how to prepare models in stresscheck for deployment in ...11. append xps and model icon: use the...

How to Prepare Models in StressCheck® for Deployment in

CAE Handbook

Document Version 1.3 March 2017

Engineering Software Research & Development, Inc.


Handbook Model Creator's Guide

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Table of Contents

Instructions for Handbook Model Preparation......................................................................................3

Regions ..........................................................................................................................................5

Laminate Stacks ..............................................................................................................................5

Example: Constructing a Handbook Model in StressCheck.....................................................................6

Problem Description .......................................................................................................................6

Model Construction ........................................................................................................................6

CAE Handbook Report....................................................................................................................... 14

Mapping Between StressCheck and CAE Handbook ............................................................................ 17

The Summary Panel ...................................................................................................................... 17

The Parameter Panel..................................................................................................................... 18

The Materials Panel ...................................................................................................................... 18

The Rules Panel ............................................................................................................................ 19

The Model Diagram Panel ............................................................................................................. 20

The Model View............................................................................................................................ 21

Extractions with Graphical Output ................................................................................................. 22



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Instructions for Handbook Model Preparation

When constructing a new model in StressCheck to be deployed in the CAE Handbook, it is important to consider the general recommendations given in the StressCheck Master Guide. A well posed Handbook problem should provide parameters which control the critical dimensions of the model problem, and if appropriate, parameters should be provided to give the user control over other variables such as material coefficients and load magnitudes. It is important to design the finite element mesh so that the elements will not be overly distorted over a wide range of parameter settings; this is usually the most difficult part in designing Handbook models.

It is also important to determine the maximum and minimum value of each parameter so that an appropriate parameter range may be assigned which will maintain the integrity of the mesh, and to provide the rules describing the relationships among parameters to protect mesh integrity. In summary, the following guidelines should be considered when preparing handbook problems:

• Provide parameters for critical dimensions, material properties and boundary conditions. • Design the mesh to be valid over a wide range of parameter settings. • Determine minimum and maximum values for each parameter. • Provide rules which describe relationships among parameters. • Provide solution and extraction settings appropriate for the model.

With these guidelines in mind, the usual sequence in the preparation of a Handbook model is as follows:

1. Model Information: Enter the model Title, Comments, and Keywords in the Model Information interface. Use a descriptive title for the problem (i.e., "Thin elastic plate with central hole under tension load"), and complement it in the Comments area (for example, by including a reference: "Peterson (1974), Stress Concentration Factors, John Wiley & Sons, Figure 86").

2. Parameters: Define the Parameters to be used during the construction of the model. i. Choose consistent letter case for similar parameters like dimensions, properties, and

boundary conditions. ii. Include a useful Description and assign the parameter Class. General parameters are used

for dimensions, Property parameters define material properties, and B. Cond. parameters are used for loads and constraints.

iii. The Sort field can be used to control the order of parameters in the Handbook. iv. Parameters defined using expressions will be hidden to the Handbook user, but can be a

useful feature for the model creator. 3. Rules: Define parameter rules that will enforce valid parameter values (lower and upper

bounds), control relationships among parameters to preserve the integrity of the mesh, and protect the Handbook user from conceptual mistakes.

4. Model Icon: Create a model icon to provide a visual feedback while browsing the Handbook library. Image capture tools are available in the Model Information interface, but any image editing program can be used.

i. Avoid including information not strictly related with the model, like a rule or a material name.

ii. A good icon will show how geometric dimensions are driven by parameters.



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5. Build the Model: Create the model geometry and mesh, and define the material properties and boundary conditions using the parameters previously created. Create a solution record identifying the load and constraint pair to be executed during the analysis.

i. Test the full range of parameter values to ensure that no input can invalidate geometry or overly distort the mesh.

6. Default View: Save a default view of the model. When the Handbook problem is loaded, it will appear in this view in the Model window.

i. For 2D problems a front view is recommended, while for 3D problems a view in perspective is preferable.

