b. loading at rate of 9kN/min until failure of the specimen.

Thanks in advance,

Praveena

]]>I would like to perform an harmonic analysis usin viscoelastic materials in WorkBench.

First I was having some problems to define viscoelastic properties, but was able to manage it using command snippets. However the results I have don't match with my experimental data:

In red my experimental data, in blue the results i got using APDL only.

Appart from the mesh i think both analysis are the same in WB and APDL, however the results obtained in WB are far away from what I expected.

Can anyonde help?

I am attaching the WB project as well as the APDL script.

Engineers learn to compare the state of stress with values provided by a failure theory to decide if the part has failed. This is done by comparing a maximum stress in the model with some limiting value. For example, if the material is ductile, a quick linear elastic analysis will calculate a von Mises Equivalent Stress that can be compared with the Tensile Ultimate Strength. If the maximum stress is larger than the strength, the conclusion is that the part would have fractured. A common method to show failure in a linear elastic model is to set the threshold for the last bar on the legend, which is red, equal to the Tensile Ultimate Strength. If red appears on the contour plot of Equivalent Stress, then it is easy to say that the part has failed under this load and where the part would crack. But people still want to see the crack.

One way to show the crack without using Explicit Dynamics is to use the APDL command ekill. This command removes the element from the model when it reaches the failure criterion; the trick is how to get the model to continue solving after removing the element and incrementing the load.

SimuTech Group, a Premier ANSYS Partner, provided me with an APDL script and permission to share it with anyone. The script implements ekill in a way that allows elements to be removed and the solution to continue. It works best with displacement loads, not force loads. I was successful following the directions to use the script on one model and then another. I release this script into the community, as is, with no support and no warranty. I hope someone else finds it useful.

To show the script in use, I created a 2D plane stress model so each solve would be very fast. The model is a hook with an end load. The question is how much load can the hook support without failure.

I have three systems: Linear Elastic, Elastic Perfectly Plastic and Ekill Script.

In the Linear Elastic model, the legend has been configured so the color red shows elements that are above the Tensile Ultimate Strength of 640 MPa

ANSYS provides a stress tool to make a Safety Factor plot that divides the Tensile Ultimate Strength by the von Mises Equivalent Stress at each node. Therefore when SF < 1 the part has failed, and when SF > 1 the part has not failed.

In the Elastic Perfectly Plastic model, Bilinear Kinematic Hardening plasticity has been added to the Structural Steel model using the Yield Stress that was defined for that material and setting the Tangent Modulus to zero. During the solution, any element that exceeds the yield stress will plastically deform. This behavior can go on way past the point when the material would have failed. If you keep pulling, the element will keep stretching until the shape collapses on itself and the solver will stop because the element has become invalid.

In the plot below, the strain is over 50%, way past the point of fracture.

In the Ekill Script model, the analysis settings are configured with a large End Time of 500 seconds. That means after each one second increment of time, the script will find any elements that have exceeded the strain threshold, remove them from the model using ekill, then submit the job to solve for the next second.

The above sequence is what some Engineers want to see.

The attached project archive for ANSYS 19.0 has the three systems described.

]]>I am trying to perform a simulation on a flange system with a metal gasket. When I apply a load of 30 KN on the bolts on each side (See attached image 1). Then, the tension chain will move down. When the tension chain moves down, the flank surface of the tension chain meets the flank of the flange and pushes both the flanges in an inward direction which compresses the gasket (See Fig 2). Hence, there is a force (60 KN acting on the flank of the flange from the chain). Now, I want to do a simulation only with the tension chain to check whether it can withstand the applied force without any deformation. While doing so I get different results when I fix (Fixed support) different surfaces of the tension chain. I am not sure about on which face I should use fixed support so that it represents the actual problem. Can someone tell me which face should I fix? e.g. The flank of the tension chain, drill hole.

Looking forward to your response.

Thanks in advance.

Bharath

I am working with a model that contains many solid bodies connected in various ways. I am using EKILL and EALIVE to activate and deactivate the elements in certain bodies at various load steps. Is there a way to assign many solid bodies to the same matid with a command snippet? I am using the following command snippets under each solid body.

