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[Solved] limits of Bergstrom_boyce model

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Posts: 20
Topic starter
(@Kinsy2324)
Eminent Member
Joined: 10 years ago

Hello to all,

I have used the Bergstrom Boyce model to predict Hysteresis curves.

My worry is that this model has good predict for a large deformation (30% .. 50%) But the less than 20% deformation we have not a good curve??!!!

My question :

the bergstrom boyce model has it a limit in deformation to predict a good curve??

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

No. The Bergstrom-Boyce (BB) model should work very well for both small and large deformations.
Can you provide a figure showing the problem that you mentioned?

-Jorgen

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Posts: 20
Topic starter
(@Kinsy2324)
Eminent Member
Joined: 10 years ago

Hello,

the first figure it is for 50% of deformation, the BB model have a good predict (low error).

The second figure it is for 20% of deformation, the hysteresis havent a good predict.

tell me please , why we have this bad predict, and what is the reason

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

How did you calibrate the BB model for the two cases?

You should be able to calibrate the BB model so that it matches both data sets very well.

/Jorgen

Posts: 20
Topic starter
(@Kinsy2324)
Eminent Member
Joined: 10 years ago

for the two cases, I have used the methodologie found in your thesis ( LARGE STRAIN TIME-DEPENDENT BEHAVIOR OF ELASTOMERIC MATERIALS By Jorgen S. Bergstrom.)

in order to determine the Hysteresis parameter ( S, A, m, c ).

for the two cases, i have changed between them just the initial shear modulus ( mu0) ( experimental value ) to determinate the equilibrium curve, as well as the strain rate.

Please tell me where/ what is the problem???

thank you in advance

Posts: 20
Topic starter
(@Kinsy2324)
Eminent Member
Joined: 10 years ago

Hello Jorden,

Probably, I have used a false formulas to calculate the strain rate.

in the following you find the process to calculate the strain rate , and please confirm me this process? if it is not correct tell me How determine the strain rate ????

the vitesse (v) applied in a machine = 5 cm/min

the initial length = L0 = 60mm

the deformation = L=28mm

So, the time t=L/v=(60*28)/50

the strain rate = [(L-L0)/L0]/t ( Please it is correct!!!)

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