7. Solution Settings: Save solution settings (Linear/Modal/Buckling/Nonlinear) which will be automatically run when the Handbook Solve button is pressed.

i. Be sure to run at least three p-levels to provide error estimation, though more p-levels are recommended.

ii. More than one solution can be specified. For example, nonlinear problems require both linear and nonlinear solution settings.

8. Extractions: Save post-processing settings for the desired Handbook extractions. Each extraction should have a Name (up to 15 characters) and a Title (up to 30 characters) complementing each other. For example, Name: "S1 Plot", Title: "Contour plot of Sigma 1".

i. For plots, it is a good practice to select mid-sides to be 10 to produce high quality contours, and to set the View to Default so that the model is displayed in the saved view after solution (regardless of the position of the mesh in the Model window at the time Solve is selected).

ii. For Min/Max graphs: Select the same number of mid-sides as in Plot. Make sure the ‘Display pts’ button is off to prevent unnecessary markings appearing in the model window during post-processing. When appropriate, select faces (3D) or edges (2D & 3D) 10.

9. Testing: Solve the model in StressCheck using the saved solution settings, and exercise all saved extraction settings before deploying it in the Handbook.

10. Model Information Document: Prepare a companion model information document and save it as an XPS file. The model information documents distributed with the current Handbook version were designed to complement the information provided by the Title and Description indicated above and provide examples of information to include. They include the following sections:

i. Problem description and icon ii. Description of parameters, including details diagrams for the dimensions

iii. Description of the boundary conditions: Loads and constraints iv. Description of material properties and assignments v. Default Parameter values and rules among parameters

vi. Results for default parameter values. Example: Estimated error in energy norm; First principal stress distribution; Maximum first principal stress; etc.

11. Append XPS and Model Icon: Use the handbook interface inside of StressCheck to append the created XPS document and icon image. Select the StressCheck Handbook Library icon and within the Model Info tab select “Add Icon…” to add the model icon. Similarly, select “Add Info…” to add the XPS document.

12. Export: Export the SCW file in a Handbook folder.



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i. The appended document information XPS and model icon JPG files will be packaged into the SCW file.

Regions

For Handbook models with multiple areas of interest or multiple parts, mesh regions can be defined to allow the user to hide elements and show hidden or internal regions. This is particularly useful for contact problems. For example, it may be impossible to view an important fringe plot on a bolt shank because it is hidden by other contacting bodies; mesh regions allow the user to view the shank by hiding all the other elements.

To define a mesh region, create a set of type 'Any Element' that does not begin with the word "SET". For an example implementation, see any of the LugClevisBolt Handbook models in the Parts folder. These have element sets called "BOLT", "CLEVIS", and "LUG", which appear under the Regions dropdown on the Handbook ribbon.

Laminate Stacks

The Handbook provides an editor for changing the definition of laminate stacks. Stacks are only editable by the Handbook user if specific rules are followed. Otherwise, the stack can be used in a model but will not appear in the editor. Rules for a stack definition:

Only laminate orthotropic properties may be used for a ply material.

All plies must use the same material.

All plies must use the same modeling type (ply or lump). All plies must have the same thickness.

Symmetry can be used if desired. Note that the number of plies (layers) must be the total ply count after the symmetry is applied. Even symmetry must have an even number of plies, odd symmetry must have an odd number of plies.

If the number of plies is entered as a number, the Handbook user will not be able to change the number of plies. Only the ply orientations will be editable.

If the number of plies is a parameter, the Handbook user can change the parameter (if it is not defined as an expression). For this case both the number of plies and their orientations are editable.

The stack use must be set to proportional.

If the number of plies is a parameter and the stack is defined using even or odd symmetry, it is possible for the Handbook user to specify an even (respectively, odd) number of plies for an odd (respectively, even) symmetry laminate. These are invalid configurations. One possible way to prevent this is to define an additional parameter using the mod() function as its expression:



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Then, define a rule for the ply_check parameter that ensures ply_check is zero for even symmetry and one for odd symmetry.

