Low Cycle Fatigue in Abaqus

**Ivasiev** · 2010-11-15, 16:00

Dear All,

Curently I'm trying to implement the Damage initiation and Damage Evolution in Abaqus LCF with the parameter =Hysteresis Energy.

The Calibration of this model requires 4 constants c1, c2, c3, c4, I have found example constants but cannot find the way in which they are derived, or where they come from for that matter.

Does anyone know what model the Hysteresis Energy damage in Abaqus is based on and how one would find these constants for their material.

Thanks in advance!

**Jorgen** · 2010-11-20, 13:22

Can you remind me what LCF stands for?
What version of Abaqus are you using?
What section of the user's manuals discusses the damage model that you are trying to use?

-Jorgen

**Ivasiev** · 2010-11-20, 13:42

Hi jorgen, Thank you for the reply,

LCF is low cycle fatigue, the version of Abaqus is 6.9, 6.10.

The section is 6.2.7 Low-cycle fatigue analysis using the direct cyclic approach: http://abaqus.civil.uwa.edu.au:2080/...06s02at06.html
and more specifically: 21.4.3 Damage evolution for ductile materials in low-cycle fatigue: http://abaqus.civil.uwa.edu.au:2080/...ageevolfatigue

I have a rough idea of how to do it but the presence of the L parameter means that it will differ with element size, any advice would be great.

-I

**Panos** · 2011-03-01, 06:14

Hi all,
I dont know if anyone experiences the same problems. I am trying to use low cycle fatigue in Abaqus (abaqus 6.10, but the procedure is also available in previous versions as well). I am experiencing the following considerations-problems, when using direct cycle approach:
1. it seems the time of fatigue cannot be imposed by one parameter. But it is a multiplication of cycle time period and maximum number of cycles.
2. the cycle increment size in damage extrapolation is not as it should have been the damage evolution over a number of cycles, but it determines the time period of one cycle.
3. the number of fourier terms should be set to 1 to be able to not to disturb your defined load. Messing with this parameter changes your defined load.

For example I am trying to model LCF under a sinusoidal loading. So I impose a periodic loading. And the above parameters have to be set:
cycle increment size=1
fourier terms=1 (all of them)

So I dont see the effort working with the direc cyclic approach of Abaqus. I wish someone can prove me wrong. But I have the feeling that the direct cyclic approach doesnt do what it is supposed to do!!!

Regards,
Panos

**hernang** · 2012-07-29, 11:02

Hello Ivasiev,
were you able to define c1,c2,c3,c4? I found some information for most of them but not yet for c1.
Also, how do you perform the LCF analysis? I have no idea how to visualize the results...
Thanks!

**waqas.hf** · 2012-07-30, 21:39

Hi Herang,

I had been struggling with c1,c2,c3 and c4 for the past 1 week now. I would really appreciate if you can tell me what they are physically. If i am not wrong, c3 and c4 are paris laws coefficient and exponent respectively but i dont know about c1 and c2. Lets discuss..

Waqas

Originally Posted by hernang

Hello Ivasiev,
were you able to define c1,c2,c3,c4? I found some information for most of them but not yet for c1.
Also, how do you perform the LCF analysis? I have no idea how to visualize the results...
Thanks!

**hernang** · 2012-07-31, 06:40

Yes you are right about c3 c4, I have some examples and can let you know how to get them, I could send you my thesis (draft) document which I'm working on, it explains how to obtain them, also the paper from where I took the values, Can I have your email address?
regarding c1 c2 I have absolutely no idea... I've been trying to find the for over 2 months now, I contacted Abaqus representative for my company but they said they only have the help available...

Originally Posted by waqas.hf

Hi Herang,

I had been struggling with c1,c2,c3 and c4 for the past 1 week now. I would really appreciate if you can tell me what they are physically. If i am not wrong, c3 and c4 are paris laws coefficient and exponent respectively but i dont know about c1 and c2. Lets discuss..

Waqas

**waqas.hf** · 2012-07-31, 10:54

Hi,

My email address is waqas.hf@gmail.com

Well as for my problem, i am working on a pressure vessel exposed to fatigue loading. When i check the abaqus manual, c3 and c4 make sense BUT only for delamination problems. In my case (bulk material) i am not sure that c3 and c4 mean the same. In my opinion they might be fatigue ductility coeffciecnt and exponent respectively. C1 and C2 in my case might be hardening coefficient and expoenent respectively too.

Just send me your thesis and references from where you captured c3 and c4. Exchange your email with me and i will send you a report that made me think that c1 to c4 might be ductility and hardening properties. Lets solve the problems together

Waqas

Originally Posted by hernang

Yes you are right about c3 c4, I have some examples and can let you know how to get them, I could send you my thesis (draft) document which I'm working on, it explains how to obtain them, also the paper from where I took the values, Can I have your email address?
regarding c1 c2 I have absolutely no idea... I've been trying to find the for over 2 months now, I contacted Abaqus representative for my company but they said they only have the help available...

**fahadbakhtyar** · 2012-11-02, 15:50

Herang

I am going through a similar problem , if you could send me the paper as well, it would be really gr8. My email address is fahadbakhtyar@gmail.com .

Regards

Fahad

Originally Posted by hernang

Yes you are right about c3 c4, I have some examples and can let you know how to get them, I could send you my thesis (draft) document which I'm working on, it explains how to obtain them, also the paper from where I took the values, Can I have your email address?
regarding c1 c2 I have absolutely no idea... I've been trying to find the for over 2 months now, I contacted Abaqus representative for my company but they said they only have the help available...