Figure 1. Assembled test rig ready for testing.
A representation of a creep curve is shown in Figure 2. At lower levels of creep the traction increases linearly. This linear zone is due to more and more of the contact sliding as opposed to rolling. At a certain percentage creep, the contact becomes fully sliding, sometimes referred to as saturated. The traction forces are then dependent on the metal surfaces and any top of rail material. Three possible scenarios are shown in Figure 2. Curve “A” shows a traction force falling with increasing creep. This is thought to indicate an unsteady system for the rail/ wheel contact, as the sliding speed can alternate very rapidly between two lower points, either side of the saturation point. It is thought that this alternation between speeds can occur by the two wheels across the axle, and by a single wheel. Both situations will lead to the development of vibration and ultimately noise. Curve “B” is thought to suppress noise, due to the removal of the negative damping effect of the system depicted in Curve “A”. Curve “C” depicts the ideal system with high overall traction and a positive slope after the saturation point.
Figure 2. Representation of an idealised creep curve. Curve “A” would indicate noise generation in the field. “B” with a positive slope would suppress noise. Curve “C” with high overall traction and a positive slope is the ideal system.
Eleven materials were supplied to help develop the new test method. These included TOR materials, flange lubricants and dual products. Flange products are closer in composition to conventional greases and are required to reduce friction between the wheel flange/rail interface. Dual products are those that could work on both the top of rail and the flange.
Continued on page 12 LUBE MAGAZINE NO.150 APRIL 2019 11
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
