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@MSKDS Do you have any idea about my last post? Your comments will be appreciated.

@mskds545 How about step 13 of para. 10.5.2.3 of ASME FFS-1 2016 ? There is a criterion for accumulated inelastic strains in table 10.3. But it is independent of stress state.

@r6155 Two action plans has been started together. One short term plan to allow start-up of the plant as soon as possible including complete NDE on all of the line joints and repair of revealed cracks. The first plan has been started at site. The long term plan will be implemented in the first...

Please take a look to PVP2014-28797 It has been mentioned on page 10.

Do you mean to use continuum elements for the elbow and pipe elements for other parts of the system and then to connect continuum and pipe elements to each other?? I don't know if it is possible in Abaqus. Please advise me. Also I think the elastic follow-up always occurs and with help of...

@r6155 Our company is currently closed because of corona virus and I don't have access to the information. I will send as soon as possible

@mskds545 You are right. With help of this method (applying force boundary condition) I am able to obtain very conservative upper bounds of inelastic strains and as you mentioned the real strains are lower and need the behavior of the entire structural system. But modeling of such a complex...

Following on from the previous post: Apart from material considerations, I also want to have your comments about my analysis method. Indeed, I did the initial elastic analysis through CAESARII software. You can see the piping system in the attached figure. Based on this analysis, all of the...

@r6155 You are probably right. But there are a lot of papers which show how elastic follow up caused by creep condition causes severe cracks. Therefore I think it is reasonable to investigate the system based on this aspect. @mskds545 As you recommended I started to use Omega-model to see what...

Many thanks for the comments. So let me tell you my problem in detail. In one of our projects, there is a piping system which operates in creep range. These are the characteristics: Design Temp. = 675 C // Design pressure = 3900 Kpa // Material = A312 TP321H // Pipe OD = 34” (thickness=71 mm)...

@mskds95 Many thanks for your response. Did you ever use the method mentioned in para. 10B.5 of ASME FFS-1 2016 to obtain Isochronous curves? Is it a good solution? In this method, I have problem with Δcd (adjustment factor for creep ductility) and also with Δsr (adjustment factor for creep...

@TGS4 Would you please tell me your opinion about my post @ 31 Dec 19 12:28 ? I read the answer of mskds545 @ post 4 Jan 20 22:55, However, your answer is also very important. Thank you.

Is it possible to use Isochronous stress strain curves instead of direct creep analysis(with a creep material model) to analyze systems that operate in creep range? I want to obtain the amount of strains for a system which operate in creep range after 10000 hrs. Therefore I want to perform...

@TomLee777 I doubt your suggestion would be a suitable solution since the stress values are strongly dependent on the radius value.

@mskds545 Thanks for you reply.

Refer to this AISC book : "The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Applications"

@IdanPV I'm not experienced in FEA but I usually use elastic-plastic analysis. because I no longer have to deal with the problem of stress linearization and categorization.

@IdanPv I have already checked the example 5.5.4 of PTB-3. But there is no singular point in that model. My concern is whether the amount of strains in singularities are valid or not.

@TGS4 So, Do you believe that unlike stresses, the strain will converge at a singular point and the required value for fatigue evaluation could be obtained? Would you please explain me what is the reason ? about the material model: It's easier for me to use Twice yield method and therefore a...

@IdanPV I read the article and thank you so much for sharing. Two methods have been recommended for singularity problem that one of them is well known for me. one is hot spot with SSE(Surface Stress Extrapolation) and another is something like the method that was recommended by kalnins(passing...