"solid_1=matid" (under body 1)

"solid_2=matid" (under body 2)

etc. etc.

I then use following command snippets in the Static Structural (A5) branch of the Project tree.

esel,s,matid,,solid_1

ekill,all

allsel

esel,s,matid,,solid_2

ekill,all

allsel

etc. etc.

Is there a way to assign multiple solid bodies to the same matid? Meaning, can I use the same command snippet --> "solid_1=matid" for multiple solid bodies? I've tried to do this, to reduce the labor involved with typing individual command snippets, but ANSYS seems to only recognize the first command snippet in the tree, and the rest are ignored.

This is an issue for me because my model has hundreds of solid bodies and I'd like to make this more efficient.

Thank you very much!

Justin Warren

NCSU Graduate Student

]]>I am working on the automation of a semiconductor thermomechanical simulation. I am using Spaceclaim scripting functionality to generate my CAD model and using the Mechanical to mesh and simulate the model.

When I import the CAD model from Spaceclaim to Mechanical with shared topology (which is necessary in my case as different components with different materials should share the nodes in the interface) it takes 20 Mins for the geometry import. However if I set the shared topology to none in Spaceclaim and import the model it takes only 4 mins to import the geometry.

Kindly give me your suggestions to reduce the time for importing the CAD and at the same time having a connected mesh between components.

Thanks in advance,

Abisheik

]]>Full QTF cannot be calculated for more than 3 structures.

Can somebody tell me why there is a limit of 3 structures when calculating the full QTF and if there is a way to work around this error?

]]>Hello Dear all.

I am observing interaction between tube (shell) and rode (line element) under axial compression loading. I suppose to there is friction/frictionless contact is compatible. But I think it was wrong. The contact tool does not work.

How to contact these two bodies by outside surface in rode (beam188) inside surface in tube (shell)?

Any advice I appreciate.

UNUR

I am trying to simulate Dielectric elastomer actuator as my Final year project, and I defined my material properties using curve fitting by inserting uniaxial test data and I choose the best hyperelastic model that fit My curve of the uniaxial test data.

From my research I can find that in Workbench they define element to a solid when modeling hyperelastic material. So, is it really necessary in my case to define element type like Solid168 before I solve ? If yes, can you tell me how please.

What I am trying to simulate is similar to the link bellow :

I want to apply a voltage on the top and bottom of the sheet and find the deformation of the Elastomer. My knowledge in Ansys is quite limited so I am really confused how I can preform my simulation really need help and guidance. 🙏

Thank You In Advance!

]]>Now I want to modify the geometry such that it wont fail. How can I do this? For example, if I can find if the failure is happening due to high bending stresses, or tensile/compressive stresses, or shear stresses, or buckling stresses, then that can help to have an idea how the geometry should be altered.

]]>Now, if I only restrict the translational DOFs on the supported end, then this would automatically mean that the rotation at that end is restricted since rotation requires a tranlational motion of the nodes on the supported end. Will there be a rigid body motion in this case? Why won't I still see a moment reaction at the supported end? What is the basic difference in restricting the translational DOFs and rotational DOFs?

]]>I am looking at the forum at the current moment as well.

Thank you very much for your time.

Just prior solve command, I want to create Command (APDL)

*nsel,s,loc,x,(**1500**/2)*

*nsel,r,loc,y,(**1500**/2)*

*cm,middle,node*

*D,middle,UX,0*

*D,middle,UY,0*

*nsel,all*

to select that middle node and add constraints UX=UY=0. This works fine no problem. However, I have set "a" and "b" as parameters that I change from Workbench. When I change the size to e.g. a=3000, b=3000, I have to change that **1500 **in above command to 3000.

How can I get something that would print me the length of edge that I can input instead of the numerical value for each plate size? As an example, for something like this:

*nsel,s,loc,x,(**a**/2)*

*nsel,r,loc,y,(**b**/2)*

*cm,middle,node*

*D,middle,UX,0*

*D,middle,UY,0*

*nsel,all?*

I see if I make named selection of edge (called "a"), there is statistic that says the length is 1500mm. But how can I access this e.g. using *GET command?

