Engineering Analysis with Ansys Software Episode 2 Part 9 pot

Ch07-H6875.tex 24/11/2006 18: 34 page 344 344 Chapter 7 Application of ANSYS to contact between machine elements Figure 7.20 Model after meshing process. A Figure 7.21 Size and Shape control of element edges. Ch07-H6875.tex 24/11/2006 18: 34 page 345 7.2 Example problems 345 A Figure 7.22 Contact Manager. A B D C Figure 7.23 Contact Wizard. Ch07-H6875.tex 24/11/2006 18: 34 page 346 346 Chapter 7 Application of ANSYS to contact between machine elements A Figure 7.24 Select Areas for Target. A Figure 7.25 Select Areas for Contact. Figure 7.26 Pin contact area. Surface area of the pin should be picked as the area for contact. When it is done and the [A] OK button pressed, Contact Wizard frame appears (see Figure 7.23). Pressing Next [D] button produces a frame in which Material ID =1, Coefficient of friction =0.2 should be selected. Also, Include Initial penetration option should be checked. Next, Optional set- tings button should be pressed in order to further refine contact parameters. In the new frame, Normal penalty stiffness =0.1 should be selected. Also, Friction tab located in the top of the frame menu should be activated and Stiffness matrix =Unsymmetric should be selected. Afterward, pressing the button OK and next Create results in the image shown in Figure 7.26. Also, Contact Wizard frame appears in the form shown in Figure 7.27. The message is that the contact pair has been created. Pressing [A] Finish button closes the Contact Wizard tool. Contact Manager frame appears again with the information pertinent to the problem considered. It is shown in Figure 7.28. Ch07-H6875.tex 24/11/2006 18: 34 page 347 7.2 Example problems 347 A Figure 7.27 Contact Wizard final message. Figure 7.28 Contact Manager summary information. 7.2.1.6 SOLUTION In the solution stage, solution criteria have to be specified first. As a first step in that process, symmetry constraints are applied on the quarter-symmetry model. From ANSYS Main Menu select, Solution → Define Loads →Apply → Struc- tural → Displacement → Symmetry BC → On Areas. The frame shown in Figure 7.29 appears. Four areas which were created when the full configuration model was sectioned to produce quarter-symmetry model should be picked as shown in Figure 7.30. When that is done, click [A] OK button in the frame shown in Figure 7.29. The next step is to apply boundary constraints on the block of which the pin is an integral part. Ch07-H6875.tex 24/11/2006 18: 34 page 348 348 Chapter 7 Application of ANSYS to contact between machine elements A Figure 7.29 Apply SYMM on Areas. Figure 7.30 Selected areas on which symmetry constraints are applied. Ch07-H6875.tex 24/11/2006 18: 34 page 349 7.2 Example problems 349 A B Figure 7.31 Apply U,ROT on Areas. From ANSYS Main Menu select Solution →Define Loads →Apply → Struc- tural →Displacement →On Areas. Backside of the block should be picked and then OK button pressed. The frame shown in Figure 7.31 appears. All degrees of freedom [A] All DOF should be constrained with the displacement value equal to zero (see Figure 7.31). Clicking [B] OK button applies the constraints. Because the original problem formulation asks for stress analysis when the arm is pulled out of the pin, the analysis involves a large displacement effects. The first type of load results from the interference fit between the pin and the arm. From ANSYS Main Menu select Solution → Analysis Type → Sol’n Controls. The frame shown in Figure 7.32 appears. In the pull down menu select [A] Large Displacement Static. Further selected options should be [B] Time at end of load step =100; [C] Automatic time stepping (pull down menu) =Off; and [D] Number of substeps =1. All specified selections are shown in Figure 7.32. Pressing [E] OK button applies the settings and closes the frame. The next action is to solve for the first type of load, i.e., interference fit. From ANSYS Main Menu select Solution →Solve →Current LS. A frame show- ing review of information pertaining to the planned solution action appears. After checking that everything is correct, select File →Close to close that frame. Pressing OK button starts the solution. When the solution is completed, press Close button. In order to return to the previous image of the model, select Utility