Latest Discussions - COMSOL Forums Most recent forum discussions Thu, 27 Jan 2022 19:07:11 +0000 COMSOL Forum: Latest Discussions observing the effect of thermal expansion in resonance frequency <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>Hi I have the kind of same issue and the frequency does not change for me. Also, the links yopu provided is out of access right now. I have two material slab (one silicon and one LT) and want to see how the frequency of specific resonance mode will change by temperature. I know the thermal expansion of these two materials are significantly different that it might cause an stress that creats deformation and it might change the resonance frequency by increasing or decreasing the temperature. Before I saw the effect of stiffness on frequency change by changing the temperature but I have not been able to model the thermal expansion so far. Could you please help me on that? Thanks</p> Thu, 27 Jan 2022 19:07:11 +0000 4.2022-01-27 19:07:11.303102 Time-Dependent Solver does not progress <p>Hello, I try to simulate to coils where I want to know the temperature behavior of the one coil. So it is a multiphysics problem (magntic fields ans heat transfer in solids). The problem is that the programm does not progress by the time depent solver. You can see it on the picture. It can't be because of the meshing. I've already set that up.</p> <p>Does somebody has any idea?</p> <p>Thank you</p> Thu, 27 Jan 2022 18:31:11 +0000 4.2022-01-27 18:31:11.303101 How to model plasticity problem in COMSOL if I have the true stress- strain curve? <p>Hello,</p> <p>I am modeling a nonlinear problem in which a large plastic deformation of a new alloy is to be done. As a material property of the alloy, I have the true stress-strain curve of the material and the young modulus of elasticity and Poisson ratio. How to implement the data of this true stress-strain curve in giving the material properties of plasticity problem with isotropic hardening in the COMSOL- Multiphysics 5.6?</p> <p>Thank you!</p> Thu, 27 Jan 2022 17:58:31 +0000 4.2022-01-27 17:58:31.303091 Heating & cooling In COMSOL <p>Hello Everyone,</p> <p>I am a research student working on a CFD project. I have been working on ANSYS since last year. but I would like to work on COMSOL as it is one of the strong simulation software. I am looking for the possibilities to implement the heating and cooling freely method on large work pieces. I have a test rig which is heated with the help of the heat mats power 200watts. intially it is heated up for 180mins and cooled without any external support in for 120mins time frame the total simulation time is 300mins. this helps to find the thermo-elastic behaviours of the body. But my question is there any possiblity to give a time framed simulation with both heating and cooling phase in COMSOL. if yes, Please guide me in doing so. I will be looking forward to your replies.</p> <p>Thank you in advance!</p> Thu, 27 Jan 2022 13:42:11 +0000 4.2022-01-27 13:42:11.303081 double click can't open comsol model files <p>Now when double clicking any comsol user model files, what pops up is the comsol start up interface, which is blank. What should I do to enable double clicking to direct me to the user model interface with user settings?</p> Thu, 27 Jan 2022 10:02:28 +0000 4.2022-01-27 10:02:28.303063 Material properties removal <p>How to remove some unwanted matertial properties from material content section.</p> <p>Thank you</p> Thu, 27 Jan 2022 06:30:19 +0000 4.2022-01-27 06:30:19.303061 Applying boundary condition on imported mesh <p>Hi, I've imported 5 different mesh (3D tetrahedral) files (head geometry) as NASTRAN format into COMSOL under component>mesh and want to run a opto-thermal simulation. But I want to make a surface domain (a circle) with a radius of 15-20mm onto a 3D mesh (like attached) where I'd like to assign a boundary condition. Is it possible in COMSOL? If so, can anyone please assist me of doing this?</p> <p>NB. I'm not making geometry from mesh. Directly applying the boundary condition into the mesh. Using COMSOL 5.6.</p> <p>Thanks a lot in advance.</p> <p>Best regards, Chironjeet</p> Thu, 27 Jan 2022 04:42:36 +0000 4.2022-01-27 04:42:36.303052 von mises stress error <p>I wanna add von mises stress at tutorial named Lithium-Ion Battery with Single-Ion Conducting Solid Electrolyte</p> <p>I checked Calculate stress and strain at Particle Intercalation1 (figure1) next, I clicked Compute at Step1 and Step2 in Study1 next, I checked domain1 and made Line Graph at 1D plot table and then, I choose liion.mises_pce1 at y-Axis Data</p> <p>I received Error message (figure2) Undefined variable Variable: comp1.liion.mises_pce1 Geometry: geom1 Failed to evalutate expression Expression: comp1.liion.mises_pce1 Plot: Ingr1(Line graph)</p> <p>I wonder what is mean things such as liion.mises_pce1, liion.Ws_tot_pce1 and so on I wonder why can't calculate stress and strain</p> Wed, 26 Jan 2022 12:20:21 +0000 4.2022-01-26 12:20:21.303031 Creep strain vs plastic strain <p>I had a calculation result using creep and elastic matrial properties. There is no plasticity in my material, so there is no plastic strain. But the Regulator agent is requesting to report the plastric strain. Do I have to report the creep strain as the plastic strain? Can I say that creep strain is sort of plastic strain?