With best regards,

Jaboust

]]>Thanks in advance.

Regards

]]>After this warning the problem does not converge at all. I have looked up this issue, and was recommended to use sub steps to gradually apply the loads.

Contact type : Frictionless

The thing is the problem converges if the applied force does not cause the contacts to separate, but it will throw this warning and does not converge if the applied force is significant to cause the separation.

Any solutions ? How do I use sub steps ? or is there any other Analysis or contact settings I need to be aware of ?

]]>I have to understand the flow dynamic through the gas cylinder with inlet and outlet and it include the piston too, outlet fluid is affected by the vertical oscillation movement of the piston.

a. I have created the body in the solid work, which will be best .extension to import, I am using Parasolid?

b. How can we create that movement using moving mesh, do I need to write udf? For UDF, can we use matlab or just C++ code?

c. I am not sure, how can create the movement or start tacking this problem? Can anyone suggest any good example to begin with, later on I can look for the complexity?

]]>Thanks

Best Regards'

ADEEL_khan

]]>i am making a modal analysis of a cube with wokbench and i was wondering if is possible to get as a result the displacement over time of the vertices (referring to any coordinate system)

]]>two types of contact are used (each contact surface is defined by 2 types) Bonded and Frictional (to include the friction coefficient). also the bonded contacts are combined with CZM (Separation-Distance based Debonding) to include the separation.

When I solved the model the following errors and warnings occurred in solver output:

WARNINGS

1- Element shape checking is currently inactive. Issue SHPP,ON or SHPP,WARN to reactivate, if desired.

2- Real constant 1 referenced by at least element types 1 and 2.

3- Material number 2528 (used by element 136227 ) should normally have at least one MP or one TB type command associated with it. Output of energy by material may not be available.

4- ANSYS has found the contact pairs have similar mesh patterns which can cause over-constraint. ANSYS will deactivate the current pair and keep its companion pair.

5- Maximum friction coefficient 0.7 is defined in the model. Switch to the unsymmetrical solver (NROP,UNSYM) instead if convergence difficulty is encountered.

6- Coefficient ratio exceeds 1.0e8 - Check results.

7- Contact element 84257 (real ID 1322) status changes abruptly from contact (with target element 84191) -> no-contact.

8- Contact element 47726 (real ID 310) status changes abruptly. We assume that the status of this element (and possibly others) represents a spurious contact.

9- The geometrical penetration may be too large. Increase pinball if it is a true geometrical penetration. Decrease pinball if it is a false one.

10- The geometrical gap may be too large. Increase pinball if it is a true geometrical gap. Decrease pinball if it is a false one.

11- The unconverged solution (identified as time 1 substep 999999) is output for analysis debug purposes. Results should not be used for any other purpose.

ERRORS

1- The value of UZ at node 28466 is 5980424.25. It is greater than the current limit of 1000000 (which can be reset on the NCNV command). This generally indicates rigid body motion as a result of an unconstrained model. Verify that your model is properly constrained.

2- If one or more parts of the model are held together only by contact verify that the contact surfaces are closed. You can check contact status in the SOLUTION module for the converged solutions using CNCHECK.

3- Rigid body motion can also occur when net section yielding has occurred resulting in large displacements for small increments of load

or when buckling has occurred. You can plot the time history curve for node 28466 in the UZ direction to check for stiffness (slope of

the curve) approaching zero.

I tried for many moths to solve those problems but I didn't find the solution. Knowing that when I suppress the CZM the model converge without problem but the results go so far compared to experimental. When I include the CZM the model diverge but the results obtained are close to experimental.

the following messages occurred in workbench:

Any help would be very appreciated

]]>Hello,

I have been using 'Thermo-Mechanical Fatigue Lifing ACT' for my research project. After I download the ACT I found a help document (attached) and a workbench file which demonstrates the TMF damage calculation by this ACT over a cast-iron exhaust manifold.

