Contact and sub surface stress calculations 3

[Timusop]

Does anyone know where I can find the equations used behind these calculations:

http://www.mesys.ch/calc/hertz.fcgi

I am particularly interested in calculating the subsurface stresses and shear stresses in the x,y,z directions.

 

[GregLocock]

Hertzian contact stresses are probably in Roark, and certainly in Timoshenko.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[bernoullies123]

Roark chpt 14.

 

[Timusop]

Thanks for your help and suggestions. It seems that Timoshenko covers it, but Roarks only deals with the surface contact pressures, not the sub surface stress and shears.

I hope the Timoshenko can provide what I need.

Thanks again.

 

[saplanti]

Why don't you look at the software documentation. The link is below:

http://www.mesys.ch/?page_id=157&lang=en

 

[Timusop]

Thanks saplanti, but I couldn't find the background calculations behind this software from the link?

 

[dhengr]

Timusop:
You asked essentially the same question a couple weeks ago, re: contact pressure and friction, and I thought there were several good links and references offered in that thread. This is some pretty high powered Theory of Elasticity, etc. and you just have to do some serious digging and learning.

Regarding software and its documentation; you are supposed to pay a lot of money for each piece of software, and smile when you do that; have absolute faith that the producer of the software knew what they were doing, covered every possible situation and fully debugged the software, so what do we need to know the formulas for, it’s magic, leave it at that; until it doesn’t work correctly, and you may not even know it, and then they disclaim all responsibility and just keep your money, read the fine print. Who needs good documentation any longer, the internet can do everything. Oh ye of little faith.

 

[Timusop]

Thanks dhengr,

My post a few weeks ago was regarding the relationship between contact pressure and friction.

http://www.eng-tips.com/viewthread.cfm?qid=311294

They are different questions, but you are right the answers are available in the same places.

With regards to the software, I fully understand and appreciate your thoughts on this.

Thanks again.

 

[CRG]

dhengr, I hope that you were joking with the statement, "it's magic, leave it at that." I could not recommend that anyone use a piece of software unless they can understand the underlying theory and equations; otherwise, how else can you understand the limitations of the software. Just because the answer can comes out with 5 decimal place accuracy doesn't mean that that the model is any more accurate than plus or minus XX%.

 

[mraabe]

You can find the full set of equations for the subsurface stresses in Boresi: 'Advances mechanics of materials', chapter 17 Contact mechanics.

This source is also shown here :

http://www.mesys.ch/?page_id=17&lang=en

Only the approach for line contact is calculated according to Lundberg, since there is no analytical solution. All other results are calculated according the literature mentioned above.

 

[metman]

Timusop (Mechanical)


Try this: Steel Selection (A Guide for Improving Performance and Profits) by Roy F. Kern and Manfred E. Suess (Pronounced Seece NOT Sooose) See pages 169, 185,and 194

This does not actually give equations for Hertzian stresses but might help you to understand your problem. It gives equations for determining case depth based on stresses and/or loads.

In the references there are several listings with no titles and possibly one of these would have the Hertzian equations.

I suggest that you call Timken, ask for their technical group and surely they can give you a reference to the needed publication. Or Gleason Gear Works. They once provided me with some good in-depth (no pun intended) calc's.


Design for RELIABILITY, manufacturability, and maintainability

 

[dinjin]

thread821-209203

check out this thread
I remember reading something by AB Jones a number of years back illustrating and listing the equations.

 

[dinjin]

http://www.nrel.gov/docs/fy10osti/42362.pdf

This may be of interest to you as it explores sub surface stresses within the hard case as well as the subsurface
stresses in the below case hardness support material.

 

[metman]

stresses in the below case hardness support material.

dinjin, I think you meant strength below the case support stresses in the case. Or is this talking about residual compressive stresses beneath the case? I could not bring up the link.

Design for RELIABILITY, manufacturability, and maintainability