Adding shear heating

[tan2]

We should add shear heating term into the energy equation in update_temperature(). However, we need to decide how to deal with elastic strain.

The elastic strain is reversible and would not generate shear heating. However, the code doesn't differentiate elastic vs. non-elastic strain. It only has total strain and strain rate. We have two options:

1. Ignore the distinction. Assuming elastic strain is small and doesn't contribute much to shear heating. Use the total strain rate to compute shear heating. This is also the approach taken by geoflac.
2. Compute the elastic strain rate and remove its contribution from shear heating. The computation is like the followings:
   • ds is the incremental stress tensor of this time step, and edot is the strain rate tensor
   • Compute de_elastic from ds, based on linear elasticity
   • edot_elastic = de_elastic / dt
   • edot_nonelastic = edot - edot_elastic
   • Shear heating is the total stress tensor contracted with edot_nonelastic

I am not sure which option to take. Any opinions?

[sungho91]

I have already implemented plastic shear heating for plastic deformation in my local, unpushed code.

My reasoning was that shear heating should come from rapid irreversible deformation, such as during earthquakes, so plastic strain is a natural first term to include.

I also thought about using the total strain rate, but I was not sure whether it is physically natural to generate heat every time elastic energy is accumulated. Since elastic deformation is reversible, I thought it may be safer to avoid including the elastic part in the heating term for now.

I also considered viscous shear heating, but I am still not sure whether it should be included for slow viscous flow, or how important that contribution would be in our formulation.

[LucLavier]

Yes only viscous shear and plastic shear would generate heat in that formulation. When it was implemented we only used it for viscoelastic behavior. The best way is to remove edit_elastic from edit Get Outlook for Mac <https://aka.ms/GetOutlookForMac> From: Sungho Lee ***@***.***> Date: Tuesday, April 28, 2026 at 8:10 AM To: GeoFLAC/DynEarthSol ***@***.***> Cc: Lavier, Luc L ***@***.***>; Assign ***@***.***> Subject: Re: [GeoFLAC/DynEarthSol] Adding shear heating (Issue #61) [https://avatars.githubusercontent.com/u/40257026?s=20&v=4]sungho91 left a comment (GeoFLAC/DynEarthSol#61)<#61 (comment)> I have already implemented plastic shear heating for plastic deformation in my local, unpushed code. My reasoning was that shear heating should come from rapid irreversible deformation, such as during earthquakes, so plastic strain is a natural first term to include. I also thought about using the total strain rate, but I was not sure whether it is physically natural to generate heat every time elastic energy is accumulated. Since elastic deformation is reversible, I thought it may be safer to avoid including the elastic part in the heating term for now. I also considered viscous shear heating, but I am still not sure whether it should be included for slow viscous flow, or how important that contribution would be in our formulation. — Reply to this email directly, view it on GitHub<#61 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AUX7EVCDCD2Y3V44QF767B34YBDMRAVCNFSM6AAAAACYI3MIOWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DGMZSG43TEMRYGQ>. Triage notifications on the go with GitHub Mobile for iOS<https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android<https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you were assigned. This message is from an external sender. Learn more about why this matters.<https://ut.service-now.com/sp?id=kb_article&number=KB0011401>

[chaseshyu]

I am also using shear heating locally with total strain rate only, but option 2 seems more reasonable to me. In this case, the handling of ds will be crucial in the implementation.