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How to simulate a point-wise concentrate load traveling along a structure?

Posted May 26, 2020, 9:09 a.m. EDT Structural & Acoustics, Acoustics & Vibrations, Structural Mechanics Version 5.5 1 Reply

ZH Lau
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Now I'm working on the moving-load problems of the beams and plates. I want to use comsol to simulate a point-wise force or mass traveling along a beam, or traveling along a path on the plate surface, and explore the deformation of the beam and plate. I have read the post concerning this topic, but I still have no idea on how to deal with the concentrate moving load. Should I use the delta function? Is is possible to use comsol to consider the moving mass problem in which there exist the inertial interaction between the supporting structure and moving mass?

1 Reply Last Post May 27, 2020, 5:06 p.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago May 27, 2020, 5:06 p.m. EDT

Hi,

What’s special with the point load it that the built-in point loads are assumed to act at points (which after meshing always will be mesh nodes). An arbitrary path may however place the load at any location on the element face. Mathematically, we need to evaluate all shape functions in the element in that point, so that the load can be distributed to the mesh nodes consistently.

One way to deal with the point load is shown in the attached model. The load is applied using a Weak Contribuiton node. A parametric sweep is used to move the load, but it will work just as well with a time-dependent analysis. Note that the local stress distribution will be rather distorted; a point load on a solid causes a singularity. It will not be as bad for a beam or plate.

The blog post you referred to still provides useful information about how to set up load paths.

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Henrik Sönnerlind
COMSOL
Hi, What’s special with the point load it that the built-in point loads are assumed to act at points (which after meshing always will be mesh nodes). An arbitrary path may however place the load at any location on the element face. Mathematically, we need to evaluate all shape functions in the element in that point, so that the load can be distributed to the mesh nodes consistently. One way to deal with the point load is shown in the attached model. The load is applied using a Weak Contribuiton node. A parametric sweep is used to move the load, but it will work just as well with a time-dependent analysis. Note that the local stress distribution will be rather distorted; a point load on a solid causes a singularity. It will not be as bad for a beam or plate. The blog post you referred to still provides useful information about how to set up load paths.

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