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Creep Analysis for thermoplastics

Question asked by Richard Obrien on Mar 18, 2009
Latest reply on Jan 9, 2017 by Ananda Ganesh Madheswaran

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Is there a simple way to enter creep data into the material editor? When I choose "Include creep effect", I get a dialogue for (3) Creep constants (1,2 &3). From the help it seems Simulation uses the "Classical Power Law for Creep (Bailey-Norton law) which also has (3) constants (0,1 &2). Are they the same and in the same order? And finally, how do you derive these constants from standard isochronous stress-strain families of curves?
Thanks
Rick

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Stephen Endersby Mar 30, 2009 7:40 PM
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Hi,

SW Simulation maps the constants as you assumed
C0 = CreepConst1
C1 = CreepConst1
C2 = CreepConst1
CT = CreepTC

To calculate these constants you need two sets of time, temperature and stress results to produce a given strain. An example of this for stainless steel can be found here http://www.fanagalo.co.za/tech/tech_grade_310.htm .

Once you have this data you have to solve the power law eqations as a set of simultaionus equations, so break out your old math books.

I hope this helps.

Regards

Stephen
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- Richard Obrien @ Stephen Endersby on May 22, 2009 11:49 AM
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  Hello Stephen,
  
  Have you had any success using creep analysis in 2009? I believe we have the proper creep constants for nylon and it always aborts on the first step (regardless of sing elim factor, conv tolerance etc). The cosntants we are using are:
  C1 2.802e-11
  C2 1.117
  C3 0.059
  CTC 0 (isothermal case)
  
  Do you have a set of constants for any material that is known to work?
  
  Thanks
  Rick
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  - Ananda Ganesh Madheswaran @ Richard Obrien on Jan 9, 2017 10:06 PM
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    HI Rick,
    I have used the creep constants for the nylon and got a abort on the first step.
    Now i have changed the convergence tolerance to .05 then it got solved.
    
    Thanks.
    Can you please send me the creep data's for nylon (i.e) any strain vs time curve
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Jose Eduardo Fernandes de Camargo Aug 18, 2009 11:25 AM
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Hello folks,

Is everything ok?

Could you please tell me if there's any source of creep datas?

Best regards,

Eduardo Camargo
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Jack Lynch Sep 13, 2010 4:45 PM
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Bumping this old post.

I have been searching and requesting data from our supplier (custom blender) and have come up empty on finding the proper time, temp, stress data on a 25% glass filled 66 nylon needed to calculate the creep constants. I have been able to come up with a creep modulus chart (BASF Ultramid materies are one of the few that list this information) for various stress levels at different temperatures over a time period. Is it valid to just solve with the much lower creep modulus and not use "include creep affects" and the C0, C1, C2?

For example the room temp tensile modulus is 1,200,000 psi. From this chart the room temp creep modulus at a 4,300 psi stress level at 10,000 hours is about 51,000 psi.
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Creep Analysis for thermoplastics

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