Simulation Tech Tip: How can I simulate freezing water expansion?

Now that spring is here ice is probably the last thing on your mind. Unless your designing a product where stress induced from freezing is a problem. One of my customers posed an interesting question.  How might we emulate freezing water in FEA ?

 As you may know water expands when freezing and this can wreak havoc on any structure where water is contained or trapped.  Hence all the lovely pot holes in the spring punishing our fancy alloy wheels.

To emulate the expansion of a water volume as it freezes I followed this basic process:

1. Use the thermal expansion coefficient (CTE) and a temperature boundary to create the expansion.

2. Verify that my CTE creates the desired volumetric expansion of my ice body by simulating the ice body on it’s own and checking the change in linear dimensions.

3. Adjust materials stiffness (modulus) to emulate that of ice. This is probably the biggest unknown in the simulation.

The paper referenced in the video has more insight into that variation:

“The Mechanical Properties of Ice“, K.F. Voitkovskii , American Meteorological Society, 1960.

Check out this short video to see the process on this simple vessel: