ELLIPTICAL CONTACT STRESS 2

[dleesukEB]

Hello All,

I am currently designing a RAIL for a crowned roller to run along.

I have been trying to find information on ELLIPTICAL CONTACT STRESS between the roller and the rail, to no avail.

Using HERTZIAN stess calcs. gives me a certain figure when I use the radius of the roller and another, considerably smaller figure, when I use the crown radius.

The smaller figure (using crown rad.) is around 1.2GPa, which would be ok(ish).

The larger figure (using roller rad.) is around 3.9GPa which is outside the acceptable limit for the material I am looking at for the rail.

I know that the value for the elliptical stress will lie somewhere in between these values, but I don't know how to calculate this.

Can anyone give me any pointers as to where I should be looking or what I need to do to calculate the ELLIPTICAL CONTACT STRESS, please?


Regards and Thanks in advance.

Darren

 

[ione]

Google search for "shingley contact stress" or "elliptical contact stress rail formulas" and you'll find what you need

 

[kingnero]

look also in railroad engineering:
thread

http://www.eng-tips.com/viewthread.cfm?qid=280411&page=1

1200 Mpa is quite high! about double of the normal (static) contact pressure.

Can I ask you what material you're using for the rails?
In that thread I'm talking about standard steel (no exotic alloy) but with .8-1.0 % Carbon, according to EN 13674-1

 

[dleesukEB]

Thank you IONE.
I have had a look and found some small snippets of info.

Thank you KINGNERO.
The material I was thinking about was HARDOX 500 (Swedish Steel).

 

[ione]

Regards

http://www.ntn.co.jp/english/products/review/pdf/NTN_TR75_en_P140.pdf

http://eb-cat.ds-navi.co.jp/enu/tech/ej/img/no159e/159e_16.pdf

 

[bradleyelwood]

dleesuk,
You might reconsider the use of hardox 500. How are you going to attach the hardox 500? How are you going to cut the plate? How are you going to secure the plate to the rest of the structure?

I worked for a company where hardox 500 was used for wear applications for ground engaging surfaces like Cat blades, and for crusher wear surfaces. We always bolted the plates, never welded them and never used them in structural applications. We found that in a few cases, a part was prepared by flame cutting to shape, and fractured before it went into service (after several weeks just sitting in inventory). Scandia makes quality steel, but you might get in touch with them before using hardox 500 for this application.

 

[dinjin]

Rather than Shingley it is Shigley contact Stress that you want to search on.

 

[unclesyd]

There are several references in these papers to J.J. Kalker someone a little search or contacting someone like the Linda Hall Library if you need more information.

On the first link start at around page 70 I think it will have all the information you need. This discussion uses Kalker's approach, along with others.

http://www2.imm.dtu.dk/pubdb/views/edoc_download.php/1000/pdf/imm1000.pdf

http://www.md.kth.se/~ulfs/Publications/Pitt_5.pdf

http://www.cjmenet.com.cn/xuebaoenglish/papersed/allpapered/newaccepted/fulltext/2009-300.pdf

http://www.students.ncl.ac.uk/gordana.vasic/PGC-GV-20070306.pdf

 

[dleesukEB]

Bradleyelwood,

Thanks for the info regarding Hardox 500

We, as a company, have used Hardox 500 on a number of occasions for sub-sea 'scraper' blades on cable ploughs. I know it is a very hard-wearing material.

The rails are definitely not structural and I am intending to bolt them to the structure.

The problem we have is the rails are very thin (140 W x 50 thk.) and relatively short (3m), so we can't heat treat due to excessive warping. So we are looking for a steel which is hard in it's NATIVE state. Ideally it will be only slightly softer than the rollers (60Rc). This, I assume, will allow some 'bedding in' of the rollers and actually offer additional support around the profile of the roller, thus reducing the stress in this area.

I have attached 2 pdf's for clarity. F = 300 kN)

http://files.engineering.com/getfil...da-91cbb82d456d&file=Rail_Layout_Sketch_1.pdf

http://files.engineering.com/getfil...af-a33973121dfd&file=Rail_Layout_Sketch_2.pdf

Any further information would be incredibly useful.


Thanks in advance

Darren

 

[dleesukEB]

Thanks and appreciation to all who have replied so far.





Darren

 

[unclesyd]

I have to recommend that you look at one of my favorite steels Astralloy V ,high initial hardness, work hardening, air hardening, and weldable.. We use this steel on wheel and roller applications similar to yours with slightly different designs. Every place I've used this material where wear was a concern it has made improvements from 20% to over 100% in component life.
If you use this material make sure you sweeten up the machine shop prior to having them machine Astralloy V, it is tough.

There is excellant data on this link.

http://www.astralloy.com/products.asp

 

[dleesukEB]

Thanks UncleSyd

Do you know of a UK distributor?



Regards

Darren

 

[unclesyd]

Not right off.
They are now a AArcelormittal division they might help as I know they have/had worldwide distribution. Before that they were part of IMS who I think was based in the UK. IMS might still distribute the material.

I'll see what I can do tomorrow.

The reason I'm up is we lost power about 90 minutes ago so we had to get up and open some windows. It has been coming and going while I was responding your post. The computer is on generator power.

 

[unclesyd]

I called the Birmingham, Alabama main office and found out there is no European Distribution Center for Astralloy V. There is no equivalent to the steel.

Sorry about taking you down a blind alley.

 

[dleesukEB]

Thanks UncleSyd for your assistance anyway.

 

[dinjin]

http://www.ssab.com/en/Brands/Hardox/Products-2/