I have set the stiffness value equal to the young's modulus (I have assumed an isotropic elastic material). The higher the penalty factor the less the overlap between the surfaces (and hence more accurate solution) yet the more ill-conditioned the stiffness matrix will be. hi,
If you have to modify the solver sequence, this separate segregated group should still be kept, and solved for after the displacements. Suggestion de Produits Tlchargez les fichiers du modle To start a new discussion with a link back to this one, click here.
Thank you! During her career, she developed standards for water quality and.
Using a penalty function for contact problem is good alternative of the augmented Lagrangian method available in the structural mechanics module. When solving a Stationary study, you will want to ramp up the prescribed displacements, loads, or spring foundations on unconstrained domains. Veryst Engineering. and the sensor has a softer silicone rubber in his structure under the beam. Is that what did you mean? And I tried to apply the penalty method instead of the augmented method but still not working. To do this, I used a stationary study and a linear elastic material: aluminum billet (or cylinder) contacting a flat, thick plate (fixed constraint). You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Yajuan, Hi everybody,
The mapping between the source and destination boundaries will be computed only once, based upon the initial positions of the domains, which leads to faster and more stable convergence. The peak value of spring stiffness, k0, should be chosen such that the displacement due to the full applied load is about equal to the element size of the contacting boundaries. Is there any other recommendation about this problem? Where is the contact pressure variable and also I can't find the Lagrangian solver option in order to deselect it. Thanks again
There are three contact constraint enforcement methods available in Abaqus/Standard : The direct method attempts to strictly enforce a given pressure-overclosure behavior per constraint, without approximation or use of augmentation iterations.
Pasquale, Hi Dear Ahmad,
Thanks alot. 1 Reply, Please login with a confirmed email address before reporting spam. Test fit your tuner, import, track car with our new wheels by Ultra Wheel . Build & Customize Your Car With Ultra Wheel Car Builder!
Penalty contact adds stiff springs (penalty factor) between the contacting surfaces that are only active when the surfaces overlap. A single Contact feature can be applied to all Contact Pair definitions at once. Right now I have no idea what cause convergence problems. go to physics>boundary settings>pairs>contact>"pn". Pasquale
however, when I enter the initial values of the E for the slave material "hyperealstic" divided by its maximum mesh size, the convergence will not occur. In this way you are modifing the default boundary constraint equation. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version
I also am trying to simulate contact between stent device and blood vessel. However, once I included the denpendence of the expansion rate on the stress, the contact part of the problem simply could not converge.
Concerning about constraints before in contact between two parts, I already test each part is fully constraint or not. When I choose the penalty factor as E/k (I know elastic modulus and I get average mesh size from statics), the result is so strange. If your contact simulation does involve friction, set up and solve the problem without friction first. I stopped using the Comsol contact pair model and instead defined my own boundary force due to problems with convergence. Using a penalty function for contact problem is good alternative of the augmented Lagrangian method available in the structural mechanics module. Best regards
Version 3.5a
I understand how it is used in the augmented Lagrangian method. If it did not converged, change the contact discritization to 1.
As you suggest, the penalty method is more stable than the lagrange one and thus the automatic procedure may be performed with few problems by using a penalty function. Within the Parametric settings, changing the Predictor to Constant will make the convergence more robust, but slower. If the initial overlap is too much convergence may be a problem, but you have them initially forming a line contact which is fine. When spring foundations and applied loads are in a single model, the applied loads should be ramped up linearly at the same time as the spring constants for the spring foundations are ramped down nonlinearly using the above expression, and shown in the plot below. Could not obtain license for COMSOL Multiphysics GUI. I have a model that contains an elastic beam that when deflected comes in contact with two different hyperelastic materials one on each side. P.S. For more details on the usage of Form Assembly, see Knowledgebase Article 1216. A PML can be treated as an anisotropic ab-1 Excerpt from the Proceedings of the COMSOL Conference 2010 Boston. if you can, please attach your model so we can see better your settings. More generally regarding this thread: The previous discussions in this thread do refer to much earlier versions of the software. it helps alot. When using the augmented Lagrangian formulation, it is necessary to manually scale the variables in a contact problem. Jay. If you have a specific problem, please post much more details, so I can better understand your problem. All contact pairs, both manually and automatically created, are defined at: Component > Definitions > Contact Pairs. I am using comsol 4.2 to simulate a contact problem. Ahamad, Hi Ahmad,
COMSOL does not assume any legal liability for the accuracy of the data disclosed. Then remove the contact pressure variable from the solve for list in the solver manager. 4. define a parametric solver to fine-tune the load step (use a small parameter-step if the convergence does not appear). Thank you for the response.
