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volumetric shrinkage
Posted 04.07.2013, 12:54 GMT-4 Materials, Parameters, Variables, & Functions, Structural Mechanics Version 4.4 3 Replies
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I have a question regarding the setting of initial volumetric shrinkage rate of a geometry.
I want to simulate the polymerization process, during which volumetric shrinkage happens when liquid changes to solid. Is there a way in Comsol to set volumetric shrinkage rate to a geometry such that its volume shrinks 2% when the phase change happens? BTW, I am using structural mechanics module and hoping to simulate the final shape of polymerization part. Thanks in advance!
Best,
Eric
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I have done this using the "Initial Stress and Strain" function added by right-clicking on the "Linear Elastic Material" node. Then, I set the "Initial Strain" tensor to expand based on a step function defined under local "Definitions" that is a function of temperature. The step function should define the change in volume between the liquid and the solid phase based on temperature.
Also, since you will be modeling the liquid phase as a continuum solid you will want to approximate the fluid mechanic behavior by setting the Young's modulus to something close to zero and the Poisson's ratio something close to 0.5 (incompressibility). I say "close to" because you could run into convergence and singularity issues if you set the values all the way to zero and 0.5. You will then want to step these values using a similar step function that depends on Temperature to represent the phase change to solid.
Also, under Linear Elastic Material, I'd recommend clicking "Nearly incompressible material" if you have a Poisson's ratio close to 0.5. This will help the solver converge. See previous posts for a discussion on what COMSOL does here.
Of course, you will also need to run a Heat Transfer analysis and then couple the Temperature field data into the Solid Mechanics physics equations.
In this way, you can simulate volumetric expansion/shrinkage due to a phase change.
Best regards,
Josh Thomas
AltaSim Technologies
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I will try according to your suggestions.
Best,
Eric
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According to different discussion, I have understood that you are familiar and expert in moving mesh and solid mechanics interface. Basically, I am doing drying of apple with considering shrinkage. Where, I have to add heat transfer in solid, transportation of diluted/concentrated species ( diffusion/& convection), solid mechanics ( stess - strain due to gas pressure) and moving mesh (ale).
Could you guide me , in particular, the coupling of solid mechanics and moving mesh.
Upload of any example would be highly appreciated.
Thank you in advance for your time and kind cooperation.
Kind Regards,
Mohammad Joardder
QUT, Australia