Latest Discussions - COMSOL Forums

Fatal error when starting program

Sun, 29 Dec 2024 12:40:23 +0000

After greetings..... Fatal error when starting program. Could not load file or assembly 'JavaBridge.dll' or one of its dependencies. The specified module could not be found.

The above message appears when trying to open the program, noting that I installed the program on another laptop and it worked for me.. the comsol after installing version 6.2.

     Please help me

Magnetoelectric coupling in the material constitutive relationship

Sun, 29 Dec 2024 09:34:06 +0000

I want to conduct simulation analysis of the magneto-electro-elastic(MEE) structure. The constitutive relationship needs to consider piezoelectric, piezomagnetic and magnetoelectric coupling, but no term related to magnetoelectric coupling can be found in the material constitutive relationship of comsol 6.3.

The J integral in 3D case

Sun, 29 Dec 2024 09:20:10 +0000

Hello, I am working on a fracture mechanics simulation involving a 3D structure, and I need to calculate the J-integral to evaluate the energy release rate around a crack front. I am familiar with the built-in tools for computing the J-integral in 2D models, but I am unsure how to extend this approach to a 3D case.

2D coordinate systems

Sat, 28 Dec 2024 23:48:52 +0000

I'm curious why there are so many 2D coordinate systems in my 2D Component Definitions. I'm trying to simulate a bulk thickness mode of a simplified piezoelectric material. I've reduced the strain-charge form coupling matrix to only have a 33 component, since I'm having a hard time making sense of the eigenmode shapes. There are 6 2D planes in the Component Definition; none have the option to delete. The Geometry and the Rectangle within do not seem to reference any coordinate system. I'm unsure what coordinate system the material properties (and specifically the 33 component) are in reference to. My intention is is for the induced strain and stress to only be in line with the electric field, which should just be vertical between the top terminal and bottom ground. This would give rise to the thickness mode, as I understand it. The documentation doesn't address my question. (With my understanding of eigenmode shapes, I should be able to enforce 1D modes that are harmonics of a fundamental, right? I've set up the eigenfrequency search using where for aluminum nitride and is roughly the thickness of the material.

how to add unbalance mass in rotordynamics

Sat, 28 Dec 2024 18:57:37 +0000

hi i have beam rotor with disk ( jeffcott) , i want to add unbalance mass in the disk how i can do that in the comsol multiphysics program

Transformer Simulation

Sat, 28 Dec 2024 14:54:38 +0000

How to select the domain for oil (in void space) as a material in the power transformer simulation after making the geometry?

How to resolve Undefined variable and Failed to evaluate expression in battery modeling.

Fri, 27 Dec 2024 06:52:48 +0000

How to resolve this error that i get during plot in battery modeling.

"Undefined variable. - Variable: comp1.liion.stheta_pce1 - Geometry: geom1 - Domain: 1 Failed to evaluate expression. - Expression: comp1.liion.stheta_pce1 - Plot: Line Graph 1"

Simulation of 3D impedance tube for sound absorption calculation of MPP along with porous absorber using comsol multiphysics

Thu, 26 Dec 2024 13:33:08 +0000

Hello all, i want to simulate a 3D impedance tube consisting of MPP having conical holes combined with porous absorber. i have given PML and background pressure field as seperate domains. So how to get the combined sound absorption coefficient of the combination. what additional settings are required?

Mesh Size

Thu, 26 Dec 2024 05:32:44 +0000

Hello, I hope you're doing well. I have a few questions about meshing and its effect on accurately measuring displacement. I'm working on a structure that is designed to displace by 20 nanometers, and I'm facing some challenges in determining the right meshing parameters. 1. What would be the recommended minimum and maximum element size for the mesh to accurately capture the 20-nanometer displacement? 2. Since my structure is quite complex (it includes springs and several sensing fingers), what meshing strategy or type would you recommend to ensure the most accurate results with minimal error? 3. Finally, does reducing the mesh size always improve accuracy? Or is there an optimal mesh size range beyond which further refinement doesn't provide significant benefits? By the way, I've also attached the dimensions and size of the sensor finger and its gap (d1 and d2). In the attached figure, there is a 20-nanometer displacement along the x-axis in the d1 direction. I would greatly appreciate any advice, tips, or insights on this matter.

