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HOW TO APPLY CYCLIC LOADS IN ABAQUS

I've performed a experiment in fatigue.I need to now perform analysis in ABAQUS and validate the results.

MY QUESTION IS - HOW TO APPLY CYCLIC LOADINGS IN ABAQUS,SAY FOR INSTANCE I'VE RUN 60000 CYCLES AT 10 HZ AT A MAXIMUM-MINIMUM LOAD OF 18 KN - 2KN

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T = 1/10 = 0.1s.

 So for 60000 cycles define an amplitude function (better in terms of total time) of duration 60000*0.2 = 12000 s. It will be a series of triangular loading cycles where in 0.1 , peak load is reached and then in next 0.1s unloading is done. So a total of 30000 triangular units each of 0.2 s duration. Recommendation will be to load in one step and unloading in another step (that's why amplitude definition in total time). Use restart analysis as it will generate massive output file.

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The world started with 0, is progressing with 0, but doesn't want 0.

Can it be extended for sinusoidal loading?If yes,how???With this method,will the results be accurate,close enough to what we get when using FE-safe software which people use specially for this purpose??Thanks in advance!

If it is just for a single cycle,then what does A and B in create amplite dialog box refer to?How to give values to them??

can anyone help me out with a reverse cyclic test of a wall panel with first 4 cycles in force control environment and than 20 cycles in a displacement controlled environment using ABAQUS????

hi.

i am modelling a composite plate subjected to a cyclic loading

i wnat to model a 1000 cycle with 10 hz frequency.

 i have some question from you.

is it possible to use static,general as step?

on the other hand , i use  umat subroutine for egradation of properties, i want to have a degraded properties,in each cycle.

is it true that i assme  that every increment is 1 cycle?

and at last, i dont understand what exactly,do you mean in this sentences "Recommendation will be to load in one step and unloading in another step"

can you explain it?

 

thanks 

mmalekan's picture

 

When two-step loading being used and based on Abaqus step chronically, Is this type of loading definition (actually, step definition)can be called a Fatigue load?

You have to create a periodic amplitude and apply it on your loading.

create a periodic amplitude which content :

circular frequency : 2*pi*f 

starting point : as you want

initial amplitude : average load 

Write in A & B as :

A*cos(wt)+B*sin (wt)

You have to create a periodic amplitude and apply it on your loading.

create a periodic amplitude which content :

circular frequency : 2*pi*f 

starting point : as you want

initial amplitude : average load 

Write in A & B as :

A*cos(wt)+B*sin (wt)

Thanks for the reply.But,what should be the value for A and B??Is it like random or does it have any kind of calculations involved???
Can 60000 cycles be generated with the method available in abaqus??

Under Direct cyclic analysis,Nonlieargeom is by default off...also there is no edit button to switch it on!!!So,does it mean that the cyclic analysis option cannot be used if the material goes to plastic state??

Qaleem

Hi Friends, 
I am really stuck in applying cyclic loads to a simple 2-3D beam in Abaqus. The material is defined just as elastic. I want to apply half-sine loads. So I have defined Tabular data in Amplitude curve like this instead of using Periodic option of Amplitude (as it gives the whole sinusoidal load and not the half-sine): 
0 0.00 
0.05 0.31 
0.1 0.59 
0.15 0.81 
0.2 0.95 
0.25 1.00 

On the other hand, I have defined my pressure load equal to 10MPa. The problems are: 
1. I cannot see any displacement stresses after completing the job, seems there is a problem with reading the Tabular data because when I run the program without assigning Amplitude and just the ramp loading, it gives outcomes! 
2. Can I define for example 1000 half-sine cycles in Tabular data in Amplitude curve section? or I need to go through other options. 

Please consider my question as I really need help. Thanks Pals! 

P.S.:I defined a crack with XFEM at the bottom of the beam.

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