Composite Bike Frame Optimization (Updated to , by Premanand Suryavanshi)

Transcription

1 Composite Bike Frame Optimization (Updated to , by Premanand Suryavanshi) In this tutorial, you learn the steps required to perform a ply orientation optimization for a composite structure. The figure below illustrates the model that will be used for this exercise. The optimization problem for this tutorial is stated as: Objective : Minimize volume. Constraints : A given maximum Nodal Displacement. Design Variables : Layer thickness. In this tutorial, You will : Set-up a size optimization of a Composite Bike Frame. Post-process the composite size optimization results in Hyperview. 1

2 1. Import the model: Goto file > open > bicycle_frame.hm > open. You can see bicycle_frame model in the graphic area Note that Properties, Materials and Control cards are already assigned to the model 2

3 2. Create Load Collectors: The first load is a point load on the pedal (downward direction) and second will be the moment caused due to pedalling. To define the above loads, right click on the model browser > Create > load Collector > name it as Crank. Then from Analysis panel goto Forces > Create > nodes, select a node at the centre of the spider (RBE3) as shown in the image below. Enter value for the magnitude as -100 (downward load) and direction to Z-axis and leave rest all the parameters as shown in the image. Click Create. You should a force of magnitude 100N created as shown in the image. 3

4 Now keeping same (Crank) load collector current apply moment load. Goto Analysis panel > Moments > Create > nodes, select the same centre node of the spider as before. Let the magnitude be 100 and direction X-axis (Pedalling Direction), leave rest all parameters same as shown in below image. Click create. A moment around X is applied 4

5 3. Defining Boundary Constraints: Constraints will be applied to the rear wheel pivot location of the frame and to the Head-tube location (Handle) of the frame. Right click on the model browser > create > Load collector, name it as SPC. Now, goto Analysis panel > Constraints > create > nodes, select the two node as shown in the image below and set all other parameters as shown. Click create. *SPC applied to the rear wheel location of the frame 5

6 Similarly assign constraints for the Head-Tube. *SPC applied to the Head-tube (Handle location) of the frame 4. Creating Load Steps: Goto Analysis panel > Load steps, click name and enter Crank. Toggle type to Linear-Static. Check the box preceding SPC, click on the entry field and select the SPC load-collector from the list. Next, check the box preceding load. Click on the entry field and select the Crank Load-collector from the list. 5. Set-up the Design variables: To setup size parameters, goto 2d panel > Hyperlaminate, Perform the following steps: i. Expand Design Variable in the laminate browser, the DESVAR branch will appear. ii. Right click on DESVAR, click New. iii. Rename it as thk1 and set all other parameter as shown below. 6

7 iv. Where, Initial value is the thickness of the original ply and Upper-bound value is the allowable deformation value. In a similar manner, and with identical values, create a total of 5 Design Variables. v. Now, the above Desvar s is assigned to Seat-Tube. In the same GUI, click on laminates in the laminate browser and expand the PCOMP tree and select Seat-tube laminate. Check the optimization box. New fields appear in the Ply lay-up order table, which allows you to assign the Design Variables to each ply. Click on the field under Designvar and assign thk1 to the first ply and thk2 to the second and so on as shown in below image. 7

8 vi. vii. Now in the same manner assign the Design variables to top-tube and bottom-tube lamintaes. Exit the Hyperlaminate GUI by closing. 6. Create a Displacement and Volume Response: Create a response to measure the total displacement of the node where the loads have been applied and set the objective to minimize this response. Goto Analysis panel > Optimization > Responses, name the Response = Disp. Click the response type and switch to Static displacement. Click on nodes and select the node at the bottom bracket on which loads were applied, click total disp. Click create. In same panel rename Response = Volume, switch the response type to Volume > Total. Click create. Return to optimization panel. 8

9 7. Create constraints on the Displacement Response: In the optimization panel, goto > dconstraints, constraint name = Disp. Set the upper-bound value as 1.8. Click response and select Disp from the response list. Click on loadsteps and select Crank. Click create. *A constraint is defined on the Response Disp. It states that any solution (min vol) needs to have a displacement lesser than 1.8mm is to be feasible. 8. Define Objective: The objective is to minimize volume. To define this, goto Analysis > optimization panel > Objective, toggle to min and Response = Volume. Click create. Return twice. 9. Run the optimization: In the Analysis panel, Click optistruct. Set all other parameters as shown in the image below and click save as. Click optistruct to run the Analysis. After the analysis is complete, a dialogue box opens as shown below. 9

10 10. Post-Processing the composite size optimization results in the Hyperview: ( Reviewing the results in Hypergrapgh) In the same window shown in the above image click on view and select bicycle_frameopt_hist.mvw file. It takes you to Hypergrapgh window. This file contains Objective, Constraints and Design Variable s against iteration history. You should see 9 windows of graph by clicking you can navigate to different windows arrows 10

11 The first page shows the Objective function. *In the above graph, you can see how the volume is minimized throughout the iteration. Second page shows Maximum Constraints Violations. 11

12 The next pages shows the Design Variables for each iterations. *Desvar thk5 *Desvar thk4 *Desvar thk3 *Desvar thk2 *Desvar thk1 12