Calculation of high-order fatigue loading

Thu, 26 Dec 2024 03:19:31 +0000

When I am using COMSOL for high-order fatigue loading calculations, the cycle count can be set to 800, but when I change it to 1000 or greater, the model cannot calculate the results, the calculation step size does not change, and the progress is particularly fast. It seems that actual calculations have not been carried out. May I ask if it is due to computer hardware such as computer memory? How can we solve this problem? thank you!

Simulation of corrosion via COMSOL.

Tue, 24 Dec 2024 21:28:18 +0000

Dear Sir, I am simulating a Galvanic corrosion event via COMSOL. But, I want to get ultimately the potentiodynamic polarization plot or roughly speaking the "Tafel" plot. So, for that I have done a parametric sweeping study with the varying applied potential with a range and step size. I want to ask about the data extraction and plotting the potentiodynamic polarization plot by the extracted data. The result section is huge and confusing. Please give a few instructions. Also, where in the model, I should add that parametric sweeping E_applied as a boundary condition?

Regards.

issues in expanding the "hydrogen diffusion in metals" example to an axisymmetric model

Mon, 23 Dec 2024 22:02:31 +0000

Hello,

I'm a novice COMSOL user, so please excuse my lack of expertise.

I'm attempting to adapt the "Hydrogen Diffusion in Metals" example to an axisymmetric model. Specifically, I want to simulate stress-induced hydrogen diffusion in a cylindrical tensile specimen as it begins to neck.

I successfully modeled the necking behavior using the "Voce" plasticity model. Following the example, I incorporated hydrogen diffusion into the simulation. However, I encountered an issue when modifying the External Flux expression.

In the original 2D example, the External Flux is defined as: D_sigma * d(-solid.pm, X) * para

For the axisymmetric model, I changed it to: D_sigma * d(-solid2.pm, X) * para

I assumed this change was necessary because the solid.pm variable is unavailable in axisymmetric simulations.

After making this adjustment, I ran the simulation but encountered the following error:

"Feature: Time-Dependent Solver 1 (sol1/t1) The second argument of the d() operator must be a variable name."

The only differences between the example and my setup are:

The modified External Flux expression mentioned above.
My simulation runs from 0 to 1 seconds with 0.01-second increments. The specimen deformation ramps from 0 to 6 mm during this time.

I would greatly appreciate any guidance on resolving this issue.

Thank you, Rashiga

Global evaluation while computing my model

Mon, 23 Dec 2024 11:56:44 +0000

I am trying to evaluate my global evaluation expression while solving, as it is done on the uni servers.

When I try to evaluate after solving it takes a very long time on my local machine, and was wondering if it could be automated. I tried to create a table and link it to my global evaluation, and compute my model, but ended up with only a time column in my table.

Regards,

Unable to Start COMSOL, Facing Error

Sat, 21 Dec 2024 01:18:19 +0000

Getting the following error message when attempting to open COMSOL Multiphysics 6.2:

Could not obtain license for COMSOL Multiphysics GUI. License error: -15. Cannot connect to license server system. ** The license server manager (lmgrd) has not been started yet, the wrong port@host or license file is being used, or the port or hostname in the license file has been changed.** Feature: COMSOLGUI License path: C:\Program Files\COMSOL\COMSOL62\Multiphysics\license\license.dat;6601@a2.cmc.ca;6091@a2.cmc.ca; FlexNet Licensing error:-15,29

I tried addressing the items that were bolded but this same error remains. I believe the error is because of the 6091@a2.cmc.ca port that is mentioned in the license path. If this is the source of the error, how do I remove this from the license path?

Thanks for the help!

