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Published byDuane Lindsey Modified over 8 years ago
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Error calculations and error convergence Winter Semester 2009-2010
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2 Goals In this workshop, an underground pipe shield will be analyzed under singularity conditions. You will try to reduced the error value by enlarging the number of elements. You will use the convergence tool in order to explore the solution accuracy. The convergence tool controls the relative accuracy of a solution by refining solution results on a particular area of a model. We will run this analysis 4 times, each time we will change the analysis parameters.
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3 Assumptions We will assume that a system of pipes, leading sewage water, is protected by a concrete shielding. The pipe shielding in this workshop, is only a part of the entire system. A force with magnitude of 200N in acting on the shield ’ s edge. The pipe shielding is mounted with fixed support to the ground.
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4 Pipe Shielding Description
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5 Model number 1
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6 Start Page From the launcher start Simulation. Choose “ Geometry > From File... “ and browse to the file “ pipe_shielding.x_t ”.
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7 Preprocessing Set the working units to Metric (mm). “ Units > Metric (mm, kg, N, C, s) ”. Change the material of the pipe to “ concrete ” Highlight the part in the tree. In the detail window click in the material field and “ Import Concrete ”.
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8 Preprocessing Start new structural analysis, under the “ New analysis ” menu. Highlight the “ Static structural ” branch and insert loads and supports. Load – under the loads menu, add force of 200N along the pipe ’ s edge.
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9 Preprocessing Supports – from the supports menu, add fixed support to the pipe ’ s bottom surfaces
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10 Solution Highlight the solution branch, RMB, add: Equivalent stress, Error. Solve the model
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11 Results Examine the max error values: Examine the stress result at specific location:
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12 Model number 2
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13 Preprocessing Highlight the model branch and duplicate it by clicking RMB “ Duplicate ”
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14 Refining the mesh Highlight the “ Mesh ” branch Under the “ Mesh control ” menu add “ sizing ” Change the element size to 4mm. RMB on the “ Mesh ” branch ” Generate mesh ” Camper the element ’ s number between the models.
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15 Mesh comparison
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16 Solution Solve model 2. Compare the error results. Examine the differences in the stress results. Error results:
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17 Model number 3
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18 Preprocessing Duplicate model number 1 (the first model). A new model, name ‘ model 3 ’, will appear. Highlight the equivalent stress branch and add a convergence tool. RMB Insert Convergence. Note that the default convergence criteria is 20%
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19 Convergence Set the convergence max refinement loop number to 1 and the refinement depth to 2. Highlight the solution branch and set these values under the Details window. Notes: Note number 1: The first calculation loop is default. We can add refinement loops by setting the max allowed loops. It will add loops until the accuracy required will be archived. Note number 2: In case that the required accuracy has been achieved using less loops than defined, the solution will be stopped.
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20 Solution Highlight the model 3 branch and solve the model. Examine the convergence result. Note the red exclamation mark near the “ convergence ” ; It means that the solution was not converted.
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21 Model number 4
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22 Preprocessing Duplicate model number 3. A new model, name ‘ model 4 ’, will appear. Add another equivalent stress for the interior face only.
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23 Preprocessing Solve model number 4. Add a convergence tool to the equivalent stress calculated for the interior face. The solution will be stopped only after solution convergence for this specific face has been achieved, regardless the singularity ’ s condition. Re-solve the model
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24 Solution Examine the convergence results. Note the green check mark near the convergence branch
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