workCONT-WK05-Q-InterfFit

W5.8Note: This workshop provides instructions in terms of the Abaqus Keywords interface. If you wish to use the Abaqus GUI interface instead, please see the “Interactive” version of these instructions. Please complete either the Keywords or Interactive version of this workshop.IntroductionThis workshop simulates the interference fit of two circular rings. The model is shown in Figure W51. Both rings are assumed linear elastic and are modeled with CPE4 elements. Frictionless contact is assumed. The inner ring is overclosed relative to the outer ring by a constant radial distance of 0.05 units. Three analyses are performed. They differ in how the surface adjustments are applied and whether surface smoothing is employed. Figure W51. Model undeformed configurationPreliminaries1. Change to the ./contact/keywords/interference directory. 2. Open the input file w_interf.inp, which already contains the nodes, elements, and material model data for the analysis. You will edit the input file to include the contact, step and boundary condition definitions.Contact propertiesFrictionless contact is assumed between the parts. Use the penalty constraint enforcement method with the default penalty stiffness. The options to define these properties are as follows:*Surface Interaction, name=noFric*Surface Behavior, penaltyPart 1: Analysis with surface smoothingThe first analysis in this exercise considers the effects of surface smoothing on the solution. Here general contact will be used with a non-default contact initialization setting so that initially overclosed nodes are treated as interference fits. Geometric smoothing will also be used to improve the accuracy of the contact stresses and reduce solution noise.The following options define the general contact interaction:*Contact*Contact Inclusions, ALL EXTERIOR*Contact Property Assignment , , noFricDefine interference fit:1. Define a contact initialization property to specify that initially overclosed slave nodes will be treated as an interference fit. The required option is given below:*Contact initialization data, name=fit-1, INTERFERENCE FIT2. Assign the property to the model. The required option is given below:*Contact initialization assignment , , fit-1Define geometric smoothing:Apply geometric smoothing to the surfaces of the rings. Surfaces have been predefined on the rings (cp-inner is the outer surface of the inner ring; cp-outer is the inner surface of the outer ring). The required option is given below:*Surface property assignment, property=GEOMETRIC CORRECTIONcp-inner, Circumferential, 0., 0.cp-outer, Circumferential, 0., 0.Defining boundary conditionsYour next task is to define the boundary conditions that will act on the assembly. In the first step of the analysis, both rings are held fixed; in the second step, the outer ring is held fixed while the inner one is rotated. A distributing coupling constraint is used to transmit the rotation to the inner ring. It has already been defined for you. The following options define the boundary conditions (you may add them to the model data). The sets fix-x and fix-y indicated below correspond to the locations on the outer ring that will be fixed; the set refPt corresponds to the reference node of the distributing coupling constraint.*Boundaryfix-x, 1, 1fix-y, 2, 2refPt, 1, 6Step definitionThe analysis consists of two general static steps. The steps will consider geometric nonlinearity. In the first step the interference fit will be resolved; in the second step, the inner ring will be rotated 360 while the outer ring remains fixed.The following options define the steps and history data: *Step, name=Step-1, nlgeom=YES, unsymm=YES resolve interference fit*Static*End Step*Step, name=Step-2 rotate inner ring*Static0.05, 1.*Boundary refPt, 6, 6, 6.28319*End StepRunning the job and visualizing the results:Save the changes to a file named w_interf_smoothing.inp.Run the analysis using the following command:abaqus job=w_interf_smoothingVisualizing the analysis resultsAfter the analysis is complete, you will review the results in Abaqus/Viewer.1. Open the output database file w_interf_smoothing.odb.2. Click to plot the Mises stress, as shown in Figure W52. In this figure some nodes on the inner ring have been highlighted to allow us to track the rotation.Figure W52. Mises stress distribution with smoothing at end of interference fit step3. Animate the solution history. Figure W53 shows the configuration when 25%, 50%, and 75% of the rotation has been applied. Note the position of the highlighted nodes in each case and how the contours of Mises stress remain smooth and constant throughout the entire simulation. This is the expected result since the sliding between the surfaces occurs in the absence of friction. Figure W53. Mises stress distribution with smoothing at three different configurations during rotation stepPart 2: Analysis without surface smoothingHere general contact will be used as before. This time, however, the geometric smoothing will be suppressed.1. Copy the file named w_interf_smoothing.inp to one named w_interf_no_smoothing.inp.2. Edit the new file to delete the *Surface property assignment option and its corresponding data lines.3. Save the changes to a file and run the job. While the job is running, monitor its progress.4. After the analysis is complete, evaluate the results in Abaqus/Viewer. The Mises stress at the end of the first step is shown in Figure W54. Note the noise in the solution. The beneficial effects of geometric surface smoothing are clearly evident when compared to the earlier solution.Figure W54. Mises stress distribution without smoothing at end of interference fit stepPart 3: Analysis using contact pairs with precise adjustmentsHere contact pairs will be used instead of general contact. A combination of strain-free initial adjustments plus direct user specification of the interference distance will be used. This technique is particularly useful when you are not sure of the interference required or wish to perform a parametric study. Rather than create a distinct mesh for each value of interference, the same mesh is re-used and the overclosure value is specified directly.1. Copy the file named w_interf_smoothing.inp to one named w_interf_adjust.inp.2. Delete the general contact interaction and its related suboptions.3. Define a contact pair between the surfaces on the inner and outer rings (cp-inner and cp-outer , respectively). Choose cp-outer as the master and cp-inner as the slave. Adjust the slave nodes so that they are moved precisely onto the master surface (and therefore eliminate the overclosure defined by the mesh). The required option is given below:*Contact Pair, interaction=noFric, adjust=0.2cp-inner, cp-outer4. Define an interference fit between the two surfaces. Note that since we have removed the interference from the mesh (via adjustments), a special technique is required to model the interference. This technique requires an “upwards” ramp function together with a negative value of interference. The required options are given below (they should be added to the first step):*Amplitude, name=rampUp0., 0., 1., 1.*Contact Interference, amplitude=rampUpcp-inner, cp-outer, -0.05Note: The default ramp function for an interference fit tends “downwards” (as opposed to the default ramp for loads and boundary conditions which tends “upwards”). The default ramp function is appropriate if the interference is explicitly defined by the mesh nodal coordinates (the magnitude of the interference is automatically detected and ramped down). This is not the case here. For this reason the non-default ramp function is used, as described above.5. Save the changes to a file and run the job. While the job is running, monitor its progress.6. After the analysis is complete, evaluate the results in Abaqus/Viewer. The Mises stress at the end of the first step is shown in Figure W55 (left). Note that the solution is smooth at the end of the interference fit step; solution noise appears, however, as the inner ring is rotated (see Figure W55, right). This is related to the fact that the corrections for this case are associated with individual contact constraints, whereas the corrections for the geometric smoothing used earlier are associated with the surfaces.Figure W55. Mises stress distribution using contact pair adjustments: in