FEA Model versus Actual Results 4

[rpm63]

I have modeled several simple metal cantilever beams in Algor and have compared the results to actual Instron pull (push) test data. I have applied a small displacement at one end. The models calculated force is always 30 – 50% higher than actuals. The FEA results agree with the hand calculated force using formulas from the Machinists Handbook. Any suggestions?

 

[RPstress]

I'm tending to think that the cantilever results differ from theory because of less than perfect stiffness at the constrained end plus maybe low modulus. However, I'm still a bit worried that the simply supported test gave similar results to the cantilever... I haven't been able to investigate the theoretical effects of varying a simply supported specimen's supports, etc., but you've got to think that a simply supported specimen is more accurate than cantilevered (fewer real-world things to go wrong).

 

[rpm63]

The simply supported results were better than the cantilever. I tested brass and steel. I was 8 – 17% off for simply supported and 19 - 23% off for the cantilever.