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<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Dear Matt and Jed,</span></div>
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<div class="elementToProof"><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">Thank you for your answers. I'll have a look at Ratel to see how to set-up a quasi-static
nonlinear problem with TS and SNES.</span></div>
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<div style="margin:0px"><font size="3" face="Calibri,sans-serif">Best regards, </font>
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<div style="margin:0px"><font face="Calibri,sans-serif"><font size="3" style="">Nicolas<br>
<span style="font-size:11pt">--</span></font><br>
</font><font size="2" face="Arial,sans-serif" color="#ff8100"><span style="font-size:9pt"><b>Nicolas Tardieu</b></span></font><br>
<div style="margin:0px"><font size="2" face="Calibri,sans-serif"><span style="font-size:11pt"><font size="1" face="Arial,sans-serif" color="#ff8100"><span style="font-size:8pt"><b>Ing PhD Computational Mechanics</b></span></font><font size="1" face="Arial,sans-serif" color="#ff8100"><span style="font-size:8pt"><b><br>
</b></span></font></span></font></div>
<div style="margin:0px"><font size="2" face="Calibri,sans-serif"><span style="font-size:11pt"><font size="1" face="Arial,sans-serif" color="#0062e1"><span lang="en-US" style="font-size:8pt">EDF - R&D Dpt ERMES</span></font><font size="1" face="Helv,sans-serif" color="#0062e1"><span lang="en-US" style="font-size:2pt"><br>
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<div style="margin:0px"><span style="font-family: Arial, sans-serif; font-size: 8pt; color: rgb(0, 98, 225); background-color: rgba(0, 0, 0, 0);">PARIS-SACLAY, FRANCE</span></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>De :</b> jed@jedbrown.org <jed@jedbrown.org><br>
<b>Envoyé :</b> lundi 19 décembre 2022 14:40<br>
<b>À :</b> Matthew Knepley <knepley@gmail.com>; TARDIEU Nicolas <nicolas.tardieu@edf.fr><br>
<b>Cc :</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>Objet :</b> Re: [petsc-users] SNES and TS for nonlinear quasi-static problems</font>
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<div class="PlainText">Indeed, this is exactly how we do quasistatic analysis for solid mechanics in Ratel (<a href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2Fmicromorph%2Fratel&data=05%7C01%7Cnicolas.tardieu%40edf.fr%7C08e0ffed6942443fe5e908dae1c6c819%7Ce242425b70fc44dc9ddfc21e304e6c80%7C1%7C0%7C638070541137140223%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9E63JeIqTU1efxC8ij5OaL6XWPcErHbaVAAZwpvPY3o%3D&reserved=0">https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2Fmicromorph%2Fratel&data=05%7C01%7Cnicolas.tardieu%40edf.fr%7C08e0ffed6942443fe5e908dae1c6c819%7Ce242425b70fc44dc9ddfc21e304e6c80%7C1%7C0%7C638070541137140223%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9E63JeIqTU1efxC8ij5OaL6XWPcErHbaVAAZwpvPY3o%3D&reserved=0</a>)
-- make sure to choose an L-stable integrator (backward Euler being the most natural choice). Implicit dynamics can be done by choosing a suitable integrator, like TSALPHA2, with almost no code change to the residual (only adding the mass term in DMTSSetI2Function()).<br>
<br>
Matthew Knepley <knepley@gmail.com> writes:<br>
<br>
> On Mon, Dec 19, 2022 at 6:12 AM TARDIEU Nicolas via petsc-users <<br>
> petsc-users@mcs.anl.gov> wrote:<br>
><br>
>> Dear PETSc users,<br>
>><br>
>> I plan to solve nonlinear quasi-static problems with PETSc. More<br>
>> precisely, these are solid mechanics problems with elasto-plasticity.<br>
>> So they do not involve "physical time", rather "pseudo time", which is<br>
>> mandatory to describe the stepping of the loading application.<br>
>> In general, the loading vector F(x, t) is expressed as the following<br>
>> product F(x, t)=F0(x)*g(t), where g is a scalar function of the<br>
>> pseudo-time.<br>
>><br>
>> I see how to use a SNES in order to solve a certain step of the loading<br>
>> history but I wonder if a TS can be used to deal with the loading history<br>
>> through the definition of this g(t) function ?<br>
>><br>
><br>
> I believe so. We would want you to formulate it as a differential equation,<br>
><br>
> F(x, \dot x, t) = G(x)<br>
><br>
> which is your case is easy<br>
><br>
> F(x, t) = 0<br>
><br>
> so you would just put your function completely into the IFunction. Since<br>
> there is no \dot x term, this is a DAE,<br>
> and you need to use one of the solvers for that.<br>
><br>
><br>
>> Furthermore, since too large load steps can lead to non-convergence, a<br>
>> stepping strategy is almost always required to restart a load step that<br>
>> failed. Does TS offer such a feature ?<br>
>><br>
><br>
> I think you can use PETSc adaptation. There is a PID option, which might be<br>
> able to capture your behavior.<br>
><br>
> Thanks,<br>
><br>
> Matt<br>
><br>
><br>
>> Thank you for your answers.<br>
>> Regards,<br>
>> Nicolas<br>
>> --<br>
>> *Nicolas Tardieu*<br>
>> *Ing PhD Computational Mechanics*<br>
>> EDF - R&D Dpt ERMES<br>
>> PARIS-SACLAY, FRANCE<br>
>><br>
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