Properties of Railway WheelsL. Strasberg, N. Perfect, G.L. Elliott Systems Research and Development Branch Research and Development Division Ontario Ministry of Transportation and Communications 28

28

P r o p e r t i e s o f Railway Wheels

L. S t r a s b e r g , N. P e r f e c t , G.L. E l l i o t t Systems Research and Development Branch

Research and Development D i vi s i o n

O n t a r i o M i n i s t r y o f T r a n s p o r t a t i o n and Communications

I N T R O D U C T I O N

T h e u r b a n r a i l w a y is i d e a l l y s u i t e d for h i g h d e n s i t y

c o r r i d o r s or for t h o s e a r e a s w h e r e u r b a n g r o w t h is c o n s i d e r e d d e s i r a b l e . H o w e v e r , u r b a n r a i l w a y s a r e l i m i t e d in t h e i r

a p p l i c a t i o n b y h i g h c a p i t a l r e q u i r e m e n t s a n d b y t r a i n n o i s e w h i c h c a n d i s t u r b t n e c o m m u n i t y s e r v e d b y t h e s y s t e m (1).

P r e v i o u s i n v e s t i g a t i o n s i n t o t h e n a t u r e o f r a i l w a y n o i s e (2) h a v e s h o w n t h a t w h e e l / r a i l n o i s e is d o m i n a n t , a t l e a s t i n s o f a r as e l e c t r i c t r a i n s a r e c o n c e r n e d . It h a s b e e n s h o w n t h a t s o u n d r a d i a t e d b y t h e w h e e l is a s i g n i f i c a n t p a r t of t h e t o t a l n o i s e . M a n y d i f f e r e n t t y p e s o f r a i l w a y w h e e l s h a v e b e e n t e s t e d o n t r a n s i t s y s t e m s w i t h v a r y i n g d e g r e e s of s u c c e s s . H o w e v e r , l i t t l e h a s b e e n p u b l i s h e d w h i c h w o u l d e n a b l e an

o p e r a t o r to c o m p a r e t h e d i f f e r e n t w h e e l s o n t h e b a s i s o f t h e i r f u n d a m e n t a l m e c h a n i c a l p r o p e r t i e s . T h e p u r p o s e o f t h i s p a p e r is to p r e s e n t s o m e l a b o r a t o r y d a t a o n f o u r c o m m o n r a i l w a y w h e e l s .

B E H A V I O U R O F E X I S T I N G W H E E L S

W h e e l s w h i c h a r e p r e s e n t l y m a n u f a c t u r e d c a n b e g r o u p e d i n t o t w o c a t e g o r i e s - s o l i d a n d r e s i l i e n t . In T a b l e 1, t h e s t a n d a r d w h e e l is r e p r e s e n t a t i v e of t h e f o r m e r g r o u p s i n c e it is m a d e e n t i r e l y of s t e e l .

T h e r e s i l i e n t w h e e l s u s e an e l a s t o m e r i c e l e m e n t to s e p a r a t e t h e w h e e l t r e a d f r o m it s h u b . T h e e l a s t o m e r r e d u c e s th e

u n s p r u n g m a s s o f t h e w h e e l / r a i l s y s t e m a n d a d d s d a m p i n g to t h e w h e e l . T h i s d a m p i n g r e d u c e s t h e s q u e a l n o i s e w h i c h c a n o c c u r o n s h o r t r a d i u s c u r v e s in t h e t r a c k . O n t h e o t h e r h a n d , f i e l d e x p e r i e n c e i n d i c a t e s t h a t r e s i l i e n t w h e e l s d o n o t a p p r e c i a b l y r e d u c e t h e r o l l i n g n o i s e w h i c h o c c u r s o n s t r a i g h t t r a c k .

F o r t h i s s t u d y , f o u r p r o p e r t i e s of t h e w h e e l s w e r e s o u g h t s f r e q u e n c i e s ; m o d e s h a p e s ; m o d a l d a m p i n g r a t i o s ; a n d t h e d e g r e e o f c o u p l i n g b e t w e e n i n - p l a n e a n d o u t - o f - p l a n e w h e e l v i b r a t i o n s . T h i s s o - c a l l e d " r a d i a l / a x i a l " c o u p l i n g h a s b e e n p o s t u l a t e d as a n i m p o r t a n t m e c h a n i s m in t h e g e n e r a t i o n o f r o l l i n g n o i s e (3).

