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From: Vikram Garg <simulationist@gm...>  20120624 18:41:14

Hey Kyunghoon, Unfortunately, I am not very familiar with reduced basis methods (or with linear elasticity). If you were using regular Finite Elements, then going by this formulation of linear elasticity ( http://en.wikipedia.org/wiki/Linear_elasticity#Direct_tensor_form), the strain is the gradient of the displacement that is solved for. So I believe, one would use element_postprocess.C, but instead of computing interior_value, one would use compute interior_gradient to compute the strain, and then use Hooke's law to get the stress. This would work if you needed average stress over a subset of the domain. However, if you needed stress and strain at a point, you might want to use point_gradient. See line 464 in libmesh/examples/fem_system/fem_system_ex1/naviersystem.C , it gives an example for point_value but the idea is the same for point_gradient. The definitions for point_value and point_gradient are in libmesh/src/systems/system.C . Thanks. On Sun, Jun 24, 2012 at 12:11 AM, Kyunghoon Lee <aeronova.mailing@...>wrote: > On Sun, Jun 24, 2012 at 11:33 AM, Vikram Garg <simulationist@...>wrote: > >> Hey Kyunghoon, >> If you are using FEMSystem, see >> element_postprocess.C and side_postprocess.C in this example: >> libmesh/examples/adjoints/adjoints_ex1 ( >> http://libmesh.sourceforge.net/adjoints_ex1.php) >> >> If you are not using FEMSystem, I believe all you will have to do is to >> write a loop over all elements, and then adapt the contents of >> element/side_postprocess.C to the interior of that loop. >> >> Thanks. >> > > Hi Grag, > > Thank you for the suggestion. I'm working on Reduced Cantilever Problem ( > http://libmesh.sourceforge.net/reduced_basis_ex5.php), so I guess I'm > using FEMSystem. I checked the two files, element_postprocess.C and > side_postprocess.C, but I cannot figure out how I can use them for my > strain & stress evaluations. Can you elaborate, plz? > > K. Lee. >  Vikram Garg PhD Candidate Institute for Computational and Engineering Sciences The University of Texas at Austin http://users.ices.utexas.edu/~vikram/ http://www.runforindia.org/runners/vikramg 