Example: Constructing a Handbook Model in StressCheck

The main ideas for creating a handbook problem to be deployed in the Handbook will be illustrated with an example. The problem description and the creation steps are indicated below. This example problem can be loaded from the Details folder of the Handbook (file: CircularHole3D01.sci).

Problem Description

A rectangular panel of length L, width W, thickness th, and a central hole of diameter D, is subject to an uniform traction Tx. The material properties are defined using the parameters Em (Elastic Modulus), and nu (Poisson’s ratio). The objective of the analysis is to compute the maximum first principal stress (S1) at the hole, the stress distribution in the ligament along the mid plane of the plate, and the variation of S1 through the thickness of the plate at the location of the max stress in the hole.

Since the default value of the applied traction is unity, the max principal stress represents the gross stress concentration factor of a finite width plate including thickness effects. Because of symmetry, only a quarter of the plate will be considered for analysis. The following default values of the parameters are considered:

L = 15.0, W = 5.0, th = 0.5, D = 1.0, Tx = 1.0, Em = 1e7, and nu = 0.3.

Model Construction

Open StressCheck and make sure the reference and theory selectors are set to Planar Elasticity, and that the Units selector is set to ‘Other’. The mesh will be defined in Planar and then extruded to perform the 3D analysis.

(1) Model Information interface

In the Main Toolbar, click on the Model Info icon and when the dialog window appears, enter the following information in the Model Info interface:

Title: Plate with central hole in tension

Comments: The model was designed to provide the stress concentration factor for a plate with a central hole, including width, length, and thickness effects. Reference: Peterson (1974), Stress Concentration Factors, John Wiley and Sons, Figure 86.

Keywords: 3D, Elasticity, Hole



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Select the Parameters tab and enter the following information:

Name Description Expression Value Limit Class Sort

L Plate length 15.0 > 0 General 01

W Plate width 5.0 > 0 General 02

Th Plate thickness 0.5 > 0 General 03

D Hole diameter 1.0 > 0 General 04

Em Modulus of Elasticity 1.0e7 > 0 Property 05

Nu Poisson’s ratio 0.3 > 0 Property 06

Tx Appl ied traction 1.0 > 0 B. Cond. 07

Select the Rules tab and enter the following:

Relational Expression Error Message

L >= 2*W L must be equal to or greater than 2W

D <= 0.75*W D must be equal to or less than 0.75*W

W <= 10*D W must be equal to or less than 10*D

L <= 5*W L must be equal to or less than 5*W

Th < W th must be less than W

Nu < 0.5 nu must be less than 0.5

(2) StressCheck Input interface

Open the StressCheck Input window by clicking on the Create Model icon in the Main Toolbar. Then, select the Geometry tab, to create geometric objects:

Create > Rectangle > Locate > X: 0.0, Y: 0.0, Z: 0.0, Width: L/2, Height: W/2, Rot-Z: 0.0 > Accept.

Create > Circle > Locate > X: 0.0, Y: 0.0, Z: 0.0, Radius: D/2, P1-Min: 0, P1-Max: 90, Rot-Z: 0.0 > Accept.

Create > Circle > Locate > X: 0.0, Y: 0.0, Z: 0.0, Radius: (W+D)/4, P1-Min: 0, P1-Max: 90, Rot-Z: 0.0 > Accept.

Create > Circle > Locate > X: 0.0, Y: 0.0, Z: 0.0, Radius: (W+5*D)/12, P1-Min: 0, P1-Max: 90, Rot-Z: 0.0 > Accept.



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Create > Line > Locate > X: W/2, Y: 0.0, Z: 0.0, Length: W/2, Angle: 90 > Accept.

At the end of the last operation, the geometry should look as shown in Figure 1.