T h e v i b r a t o r y p r o p e r t i e s of t h e w h e e l s w e r e d e t e r m i n e d b y m o u n t i n g t h e w h e e l o n t h e a p p a r a t u s s h o w n in F i g u r e 2, a n d

s t r i k i n g t h e w h e e l w i t h a h a m m e r . T h e r e s u l t i n g v i b r a t i o n w a s

detected by an accelerometer and decompo se d by a real-time

analyser into the fundamental frequencies. Damping ratios were found by passing the signal through a narrow band filter and me a su rin g the decay rate. The radial/axial coupling was de te rmi ne d pr i ma ri ly by static loading. Further evident was obtained by the dete cti on of the same frequency using

accelero me ter s with axial and radial orientations.

Typical vi br at ion patterns for the wheels are shown in Figures 3 through 6. In each case, P represents the di rection and location of the impact and A represents the di re cti on and location of the accelerometer. It is important to note that the scales are dif fer en t in each figure and that no attempt was made to control the magn it ude of the impact. Compl ete results for the wheels are available in (4) and (5).

The laborat ory data was compared to trackside audio

recordings taken at a curve on the Toronto Tr ansit Commis sio n subway system. (Refer to Figure 7.) It was apparent that there is strong cor res po nde nce between the noise spectrum and the wheel frequencies at 5.24, 11 and 17 k H z .

The damping ratios for the wheels showed co nsiderable scatter (Table 2). The standard wheel was, for all pr actical purposes, undamped while the Aco ustaflex wheel produced the highest damping ratios. For all wheels except the Acoustaflex, only one sample was available for testing. Four Acou sta fle x wheels were tested and these showed consider ab le variance in damping ratios. It is not known if such variance is typical of resilient wheels or if this behaviour is restricted to the

sample tested.

To study radial/axial coupling in more detail, a Bochum wheel and a standard wheel were analysed using a static finite el ement model. In addition these wheels were subjected to radial and axial loads to de termine stress and def le c ti o n behaviour. The slope of the web causes a load ec c en tri cit y which enhances radial/axial coupling. It was apparent from the model that the po sit ion of the load alters this ec ce n tr ic it y and mo dif ies the coupling. Since the railway ve hicle is free to osci ll ate across the rail head, the pos it io n of the actual load on the wheel is varied. This effect is one source of v a ri ab i l i t y in the vi br ati on behaviour of wheels (Figure 9).

The effect of load ecc en tr ic it y can be reduced by various means. Two such met ho ds are shown in Figure 10 and their def le ct io ns are compared to a standard wheel. It is apparent that a straight web reduces the defl ect io ns of the wheel and that they can be made very small by the use of an "A" frame.

30

R E S U L T S F R O M T W O P R O T O T Y P E W H E E L S

T h e i n v e s t i g a t i o n i n t o e x i s t i n g p r a c t i c e s h o w e d t h a t

s e v e r a l d e s i g n c o m p o n e n t s o f r a i l w a y w h e e l s c o u l d b e i m p r o v e d . T h e s e i n c l u d e d :

(a) d a m p i n g r a t i o s ;

(b) r a d i a l / a x i a l c o u p l i n g ? (c) u n s p r u n g m a s s .

T w o p r o t o t y p e w h e e l s w e r e d e s i g n e d to d e m o n s t r a t e t h e s e i m p r o v e m e n t s ( F i g u r e 1). S e v e r a l n e w f e a t u r e s d i s t i n g u i s h e d t h e m f r o m m o s t e x i s t i n g w h e e l s :

(a) a t h i n r i m to r e d u c e t h e u n s p r u n g m a s s a n d a t t e m p t to i n c r e a s e t h e w h e e l / r a i l c o n t a c t a r e a ;

(b) a s t r a i g h t w e b ( w h e e l A) or an "A" f r a m e c o n s t r u c t i o n ( w h e e l B) t o r e d u c e r a d i a l / a x i a l c o u p l i n g ;

(c) a l u m i n u m c e n t e r s to r e d u c e t h e t o t a l w h e e l m a s s ; (d) m o r e f l e x i b l e e l a s t o m e r s to i m p r o v e t h e d a m p i n g

r a t i o s ; a n d

(e) b o l t e d c o n s t r u c t i o n for e a s i e r a s s e m b l y .