</p> Wed, 26 Jan 2022 11:11:00 +0000 4.2022-01-26 11:11:00.303021 Electrical conductivity of a Hall Effect sensor <p>Hello!</p> <p>I am simulating the effect of the Hall sensor by moving a magnet towards a semiconductor plate and watching how the Hall potential changes. So, the closer the magnet, the higher voltage.</p> <p>My model consist of a circle magnet that slides along an iron rod (translation along z-axis) towards the Hall effect sensor, which is a semiconductor plate with potential difference of 5V.</p> <p>The challenge is to define the electrical conductivity of Hall Effect sensor correctly. As I understand, this task is almost the most important in my experiment. And when I chose sigma to be "from material" (i.e. default value), I do not get a desired result, but instead a constant potential.</p> <p>Please, help me to define conductivity within Hall sensor, so that the Hall voltage would increase as the magnet moves closer to the sensor.</p> <p>I am attaching the screenshots.</p> <p>Thank you!</p> Wed, 26 Jan 2022 10:01:52 +0000 4.2022-01-26 10:01:52.303011 How to enforce uniform electrical power of area-occupying conductor? <p>Dear experts,</p> <p>I am facing in dealing with simulation with highly thin patterned conductor.</p> <p>The conductor pattern is designed to fully occupy the unit square with highly thin width, relative to the size of the unit square.</p> <p>The end of the conductor, the electrodes to inject current and generate the joule heat, is located at the diagonal corners of the square.</p> <p>Our trial on simulating the joule heat with the current design failed due to the intensive mesh generation for the mesh design.</p> <p>Therefore, we want to try to approximate the conductor pattern as an area that is exerting an uniform heat flux across the area.</p> <p>However, it is a bit hard to find the way to realize it for us, because we are not that expertized.</p> <p>We would kindly ask the experts for the way.</p> <p>Thank you in advance for your help.</p> Wed, 26 Jan 2022 06:02:31 +0000 4.2022-01-26 06:02:31.302991 imaginary part of refractive index calculation <p>k_interp(c_const/freq), this expression is written to calculate the imaginary part of refractive index. what is the mening of that? please explain</p> Tue, 25 Jan 2022 17:10:19 +0000 4.2022-01-25 17:10:19.302961 Which is correct: Surface-to-Surface Radiation or Thermal Contact? <p>Which result is correct, please? The <strong>Thermal Contact</strong> setting seems to overwrite the <strong>Diffuse Surface</strong> at the contact?</p> <ul> <li>I'm using Surface-to-Surface Radiation Multiphysic for metal/glass heat transfer.</li> <li>I obtained 2 different results for including and excluding <strong>Thermal Contact</strong> setting: Heat Transfer in Solids > Thermal Contact > Constriction Conductance > User Defined > 1000 W/(m^2.K)</li> </ul> <p>Please see attached screenshots and COMSOL file. Thank you very much!</p> Tue, 25 Jan 2022 11:41:14 +0000 4.2022-01-25 11:41:14.302941 Unit issue in parameter's expression <p>Hi, I am using COMSOL 5.3a version, when I enter the unit of Vmax(rate) that is 4.67e-3&#91;ng/(s&#42;10^5&#42;cells)&#93; in parameter expression it turns into orange color and show invalid unit syntax. Can you please help me how can I enter such type of units in which keyword "cell" is mentioned?</p> <p>Hope to hear back soon</p> Tue, 25 Jan 2022 11:07:31 +0000 4.2022-01-25 11:07:31.302931 On setting thermal boundary conditions <p>Hi, am thinking of a rectangular model composed of air, 3nmAu , and quartz glass in that order.We want to consider the heating of Au when light is incident on it. The left and right sides of the rectangle are set to periodic conditions, but which conditions should be used for the top and bottom edges? When the temperature was fixed at 20°C, sufficient heating did not occur due to the close proximity to the gold. There may be some flaws in my English, but please help me.</p> Tue, 25 Jan 2022 10:37:51 +0000 4.2022-01-25 10:37:51.302921 3D trenches with variable angle with or without "design module" [geometry] <p>Hi,</p> <p>I am modelling a material which, when chemically etched, will not produce 90deg vertical sidewalls but can have a slope of variable angle. If I would draw in my etch mask 2 vertical lines and 2 horizontal lines of equal size to produce a separate square of this material, it would not produce a cube but a trapeziodal prism. If I would get a slice of this structure, I would obersve an isoceles trapezoid:</p> <p>On the 2D plane, the ojects I am modelling aren't just a square but can be an assembly of many rectangles.