Figure 1 - Example problem - Geometry

Select the Mesh tab and provide the following information:

Create > Node > Offset > Repeat # = 3 > Offset: 0 + 45. Use the mouse cursor to select the three circles. Other creation methods can be used to create the nodes, such as intersection and mid-offset.

Create > Node > Intersection. Select the pair of lines at each intersection where nodes should be located.

Create > Quadrilateral > Selection. Create 7 quadrilateral elements by selecting four appropriate nodes.

At the end of the last operation, the mesh should look as shown in Figure 2.

Figure 2 - Example problem - Mesh

Select the Thickness tab and enter:

Select > All Elements > Selection > Thickness: th > Accept.



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Select the Material tab and provide the following information:

Define tab > ID: prop > Material: Linear > Type: Isotropic > Case: Pl. Stress (Plane Stress) > E: Em, v: nu > Accept.

Assign tab > Select > All Elements > ID: prop > Color: Select a color from the list > Accept. Select the Load tab and enter:

Select > Any Curve > Traction > ID: LOAD > Direction: Norm/Tan > Normal: Tx. Use the mouse cursor to select the right side of the rectangle. Click on the Accept button.

Select the Constraint tab and provide the following information:

Select > Any Curve > Symmetry > ID: CONST. Use the mouse cursor to select the left side of the rectangle and then holding the Shift key click on the lower side of it. Click on the Accept button.

Next, change the reference selector to Extrude, and add a nodal constraint record in the z-direction.

Select > Node > Node > Data Type: Fixed > Turn on toggle for Z > Select any node and Accept.

Figure 3 shows the mesh and boundary conditions after the completion of the last step.

Figure 3 - Example problem - Complete model

Next, select the Solution ID tab and enter:

Solution ID: SOL > Constraint ID: CONST (or click on item in list-box) > Load ID: LOAD (or click on item in list-box). Click on the Accept button.

(3) Setting solution and extraction records

Solution by p-extension: Click on the Compute Solution icon in the Main Toolbar, and when the Solver window opens, complete as follows:

Linear tab > Extension: Upward-p > p-limits: 1 to 8. SOLVE! tab > Execute: Initialize > Run Mode: Automatic > Method: Direct > Converge: None.

Settings tab > Type ‘Linear’ in the input field and then, click on the Save button.



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Solve tab > Click on the Solve button to initiate the execution. Once the solution is complete, click on the View Results icon (in the Main Toolbar) to perform post-processing operations. Error Estimation: Click on the Error tab, and then complete the following information:

Select > All Elements > Selection > Settings tab > Solution: SOL > Run: 1 to 8 > Estimate button on > Title: Error estimate in energy norm > Name: Global Error; click on the Save button.

Select the Input tab and then, click on the Accept button to see the output. Check that for run # 8 (2673 DOF), the % Error is less than 0.10. The result should look as those shown in Figure 4.

Figure 4 - Example problem - Error Estimation

Contour Plot: To plot the first principal stress distribution, click on the Plot tab, and then provide the following information:

Select > All Elements > Selection > Settings tab > Solution: SOL > Run: 8 > Plot: Solution > Contour: Fringe on > Shape: Undef. > View: Default > Functions: S1 > System: Global > Mid-sides: 12 > Title: Contour plot of Sigma 1 > Name: S1 Plot; click on the Save button.

Select the Input tab, and then click on the Accept button to see if the save extraction setting provides the expected result. The result should look as those shown in Figure 5.

By selecting View: Default in the plot setting, the Model window of the Handbook will show the contour plot of the model in the saved view regardless of the position the model at the time that Solve is selected.



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Figure 5 - Example problem - First Principal Stress

Maximum First Principal Stress: To compute the max value of S1 at the hole wall as a function of the run number, click on the Min/Max tab, and then enter:

Select > Face > Grid > Settings tab > Solution: SOL > Run: 1 to 8 > Function: S1 > Maximum button on > Sys: Global > Title: Maximum Sigma 1 > Name: Max S1 > Click on the two faces in the hole wall, and finally on the Save button.

