K values stays constant and spring structure gets deformed on force application in COMSOL

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Hello Experts,

I recieved an error in my 3D model in comsol for a force sensor . We use the concept F = Kx(Hooke law)

On point of application of the force as shown in K values error screenshot, the spring gets deformed when I run the l6 parameter defined value from (5,1,7) mm range. I attached the screenshots of the error.

1) displacement_z direction screenshot : denotes the displacement of the spring in z direction. 2) k variable formula screenshot: shows the formula to evaluate the k value . 3) k values error screenshot: shows the k value as constant even when we vary the parameter range from 5 mm to 7 mm range since the springs gets deformed as can be seen in the diagram. The point of application of force F is shown in the diagram.

Can you please suggest the cause behind this error and how can i fix it?

P.S: The .mph file is 30MB therefore it is not possible to upload in the post as we have upload file limit of 5MB

Kind regards Amit



4 Replies Last Post Jun 14, 2024, 9:13 a.m. EDT
Jeff Hiller COMSOL Employee

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Posted: 5 months ago Jun 13, 2024, 10:43 a.m. EDT

Clear the mesh and solution; the file will then likely be under 5MB.

Best,

Jeff

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Jeff Hiller
Clear the mesh and solution; the file will then likely be under 5MB. Best, Jeff

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Posted: 5 months ago Jun 14, 2024, 8:19 a.m. EDT
Updated: 5 months ago Jun 14, 2024, 9:17 a.m. EDT

Hi Jeff, I added the mph file which has the 3D design model without results and mesh size.

My requirement is to get the value of K when the displacement is done in the z direction in blue color as shown in the screenshot Displacement_req.jpg for a given force applied in red color arrow below and the fix or hinged point is highlighted in green as shown in the attached screenshot.

Now when i apply the force in red ,it deforms the spring for a range say 5 mm to 20 mm of thinkness of l6 parameter therefore, l6(shown in red) is initially set to 5mm and it should increase slowly to 20 mm though a step size of say 2mm like range(5,2,20) in parameter sweep but i see no change in the thickness when i run the results rather it simply deforms the springs as shown in Displacement_req and shows the K value as fixed as -1.5088 E-6. K value doesnt change at all and the l6 spring gets deformed as soon as we run the model.

For various l6 values it should show various K values for displacement of 1e-6(1µm) in z direction as set in the comsol. so i need l6 vs k, please help

Also I created the 3D CAD model first in Autocad inventor,2024 and then connected to COMSOL Multiphysics(6.0.0.405) in the addin (screenshot comsol_inv.jpg)and then used COMSOL multiphysics to set the parameters and execute the results. I added my .ipt file as well in the atachment for your reference

Could you please take a look and let me know how can i fix this issue as I tried every possiblity in comsol but it is not working.

Kind regards Amit

Hi Jeff, I added the mph file which has the 3D design model without results and mesh size. My requirement is to get the value of K when the displacement is done in the z direction in **blue color** as shown in the screenshot **Displacement_req.jpg** for a given force applied in **red color** arrow below and **the fix or hinged point is highlighted in green** as shown in the attached screenshot. Now when i apply the force in red ,it deforms the spring for a range say 5 mm to 20 mm of thinkness of l6 parameter therefore, **l6**(**shown in red**) is initially set to 5mm and it should increase slowly to 20 mm though a step size of say 2mm like range(5,2,20) in parameter sweep but i see no change in the thickness when i run the results rather it simply deforms the springs as shown in Displacement_req and shows the K value as fixed as -1.5088 E-6. K value doesnt change at all and the l6 spring gets deformed as soon as we run the model. For various l6 values it should show various K values for displacement of 1e-6(1µm) in z direction as set in the comsol. so i need l6 vs k, please help Also I created the 3D CAD model first in Autocad inventor,2024 and then connected to COMSOL Multiphysics(6.0.0.405) in the addin (**screenshot comsol_inv.jpg**)and then used COMSOL multiphysics to set the parameters and execute the results. I added my .ipt file as well in the atachment for your reference Could you please take a look and let me know how can i fix this issue as I tried every possiblity in comsol but it is not working. Kind regards Amit

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Posted: 5 months ago Jun 14, 2024, 8:22 a.m. EDT
Updated: 5 months ago Jun 14, 2024, 8:22 a.m. EDT

Clear the mesh and solution; the file will then likely be under 5MB.

Best,

Jeff

sure Jeff, i added the files along with the requirement explaination and fix value of K error which i am getting in comsol in the attachment , please check the latest post thread- files added are 1. Displacement_Req.jpg 2. l6 param .jpg 3. comsolfinalmodel_7.zip 4. Bauteil5.ipt

I have given mph in zip format and also i attached ipt file(inventor), you may not need it as for me mph opens without need of ipt but just in case

>Clear the mesh and solution; the file will then likely be under 5MB. > >Best, > >Jeff sure Jeff, i added the files along with the requirement explaination and fix value of K error which i am getting in comsol in the attachment , please check the latest post thread- files added are **1. Displacement_Req.jpg 2. l6 param .jpg 3. comsolfinalmodel_7.zip 4. Bauteil5.ipt** **I have given mph in zip format and also i attached ipt file(inventor), you may not need it as for me mph opens without need of ipt but just in case**

Jeff Hiller COMSOL Employee

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Posted: 5 months ago Jun 14, 2024, 9:13 a.m. EDT
Updated: 5 months ago Jun 14, 2024, 9:31 a.m. EDT

Hello Amit,

In a typical analysis aimed at determining the stiffness of a spring, you fix the spring in one location, apply a force somewhere and measure a displacement that results (usually in the same location where the force is applied). Here you are simultaneously applying a force in one location and a displacement in another, while -perhaps- measuring some other displacement yet somewhere else (?). It would be most helpful if you could explain what the device is, what loads and boundary conditions you would like to apply to it, and what you are trying to determine from the simulation - All this with great specificity. Right now, we can only guess because you're conflating what the model is doing and what you think it is doing.

For instance, your aveop1 operator is not fully set up (you have not specified on what part of the geometry it is to average its argument), and when you call it you apply it to the x component of the displacement, not the z component as you claim in your previous messages. Also, your entire geometry is about 1mm long, so I do not understand what is supposed to be 5 to 20mm long. At least those things need to be sorted out. Without Inventor though I will not be able to run your model. I would recommend you start by removing the parametric sweep, set up the model entirely correctly for one geometry, check that the results make sense, and only then worry about the parametric sweep.

Best,

Jeff

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Jeff Hiller
Hello Amit, In a typical analysis aimed at determining the stiffness of a spring, you fix the spring in one location, apply a force somewhere and measure a displacement that results (usually in the same location where the force is applied). Here you are simultaneously applying a force in one location and a displacement in another, while -perhaps- measuring some other displacement yet somewhere else (?). It would be most helpful if you could explain what the device is, what loads and boundary conditions you would like to apply to it, and what you are trying to determine from the simulation - All this with great specificity. Right now, we can only guess because you're conflating what the model is doing and what you think it is doing. For instance, your aveop1 operator is not fully set up (you have not specified on what part of the geometry it is to average its argument), and when you call it you apply it to the x component of the displacement, not the z component as you claim in your previous messages. Also, your entire geometry is about 1mm long, so I do not understand what is supposed to be 5 to 20mm long. At least those things need to be sorted out. Without Inventor though I will not be able to run your model. I would recommend you start by removing the parametric sweep, set up the model entirely correctly for one geometry, check that the results make sense, and only then worry about the parametric sweep. Best, Jeff

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