Needle Piercing Simulation: Abnormal Results (Solid Mechanics, Stationary Study)

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Dear all, For the past week, I've been trying to set up a simulation comprising an arrow-like needle piercing a skin-like substrate. As I haven't found a similar (3D) example in COMSOL's Application Gallery or Learning Center so far, I have followed analytical step-by-step instructions by three different AI chatbots (Gemini, Perplexity, Claude). After days of trial-and-error and diagnostic tests, I have reached the point where all three of them agree with each other that my method was set up correctly. Nevertheless, the results (see 1.png in attachments) indicate abnormally low pressure values on the needle, with the appearing scale being on the order of E-4 N/m2 (whereas, e.g., atmospheric pressure is at E5 N/m2), while zero pressure appears on the skin-like substrate. The AI chatbots claim that the needle is faulty (it's an imported .stp file from Autodesk Inventor), but I cannot really trust them. All my Model Builder data can be seen in the 2.png attachment. I'm also attaching the simulation file (NP.mph).

Any kind of help will be sincerely appreciated! Thank you everyone in advance.



2 Replies Last Post 22.05.2026, 06:42 GMT-4
Acculution ApS Certified Consultant

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Posted: 1 day ago 21.05.2026, 04:53 GMT-4
Updated: 1 day ago 21.05.2026, 04:59 GMT-4

You have a negative sign on the parameter disp under the Prescribed Displacement, but also a negative sign on the values for disp in the parametric sweep. So, the needle is moving the wrong way. There is probably a lot more to it than that, but that must be an important point.

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René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com
You have a negative sign on the parameter disp under the Prescribed Displacement, but also a negative sign on the values for disp in the parametric sweep. So, the needle is moving the wrong way. There is probably a lot more to it than that, but that must be an important point.


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Posted: 1 hour ago 22.05.2026, 06:42 GMT-4

You have a negative sign on the parameter disp under the Prescribed Displacement, but also a negative sign on the values for disp in the parametric sweep. So, the needle is moving the wrong way. There is probably a lot more to it than that, but that must be an important point.

Thank you very much for your advice! I put negative signs on my parameter and its sweep values so that the needle would move downward onto the substrate on z axis. I tried out what you proposed (using positive signs instead), and the results show nil pressure in my system whatsoever (see attached), which I assume means that my projected geometries have zero contact in this study. Have I maybe missed something? Any further remarks will be greatly appreciated! Also, in your attached image, the simulation looks great! Could you provide how you did it?

>You have a negative sign on the parameter disp under the Prescribed Displacement, but also a negative sign on the values for disp in the parametric sweep. So, the needle is moving the wrong way. There is probably a lot more to it than that, but that must be an important point. Thank you very much for your advice! I put negative signs on my parameter and its sweep values so that the needle would move downward onto the substrate on z axis. I tried out what you proposed (using positive signs instead), and the results show nil pressure in my system whatsoever (see attached), which I assume means that my projected geometries have zero contact in this study. Have I maybe missed something? Any further remarks will be greatly appreciated! Also, in your attached image, the simulation looks great! Could you provide how you did it?

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