Select the Input tab and then, click on Accept to see if the save extraction setting provides the expected result.

The results should look as those shown in Figure 6.



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Figure 6 - Example problem - Maximum First Principal Stress

Normal stress along the mid plane ligament: To obtain the distribution of normal stress Sx along the mid-plane of the ligament between the edge of the hole and the edge of the plate , click on the Points tab, and then provide the following information:

Select > Edge Curve > Selection > Settings tab > Solution: SOL > Run: 8 to 8 > Function: Sx > # of pts: 21 > Plane button on > Z-plane: 0.0 > Sys: Global > Title: Mid-plane stress distribution > Name: Ligament Sx; select any edge along the symmetry plane at the location of the hole in the width direction and then click on the Save button.

Note: By selecting edges and Z-plane=0, the extraction is performed at the mid-plane of the plate (Z=0) along a path parallel to the selected edges.

Select the Input tab and then click on Accept. The result should look as those shown in Figure 7.

Figure 7 - Normal stress along mid-plane ligament (Points)



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Changing the independent variable of the graph to be ‘Y’, the result should look as shown in Figure 8.

Figure 8 - Normal stress along mid-plane ligament (Y-axis)

Normal stress through the thickness: To obtain the distribution of normal stress Sx through the thickness of the plate at the location of the max S1 in the hole, complete the following information in the Points tab:

Select > Edge > Selection > Settings tab > Solution: SOL > Run: 8 to 8 > Function: Sx > # of pts: 21 > Sys: Global > Title: Thru-thickness stress > Name: ThruHole Sx; select the element edge at the location of the hole where S1max was computed, and then click on the Save button.

Select the Input tab and then click on Accept. The result should look as those shown in Figure 9.

Figure 9 - Normal stress through the thickness



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(4) Save model and load it in the Handbook

It is recommended to create an icon file (*.jpg) and document information file (*.xps) for the model created. To append these files to the current session, go to the handbook library interface in StressCheck and select “Add Icon” or “Add Info” to append the files to the current session.

Figure 10 – Append image and report to session

To save the current model input file and support files, select File from the Main Menu Bar of StressCheck and when the File pull down menu appears select Export. Enter a File name in the corresponding input field and export the model as an SCW file. Place this file in a directory that will serve as a handbook directory, so anyone can have access to this problem from the Handbook interface.

Load the model in the Handbook interface and obtain a solution for the default value of the parameters to confirm that all the saved extraction settings work as expected.

CAE Handbook Report

The Handbook will generate an automatic report based on the saved extraction settings defined for the model problem. In addition, the report will include several sections to provide a complete summary of the input data and results of the analysis. The report is produced in a non editable XPS format, so that it cannot be altered by the user. The report consists of the following sections:

1.0 Overview



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Title: As it appears in the Model Info interface under Title. Description: As it appears in the Model Info interface under Comments.

Reference, Theory, Units and File name.

Parameter table: The ordering of parameters in the table appears grouped by class. The icon of the model problem with a caption.

2.0 Finite Element Mesh The screen capture of the Model window for the default saved view of the model after it has been centered.

3.0 Results Using the StressCheck Results tab ordering, the post-processing is presented by extraction type:

Error Estimate Function Plot

Min/Max Extraction

Point Extraction Resultant Extraction

Property Extraction

Fracture Extraction A section title (i.e. Error Estimation) exists only if an extraction of that type exists. If multiple extractions of the same type exist, they are ordered alphabetically by name within the type category. The section title is auto numbered. For each saved extraction setting created in StressCheck, the Name appears as part of the section heading, while the Title is used for the caption of the associated figure. For each plot extraction, a screenshot of the Model window is taken using the centered default saved view and inserted in the Handbook Report. Loads and constraints are turned off during the capture. For extractions including a graph, the tabular data followed by the associated figure is shown in the Handbook Report.

