Time curve ignores points after step 63?

Question

Time curve ignores points after step 63?

jeffreybcox (Mechanical)

(OP)

26 May 11 21:02

I'm an experienced user having trouble with the time curve in a linear dynamic analysis I'm working on.  Has anyone else had this problem?  I've defined a time curve for my load with (ideally) 181 points.  Trouble is, on a simple test model the points after 63 are ignored (i.e. load is applied as zero).  This is very easy to see happening in the results.

In my more complicated model, having more than 63 points defined in the first place spits out an error that says: "Dynamic stress.  Error.  Curve points are out of order."  The analysis then fails.

Anyone else seen this?  Figured out a workaround?

Thanks,
Jeff

kellnerp (Mechanical) · Answer 1 · 2011-05-26 21:22:37

Seems like something in the back of my mind recalls that Cosmos/M had this limitation. You might check the Cosmos/M docs.

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jeffreybcox (Mechanical) · Answer 2 · 2011-05-27 00:32:10

I'll try the CM docs, but the FEA docs claim you can define up to 5000 points (see: http://help.solidworks.com/2011/English/SolidWorks/cworks/LegacyHelp/Simulation/Dialog_Box_Help/IDH_HELP_EDIT_DEFINE_FUNCTION_CURVE.html )

--Jeff

kellnerp (Mechanical) · Answer 3 · 2011-05-27 07:00:21

They sure do. That number 63 looks suspicious as it is the maximum you get with 7 bits.

Can you input through the .cwcur file?

Can you post a plot of the curve you are trying to use?

Have you tried an alternate time curve that is different around step 63?

Are there any vertical or near vertical steps in the TC?

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jeffreybcox (Mechanical) · Answer 4 · 2011-05-27 14:31:41

I have tried inputting manually and also through cwcur. Both behave the same. My original load curve was essentially two cycles of a sinusoid with a large gap between, so I wondered whether there was something problematic about that. I've run into the problem of force-control vs. arc-length-control methods before with complicated loading.

So my simple test model is a monotonic increasing ramp function, just rising from zero to my desired 181 steps in a smooth fashion.

--Jeff

kellnerp (Mechanical) · Answer 5 · 2011-05-28 14:33:09

I suppose a call to the VAR is in order then.

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jeffreybcox (Mechanical) · Answer 6 · 2011-05-31 11:35:45

You're right. I checked with them and was told that 2010 has the problem but 2011 doesn't. We haven't gotten ahold of 2011 yet, so my temporary solution, in case anyone is interested, is this:

My input time curves had a lot of zeroes between the interesting pieces of loading (i.e. interesting loads occurred at different times in different portions of the load surface), so I was able to reduce the number of input data points by allowing CW to interpolate a lot. So far so good. It's not a universal workaround, but I seem to be able to get my situation to work without coarsening the fidelity of the interesting loads.

--Jeff

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Time curve ignores points after step 63?