Download - Functional Loading in ANSYS/Mechanical

Advanced Loads W biWebinar

Patrick CunninghamJ 2013January 2013

CAE Associates Inc. and ANSYS Inc. Proprietary© 2013 CAE Associates Inc. and ANSYS Inc. All rights reserved.

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Topics

1 Using Tabular and Functional loads in ANSYS/Mechanical1. Using Tabular and Functional loads in ANSYS/Mechanical2. Mapping imported data onto the ANSYS Mechanical model

using the External Data Utility. g y

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Tabular and Functional Loads in Functional Loads in ANSYS/Mechanical


Load Definition in ANSYS/Mechanical

Most loads in the ANSYS/Mechanical environment can be defined in one Most loads in the ANSYS/Mechanical environment can be defined in one of the following ways:

— Constant: The magnitude of the load does not vary by position and can vary only linearly with time throughout the duration of the load step.only linearly with time throughout the duration of the load step.

— Tabular: Can be defined by a table of the load magnitude and one primary variable (x, y, z, time).

— Functional: A math expression is used to define the load magnitude as a p gfunction of one primary variable (x, y, z, time).

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Variable Loading in ANSYS/Mechanical

A cantilever beam is loaded with the following: A cantilever beam is loaded with the following:— A pressure distribution in the top surface that varies along the length. — A periodic load at the free end.

A transient analysis is needed to combine the effects of the constant and A transient analysis is needed to combine the effects of the constant and time varying loads.

Constant pressure is distributed over the beam length.

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Sinusoidal force applied at the free end.

Tabular Loading in ANSYS/Mechanical

Tabular loads defined in Mechanical can be a function of one primary Tabular loads defined in Mechanical can be a function of one primary variable only (x, y, z or time).

Tabular loads can be defined in local Cartesian and cylindrical coordinate systemssystems.

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Functional Loading in ANSYS/Mechanical

Functional loads are also limited to one primary variable only (x y z or Functional loads are also limited to one primary variable only (x, y, z or time).

Specify the “Number of Segments” to control the resolution of functional load dataload data.

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Functional loads can be also defined with respect to local Cartesian or Functional loads can be also defined with respect to local Cartesian or cylindrical coordinate systems.

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Functional loads defined with respect to time can be activated and Functional loads defined with respect to time can be activated and deactivated on a per load step basis.

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If you are using a periodic function take care to set the angle units If you are using a periodic function take care to set the angle units accordingly. Example: Define a force load with the magnitude F = Fmax*sin(ωt). 1 Set the angle unit to Radians prior to defining the load1. Set the angle unit to Radians prior to defining the load. 2. Add a force load with a magnitude defined as a function. 3. Define ω in radians/s in the function. Note: Changing the units after the load is defined will not change the setting in the functionNote: Changing the units after the load is defined will not change the setting in the function.

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Tabular and Functional Loading Types

Not all load types can be defined with tables and functions as detailed in Not all load types can be defined with tables and functions as detailed in the table below:

Tabular FunctionalLoad (time) (x or y or z) (time) (x or y or z)Force + X + X

Remote Force + X + XNodal Force + + + +Moment + X + XPressure + + + +

Nodal Pressure + + + +Displacement + + + +

Remote Displacement + + + +Nodal Displacement + + + +

Bearing Load X X X XThermal Load + + + +Joint Load + X + XAcceleration + X + XAcceleration

Angular Velocity + X + X

Note: Only Pressure and Nodal Pressure tabular and functional loads are available in a Harmonic Response Analysis

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The example consists of a steel cantilever beam 0 5” in height and 25” in The example consists of a steel cantilever beam 0.5 in height and 25 in length.

A pressure load varying along the length of the beam is applied to the top surface as shown:surface as shown:

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The static displacement due to the distributed pressure is - 75986” in the The static displacement due to the distributed pressure is -.75986 in the global Y direction.

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A modal analysis shows the natural frequency of the first bending mode at A modal analysis shows the natural frequency of the first bending mode at 25.685 Hz.

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The same distributed pressure load is then applied in a transient analysis The same distributed pressure load is then applied in a transient analysis. A beta damping coefficient is input as follows:

β = 2ξcr / 2πfwhere ξcr = 1 and f=25.685 Hz

The resulting displacement is consistent with the static analysis result.

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Add a periodic load on the end of the beam at the natural frequency of the Add a periodic load on the end of the beam at the natural frequency of the 3rd bending mode:

Add enoughAdd enough function segments to describe the periodic load in the time domain.

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time domain.


Solve and compare to the previous transient solution Solve and compare to the previous transient solution.

Static pressure

Static pressure + periodic loadStatic pressure + periodic load

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The External Data Utility

We have seen how Tabular and Functional loads can be useful in ANSYS We have seen how Tabular and Functional loads can be useful in ANSYS Mechanical but what if the load distribution varies in more than one direction?

For a three dimensional spatially defined load the External Data Utility can For a three dimensional spatially defined load the External Data Utility can be used.

The External Data Utility is found in the Component Systems menu.

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Using the External Data Utility with Data Utility with

ANSYS/Mechanical



When should I use the External Data Utility? When should I use the External Data Utility? 1. When I have CFD results that I need to distribute on my Mechanical model. 2. When I have temperature results from a different finite element mesh. 3 When I have test data that I want to load onto my model3. When I have test data that I want to load onto my model. 4. When I have a non uniform thickness shell and I have a table of coordinates

versus thickness that I want to assign to my elements. Basically if you have coordinates and data the External Data Utility can Basically, if you have coordinates and data, the External Data Utility can

map it onto your model for the following quantities:

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Th E t l D t Utilit i f d i th C t S t ti f th The External Data Utility is found in the Component Systems section of the Project Page.

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The External Data Utility has an easy to use interface The External Data Utility has an easy to use interface. Setting it up requires the four basic steps shown here.

3 Label the data columns3. Label the data columns accordingly.

1. Identify the source data file.

2. Set the format type.

4. Check the data preview.

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Once the External Data Utility is set up a simple drag and drop connects Once the External Data Utility is set up a simple drag and drop connects the data to the analysis system.

Drag and drop.

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After the drag and drop a refresh of the Setup row of the analysis system After the drag and drop a refresh of the Setup row of the analysis system is required.

RMB - Refreshe es

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After refreshing the Setup row you will find an “Imported Load” folder in the After refreshing the Setup row you will find an Imported Load folder in the Mechanical environment.

RMB click on the folder to insert the desired load.

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1 Scope the imported load by either Named Selection or geometry picking1. Scope the imported load by either Named Selection or geometry picking. 2. If you have multiple data files in the External Data Utility identify the file and

quantity (column) to be imported. 3. You can display the source points to confirm that the data and the model are3. You can display the source points to confirm that the data and the model are

geometrically consistent.

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3.

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2.


RMB click on the quantity to import the load RMB click on the quantity to import the load.

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Once the load is imported and mapped onto the mesh turn off the source point Once the load is imported and mapped onto the mesh turn off the source point display.

RMB click on the imported load and insert a “Validation” to check the quality of the data mapping.

As an example, set the type to “Source Value” and “Display on Parent” to On. RMB click on the validation and choose “Analyze”.

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