Large displacement result from Pressure loading

Coreform IGA
#1

I have a pressure condition which I am trying to apply to some geometry and I believe I am holding the geometry in place by using the appropriate boundary conditions. I am getting answers that indicate that my geometry is not fully constrained though I have written boundaries that account for each translational degree of freedom. Is there something I am missing or have I misinterpreted the units for the pressure condition? the pressure is applied to the interior cavity of my part snipped below.

Finstock_Pressure.txt (2.5 KB)

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image1208×532 46.5 KB

#2

@clint.r.nicely – it appears that you’re reusing the boundary condition names (Hold_BC), these should be unique:

Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "y" ],
			function: "constant_1",
			set: "Hold",
			magnitude: 0.0,
			penalty: 1e20,
		},
Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "z" ],
			function: "constant_1",
			set: "Hold",
			magnitude: 0.0,
			penalty: 1e20,
		},
Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "z" ],
			function: "constant_1",
			set: "z-symmetry",
			magnitude: 0.0,
			penalty: 1e20,
		}

etc.

The way you can think of the JSON5 input format is that it’s similar in structure to codes like Sandia’s Sierra codes.

Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "z" ],
			function: "constant_1",
			set: "Hold",
			magnitude: 0.0,
			penalty: 1e20,
		},

roughly would translate into SIERRA as:

BEGIN BOUNDARY CONDITION Hold_BC
	TYPE = fixed
	VARIABLE= displacement
	SET = Hold
	COMPONENTS = Z
	FUNCTION = constant_1
	MAGNITUDE = 0.0
	PENALTY = 1e20
END

With the point being that Hold_BC is the unique name for the boundary condition.

#3

Thank you for letting me know about a preferred set up for each set. I had it consolidated at first as well, but I was coming upon the same answer that indicated an unconstrained model. I have changed it back to having the ‘Hold’ set be defined to have 0 displacement in the x, y, and z directions and still are getting the same results as described above.

#4

Right, but looking at your file on your server, it appears you’re still using the same name, Hold_BC twice:

Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "x","y","z" ],
			function: "constant_1",
			set: "Hold",
			magnitude: 0.0,
			penalty: 1e20,
 		 },
Hold_BC: {
			type: "fixed",
			variable: "displacement",
			components: [ "z" ],
			function: "constant_1",
			set: "z-symmetry",
			magnitude: 0.0,
			penalty: 1e20,
		}

Try calling one Hold_BC and the other Symmetry_BC

#5

AHA! Wonderful. I had been overlooking these identifiers before this but they are important, indeed. Blindly cutting/pasting has led me astray once again.

Thank you. =D

#6

lol, been there before, my friend!

copy-paste-paste

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