FEA of plastic parts 2

[oso]

Anbody have experience on FEA analysis on plastic parts? I have read some article and most people suggested that nonlinear FEA should be used. Is that true?

I understand that the stress-starin curve of plastic is different from that of metal. However, I still would like to use linear to start with and get the best insight about stress on product design.

Any experience you could share would be helpful!

Thanks in advance.

 

[jurs]

Depends on the material in question. Some plastics are linear elastic just like steel (under small displacements!) but others have a modulus that changes both with increasing strain and strain rate (also temperature). My suggestion is that you fully research the material you are using, and formulate your model accordingly. Also, be carefull about which failure criteria you use for analysis... a suitable criteria will also vary with material properties (for example, the part may fracture before it yields).

Check out the GE plastics site

http://www.geplastics.com/index.html

It's a good resource. Also, Im sure there are plenty of books on the topic at your local university library.

CJ

 

[GSC]

It is very important to characterise the plastic you are working with. If you use linear curves instead of non-linear, your final result can easily have more than 20% deviation from the real situation already at not too high strains, because plastics are much softer than metal and usually highly non-linear. Use at least bi-linear S-S curve for the first estimate, usually not much pain to set it up and if you are lucky it will not deviate more than 10%. Also there are some good easy to set up hyperelastic models to get quick answers, although that will need some further reading. All the above is true only if you don't damage your plastic part, e.g you stay in its elastic domain! If it starts to flow, creep, change phase, melt, etc... then you are in trouble.

some nice info @:

http://www.axelproducts.com/

good luck
GSC