elogesh
Mechanical
- May 10, 2002
- 187
Hai,
I got good responses with earlier thread of nonlinear analysis permeanent deformation.
Now I have a practical problem in my industry to be resolved.
We have accelerated life testing for evalauting the life of the system and components for the specified warrenty period.
In our system, a pipe connection has failed during this acclerated life testing.
We want to simulate the similar conditions using FE technique.
The pipe at one end has a dynamic member(moving member) and other end connected to static member. Inside the tube there is high pressure fluid.Therefore the tube is subjected to 1) Internal pressures 2) End forces due to the moving member.
The internal pressure is increased in the following fashion
1) First pressure load p1 with number of cycles n1
2) Second pressure load p2 with number of cycles n2
3) Third pressure load p3 with number of cycles n3
4) Fourth pressure load p4 with number of cycles n4
p4>p3>p2>p1.
How to evaluate the life using FE technique?
I may be asking very broad question? But if you can provide some tips,websites,suggestions it will be helpful to my problem?
I will try to get s-n curves from our laboratory?
I am planning to do the analysis as mentioned below.
1) Applying P1 pressure load and finding out the static equivalent stresses.Then going back to the s-n chart and finding out the number of cycles allowed(N1) for this stress condition. Then finding out the remaining life period using cumulative fatigue damage.
That is n1/N1+n2/N2+n3/N3+ .. = 1
2) The above procedure is repetated for p2 and p3,p4.
I have few queries in this regard.
1) For static failure in tube, I used to follow von-mises stress failure theory, I think that is appropriate for my ductile material condition.Now for the fatigue case whether I can consider the von-mises stress as the equivalent stress or I have to consider principal stress.If principal stress then why have to consider principal stress?
2) I am going through the stuffs like miners rule,strain life based approach,rain flow ... counting,etc.Can I have any suggestions in this regard?
IF there is something technically wrong,please correct me.
I have good knowledge of FE and ANSYS,general purpose finite element analysis package.
I keen to study and learn any text books required for the analysis.
Looking forward for your suggestions/feedbacks.
Regards,
E.Logesh
I got good responses with earlier thread of nonlinear analysis permeanent deformation.
Now I have a practical problem in my industry to be resolved.
We have accelerated life testing for evalauting the life of the system and components for the specified warrenty period.
In our system, a pipe connection has failed during this acclerated life testing.
We want to simulate the similar conditions using FE technique.
The pipe at one end has a dynamic member(moving member) and other end connected to static member. Inside the tube there is high pressure fluid.Therefore the tube is subjected to 1) Internal pressures 2) End forces due to the moving member.
The internal pressure is increased in the following fashion
1) First pressure load p1 with number of cycles n1
2) Second pressure load p2 with number of cycles n2
3) Third pressure load p3 with number of cycles n3
4) Fourth pressure load p4 with number of cycles n4
p4>p3>p2>p1.
How to evaluate the life using FE technique?
I may be asking very broad question? But if you can provide some tips,websites,suggestions it will be helpful to my problem?
I will try to get s-n curves from our laboratory?
I am planning to do the analysis as mentioned below.
1) Applying P1 pressure load and finding out the static equivalent stresses.Then going back to the s-n chart and finding out the number of cycles allowed(N1) for this stress condition. Then finding out the remaining life period using cumulative fatigue damage.
That is n1/N1+n2/N2+n3/N3+ .. = 1
2) The above procedure is repetated for p2 and p3,p4.
I have few queries in this regard.
1) For static failure in tube, I used to follow von-mises stress failure theory, I think that is appropriate for my ductile material condition.Now for the fatigue case whether I can consider the von-mises stress as the equivalent stress or I have to consider principal stress.If principal stress then why have to consider principal stress?
2) I am going through the stuffs like miners rule,strain life based approach,rain flow ... counting,etc.Can I have any suggestions in this regard?
IF there is something technically wrong,please correct me.
I have good knowledge of FE and ANSYS,general purpose finite element analysis package.
I keen to study and learn any text books required for the analysis.
Looking forward for your suggestions/feedbacks.
Regards,
E.Logesh