INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS
TRM are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
Log In
Are you an
Engineering professional?
Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving . By joining you are opting in to receive .
Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Eng-Tips Posting Policies
Applying multiple bolt loads and get a better mesh
thread799- Forum Search FAQs Links MVPsForum
Search
FAQs
Links
MVPs
(Civil/Environmental)
(OP)
10 Feb 17 08:44Hi,I am trying to build a model of a basement of a wind turbine which I will use in my bachelor thesis. I have two issues with the model:I'm trying to apply mutliple bolt loads on 192 bolts. I am only able to apply one bolt load at a time. I already selected all bolts at the same time, but Abaqus gives me a warning.Another issue I have is the mesh. I am not really happy with my actual mesh. I tried to partition the part further, but he mesh still looks arbitrary.Thanks a lot,Jan
Replies continue below
(Mechanical)
10 Feb 17 17:14What's your question?
(Civil/Environmental)
(OP)
12 Feb 17 11:37Am I able to apply multiple bolt loads at the same time? And which method is the best for not getting this warning showed in my first post.Do you have any advise to get a better mesh? It looks really arbitrary and further partitioning lead to a worse mesh.I would really appreciate any kind of help.Best regards,JanP.S.: I attached the .cae file of my model.
The company is the world’s best Mesh Bolt supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
(Mechanical)
16 Feb 17 18:17#instance bolts and couple to flat diameter
for n in range(NB/4):
x=cos(pi/180*(360/(2*float(NB))+n*360/float(NB)))*C*0.5
z=sin(pi/180*(360/(2*float(NB))+n*360/float(NB)))*C*0.5
y=t+rf
#place bolt
bolta=myModel.rootAssembly.Instance(dependent=ON, name='Bolt-%s' % str(n+1),part=bolt)
bolta.translate((x,0,z))
#bolt loads
bmid=bolta.edges.findAt(((x,0.5*y,z), ))
bloc=myModel.rootAssembly.Surface(end1Edges=bmid, name='Surf-%s' %str(n+1))
myModel.BoltLoad(boltMethod=APPLY_FORCE, createStepName='Bolt Up'
, magnitude=SAb*RA, name='BoltLoad-%s' %str(n+1), region=bloc) In the past I have used a for loop to apply loads to multiple bolts because of this warning. I was using wires for bolts. The code is below, you may be able to modify it to suit your application.It is tough to comment on the mesh just from the photo. My latest version of Abaqus is 6.14-1, so I cannot open your CAE. Photo below shows my first thoughts on the mesh.
Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.
Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.
Click Here to join Eng-Tips and talk with other members! Already a Member? Login
The mesh and engineering judgement have a large impact on the quality of the FEA results. After all, FEA is a numerical methods approach towards the real solution. Therefore, hand calculations should always be performed to verify the results. Remember that a static FEA does not consider instability, inertial effects, fatigue, etc.
Meshing the entire structures is not always feasible or particle. A good engineering practice is to break up the structures into simpler elements for inspection and analysis [1].
At least three mesh layers are required to capture the change in bending stress through the thickness [2]. Five is a desirable lower limit.
Pay special attention to the transitioning between mesh densities, since abrupt transitioning introduces errors of a numerical nature [3]. The results may be overly conservative and non-realistic. Mesh transitions should be located away from the areas of interest in a region.
For simple elastic structures, use a coarse mesh for strength analysis and a fine mesh for fatigue analysis [4]. More complex shapes or steep stress gradients may require finer meshes. Brittle materials are defined as materials with a final strain before material rupture of less than 5% (εf < 0.05). They require a much finer mesh as the lack of ductility does not permit localized yielding.
For simple elastic structures, the suggested maximum element dimension is 10 times the smallest element dimension in a strength analysis [4]. Even with more complex shapes, this serves as a good starting point with further iterations of refinement from there.
Remember to defeature you model for the mesh. The solid part may contain unnecessary details that should be omitted when you set up your FEA model. Common details to defeature include small holes, faces, engravings, faces, features, etc.
Use localized mesh controls to fine-tune your mesh to adequately model the transition zones. The standard automatic mesh provides a good starting point, but should be fine-tune through iterations and should be refined at hole locations, curves, corners, etc.
Remember to split the face to accurately model load effects, corners, areas of interest, etc. For example, in this bolt-bearing region, the entire interior face of the hole does not bear against the bolt. Rather the bearing zone from the bolt was modeled at a 25° zone and the face was split [2]. The corners and areas of concern where also split to refine the mesh density.
Remember to fillet interior corners as sharp re-entrant corners result in stress singularities. The more you refine, the more the stress never converges to the true value. Adding a fillet removes the infinite stress, but interior fillets usually need a reasonable amount of mesh refinement [2]. Exterior corners are less important at getting accurate results.
If the stress does converge but are still extremely high and unexpected, you may be modeling a stress peak. Stress peaks or concentrations do not significantly affect ductile failure. The effects of stress concentration are ignored since the material will yield locally at the stress-riser while the material further away from the riser remains below yield strength [5]. This is further verified by the allowance of highly localized stress that are blunted by confined yielding [6].
SOURCES
&#;ABOUT
Eric Kuusisto is a registered Professional Engineer (Civil-Structural). He has worked in a wide range of structural engineering projects, from skyscrapers to transmission towers to oil & gas. Currently works for HALFEN USA as an Engineering Technical Representative. Please like and comment!
If you are looking for more details, kindly visit Split Set Mining Systems.