COMSOL document says
I know the ugmented Lagrangian method and the penalty method are different. The rigid domains can have a very coarse mesh on any planar boundaries, however any curved contact boundaries will still need to be finely meshed. The rigid part should be the source in the Contact Pair. If the contacting parts are in contact at the start of the simulation, then Speed is the preferred setting. The Structural Mechanics Module User's Guide > Structural Mechanics Modeling > Contact Modeling section. I would like to try Remi 's comments and therefore I have a question and a request :). Do I need to define k and h myself, or they are already defined? As surfaces come in and out of contact, load paths and stress states will abruptly change. Pasquale
Yours,
It is a good idea to scale this expression up or down based on two factors: (i) ease of convergence and (ii) solution accuracy. Remi Magnard
I am trying to get what exactly u meant by the order of the discritization and where I can change it. Note: This discussion is about an older version of the COMSOLMultiphysics software. That page also gives the pros and cons of the penalty method compared to the Augmented Lagrangian method.
. Structural Mechanics Concerning a contact pressure, I suggest that you take a look at cylinder roller example in the library. and similarly in any other directions that need to be restrained. Posted Jun 24, 2009, 8:50 a.m. GMT+2 Are you checking the box of creat creat pair at the end of Geometry? Posted Mar 22, 2011, 5:17 p.m. GMT+1 Remi Magnard. Veryst Engineering, Dear Nagi,
I consider every aspects you guys posted here. Use more increments when the convergence is slow. Why does it have . However, Comsol returns a convergence error. The augmented Lagrangian method is more accurate, but has higher computational cost, and will require more fine-tuning to converge. Input File Usage Use both of the following options to scale the default penalty stiffnesses: CONTACT PAIR, MECHANICAL CONSTRAINT = PENALTY , CPSET = contact_pair_set_name surface_1, surface_2 CONTACT CONTROLS, CPSET = contact_pair_set_name, SCALE PENALTY = factor Abaqus/CAE Usage Posted May 21, 2013, 9:28 p.m. GMT+2 The numerical solvers within COMSOL Multiphysics expect some degree of smoothness to the solution, so solving such models is inherently challenging. Where is the Contact normal penalty factor expression located? I think all this is due to the penalty factor assignment. Use the default suggested direct solver rather than the iterative solver whenever possible. This is where the overclosure/contact formulation comes into play. I am modeling a transient contact problem using the penalty method instead of the augmented Lagrangian method. sensor model with tissue_upper and lower jack.mph, sensor model with tissue_simplyfied model.mph, Methods for Dealing with Numerical Issues in Constraint Enforcement, Finding contact stress at the interface of contact pair, How to Evaluate Gear Mesh Stiffness in a Multibody Dynamics Model. Yours,
Regards. Any advices will be helpful and appreciate! By using Matlab a "perturbed" geometry is generated, by using a morphing mesh approach. Hi dear Sungho,
If one part is significantly stiffer than the others, its deflections will be relatively negligible, and it can often be considered as rigid. Penalty contact adds stiff springs (penalty factor) between the contacting surfaces that are only active when the surfaces overlap. Prodotti consigliati Scarica i file del modello Pasquale, Hi Dear Ahmad,
Thus, question are: is there a way to solve the contact problem without calculate the pressure field at the coontact interface? In some cases, this approach can result in faster computations and provide smoother convergence when compared to the Augmented Lagrangian method. I completely agree with the previous post. I will test as soon this procedure on a 3D model and I will update you about results. Only takes a few moments to solve. [QUOTE]
0.3 N) at least. But this is an option to consider. The first part (solid.Eequ/solid.hmin_dst) is a geometry/material part of the same form as the E/k expression you mentioned that is automated to get good estimates for E and k. The material stiffness Solid.Eequ is automatically calculated based on the material of the destination surface, and the minimum element size solid.hmin_dst is automatically calculated also from the destination surface. No matter how I change the contact parameters (i.e. Marjan, Hi Everybody,
I hope at least I can give you some idea. Thanks Pasquale. Penalty Method The default penalty method is rather simple and robust method to introduce the contact condition. Ahmad, Hi Ahmad,
Using the parameter RampFactor that ranges linearly from 0 to 1, a spring foundation with spring constant kz in the Z-direction can be introduced where, kz = k0*(1-RampFactor)*2^(-RampFactor*10). As in your model the three domains are still in contact in the un-deformed configuration, you should set a small initial contact pressure (say 1e-3). The scaling of the contact pressure is used when checking the convergence, so if a too high value is used, there is a risk that the results are not correct.
