Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Time curve ignores points after step 63? 1

Status
Not open for further replies.

jeffreybcox

Mechanical
May 26, 2011
5
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
 
Replies continue below

Recommended for you

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?

TOP
CSWP, BSSE

"Node news is good news."
 
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
 
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
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor