Throw exception when running a dynamic LCM problem with no density (and other material parameters) specified

[ikalash]

The default value of the density in the code is 1.0 which is non-physical. Exception should be thrown when not specifying density for dynamic problem to prevent user from running with density = 1.0 accidentally.

[djlittl]

Agreed! A few years ago I spent several hours debugging a simulation, only to find that I had a typo in the input deck and Albany/LCM was using a default value for the elastic modulus. You guessed it, the default was 1.0, only off by ~9 orders of magnitude ...

[ikalash]

@lxmota (others welcome to join in) : should we disallow default values for the material properties for all LCM problems or only dynamic ones? I hope to finally have time to fix this issue.

[lxmota]

I think there should not be any default values for anything related to material properties. It is dangerous and we have been burned by that many times.

[jwfoulk]

I guess I'm tempted to disallow defaults in parameters that are requisite for solving the problem. In this sense, you don't need density for quasi-statics but it is needed for dynamics. Clearly, some constitutive model is needed in both cases so having default values for things like the modulus is probably not a good thing.

[ikalash]

@lxmota: This is what I thought based on our discussion yesterday, thanks for confirming. I can make this change. I anticipate having to modify a lot of input files that do make use of default values (whether intentionally or not).

[ikalash]

@jwfoulk : would you be able to give me a list of parameters that are requisite for solving LCM problems? Some are probably physics specific but I'd guess there are a lot required by all LCM problems.

[lxmota]

The parameters unfortunately are material dependent.

If you are using an isotropic elastic model, then one only needs E, nu, and for dynamics, rho.

But there are more complex material models, with many more parameters.

I guess the ConstitutiveModelInterface is where one would disable default values.

[jwfoulk]

Yes. Great point. This is what Alejandro is getting at - defaulting any material property can lead to ruin.