Ring in 2D in a side projection for Langevin

Fri, 20 Dec 2024 13:30:29 +0000

Good day. Please tell me how to draw a ring in 2D in a side projection so that the program perceives it as a whole element? Because when drawing it from the side, the ring looks like a rectangle torn in the middle. This is necessary for constructing a Langevin piezoelectric emitter in 2D. Even if these two pieces are combined in geometry, then when choosing a material, it still breaks it into two pieces.

Cannot evaluate variable

Fri, 20 Dec 2024 12:57:40 +0000

Hello everyone,

My question is about mach zehnder interferometer tutorial. You can find tutorial document in attachements.

After successfully creating structure, I finally reached point where I add electrostatic simulation for modulation. The error I got at this point is simulator cannot evaluate modulation voltage defined as V0.

The error I got is somewhat similar to the error given in the discussion below: The below post is related to an archived discussion

My error is

Undefined variable. - Variable: comp1.ewbe.epsilonrzz - Geometry: geom1 - Domain: 0 Failed to evaluate Jacobian of expression. - Expression: comp1.ewbe.epsilonrzz Failed to evaluate Jacobian of operator. - Operator: mean - Geometry: geom1 - Boundary: 3 Failed to evaluate Jacobian of variable. - Variable: comp1.ewbe.epsilonrzz - Geometry: geom1 - Boundary: 3 Failed to evaluate Jacobian of expression. - Expression: dvol_spatial((-mu0_const)((comp1.ewbe.iomegacomp1.ewbe.Jz_1)+(((-comp1.ewbe.dHdtx_1)(comp1.ewbe.alphaport_1comp1.ewbe.ny))-(comp1.ewbe.dHdty_1(-(comp1.ewbe.alphaport_1comp1.ewbe.nx)))))) Failed to evaluate Jacobian of expression. - Expression: (-mu0_const(-comp1.ewbe.dHdtx_1(test(comp1.ewbe.tEbm1zTy)+comp1.ewbe.alphaport_1test(comp1.ewbe.tEbm1z)comp1.ewbe.ny)-comp1.ewbe.dHdty_1(-test(comp1.ewbe.tEbm1zTx)-comp1.ewbe.alphaport_1test(comp1.ewbe.tEbm1z)comp1.ewbe.nx)+comp1.ewbe.iomegacomp1.ewbe.Jz_1test(comp1.ewbe.tEbm1z)))*(dvol_spatial)

Could you please help?

[start here]

How to only solve for stresses and strain and disable other quantities in Solid Mechanics Module

Fri, 20 Dec 2024 09:49:56 +0000

Hello! I hope everyone is doing well. I am trying to run simulations but the problem is that the simulation takes a lot of time and its taking a lot of space on the hard drive. So I want to solve only for stresses and strains and not other quantities in the solid mechanics modules like Guass stresses and Guass strains and strain energy and others. I would be glad if someone help me in this regard.

Objective function

Fri, 20 Dec 2024 09:34:30 +0000

How can I write objective function to enhance heat rate for cube and cylinder using following formula ? ( Topology optimization for Heat transfer) Q= 2 * Pi * K * L* (T1-T2) / log (r2/r1) for cylinder Q= KA(dt)^2 for cube [comp1.intop-------

To obtain the heat flux of the resonator in its operating mode, which research method should be used?

Fri, 20 Dec 2024 08:42:01 +0000

I have a resonator model, and the frequency of its operating mode is known. Which type of analysis should be used to calculate the heat flux at its operating frequency?

Boundary condition

Thu, 19 Dec 2024 18:59:15 +0000

Hello everyone,

I am working on a 1D model in the Heat Transfer in Solids (ht) module. I would like to improve a Robin boundary condition where I know the equation for the interface temperature, which varies over time, as follows:

Where:

T_SS(t): The temperature of my mold, which varies over time.
b_s and b_p The thermal effusivities of the steel (mold material) and the polymer (fluid), respectively.
T: The temperature from the previous step.

I tried to implement it only as a boundary temperature as

" if(t<=0, T_0, (T_SS(t)b_s + Tb_p)/(b_s + b_p)) "

but it doesn't work (T_0 is the initial temperature of my polymer ) I would appreciate any suggestions or guidance on implementing this. Thank you!