In e x p e r i m e n t s , t h e p r o t o t y p e w h e e l s w e r e f o u n d to p r o d u c e h i g h d a m p i n g r a t i o s ( T a b l e 3). It is a p p a r e n t t h a t , b y

r e d u c i n g t h e w h e e l r i m m a s s a n d t h e e l a s t o m e r s t i f f n e s s , t h e d a m p i n g r a t i o w i l l i n c r e a s e for a l l m o d e s w h i c h h a v e a r i m d i s p l a c e m e n t c o m p o n e n t . S i n c e t h e s e m o d e s h a v e a l r e a d y b e e n

i d e n t i f i e d as c o n t r i b u t o r s to s q u e a l n o i s e t h e n o b v i o u s l y an i m p r o v e m e n t is e f f e c t e d . In a d d i t i o n , t h e u s e o f b o l t e d

c o n s t r u c t i o n i n c r e a s e s t h e a m o u n t o f d a m p i n g a v a i l a b l e b e c a u s e of f r i c t i o n a l e f f e c t s .

T h e i n t r o d u c t i o n o f t h e e l a s t o m e r i c b l o c k s n e a r t h e c e n t e r of w h e e l B i m p r o v e d t h e d a m p i n g r a t i o s m a r g i n a l l y . T h e s e

b l o c k s r e d u c e d b o t h t h e a x i a l a n d r a d i a l s t i f f n e s s of w h e e l B s i g n i f i c a n t l y w h e n c o m p a r e d w i t h w h e e l A. T h e r a d i a l s t i f f n e s s of w h e e l A w a s 3 2 0 , 0 0 0 l b . / i n . (56 04 1 600 N/M) c o m p a r e d w i t h 8 0 , 0 0 0 l b . / i n . (14 0 1 1 200 N/M) for w h e e l B. T h e a x i a l

s t i f f n e s s m e a s u r e d a t t h e r i m o f w h e e l A w a s 3 0 , 0 0 0 l b . / i n . (5 254 200 N/M) c o m p a r e d w i t h o n l y 2 , 0 0 0 l b . / i n . (350 2 6 0 N/M) for w h e e l B.

CONCLUSI ONS

The dampin g ratios of establi sh ed railway wheels are low;

g e n e r a l l y belo w one percent. Of the wheels tested, the B o chum and Aco ustaflex wheels pro du ce d the highe st damping ratios.

The dampi ng ratios of resilient whe el s can be improved by judi ci ou s sel ect io n of mass and stiffness properties. Two prototype whe el s were tested to d e m onstrate this principle.

REFE RE NC ES

(1) May, D.N., "Criteria and Limits for Waysi de Noise from Trains", Journa l of Sound and V i b r a t i o n , 46(4), 1976, Academic Press Inc., London, England, pp. 537-550.

(2) Remington, P.J. et al, "Wheel/Rail Noise and Vibra ti on ", Rep ort No. U M T A - M A - 0 6 - 0 0 2 5 - 7 5 - 1 0 , U.S. De pa rtment of Transporta ti on , Urban Mass T r a n s p o r t a t i o n Adminis tr at io n, Offic e of Re se ar ch and Dev el opment, Rail Techn o l o g y

Division, Washington, D.C., 20590, 1975.

(3) Lotz, Robert, "Wheel Rail Noise: A Pro gr es s Report",

Int er^Noise 74, Washington, D.C., September 30 - October 2, 1974 .

(4) Perfect, N., "Vibration Testing of Damped and Un damped Steel Wheels", Report No. 76-TIL-4, Res earch and

Deve l o p m e n t Division, Mi n i s t r y of T r a n s p o r t a t i o n and Communicat io ns , Downsview, Ontario, Canada, 1976.

(5) Perfect, N., "Vibration Testin g of Ac oustaflex Wheels", Re po r t No. 76-TIL-25, Res ea rc h and D e v elopment Division, M i n i s t r y of T r a n s p o r t a t i o n and Commun ic at io ns , Downsview, Ontario, Canada, 1976.

32

WHEEL B o c h u m

S . A . B .