Menu → Plot →Replot. The second type of load is created when the arm is pulled out of the pin. A number of actions have to be taken in order to prepare the model for solution. First action is to apply a displacement along Z-axis equal to 2 cm (thickness of the arm) to all nodes on the front of the pin in order to observe this effect. Ch07-H6875.tex 24/11/2006 18: 34 page 350 350 Chapter 7 Application of ANSYS to contact between machine elements A B C D E Figure 7.32 Solution Controls. A B C D Figure 7.33 Select Entities. A Figure 7.34 Apply U,ROT on Nodes. Ch07-H6875.tex 24/11/2006 18: 34 page 351 7.2 Example problems 351 From Utility Menu → Select → Entities. The frame shown in Figure 7.33 appears. In this frame the following selections should be made: [A] Nodes (from pull down menu); [B] By Location (pull down menu); [C] Z coordinates (to be checked); Min, Max =4,5. Pressing [D] OK implements the selections made. Next, degrees of freedom in the Z-direction should be constrained with the displacement value of 2 (thickness of the arm). From ANSYS Main Menu select Solution → Define Loads → Apply → Struc- tural → Displacement → On Nodes. In response, a frame shown in Figure 7.34 appears. By pressing [A] Pick All button, a frame shown in Figure 7.35 is called up. As shown in Figure 7.35, [A] DOF to be constrained =UZ and the [B] Displacement value =2. Pressing [C] OK button applies selected constraints. A B C Figure 7.35 Apply U,ROT on Nodes. Options for the analysis of pull-out operation have to be defined now. From ANSYS Main Menu select Solution → Analysis Type → Sol’n Controls. The frame shown in Figure 7.36 appears in response. As shown in Figure 7.36, the following selections defining solution controls were made: [A] Time at end of load step =200; [B] Automatic time stepping (pull down menu) =On; [C] Number of substeps =100; [D] Max no. of substeps =10,000; [E] Min no. of substeps =10; and Frequency (pull down menu) =Write every Nth substep, where N =−10. Pressing [F] OK button applied selected controls. Now the model is ready to be solved for the load resulting from pulling the arm out. From ANSYS Main Menu select Solution → Solve → Current LS. A frame giving summary information pertinent to the solution appears. After reviewing the information select File → Close to close the frame. After that, pressing OK button starts the solution. When the solution is done, press Close button. Ch07-H6875.tex 24/11/2006 18: 34 page 352 352 Chapter 7 Application of ANSYS to contact between machine elements A B C E D F Figure 7.36 Solution Controls. During solution process warning messages could appear. In order to make sure that the solution is done, it is practical to issue the command in the input box: /NERR, 100, 100, 0FF. This ensures that ANSYS program does not abort if it encounters a considerable number of errors. 7.2.1.7 POSTPROCESSING Postprocessing stage is used to display solution results in a variety of forms. The first thing to do is to expand the quarter-symmetry model into full configuration model. From Utility Menu select PlotCtrls → Style → Symmetry Expansion → Periodic/ Cyclic Symmetry. Figure 7.37 shows the resulting frame. Click [A] ¼ Dihedral Sym button as shown in Figure 7.37 and press [B] OK. From Utility Menu select Plot → Elements. An image of the full configuration model appears as shown in Figure 7.38. The first set of results to observe in the postprocessing stage is to look at the state of stress due to interference fit between the pin and the hole in the arm. From ANSYS Main Menu select General Postproc →Read Results → By Load Step. The frame shown in Figure 7.39 is produced. The selection [A] Load step number =1 is shown in Figure 7.39. By clicking [B] OK button the selection is implemented. Ch07-H6875.tex 24/11/2006 18: 34 page 353 7.2 Example problems 353 A B Figure 7.37 Periodic/Cyclic Symmetry Expansion. Figure 7.38 Full model with mesh of elements and applied constraints. [...]... elements are made of steel with Young’s modulus = 2. 1 × 1 09 N/m2 , Poisson’s ratio = 0.3 and are assumed elastic Friction coefficient at the interface between cylinder and the block is 0 .2 360 Chapter 7 Application of ANSYS to contact between machine elements Figure 7. 49 Configuration of the contact between cylinder and two blocks 7 .2. 