CADFamily.com: 09/01/2011

9/21/2011

Small vs Large Deflection

Workshop 2A: Large Deflection

Goal

Compare and contrast results using small deflection theory and large deflection theory on a model with identical loads and boundary conditions.

Model Description

– 3D Spring plate

– Linear steel material

– Meshed with 3D Solid elements

– Fixed support at one end, A

– 8 MPa Pressure load at opposite end, B

Steps to Follow:

Start an ANSYS Workbench session. Browse for and open “W2a_spring.wbpj” project file.

The project Schematic should look like the picture to the right.

– From this Schematic, you can see that the Engineering (material) Data and Geometry have already been defined (green check marks).

– It remains to set up and run the FE model in Mechanical

– Open the Engineering Data Cell (highlight and double click OR Right Mouse Button (RMB)>Edit) to verify the linear material properties.

– To see relevant dialog boxes, it might be necessary to go to Utility Menu > View..

Click on ‘Properties’ and ‘Outline’

– Verify that the units are in Metric(Tonne,mm,…) system. If not, fix this by clicking on…

Utility Menu > Units > Metric(Tonne, mm,…)

Return to Project Schematic

– Utility Menu > Return to Project

Double click on the Model Cell to open the FE Model (Mechanical Session) (or RMB=>Edit…)

Once inside the Mechanical application, verify the working unit system

– “Unit > Metric (mm,kg,N,s,mV,mA)”

The spring model is already set up with a fixed boundary condition and a pressure load on the opposite end.

– Highlight the Fixed Support and Pressure Load to confirm that the model is properly supported and loaded and ready to solve.

Note the Analysis Settings Specifications

– Auto Time Stepping = Program Controlled

– Large Deflection = Off

http://www.cadfamily.com/html/Article/Small%20vs%20Large%20Deflection_833_1.htm

Taylor Test – “What if” Study

Goal:

Conduct “what if” study on previous Taylor impact test model by tracking

maximum equivalent plastic strain as a function of initial rod velocity.

Procedure:

Duplicate the existing Explicit Dynamics (ANSYS) Analysis System Project

Assign a parameter to the initial velocity condition of the rod

Assign a parameter to the maximum equivalent plastic strain

Run the parameterized system from the Project Schematic

Review the results – Equivalent plastic strain plots are shown below

corresponding to the initial velocities indicated above each image:

Abbreviations used in Procedural Steps

As in the preceding workshops, the following abbreviations are used:

– DC = Double Click with Left Mouse Button

– SC = Single Click with Left Mouse Button

– RMB = Right Mouse Button Selection

– D&D = Drag and Drop = Hold Left Mouse Button down on item while dragging it to new location and then release it (i.e., Copy or Move)

Note: Throughout these Workshops, the procedures shown are not always the only way to accomplish the desired tasks, so feel free to investigate the other methods outside of this course. Consult the documentation for additional details.

Step 1 – Duplicate the Existing Project System

1.a Start ANSYS Workbench and open the Project taylor_basic.wbpj

1.b Copy the Project to taylor_what_if.wbpj via the Save As icon.

1.c Edit the Setup cell in the new Project System.

1.d Verify that the MKS unit system is still active.

2.a Select the Velocity branch under the Initial Conditions branch in the tree.

2.b Click on the empty box to the left of the Z Component. A blue “P” will appear in the box indicating that the value is now a parameter.

This input parameter will be controlled from the Project Schematic. Initial velocities of 100 m/sec and 500 m/sec will also be studied.

Step 3 – Parameterize the Max Eqv Plastic Strain

3.a Select the Equivalent Plastic Strain branch under the Solution branch in the tree.

3.b Click on the empty box to the left of the Maximum Result. A blue “P”will appear in the box indicating that the value is now a parameter. This output parameter will be a function of the initial rod velocity, which will be controlled from the Project Schematic. Since it is plastic strain, the final result is sufficient, as the maximum plastic strain that occurs over time will still exist at the end of the run, assuming no erosion occurs.

Step 4 – Modify the Input Parameter

Design Point Table appears at top right of Project Schematic

4.b Define two new initial velocity conditions (-100 and -500 m/sec) by typing them in underneath the current -300 m/sec condition. Design Points DP 1 and DP 2 will be created.

4.c Export the results to retain them.

Step 5 – Solve the Design Points

5.a Run the new model configurations via

5.b Acknowledge the condition of closing some of the editors while the design points are being updated.

5.c After each solution is completed, the output parameter is recorded.

Wait until all of the solutions have finished before proceeding. The maximum equivalent plastic strains are now shown for the three input conditions.

5.d Save the Project before continuing on.

