Thermal shrink fitting contact problem

[amolmulve1]

Thermal shrink fitting contact problem

Hallo

I am doing 2D shrink fitting contact analysis. The shaft material is 42CrMo4 and the hub material is 20Mn5.

the temperature of the shaft (inner part)is 20 C and the temperature of the hub (Outer part) is 170 C. there is a gap of 1.1 mm in between.

the hub (Outer part)is allowed to cool for 50000 sec to get shrink fitted to the shaft(inner part).

I want to calculate the contact pressure and the stresses in both shaft and hub material(Contact analysis)

Problem

I am confused in the options to be given to the contact and target elements in the contact analysis.

Does anybody have sample problem solution or macro for 2D thermal shrink fit contact analysis problem ??

Amol

 

[desertfox]

Hi amolmulve1

Have a look at this site the stresses you are looking for can be calculated based on your interference between the parts, this calculator should do it for you.

http://www.tribology-abc.com/calculators/e6_2.htm

Regards

desertfox

 

[desertfox]

hi Again

The interference between the two parts is based on room temperature, I am not sure why you are quoting the clearence between the components after one of them is heated up.

Regards

desertfox

 

[amolmulve1]

Hii

thanks for your reply

my problem is that the shaft and the hub is not cylindrical..they are conical in shape..so for conical shfat hub connection i want to find the contact stress distribution.

Procedure is that first the hub is heated up to make some clearance.. according to DIN 7190 the required clearance betwee the shaft and the hub is 1.1 mm

and for that i have calculated the temperature of the outer body thats coming out to be 170 C.

I want to simulate the cooling of the hub (outer part) so that the gap of 1.1mm becomes 0mm and the hub is fitted to the shaft..

Amol

 

[desertfox]

Hi Again

Well can you put a sketch up see we all can see the problem.
Also its the amount of mechanical interference between the two parts at room temperature that matters regardless of the shape.

regards

desertfox

 

[rb1957]

sure you want some clearance to install the disc, but you need to have a +ve interference between the bore and shaft (a couple of thou' might be enough) for the unheated parts.

also consider that with a tapered hole there may be some thrust as the pieces cool down

 

[corus]

The difference in radii at room temperature is what will decide the interference so the cooling isn't that important. Look in the pdf here

http://www1.coe.neu.edu/~smuftu/Papers/paper_jbiomechanics_2003.pdf

for a formula for interference fit for tapered sections.

corus

 

[amolmulve1]

Hallo

I am attaching sketch. I want to know the properties (options) to be given to the contact and target elements(Keypoint options)

Thanks

Amu

 

[corus]

Isn't this a cylinder to a cylinder problem with only a possible slight overlap on to the cone that would probably be ignored in contact?

corus

 

[desertfox]

Hi amolmulve

Thanks for the sketch however your sketch appears to have the parts for the shrink fit cylinderical in which case you could use the calculator I gave you the link for.
What you haven't told us yet is the diameters of the two components at room temperature so again we cannot help any further untill you do. If you have no interference between the mating parts then there will be no stress after you cool the outer part onto the inner part.

regards

desertfox

 

[amolmulve1]

Thanks

I can do it by formula but I am doing one project. for that I have to do using Contact analysis FEM.

I want to find out the temperature distribution after 50000 sec in both shaft and the hub.

I am confused about the contact properties and Contact and target element options to be given in the analysis.

 

[desertfox]

Hi amolmulve

Why are you doing a temperature distribution analysis, your first post related to the stresses due to the shrink fit after cooling which is why we keep saying what is the interference between the two components after it as cooled.
The stresses only have meaning at there final cooled temperature not at some intermediate stage. What you are now asking is a heat transfer analysis but I cannot understand why.

Regards

desertfox

 

[corus]

It depends on the software you are using. Some will allow conductivity across the gap to be related to the contact pressure. Otherwise you'd have to assume you have perfect conductivity as contact is made. Before then you'd assume radiation across the small gap. I'd ignore conductivity through the air as it tends to be negligible.
The options you refer to probably relate to the software you are using and are better posted in the relevant forum, once you know what your aims are.

corus