2 .2 MODEL CONSTRUCTION For the intended analysis a half-symmetry model... From ANSYS Main Menu select, Preprocessor → Modelling → Create → Volumes → Block → By Dimensions In response, a frame shown in Figure 7.51 appears It can be seen from Figure 7.51 that appropriate X, Y, and Z coordinates were entered to create a block (vol 1) with the length 2 cm ([A] X1 = −1; X2 = 1), width 1 cm ([B] Z1 = 0; Z2 = 1), and thickness 0.75 cm ([C] Y1 = −0 .25 ; Y2 = −1) Next, from ANSYS. .. Figure 7.40), the following are selected 7 .2 Example problems 3 59 as items to be contoured: [A] Stress and [B] von Mises (SEQV) Pressing [C] OK implements selections made Figure 7.48 shows stress contours on the pin resulting from pulling out the arm Figure 7.48 7 .2. 2 Pull-out stress contours on the pin Concave contact between cylinder and two blocks 7 .2. 2.1 PROBLEM DESCRIPTION Configuration of the... Dimensions In response, a frame shown in Figure 7. 52 appears The input into the frame, shown in Figure 7. 52, created a solid cylinder sector with the [A] radius 0.5 cm, [B] length 1 cm, [C] starting angle 180◦, and [D] ending angle 360◦ (vol 2) 7 .2 Figure 7.50 Example problems 361 A half-symmetry model A C B Figure 7.51 Create Block by Dimensions From ANSYS Main Menu select Preprocessor → Modelling →... Pressing [C] OK implements selections made Figure 7.46 shows image of the pin with pressure contours A B Figure 7. 42 Read Results by Time or Frequency A B C D Figure 7.43 Select Entities 7 .2 Figure 7.44 Example problems 357 Pin with surface elements B A C Figure 7.45 Contour Nodal Solution Data 358 Chapter 7 Application of ANSYS to contact between machine elements Figure 7.46 Contact pressure contours... 3D analysis and advantage could be taken of the inherent symmetry of the model Therefore, the analysis will be carried out on a half-symmetry model only The objective of the analysis is to observe the stresses in the cylinder when the initial gap between two blocks is decreased by 0.05 cm The dimensions of the model are as follows: cylinder radius = 0.5 cm; cylinder length = 1 cm; block length = 2 cm;...354 Chapter 7 Application of ANSYS to contact between machine elements A B Figure 7. 39 Read Results by Load Step Number From ANSYS Main Menu select General Postproc → Plot Results → Contour Plot → Nodal Solu In the resulting frame, see Figure 7.40, the following selections A B C Figure 7.40 Contour Nodal Solution Data 7 .2 Example problems 355 are made: [A] Item to be contoured... (vol 2) should be picked and [A] OK button pressed As a result of that, block and cylinder are overlapped and three volumes created, i.e., volume 5 (block), volume 3 (section of the cylinder within the block), and volume 4 (remaining of the cylinder after a section of it has been subtracted) From ANSYS Main Menu select Modelling → Delete → Volume and Below The frame shown in Figure 7.54 appears 3 62 Chapter... Name = 174 The element with the number 174 was introduced automatically during the process of creation of contact pairs described earlier It is listed in the Preprocessor → Element Type → Add/Edit/Delete option Selections are implemented by pressing [D] OK button From Utility Menu select Plot → Elements Image of the pin with surface elements is produced (see Figure 7.44) From ANSYS Main Menu select... contact pressure on the pin resulting from the interference fit, it is required to read results by time/frequency From ANSYS Main Menu select General Postproc → Read Results → By Time/Freq In the resulting frame, shown in Figure 7. 42, the selection to be made is: [A] Value of time or freq = 120 Pressing [B] OK implements the selection From Utility Menu choose, Select → Entities The frame shown in Figure . 24 /11 /20 06 18: 34 page 345 7 .2 Example problems 345 A Figure 7 .22 Contact Manager. A B D C Figure 7 .23 Contact Wizard. Ch07-H6875.tex 24 /11 /20 06 18: 34 page 346 346 Chapter 7 Application of ANSYS. elements A Figure 7 . 29 Apply SYMM on Areas. Figure 7.30 Selected areas on which symmetry constraints are applied. Ch07-H6875.tex 24 /11 /20 06 18: 34 page 3 49 7 .2 Example problems 3 49 A B Figure 7.31. were entered to create a block (vol. 1) with the length 2 cm ([A] X1 =−1; X2 =1), width 1 cm ([B] Z1=0; Z2 =1), and thickness 0.75 cm ([C] Y1 =−0 .25 ; Y2 =−1). Next, from ANSYS Main Menu select Preprocessor