what is wrong with my spring and base?

is there anyone telling me how to operate a CAE analysis of a compressed spring in Catia ? the key problem is why it had errors when i add a base to the spring?is it proper to restrict and give loads to them in my operation? the figures in below.

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2 Answers

Hi,
If you work with a Product, I think that you forgot the contact connection between the base and the spring.
If you work with a Part, it may have a breaking of the spring that implies infinite elongation.

 
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Good morning,

I see that you use Catia to check your spring deformation. I´m user of ANSYS. So, the principle is the same in this type of study. I will specified here some points which from my point of view will can help you:
1. On the bottom of spring, eliminate in the first stage any support and apply constraints directly on the seat surface of spring. Use constraints in all directions (ux=uy=uz=rx=ry=rz=0).
2. On the top of spring apply a force in vertical direction to compression spring. First study running without other constraints on upper side. Don´t use acceleration of gravity. Apply Force in a single step (min=0; max=your value). If you will encountered divergence, try to apply the same force in more steps, gradually (for example: min=0N; F1=5N; F2=10N; ....; Fn=max).
In this manner you will observe better at which force occurs divergence. Because is an problem which is treated very well in all books reffering to strength of materials, you can compare analytical calculus with FEM calculus, and control the solution. Other reason for divergence can be missing contact betweens wires, and higher force applied in a single steps.
3. If not converge using specifications from step 2, then try to apply on the same region of applied loads some constraints which constraint model to displace only in vertical direction and permit rotation along their vertical axe (under compression spring tends to rotate their upper side along their vertical axe).
4. If you have possibility to use in Catia material with stress-strain curve, use it. If you have possibility to choose analysis which allows large deformations use it. If you have possibility to choose contacts betweens surfaces or wire use it (to obtain self contact) because this is the real model of work for spring.
5. Try an finner mesh to see the effect.

So, keep in touch with your study. You can learn very much things from this study.

Best regards.

 
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