So could you please tell me if the non-linear material properties of the Exhaust Manifold as available in the workbench file and the 'A', 'm' & 'n' values in the document are obtained analytically/experimentally? Do they have any significance or they are mentioned just as a demonstration?

Thanks,

Abhilash

]]>I want to model a frictional connection between two shell edges, could I solve it by ansys? I have used the conta177 and targe170 to stimulate this contact, and I also tried using general contact, but the program always reports errors.....😣

]]>Would like to ask if I want to simulate the rigid body dynamic analysis of the gear and chain , can I apply pressure on the pedal? Thank you!

I am trying to model the effect of an interference fit of a rotor on a shaft for an electric motor. My current understanding is that to gain the effect of the interference fit, a pre-stress modal analysis must be used. The pre-stress involves a static structural analysis to gain the stress state of the structure with the imposed interference fit. I have successfully modeled this, i.e. when I increase the interference fit via the offset command in geometry treatment within the contact settings, my natural frequencies increase throughout all the modes. The problem is, I need a free-free modal analysis to actually get the natural frequencies of the structure without the boundary conditions required for the static structural. Does anyone have any suggestions on how to model the increased stiffness of a structure due to an interference fit? Thanks.

]]>This is how I've set up the model:

Displacement and displacement2 are 0 displacement in axial direction on top and bottom sides. Other directions are free

Cylindrical support is defined as : radial = free ; axial = tangential = fixed. I set radial to free so I get the effect of the pressure load but with this I get the error:

How should I set up the model to get accurate results?

Also can you recommend contact type between the magnets and the rest of the rotor? Now it's set to bonded because magnets are glued in the rotor.

I am sure this was discussed many times, please guide me if you do have a chance where should I look for information.

My model is very simple. Bearing load, out of plane load (remote force). Elastic perfectly plastic material properties.

Due to the high value of remote force, I experience high yield at the end of the fixed support, which doesn't allow me to run the analysis.

I have tried 2 step with substeps, it didn't work. I have tried to model pipe end in elastic but then it starts to yield in the contact area between elastic and plastic parts of the pipe.

It should be quite straightforward analysis, but I miss something,

Could you please advise if you have the opportunity.

Thank you very much

I am trying to input my own biaxial test data (stress and strain) into EngineeringData, but I found that the unit for strain in the interface is mm^-1. Shouldn't the unit for strain is mm/mm or in/in....?

Another question is, is there anyway to perform curve fitting for some anisotropic materials? I saw the material models that are supported in ANSYS to do curve fitting are mostly isotropic hyperelastic.

Thanks!

Jirong

]]>I am doing a 2D static structural analysis with 2 steps and 80 substeps. My main outcomes are the penetration results of a contact pair (from the Solution Contact Tool). I am doing a parametric study and for each design point I need to export a text file with the penetration results and the time value for all 80 substeps.

I thought the best way to do that would be a Post26 APLD command added under Solution but I can't get the command to work properly. The code I am using is the following:

/post26

file,file,rst

esol,2,5729,6183,cont,pene

store,merge

*get,size,vari,,nsets

*dim,penetrat,array,size !

vget,penetrat(1),2

*dim,timearr,array,size

vget,timearr(1),1

dpFolder = '\dp'

dpLoc = STRPOS(_wb_SolverFiles_dir(1),dpFolder)

CutPath = STRSUB(_wb_SolverFiles_dir(1),dpLoc+3,6)

DirSepLoc = STRPOS(CutPath,'\')

dpNb = STRSUB(CutPath,1,DirSepLoc-1)

*cfopen,'%_wb_userfiles_dir(1)%\Penetration_dp%dpNb%',csv

*vwrite

('Time',';','Penetration')

*vwrite,timearr(1),penetrat(1)

*cfclose

In the solver output, after the "esol" function I an getting the warning "No data points are saved during this storage step." Doesn't the results file store the contact tool solution too?

The other issue is that I need the penetration result for the whole edge of the contact pair not only one element or node. Is this feasible in an APDL command?

Thank you in advance for you help!

Best regards,

Diane

]]>“nlplwk” represents the result of plastic work divided by volume. But when I export the result file, see fig. 1.

