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# how to plot creep curve for the whole specimen

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Posts: 13
Topic starter
(@Gordon)
Active Member
Joined: 15 years ago

Hi

I am trying to plot creep curve for a cylindrical specimen which is loaded along its length.

ABAQUS provides numerous options for strains and under each kind of strain again there are quite a many options and it also asks for selecting nodes and elements. But I am clueless about the strain type I should plot and also about the node/element for which I should plot.:confused:

Can you guys help me how should I get the desired plot?

Thanx

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Posts: 3998
(@jorgen)
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Joined: 5 years ago

I dont quite follow your applied load and boundary conditions. Are the stress and strain homogeneous in the cylinder? If so, you can pick any element/node.

I would pick the logarithmic strain LE.

-Jorgen

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Posts: 13
Topic starter
(@Gordon)
Active Member
Joined: 15 years ago

In my problem one end of the cylinder is fixed while the force is applied on the other end along the length of the cylinder.

Thus I feel all elements wont be having same creep behaviour.

Further for predicting creep behaviour shall I plot plastic strain along the length of the cylinder??

Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

I am afraid that I dont understand your description of the load, and the argument of the creep.

If I understand you right, would not the creep strain be the same everywhere?

Can you provide a figure? or explain more?

-Jorgen

Posts: 13
Topic starter
(@Gordon)
Active Member
Joined: 15 years ago

Hello

I have hereby attached the diagram of my problem.

And once again, I would like to put forward my doubts as follows:

Will All nodes have same deformation??

I guess elements will have different deformations and thus will give different creep plot. The point of fracture will have more creep than any other point.

Moreover what kind of strain is the correct measure of creep?? Should I plot plastic strain along z-axis to get the creep behaviour of the material??

Any help would be appreciated and forgive me if I sound too stupid.

Thanx

Posts: 124
(@bw_composite)
Estimable Member
Joined: 17 years ago

Hi there,

I will step in on this one hoping I can help a bit.

From your plot I would say strains will not be uniform, which might happen in an engineering sense only at a certain distance form the clamped edge (I am assuming form your sketch the edge is constrained both vertically and horizontally).

As a result you have to make a decision of which node to plot the strain vs. time for.

As far as the decision on which strain to plot, you could plot total elastic strain or creep strain only if you want (I use ANSYS, I am sure you could obtain the same in ABAQUS).

I assume you are obtaining large deformations, otherwise logarithmic and linear strain would be the same. I am not sure about the choice of plastic strain, which could deceive the result interpretation as, depending on what part of the specime you are interested in, plastic and creep strain could have well different meanings.

Hope this might help, my apologies if I missed anything for your description.

Thanks

Muzialis

Posts: 13
Topic starter
(@Gordon)
Active Member
Joined: 15 years ago

Hi..

Thanx Muzialis for your detailed explaination.

But I still cant figure out, for which element shall I plot the creep curve!

Should I check the deformation contours and then the region for which von-mises stress is minimum, I should plot the creep curve(elastic strain curve)??

I assume at the point of fracture von mises stress is minimum!

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