Step 6 – Review the Directory Tree

http://www.cadfamily.com/html/Article/Taylor%20Test%20–%20“What%20if”%20Study_832_1.htm

http://www.cadfamily.com/html/Article/Taylor%20Test%20–%20“What%20if”%20Study_832_2.htm

Workbench-Mechanical Assembly Contact

Goal:

– In this workshop our goal is to investigate the behavior of the pipe clamp assembly (Pipe_clamp.x_t) shown here. Specifically we wish to determine the crushing stress and deformation in a copper pipe section when the bolt in the clamp is torqued down.

-We will assume the material used for the pipe is a copper alloy while all other parts are steel.

-It is assumed the clamp is torqued to 1000 N when placed in service.

-We’ll assume the coefficient of friction between the clamp and pipe is 0.4. The other contact regions will be treated as either bonded or no separation as shown in the accompanying figures.

If previous workshop project is still in session, clear it from the project page

Utility Menu > File >New…

From the Toolbox, double click

“Static Structural” to create a new system.

RMB the geometry cell and “Import Geometry and browse to “Pipe_Clamp.x_t”

From the “Units” drop down menu:

– Set Project units to “Metric (Tonne, mm, s, C, mA, N, mV).

– “Display Values in Project Units” is checked (on).

Double Click the “Model” cell to open the Mechanical Application

Once inside the Mechanical application, set the working unit systems

“Unit>Metric(mm,kg,N,s,mV,mA)”

Expand the “Connections” branch and use the shift key to highlight all contact definitions.

In the details window change the Formulation to “Augmented Lagrange.

Highlight the first contact branch. This is the definition for the pipe to clamp contact.

In the detail for the definition change the Type to “Frictional”.
Enter a value for “Friction Coefficient” of 0.4.

Highlight the second contact branch. This is the definition for the bolt shaft to clamp hole contact.

From the details window change the Type to “No Separation”.

The remaining 2 contact regions will be modeled using the default bonded type of contact.

Create a local coordinate system along the pipe’s axis. Note, we will use the local coordinate system for post processing later.

With the Coordinate system branch highlighted:

Select the inside surface of the cylinder.
“RMB > Insert > Coordinate System”.

From the detail for the new coordinate system change “Type” to “Cylindrical”.
Change the Principal Axis to the “Z” Direction
Defined by “Geometry Selection”
“Click to Change” on Geometry , then select the inner surface of the pipe and “Apply”

http://www.cadfamily.com/html/Article/Workbench-Mechanical%20%20Assembly%20Contact_834_1.htm

http://www.cadfamily.com/html/Article/Workbench-Mechanical%20%20Assembly%20Contact_834_2.htm

Workbench-Mechanical Contact Stiffness Study

Goal:

– Perform a convergence study on contact stiffness

Steps to Follow:

If you already have Workbench open from previous workshop, start a new analysis with Utility Menu>File>New…

Browse for and open “W3a-stiffness.wbpj” project file.

The project Schematic should look like the picture to the right.

– From this Schematic, you can see that Engineering (material) Data and Geometry have already been defined (green check marks).

– It remains to set up and run the FE model in Mechanical

– Open the Engineering Data Cell (double click on it OR Right Mouse Button (RMB)=>Edit) to verify the linear material properties.

– You might have to activate important dialog boxes from Utility Menu > View >…

Properties

Outline

– Verify that the units are in Metric (Tonne,mm,…) system. If not, fix this by clicking on…

Utility Menu >Units >Metric(Tonne, mm,…)

Return to Project Schematic

– Utility Menu > Return to Project

Double click on the Model Cell to open the FE Model (Mechanical Session) (or RMB=>Edit…)

-Geometry is 2D Axisymmetric. Lower plate is rigidly constrained. Upper plate is a flexible body with a crowned contour along bottom face. The upper plate is under a 5MPa pressure load acting downward.

-Material: Both plates are default linear elastic structural steel.

A single contact pair has already been set up with the following specifications:

http://www.cadfamily.com/html/Article/Workbench-Mechanical%20%20Contact%20Stiffness%20Study_835_1.htm

9/14/2011

ANSYS -Material Models Part A

Material Behavior Under Dynamic Loading

In general, materials have a complex response to dynamic loading

The following phenomena may need to be modelled

– Non-linear pressure response

– Strain hardening

– Strain rate hardening

– Thermal softening

– Compaction (porous materials)

– Orthotropic behavior (e.g. composites)

– Crushing damage (e.g. ceramics, glass, geological materials, concrete)

– Chemical energy deposition (e.g. explosives)

– Tensile failure

– Phase changes (solid-liquid-gas)

No single material model incorporates all of these effects

Engineering Data offers a selection of models from which you can choose based on the material(s) present in your simulation

Modeling Provided By Engineering Data

Material Deformation

Material deformation can be split into two independent parts

– Volumetric Response - changes in volume (pressure)

Equation of state (EOS)

– Deviatoric Response - changes in shape

Strength model

Also, it is often necessary to specify a Failure model as materials can only sustain limited amount of stress / deformation before they break / crack / cavitate (fluids).