, type tests shall provie all the information neee to calibrate simulation moels that are usually performe by the esigner of the vehicle. As far as serial tests are concerne, the propose proceure foresees to test each amper mounte with the nominal inclination angle in service an, if require by the customer, equippe with the en mountings. One single amplitue of eformation is prescribe : 5 mm at very low frequency, as agree between the customer an the supplier. The outcomes of such a test are four force values: F c,v0 [N] amper compression force at maximum velocity of the test (measure at mi stroke in case of sinusoial isplacement) F e,v0 [N] amper extension force at maximum velocity of the test (measure at mi stroke in case of sinusoial isplacement) F c,max [N] amper maximum compression force with sinusoial isplacement F e,max [N] amper maximum extension force with sinusoial isplacement For amper acceptance, the four above parameters shall be within the tolerances provie in the amper specification. For type tests, which being performe on an limite number of specimen can be more etaile still requiring a reasonable effort, issues iscusse in sections 3.1 an 3. are all incorporate in the proposal for stanar improvement. First of all, to guarantee that the experimental tests reprouce the service conitions of the yaw amper, it is necessary to efine the cycles of eformation to be applie uring tests not only from the point of view of their frequency but also with regars to their amplitue. To this en, a list of amplitue/frequency combinations was elaborate (see appenix A), representing a synthesis of the testing conitions currently aopte by DB, SNCF an TI. For a complete efinition of amper properties, the same four parameters obtaine in the serial tests have to be compute, an aitionally the C eq [N/m/s] ynamic equivalent amping rate is introuce. The efinition of this new parameter is base on the efinitions reporte in section 3.1. Specifically, four force velocity iagrams have to be provie, allowing the immeiate evaluation of the maximum force (F e,max, F c,max ) the amper applies to the ens. Moreover the estimate of the real amping force (F e,v0, F c,v0 ) together with the epenence of the ynamic equivalent amping rate on the frequency complete the characterisation of the component. The proposal for stanar moification also provies two alternative methos to erive the parameters of the Maxwell moel C an K. These are calle Least square metho an Simplifie metho respectively. The first approach is the same as alreay escribe in subsection 3., whereas the simplifie metho is escribe below. Coming back to the equations of the Maxwell moel (fig.5a), the amper force is efine as function of the circular frequency ω an of C an K accoring to the following expression: F( t) = 0 ω + ω K ( K C ) K sin ωt + arctan ω C where the relative phase between force an isplacement is: Φ = K ω C arctan (10) an the extension force at maximum velocity of eformation is given by: (9) 10

11 0 ω K K F = e, vo sin arctan (11) ω + ω C ( K C ) Base on expressions (10) an (11), the parameters of the Maxwell moel can be erive in a simple, eterministic way. When testing the amper with low frequency, the force-isplacement phase is nearly 90 an the force at maximum velocity is nearly Fe, vo 0 ω C = v0 C, so that from the measure of F e, vo it is possible to erive the value of the C parameter. Consiering then a testing conition at high frequency, the force-isplacement phase will be significantly ifferent from 90, so that the ynamic stiffness parameter K can be compute accoring to: 4. Conclusions ( Φ) K = ω tan (1) C Stanarisation, moularisation an inter-changeability of yaw ampers is an important objective for both railway operators an vehicle integrators. Within the MODTRAIN project, the Mobogie team worke on this subject with the aim of improving the present situation in Europe. This goal has been reache both in terms of stanarisation of geometrical interfaces an overall imensions an in terms of quantities neee to efine ampers performances. Important guielines concerning the overall length an en mountings imensioning were prouce, altogether with the efinition of stanarise amper eye. Furthermore, an improve methoology for yaw amper testing an qualification was prouce, taking into account the real operative conitions of the amper. The critical issues relate to the frequency epenent behaviour of the amper an to the effect of internal amper flexibility were carefully analyse an specific quantities were efine in orer to take into account these peculiarities. It is hoper that this work will contribute to mark a step forwar in the esign, testing an characterisation of yaw ampers an in proviing an efficient an clear flow of information from amper manufacturers to vehicle integrators an operators an viceversa. References [1] M. Wrang, Instability phenomena of a passenger coach, cause by internal amper flexibility, Supplement to Vehicle System Dynamics Vol. 33, pp (000). [] S. Bruni, A. Collina, G. Diana, P. Vanolo, Lateral ynamics of a railway vehicle in tangent track an curve: Tests an simulation, Supplement to Vehicle System Dynamics Vol. 33, pp (000). [3] S. Alfi, S. Bruni, L. Mazzola, Effect of motor connections on the critical spee of high spee railway vehicles, 0th IAVSD Symposium, Berkeley, August 007. [4] G. Diana, S. Bruni, E. Maestrini, G. Mancini, G. Cau, New perspectives for High Spee rolling stock in Italy, WCRR 08 International Conference, Seoul (KR), 18- May 008 Acknowlegments The work escribe in this paper was performe within the project MODTRAIN, fune by the European Community (contract number: TIP3-CT ). 11

12 Appenix A Propose unifie testing conitions for type tests of yaw ampers Velocity [mm/s] Amplitue Frequency [Hz]