</p> <p>For vertical sidewalls, things are pretty straightforward: I import the "positive" (final desired shape, rather than trenches which are the negatives) 2D shape and then apply an extrusion.</p> <p>However, for non-vertical angles things get hairy. For a single rectangle, I have noticed that you can somewhat create the desired trapezoidal shape using the "scales" and "displacements" options of the extrude function. For some reasons I don't quite get, when using the scales option with any value other than 1 (to scale the size of the projected extruded face), the destination face is re-centered to the origin of the plane and you need to use displacements to compensate for that.</p> <p>The thing is, the displacement you need to use will depend on both the scale and the rectangle dimensions. So, if you have more than 1 rectangles in your source work plane, this technique breaks down.</p> <p>Now, you could say that a possible option is to create a plane for each rectangle and perform extrusion on each. Pretty cumbersome but why not. If you do this, you still do not get the desired shape as this would create, after extrusion, "internal slopes" between two adjacent (touching) rectangles, when we only want non vertical slopes at the periphery of the coumpound object.</p> <p>The solution used so far uses hexahedrons, simulating these slopes via direct writing of hexahedron coordinates. The hexahedrons are then placed next to the positive regular extruded shapes and then a boolean operation (substraction) is performed to create these slopes. This is working out for simple geometries. But as you can probably imagine, this is very, very cumbersome to programmatically define where the hexadron should be and each of their points coordinates when the base 2D geometry we want extruded starts to be very complex.</p> <p>We have reached out to COMSOL support which suggested the chamber feature of the design module: Unfortunately, the chamfer feature works as the radius of the rolling ball tangent to the faces adjacent to the edges: and long story short, the slope angle that you can generate with this method is 45 degree only. I really need other angles. COMSOL commented that they don't see any ways to do what we would like to do.</p> <p>I was somewhat shocked to hear this as surely, I am not the only one dealing with non-vertical sidewalls. Therefore I am calling out to the community: - am I missing some obvious method here? - did anyone come up with a clever method able to automatically generate a desired slope angle after extrusion?</p> <p>Ideally, in the extrusion options, we would get a "sized" option that generates a destination shape shrink or grown by x microns. "sizing" is a typical feature of layout softwares such as Klayout: which is why I was somewhat expecting it in the COMSOL design module.</p> <p>So I thought that maybe I could generate a "sized" 2D shape of the source shape myself, position it on a new plane above the source plane and somehow connect these 2D shapes to generate the 3D trapezoid. Is this comething that coud be done?</p> <p>In advance, many thanks for your support, comments and suggestions.</p> <p>BR, Eric</p> Mon, 24 Jan 2022 14:59:48 +0000 4.2022-01-24 14:59:48.302911 Non-linear Mechanics <p>Hi, I am new to COMSOL, and i have a doubt on how to simulate a particular mechanics.</p> <p>I want to simulate and study the non linear mechanical behaviour of a simple micro cantilever ( double clamped beam also) when we keep on increasing the amplitude of vibration. I want to visualise it as displacement as a function of time. Can someone helpme in how i can achive this. Thank you in advance.</p> <p>Regard's Toji</p> Mon, 24 Jan 2022 14:40:11 +0000 4.2022-01-24 14:40:11.302901 Different meshes <p>Hello everyone! I am building an acoustic model with a plate and an acoustical environment (sphere) around.. I would consider a mapped mesh on the plate and a tetrahedral mesh for the sphere. It is possible?</p> Mon, 24 Jan 2022 08:49:18 +0000 4.2022-01-24 08:49:18.302881 How to import non uniform current density distribution and use it to find current induced magnetic field? <p>I have a geometry of spin Hall nano oscillator. I have calculated current density distribution in the device by Electric Currents module. I exported that data also. Now I want to calculate the current indused magnetic field due to this current density deistribution. How can I do this? I have tried external current density node in Magnetic Fields module but it takes only uniform current density. I want to import current density which I have already calculated. Thanks</p> Mon, 24 Jan 2022 08:30:15 +0000 4.2022-01-24 08:30:15.302871 Scattering of light due to transparent object in air <p>Hello, My mission is to simulate a scattering experiment of a small laser beam by a 100micron object in air. The object is transparent and has a refractive index gradient. Is this possible in Comsol software?</p> <p>Thanks, Ivan</p> Mon, 24 Jan 2022 07:02:56 +0000 4.2022-01-24 07:02:56.302861