How to apply Cyclic loading 2

[san07gita]

Hello everyone! I am a new user of abaqus.I am just wandering how I can apply cyclic/fatigue loading using ABAQUS.
Please help me.
Thanks,
Sangita

 

[xerf]

The simplest way is to use amplitude curves.

Basically, for each loading cycle you define a step.

Any load (or displacement, field) in ABAQUS can be supplied
(generically) as:

Load(time) = Magnitude * Amplitude (time)

The amplitudes can be defined in terms of step time and can control the current value of the load during one step (i.e. one cycle).

 

[Yoman228]

What type of material you using? does the material go to plastic? you may need to consider to use the following.

*PLASTIC,HARDENING=combined, data type=parameters

 

[san07gita]

Thanks all for the reply. The material is silicon, which is elastic. Usually silicon bulk material does not undergo any fatigue failure. However, recent studied shows that silicon microfilm undergoes fatigue failure under high stress cycles. So I am not sure Fatigue Calculator can do that or not.
Sangita

 

[san07gita]

Hi Xref.
For using the Amplitude option I think I have to put exaxt time value. However for my case I am not sure what time it will take to deflect fully. As I want to let the beam deflect fully and then let it appear at the unloading position.Do you have any idea how I can use time period instead of time.
Sangita

 

[Cansand]

Xerf ..why for each loading cycle he has to define a step..?
one can apply as many load cycles as one likes in a single Step
san07gita ; If you have elastic material pay attention to using appropriate and accurate damping variables

 

[xerf]

To be sure you get a frame at the end of the cycle if you use automatic incrementation.

 

[san07gita]

hi helppoorpeople!
Thanks for your reply. So for silicon what will be the value of damping factor . I am need to use that factor for Steps?
Please let me know.
Sangita

 

[johnsmith2]

o.2

 

[Cansand]

Damping is dependent on frequency . Popularly used is
Raleigh damping ( the damping matrix is taken to be a linear combination of the stiffness matrix and the mass matrix) :

[C] =a [M]+ b [K]

a, b are dependent on on fraction of critical damping and the frequency of interest
e=1/2(aw+b/w)
calculate a and b by choosing the fraction of critical damping e1 and e2 at two different frequencies you are interested in.


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The coefficients apply to all modes. The corresponding friction coefficient for mode j amounts to: