Allowable bearing stress for PVC

[kjoiner]

Hello,

What is an allowable bearing stress for PVC. I'm bolting a plate to a PVC disc and need to transmit torque and to size the fasteners and qty of fasteners, I need to know an allowable bearing stress.

Thanks,

Kyle

 

[CoryPad]

Do you know what type of PVC? Plasticized or not?

In general, the allowable bearing stress (or surface pressure) can be defined based on surface indentation. For metals, this is time-independent and near the ultimate tensile strength. For polymers that stress relax, you need to keep the pressure lower to avoid preload loss.

Testing is best, but in the absence of that, I would target ~ 50% of the yield stress.

Regards,

Cory

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[kjoiner]

Thanks Cory,

I'll find the yield stress and provide a generous factor of safety.

Kyle

 

[patprimmer]

I typically recommend 1/3 of yield when designing with plastics.

A lot depends on conditions of use re temperature and duration of load.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[kjoiner]

Hello,

Thanks for the responses. Can you recommend a site with the yield stress for PVC? Most sites I've visited have every mechanical property but yield stress.

Thanks,

Kyle

 

[CoryPad]

How about the site of the supplier from whom you get the PVC? It will vary by type (hence my question regarding plasticized or not), among other things. One reason you may not find a yield stress is because unplasticized PVC has little to no plasticity, so a yield stress is not applicable.

Regards,

Cory

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[kjoiner]

Cory,

We'll be purchasing the PVC from McMaster Carr initially but will find a distributor for production quantities. I'll call them to see if they have any data. I've checked the GE polymers site and some others.

One site listed it as 40,000,000 N/m^2 which converts to about 5800 psi (check my math) but values for more familiar materials like steel and aluminum didn't seem right so I'm not inclined to trust the data.

Kyle

 

[patprimmer]

Try

http://www.matweb.com/index.asp?ckck=1

http://www.rtpcompany.com/

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.