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[WB] How to ramp a linear pressure distribution over 'time'?
 
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uffe.eriksen
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Joined: 21 Oct 2008
Posts: 69

PostPosted: Tue Jun 30, 2015 12:54 am  Reply with quote

Hi there,

I am struggling with getting WB to play nice, again.

For simplicity, let's say I have a plate, where I want to apply/map a pressure, which varies linearly with the global X-coordinate, from zero to a certain value. So far, so good; I can do this fairly easily.

But I want to run a nonlinear analysis, where the pressure distribution is ramped linearly from zero to its full value over 'time', i.e. a single load step but using several substeps, large displacement etc... And for some reason the entire pressure load is always applied fully at the very first substep and then kept constant for the remainder of the analysis.

Is there a way to achieve what I want using WB? I must confess I haven't tried doing this in Classic (oops, Mechanical APDL), but I struggle to see how a pressure distribution over an area should not work exactly like a 'standard' pressure, which ramps just nicely over several substeps?

Of course, I could manually subdivide (discretize) my area and apply single strips of 'proper' pressure according to my pressure distribution function, but... seriously?

Any help or tricks much appreciated :)
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Uffe Dal Eriksen
Ramboll Oil & Gas
Esbjerg, Denmark
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liam.mealey1
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Joined: 08 Dec 2014
Posts: 7

PostPosted: Tue Jun 30, 2015 3:35 am  Reply with quote

How are you defining the spatial pressure variation? Are you doing it via a function (for example Magnitude = 5*x)?

If so you can explicitly include time in your function (so for the example above Magnitude = 5*x*time).

If it's over the first loadstep, then time will vary from t=0 to t=1, so will linearly ramp your pressure up to the full value at the end of the loadstep. If it's not over the first loadstep you may need to normalise time appropriately, but that should be straightforward.

If you've created the pressure distribution via an imported set of data there is the option to set the Tabular Loading to Ramped under Details
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Liam Mealey
OneSubsea, Leeds, UK
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uffe.eriksen
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Joined: 21 Oct 2008
Posts: 69

PostPosted: Tue Jun 30, 2015 5:51 am  Reply with quote

Thanks Liam.

I have it working now, by multiplying my entire function with time/2 (my load step time is 2).
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Uffe Dal Eriksen
Ramboll Oil & Gas
Esbjerg, Denmark
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