Selecting the Print preview option under the Application button of the Handbook while the Report tab has focus, will provide the complete view of the report which includes a header and a footer.

The header includes the date of the analysis, the name of the analyst as determined from the user ID in the computer, the title of the problem and a company logo. The default company logo is the ESRD logo. This can be easily changed in the Options menu accessible from the application button of the Handbook.

The footer shows the StressCheck logo and the page number.

Figure 11, below, shows the first page of the report of the Plate with a central hole in preview mode. The preview mode is produced by selecting the application button of the Handbook while the report has focus and then selecting Print > Print Preview.



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Figure 11 - Print Preview of the Report for the example problem



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Mapping Between StressCheck and CAE Handbook

This section illustrates how the information entered in StressCheck during the creation of a parametric model maps into the graphical user interface (GUI) of Handbook. The mapping will be illustrated with a figure composed from screen shots of StressCheck and the Handbook interface.

The Summary Panel

The information presented in the Summary panel of the Handbook interface is extracted from the Model information, the Reference/Theory/Units selector and the file name given to the model problem. This is illustrated in Figure 12.

Figure 12 - The Handbook Summary panel



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The Parameter Panel

The information presented in the Parameter panel of the Handbook is obtained from columns 1, 2 and 4 of the Parameter tab of the Model Information interface as shown in Figure 13. The Limit for each parameter appears in the tooltip diplayed while hovering the mouse over a parameter value in the Handbook, and the information provided in the Class column is used to create the Filter list.

Figure 13 - The Handbook Parameter panel

The Materials Panel

Only materials which have been assigned to the finite element mesh are presented to the Handbook user in the Material panel. The information presented depends on the type of material assigned to the mesh and whether the material coefficients were created as parametric or constant. Constant coefficients can be changed in the Material panel, while coefficients defined in parametric form are avail able for update in the Parameter panel of the Handbook (Figure 14).



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The following material coefficients are available for user input:

Isotropic: E, ν, ρ (density) and α (CTE - coefficient of thermal expansion). Orthotropic/laminate_ortho: E11, E22, E33, ν12, ν23, ν13, G12, G23, G31, ρ, α11, α22 and α33.

Stiffness: Stiffness (used for link assignments).

Elastoplastic: E, ν, Sy (yield stress) and α (CTE). Bilinear: E, ν, Et (tangent modulus), Sy (yield stress), and α (CTE).

5-parameter: E, ν, Et (strain-hardening modulus), Sy (yield stress), Eps-2 (starting point on the linear strain-hardening part of the stress-strain relationship), S2 (stress at Eps-2), and α (CTE).

Ramberg-Osgood: E, ν, S70E (the stress corresponding to the intersection of the stress-strain curve with a line which passes through the origin and has the slope of 0.70E), n (exponent), and α (CTE).

Figure 14: The Handbook Material panel

The Rules Panel

The information presented in the Parameter panel of the Handbook is obtained from the Rules tab Parameter tab of the Model Information interface as shown in Figure 15.



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Figure 15 - The handbook Rules panel

The Model Diagram Panel

The model diagram panel is obtained from the image file associated witht the model problem that was generated using the StressCheck Model Information tools (Figure 16) or by capturing an image generated by other means.



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Figure 16 - The handbook Model Diagram panel

The Model View

The Model view displays the mesh of the model in the saved view available in the input file upon loading. After the solution is performed, the Model view will be updated based on the saved plot settings as shown in Figure 17.



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Figure 17 - Handbook Model view

Extractions with Graphical Output

When the saved extraction setting is for an extraction producing a graphical output (such as Error , Min/Max, Points, etc.), the extraction will be incorporated in the Handbook Report and will also appear as a tab in the center of the Handbook as shown in Figure 18.



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Figure 18 - Handbook Graphical output

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