Timeline for Finite Element Mass and Stiffness Matrices
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 3, 2015 at 22:45 | vote | accept | Hugh | ||
| Nov 17, 2015 at 19:50 | comment | added | user21 | @Hugh, if the system is done with ProcessEquations then extract the dependent variables. Look for the "IncidentOffsets" property in the FEMMethoddata those will give you the position in the system matrices in which the corresponding subsystems are located. | |
| Nov 17, 2015 at 12:54 | comment | added | Hugh | Thanks for the clarification. If I have a non-uniform distributed mass, a non-uniform distributed damping as well as a non-uniform set of material properties then how do I extract the matrix for each? Is this another question I should ask? | |
| Nov 17, 2015 at 7:28 | comment | added | user21 | @Hugh, (1) yes, if you call ProcessEquations then the damping matrix will be the first order system. To get the intermediate variables look at the "VariableData` extracted from the "FEMMethodData" that should have the dependent variables. Concerning (2), note that the second order time derivative, the first order time derivative and the reaction term are all the same! The just end up in different matrices. Perhaps that's the confusion? | |
| Nov 16, 2015 at 7:47 | comment | added | Hugh | (2) In your [example] (mathematica.stackexchange.com/a/57391/12558) the differential equation appears to be wrong (time should be second order) but is there a subtle trick I am missing? I am very familiar with the Rayleigh approximation but this is regarded as inadequate in careful work where damping must be represented more accurately. | |
| Nov 16, 2015 at 7:45 | comment | added | Hugh | (1) Thanks for your prompt comments.I am familiar with converting a second order system in time to a first order system by using intermediate variables.There are several approaches to this conversion particularly if you are including damping as well as mass in the starting differential equation.Does the damping matrix then always correspond to the coefficients of this converted first order system?What system of intermediate variables are used? | |
| Nov 16, 2015 at 7:33 | comment | added | Hugh | Thanks for your prompt comments. I am familar with converting a second order system in time to a first order system b | |
| Nov 16, 2015 at 6:50 | history | answered | user21 | CC BY-SA 3.0 |