A c o u s t a f l e x

S t a n d a r d

T a b l e 1

Four R a i l w a y W h e e l s M A N U F A C T U R E R

B o c h u m e r V e r e i n A.G.

W e s t G e r m a n y

S v e n s k a A k t i e b o l a g e t B r o m s r e g u l a t o r S w e d e n

S t a n d a r d S t e e l C o m p a n y U . S . A .

C a n a d i a n S t e e l W h e e l D i v i s i o n H a w k e r S i d d e l e y C a n a d a Ltd.

T a b l e 2

F r e q u e n c i e s and D a m p i n g R a t i o s of R a i l w a y W h e e l s

C O M P O N E N T F R E Q U E N C Y D A M P I N G R A T I O

kHz

S T A N D A R D 0.62 0 . 0 0 0 3 2

W H E E L 1.58 0 . 0 0 0 1 4

2.75 0 . 0 0 0 0 7 3

3.99 0 . 0 0 0 0 4 2

5.28 0 . 0 0 0 0 4 1

6.25 0 . 0 0 0 0 4 1

B O C H U M 0 .434 0 . 0 0 5 1

W H E E L 1. 24 0 . 0 0 3 1

2.20 0 . 0 0 8 3

4.60 0 .0048

S.A.B. 0 . 433 0. 0 0 2 4

W H E E L 1.19 0. 0 0 1 1

2.10 0 . 0 0 0 8 3

3.07 0 . 0 0 0 8 1

4. 09 0 . 0 0 0 5 1

5.16 0 . 0 0 0 3 9

A C O U S T A F L E X 0.46 0 .0062 0 . 0 0 2 7 0 . 0 1 1 3 0 . 0 0 4 4

W H E E L 1.35 0 .0048 0 . 0 1 6 8 0 . 0 0 8 2 0 . 0 0 7 5

2.45 0 .003 0 . 0 0 5 0 . 0 0 3 3 0 . 0 0 2 9

3.67 ^- 0 . 0 0 4 3 ^-

4.96 ^— 0 . 0 0 4 1

C O M P O N E N T

W H E E L A

W H E E L B

T a b l e 3

D a m p i n g R a t i o s of T wo P r o t o t y p e W h e e l s

F R E Q U E N C Y D A M P Ï N G ~ R Â T Ï O

330 Hz 0.008

988 Hz 0.017

1.83 Hz 0.026

2.33 0.024

2.83 0.025

3.61 0 . 02 7

4. 54 0.027

4.98 0 . 028

5.44 0.027

7.32 0.017

360 Hz 0 .032

1 .0 0 kHz 0.012

1 .84 0.017

2.36 0.040

2.84 0.034

3.60 0.032

4.56 0.022

5.52 0.021

6.44 0. 016

7.20 0.009

W HEEL A WHEEL B

Figure 1, Cross-Section o f Each Prototype Wheel

Figure 2, Test Set-Up Used to Find Natural Frequencies o f Wheels

FREQUENCY KHz FREQUENCY KHz

FREQUENCY KHz FREQUENCY KHz

Figure 3, Natural Frequencies of a Standard Wheel

36

FREQUENCY KHz FREQUENCY KHz

FREQUENCY KHz FREQUENCY KHz

Figure 4, Natural Frequencies of a Bochum Wheel

FREQUENCY KHz

- t - - - - 6s- - - h - - - - f t - -- - - - fc- - - - 4- - - - 1 - - - - 4- - - - &- - - - & - - - - (r

FREQUENCY K H . FREQUENCY K H .

Figure 5, Natural Frequencies of an S.A.B. Wheel

38

Figure 6, Natural Frequencies of an Acoustaflex Whee!

from Trackside Recording on Curved Track

R E A C TIO N S

Figure 8, Finite Element Model Used for Analysis

AX IA L D E F L EC T IO NS

.004 -

.0 0 2" -

0 " -

POSIT ION OF R A D IA L LOAD

UJ UJC>

< J 2

< <

u. _J

BENDING S T R E S S E S

© ©

POSITIO N OF R A D IA L LOAD -

(DEFLECTION I 0 3 IN.)

2 0 2 2 0 2

I---1---1---1---!— ! f---!---1---1---1

0

9 0

180

0

9 0

180

Figure 10, Axial Deflections on Back Face of Three Wheels Due to 10,000 lb. Radial Load at Position 2 o f Figure 9