ANSYS. DesignXplorer - Design for Six Sigma. Crane Hook

Transcription

1 ANSYS DesignXplorer - Crane Hook

2 Purpose Using the crane hook model at right we will demonstrate how the design for six sigma results can be used in DesignXplorer 8.1 Goal Our first goal is to verify that the safety factor for the crane hook, when in service, is above 6 and to determine what parameters are important in maintaining that level. Knowing manufacturing tolerances will effect the hook s structural performance we want to design to insure six sigma performance. Back_ds Model Description 3D model of a crane hook. The geometric variation for the 3 input parameters are known to vary approximately 1.5mm. We will inspect the Simulation model and solve before moving to DesignXplorer. Bottom_ds New Features in the Workbench. Depth_ds

3 Bring up the Workbench launcher and start a new Simulation session using the icon When the Simulation GUI opens choose Geometry and From File... In the browser locate and open Crane_Hook.agdb From the Units menu specify the working units to be Metric (mm, kg, N, C, s, mv, ma)

4 Highlight g the Mesh branch and change to Advanced control in the detail window Set Element Size to 10 mm

5 From the Environment branch apply boundary conditions shown here. Apply a fixed support to the top of the hole. Apply a 10,000 N force to the bottom of the hook s cavity (-Y direction). Note for both boundary conditions a load Note, for both boundary conditions a load patch was created in DesignModeler using the imprint face feature.

6 In the solution branch insert equivalent stress, total deformation and stress tool objects. From the detail window for each of the results check the P parameter key for maximum stress, maximum deflection and minimum safety factor Solve.

7 When the solution is complete note that the minimum reported safety factor is approximately 6.2. While this is above our stated goal we wish to include the uncertainties related to manufacturing in the calculation. To do this we ll employ DesignXplorer s PDS capabilities. Note, results may differ slightly due to different meshes.

8 Return to the Project page and choose to begin a New DesignXplorer study. Save the dsdb and project files when prompted. When DX opens notice the parameters section contains input and response parameter definitions including a default range for each input. T d hi hli ht h i t t d To proceed highlight each input parameter and modify its behavior and definition as shown on the following page.

9 Change the simulation parameter type to Uncertainty Variable. Specify that the standard deviation for each input is 0.5. Note: there are a number of distribution types available. We will use a Gaussian distribution (default) for this workshop. From the top of the GUI choose to Solve Automatic Design Points. Note: the presence of 3 input parameters will require 15 solutions. Solution times will vary according to hardware available.

10 When the solutions are complete the Views section will contain several new categories. Highlighting the Responses view allows relationships to be visualized among the various input and output parameters. Note: shown here are samples. Actual plot may vary.

11 Note that in addition to the response charts there are spider charts as well as single parameter sensitivities available. With the minimum safety factor response checked and active, highlight Single Parameter Sensitivities. We can see from the resulting plot that the input parameter Back_ds has the most influence on the safety factor for the hook. This information indicates that holding tighter tolerances on this parameter will have the most beneficial effect on the hook s performance and will result in the greatest return on investment for our manufacturing budget.

12 Highlight the view. Before postprocessing six sigma information we need to generate samples based on the scatter specified for the input parameters. DesignXplorer uses a modified Monte Carlo simulation, known as Latin Hypercube Simulation, to generate samples used in six sigma design. Click the 10,000 sample button and Generate to create the samples. Following sample generation both input and response parameters can be displayed in either histogram or cumulative distribution function form. Input parameters can be inspected to insure that the samples accurately reflect the requested input (Gaussian, exponential, etc). Inspect each input parameter to verify its distribution is as expected.

13 Recalling that safety factor was the result of concern, change the parameter display to Safety Factor Minimum. In addition to the statistics section, we have histogram and cumulative distribution function information to use in our assessment. To continue, we ll focus on the tabular data used to create the cumulative distribution function. N t lt diff li htl d t Note, results may differ slightly due to different meshes.

14 One of our stated goals was to insure the safety factor of the hook was maintained at or above 6. In this case the statistical information indicates there is approximately a 0.1% likelihood that the safety factor will fall below that goal. Note: six sigma design requires a % success rate. 0.1% failure We will proceed as follows: knowing the parameter Back_ds has the greatest impact on the design s performance we will see what the effect of holding a tighter tolerance on that value has on the overall performance of the hook. Note, results may differ slightly due to, y g y different meshes.

15 Using the Simulation tab return to the Simulation environment and reset the parameter definitions to their original values (200, 200, 60), then Choose: Update: Use Simulation Parameter Values Return to the project page and highlight Model then choose New DesignXplorer study

16 In DesignXplorer change the parameter definitions for Depth_ds and Bottom_ds as before: Simulation Parameter Type: Uncertainty Variable Distribution Type: Gaussian Standard Deviation: 0.5 Specify parameter Back_ds using: Simulation Parameter Type: Uncertainty Variable Distribution type: Gaussian Standard deviation: 0.1 Again Solve Automatic Design Points in DesignXplorer.

17 When the solutions are complete, again generate 10,000 samples and review the safety factor statistics. Note the result of tightening the input parameter variation is seen as a change in the threshold for our goal (safety factor = 6). 01% 0.1% failure Original Run Note, results may differ slightly due to different meshes.