It seems like "nlplwk" is node result, or at least expressed by node. So I'm confused what "nlplwk" really is!

Besides, when doing solder fatigue life prediction, Darveaux’s methodology is very common, and the corresponding equation is below.

Where, **ΔWave**, which is crucial most, represents the average density of dissipation energy calculated at each cycle. But the "nlplwk" is plastic work within a single element. If I want to calculate **ΔWave, **how can I do that in ANSYS.

and that one asks the reaction force of the piston (green part on the picture),

is the result obtained is 385,57 N or 385,57/2 because of the symmetry?

thank you in advance for your answers.

Philippe.

]]>Some people are saying that, we have to connect hinge support/ compression only support at Point B, and compression only/ displacement at point C. 2000N force applied at lower point. we are not getting solution. so, we need your guidance regarding the boundary conditions to put in the simulation as we are getting vwry different values of total deformation (69.22).

]]>I need an urgent help to wrap my simulation up as much as fast. The problem with my FE analysis is as following:

The steel bar (SOLID ELEMENT 186) with outer tube (SHELL ELEMENT) are used for this knee brace. Cyclic loading is applied in the tip of the cantilever beam. Nonlinear FE is assumed here. On the other hand, material and geometry NLs are considered.

- When the initial thickness of outer tube is 2 mm the convergence have done without any error. As illustrated below.
- If the thickness of outer tube increases to 4 mm or 6 mm etc, convergence failure occurs with high distorted element in the knee brace (inside bar/outside tube). The error with number of 99999 is pop up as well.

I did make more fine mesh for both tube and bar, decrease the initial loading step, change the normal stiffness 0.1-1, and changed the contact formulation between tube and bar. By the way a frictionless contact is used here. Unfortunately, I have still been faced with convergence failure. help me please.

UNUR

]]>This is the tension of the main spindle belt of my model.

I set it using elastic support.

Is this correct?

But I don’t know how much the force should be set.

Can I ask the approximate range?

]]>I am currently running a transient structural simulation that receives temperature data from a transient Fluent simulation.

In the structural simulation, I am receiving the following warning:

My material property assignments are below:

Looking through the documentation on the MP and TB commands, it looks like I have already defined some of the properties listed and I am not sure which (if any) property should be defined to address this warning.

I tried removing the high yield and ultimate strengths, which I added to prevent yielding, but the same error occurs.

Why am I receiving this warning? How can I tell if I need to define more material properties?

Thank you!

]]>Does anyone have a procedure to import Moldflow generated files to Ansys.

I generate the db and cdb files in Moldflow but than I can't retrieve the results to make a structural simulation in ANSYS

Thanks

]]>In modeling a structure under repeated impact loads (10 Pressure pulses at 10 steps)as below, I have a problem reading the results!

The problem is that logically, the structure's permanent deformation (at the center) should increase, But what I get doesn't fulfill this idea

Could anyone help me with this issue please?

PS. it's a transient structural analysis, my model has initial deformations as well as heat affected zone (reduced material characteristics) and welding residual stresses.

Materials are modeled as elastic-plastic (multilinear isotropic hardening), but I remember once one of the members told me to capture the material using Chaboche constants to get the hysteresis loop and read the permanent deformations, But the fact is that I couldn't find this constants for my material! (marine grade Aluminums)

Right now, I read the total deformations at the center of the panel. Could it be the cause of the problem? If so, what should I read instead?

I have been using the 'Thermomechanical Lifing ACT' based on BAM damage model, for my research. After I downloaded this ACT, I found 2 help documents. In one of them, there is an example of application of this ACT to cast-iron exhaust manifold (refer attached pdf) and there is a workbench file as well.

So could you please tell me if the non-linear material properties of the cast-iron as prescribed in the workbench file are experimentally obtained values?

Also, are the 'A', 'm' & 'n' values for the damage calculation, as mentioned in the support document (refer attached pdf) are obtained analytically/experimentally, do they have a significance or considered only as a demonstration of ACT?

Thanks,

Abhilash