I have applied your procedure on a 2D example and it seems to work very well. Solution Number: 1292 Applies to: COMSOL Model Manager, COMSOL Multiphysics, COMSOL Server Versions: All versions. If you are solving a stationary (steady-state) model, you will want to ramp the prescribed displacements, loads, and stiffnesses of any spring foundations during the solution. The first part (solid.Eequ/solid.hmin_dst) is a geometry/material part of the same form as the E/k expression you mentioned that is automated to get good estimates for E and k. The material stiffness Solid.Eequ is automatically calculated based on the material of the destination surface, and the minimum element size solid.hmin_dst is automatically calculated also from the destination surface. This contact algorithm is based on the penalty factor formulation related to the penetration of the solid parts in contact. However, I am still struggling with this model. The Penalty method must be used when modeling adhesion. If any one of them could work , then it would be sufficient to me. This affects the shape function and convergence as well. I would start by examining the error message that COMSOL reports. For more information on this, see Knowledge Base entry 905. [/QUOTE], Hi Sharon,
3. set a properly value of the initial contact pressure. 1- what do you call solver manager? The slate grey sky was turning to a menacing black as the light rain turned into a pelting hail. Now my question is
Finally deselect the augmented lagrangian solver option in the solver parameters (stationary page). I also implemented parametric sweep for solving. As long as your mesh is not moving, use extension instead of parametric sweep. Until now I didn't get any good results, all case I got convergence errors. This setting is shown in the screenshot below. The penalty method is not described at all. If you are solving a transient model but do not want to consider inertial effects (if you do not want to model the vibrations of the structure) then go to the Solid Mechanics interface, Structural Transient Behavior settings, and select Quasi-static, which will solve much more quickly. Good luck,
If the initial overlap is too much convergence may be a problem, but you have them initially forming a line contact which is fine.
problem with contact pair-penalty factor setting.
And the contact surfaces are defined as contact pairs. Browse the threads and share your ideas with the COMSOL community. Structural Mechanics This will automatically create Contact Pairs between mating boundaries of objects. what is the reason for that? For example the contact pair model is very sensitive to meshing. Note that while COMSOL employees may participate in the discussion forum, COMSOL software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. I dont know if this page dates back to v3.5A. I had thought that h is the average mesh size but now I learned that it is min mesh size of slave.It was a very good explanation of what I see as pn. The default is 0.005.
Introduce first a Global Parameter, such as RampFactor that multiplies all displacements, loads and stiffnesses. Marjan. I am also going to try setting both to 1 :). And I really appreciate your welling to help. But in my case one of the two contact surfaces was a static, stiff, perfect plane so defining the force equation was trivial.
If it is expected that there will be little sliding between the contacting boundaries (such as in a shrink fit or when two parts are bolted together) then go to the Contact Pair > Advanced settings, and change the Mapping method to Initial Configuration.
Yours,
Setting contact pair, meshing and solver setting looks fine, but why convergence strat oscillation up to very high value or down low finally not converge with current setting up??? Happy Birthday, Ellen Swallow Richards. [67] have verified the static contact Hertz model in COMSOL Multiphysics for the case of half gold cylinder sitting on a steel block . Discussion Closed This discussion was created more than 6 months ago and has been closed. Modeling friction is will often increase the computation time significantly, so if you can reasonably ignore friction, do so. Any help will be appreciated. Add a Contact feature within the Solid Mechanics interface. 2009 ., 02:50 GMT-4 Structural Mechanics & Thermal Stresses 27 Replies honestly do not know what to do with the model, and I have very important dead line in two weeks. Within the Contact Pair definition, choose the stiffer part as the source. The ramping of applied loads and displacements should begin from a value very close to zero, at which there is negligible, or even no, contact and should ramp up linearly to the maximum value.
Types Of Thermal Cameras,
E Commerce Research Papers 2017 Pdf,
Gillberg Smackdown Hotel,
Who Plays Jackie In Our Flag Means Death,
How To Enable G-sync On Asus Monitor,