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Valued Contributor
Valued Contributor



I'm curious as to why when you define a Multiset analysis set in FEMAP for nonlinear analysis (using Nonlinear Static, SOL106), that initial conditions can be entered for both the master boundary conditions, and also all the subcases.


This is discussed pretty thoroughly on pages 322(7.3-3) and 291 (6.5-2) of the Handbook of Nonlinear Analysis (SOL106). So it's clear to me that whenever a temperature load is applied, there must be a TEMP(INIT). But in the examples in this publication, the TEMP(INIT) only appears once at the start of the input data (.dat) file, not under every subcase.


However I find I must define a TEMP(INIT), using the initial condition drop down in the FEMAP boundary conditions window, for every subcase with a temperature load, even though it is already defined in the master. So it seems this must have changed since the Handbook of Nonlinear Analysis (SOL106) was published.


Is it possible to have different initial temperature conditions for different subcases in the same analysis? 


Why would you do this?







Re: TEMP(INIT) in SOL106


What can be analysed vs what can be defined are sometimes different.  Also, the examples are only a subset of what mighte be possible.


You do not need to (and should not) select the single Initial Condition set anywhere other than in the Master Case for a multi-case SOL106 (NL Static) thermal strain analysis.


Nonlinear analyses are sequential, not independent.  For an NL analysis sequence, NX Nastran uses the final outcome from Case 1 as the intitial conditions for Case 2 etc., so the imposition of a revised IC would suggest a conflict of information.


BUT,  looking at the NX Nastran Quick Ref guide, it says that for the TEMPERATURE Case Control command, the analysis will ONLY consider the final TEMP(INIT) for the entire analysis anyway, even if multiple TEMP(INITs) have been defined (for most solutions types).


In short, the recommended procedure is to have one set of IC's (selected only in the Master Case) and then have one or more Cases which follow on from the one initial condition.  If the physical system does not have the load conditions following sequentially, then they should not be part of a non-linear multi-case thermal strain analysis.  If you wished to consider different IC's for one or more load Set/Case sequence(s), these can be done as multiple analyses - which can be easily set to analyse in series from within Femap.