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Function for total spring constant in thin elastic layer
Posted Aug 26, 2013, 7:00 a.m. EDT Structural Mechanics Version 4.3b 1 Reply
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i'm a relatively new user with comsol, specially with the solid mechanics module.
The goal in my work is to simulate the interaction between epoxy and fiber glass. I started with a 2D-model because of a simplification, which includes a fiber glass rectangle in between 2 epoxy rectangles. The boundary load is placed similiar to a bending test.
The connection between the three rectangles (epoxy, glass fiber, epoxy) is made via the thin elastic layer function in comsol 4.3b. This function works well. You can recognize this by comparing the 2 attached files. The first file have a total spring constant of 1e15 N/m and the other uses 1e8 N/m.
In the 1D-plot group 5 is the total displacement of the right edge over the parameter para (factor for the boundary load) pictured.
What I'm now trying to implement is a function which sets the total spring constant during a specific von-mises-stress value (among the glass fiber and epoxy) on another lower total spring constant (1e15->1e8). Something like if ... then... function. What i aspect to see then in the 1D-plot is a a jump between the two graphs. I want to make that similiar to a crack between the 2 components.
I'm knowing the equation view, but I have no knowledge about using the solid.mises of a specific boundary (the boundary between the glass fiber and epoxy). Also i don't know how to add a function like this. Is it possible with the simpel parameter node?
Unfortunately the two attached files are too large (30mb each) so i had to clear the solutions. Anyway I attached them with two pictures of the 1D-graph.
Thank you very much.
Best regards,
Simon Dehmel
Hello Simon Dehmel
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First add a global parameter for your stress limit, i.e. stressLimit. Then in your thin elastic layer node, define the spring coefficients as:
1e15*(solid.mises<=stressLimit) + 1e8*(solid.mises>stressLimit)
The comparison operators return 1 if true and 0 if false. So, (solid.mises<=stressLimit) would return 1 if the von Mises stress is less than or equal to your limit stress.
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Tolga