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G
gbon1-Visitor
1-Visitor
September 24, 2013
Question

wheel braking simulation using MDO

  • September 24, 2013
  • 11 replies
  • 2578 views
Hi alls,



I have to simulate braking of a train.

The aim is to simulate braking with no slipping between wheel and rail
(optimized braking).

I have to determine braking distance.



I don't know how to model this.

- Rolling between wheel and rail without slipping

- Braking on the wheel at maximum of capabilities



Any ideas, tutorial.



Thanks,

GB










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11 replies

J
JonathanHodgson13-Aquamarine
13-Aquamarine
September 24, 2013
I have to ask... what parameters are you hoping to calculate using MDO that will affect the result, that you couldn't calculate using a spreadsheet? Weight transfer perhaps - are you assuming that the braking can be optimised on each axle separately?

From what little I know, modelling of traction between wheel and rail is quite complicated - a bit similar to traction with a rubber tyre, but certainly much more than just a simple friction coefficient. Getting this right seems critical, before you start looking at effects such as weight transfer.

In any case, I would always suggest starting with a simple calculation rather than going straight into MDO - the more complex the model, the more errors can build up.

HTH...
Jonathan
P
ptc-19327451-Visitor
1-Visitor
September 24, 2013
As long as you are not allowing slip between the wheel and the rail, it should be fairly straightforward. The train has a total inertia at speed working against the braking system maximum torque holding power and energy dissipation.

Maybe the problem could be simplified and solved using Mathcad, etc...


Christopher F. Gosnell

FPD Company
124 Hidden Valley Road
McMurray, PA 15317
G
gbon1-VisitorAuthor
1-Visitor
September 24, 2013
Thanks,

So my problem is how to know how could I brake at maximum without slipping.

What can I tell to MDO ?

Perhaps I could solve with something else but with what criteria ?



Thanks,





De : Chris Gosnell [
J
JonathanHodgson13-Aquamarine
13-Aquamarine
September 24, 2013
You could try searching for studies on "wheel rail adhesion".

This paper includes some typical coefficients in the last few pages (Fig 9; Table 1)
P
ptc-19327451-Visitor
1-Visitor
September 25, 2013
Assuming perfect wheel lockup from adequate brakes still allows slowdown no slower that the sliding friction between the wheel and the rail.

It would be straightforward to calculate the slowdown, but the wheel has theoretical line contact with the rail and this becomes unsolvable.

Time to get out the trains and do some field tests! 🙂


Christopher F. Gosnell

FPD Company
124 Hidden Valley Road
McMurray, PA 15317
I
iceblink11-Visitor
1-Visitor
September 26, 2013
I'm assuming your problem is a bit more complicated that what you ask
below, otherwise you can solve on the back of a beer coaster:

Vertical load on rails = mass * g

Assuming rolling instead of slipping tells us we can use static
friction coefficient between wheels and rails

Braking force = vertical load * friction coefficient

So your maximum deceleration is

deceleration = braking force / mass

Rewriting this gives:

max deceleration = static friction coefficient * g

If you speak of braking torque, you could add somewhere that

braking torque = braking force * wheel radius



So please tell us what more you need to know, otherwise this is solved
🙂



Of course all this is subject to many *assumptions*, such as: all
wheels bear the load equally. If that is not the case, you need 2 beer
coasters. If you wich to account for the effect that the rear wheels
will be unloaded due to the deceleration, you may need a calculator or
Mathcad. If you want to do that more accurately, accounting for springs
and dampers on the train wheels, you probably should start to use MDO or
some multibody dynamics software. If you want to model the wheel on
rails contact more accurately you probably need some more software that
can do contact simulations.

How accurate do you want it?


Best regards,
Patrick Asselman


A
A.DelNegro1-Visitor
1-Visitor
September 27, 2013
OK, here's one I seem to have to re-tackle every time I do it... Not sure why. It should definitely be easier.

What is your preferred method to get a logo into Pro/E (I'm only on WF3)?

I see that it will allow Adobe Illustrator(AI) and DWG files. I have an AI file that yields nothing. IT says it read the file, but doesn't place anything. Is there a certain version of AI I need? I have an older logo in AI format that comes right in. Not sure what the difference between the files is.

Any help would appreciated.

Tony

B
bfrandsen10-Marble
10-Marble
October 2, 2013
Hi Tony,
We never take logos into sketcher due to the constraints. Instead we use Curve From File in WF term or Get Data > Import in Creo term.

The steps are these:
Export logo from Illustrator as DXF
Import DXF to WF/Creo drawing
Scale geometry if necessary. We have do this as Illustrator exports in English units and we use metrics in Creo.
Translate the logo to have its origin reference placed in 0.0.
Turn of format frame and export file as IGES in WF or IGES/STEP/... in Creo.
Create a CSYS on the model where the logos origin is. The logo will be imported in its XY-plane.
Use Curve From File in WF or Get Data Import in Creo and use the CSYS for the import.

The logo comes in as a curve and can be displayed as that or referenced with use edge / project operations in a sketch.

/Bjarne
D
DamianCastillo1-Visitor
1-Visitor
October 2, 2013

Just so that you know. In Creo Parametric, it's a built in feature. You can open image files and place them over a datum plane to use them for tracing your curves. This is how I create logo's. In Wildfire I had to use our ISDX extension to do this because it was not a standard feature for Wildfire.


Just an FYI


ΜΟΛΩΝ ΛΑΒΕ

A
A.DelNegro1-Visitor
1-Visitor
October 2, 2013
well... After reading Bjarne's instructions I was thinking WTF? (pardon my language) But that's crazy just to import a logo. Glad to hear they did some work on that. Wonder if I write a PO for Creo if it will get through...


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