Mass Properties Management

SuperModel > Modeling and Simulation > Mass Properties Management

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Overview

The Mass Properties Management tool helps engineers estimate the weight of a structure from its finite element model and to fine tune the model weight distribution. It accomplishes this by allowing you to specify mass factors for the model to modify its weight, and then adding quantities of element nonstructural mass based on the factors. Factors can be applied both to groups that represent individual structural components and to larger assemblies in the model.

Access

Mass Properties Management is accessed from the MSC SuperModel main menu.

Procedures

Adding Mass Properties to the Model By Group

This procedure should be used to create a number of regions which have the same mass factors.


Mass Properties Management	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Create and Object to Mass Prop Region. Select the By Groups method.
Group	Select the groups from which the mass properties regions are to be created in the Group frame.
Description	Enter a description of the Mass Properties Region in the Description listbox.
Mass Factors	Enter the factors in the Mass Factors scroll frame. For each mass factor, select the Enter Value option and enter the value of the factor in the databox. The Parameter List option is available only if the Mass Properties function has been customized by the user (see Mass Properties Customization and Mass Factor Customization sections). The date and time the factor was entered are recorded automatically.
Accept	Select Accept to create the Mass Properties Region. The Mass Properties Region always has the same name as the group from which it was created.

Adding Mass Properties to the Model By Selection

This procedure should be used when a number of groups need to be combined into one region.


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Create and Object to Mass Prop Region. Select the By Selection method.
Mass Properties Region	Enter the Mass Properties Region name in the Region Name databox.
Region Definition	Select the Region Definition button to display a subform which are used to select the groups which are used to create the Mass Properties Region.
Groups	Select the groups which comprises the Mass Properties Region from the Groups listbox in the Define Region subform. Select OK to accept the groups selected.
Description	Enter a description of the Mass Properties Region in the Description listbox.
Mass Factors	Enter the Mass Factors in the Mass Factors scroll frame. For each mass factor, select the Enter Value option and enter the value of the factor in the databox. The Parameter List option is available only if the Mass Properties function has been customized by the user (see Mass Properties Customization and Mass Factor Customization sections). The date and time the factor was entered and recorded automatically.
Accept	Select Accept to create the Mass Properties Region.

Modifying Existing Mass Properties


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Modify and Object to Mass Prop Region.
Mass Properties Region	Select the Mass Properties Region which is to be modified.
Region Definition	Select the Region Definition button to bring up a subform which allows you to change the group or groups from which the region is created. Groups can be added to or removed from the Mass Properties Region.
Mass Factors	Use the Mass Factors scroll frame to change the Mass Factors. For each mass factor to be changed, select the Enter Value option and enter the new value of the factor in the databox. The Parameter List option is available only if the Mass Properties function has been customized by the user (see Mass Properties Customization and Mass Factor Customization sections). The date and time the factor was changed are recorded automatically. The Mass Properties Region description cannot be changed.
Accept	Select Accept to modify the Mass Properties Region.

Deleting Mass Properties Regions from the Model


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Delete and Object to Mass Prop Region.
Mass Properties Region	Select the Mass Properties Region which is to be deleted.
Accept	Select Accept to delete the Mass Properties Region.

Applying the Mass Properties to the Model


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Apply and Object to Mass Factors.
	If desired, select Elements Must Have Factors in the Application Options: frame. Weights can be changed only by using Nonstructural Masses.
Accept	Select Accept to apply the Mass Factors.

Deleting Mass Factors Applied to the Model


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Delete and Object to Mass Factors.
Accept	Select Accept to delete the Mass Factors.

Displaying Existing Mass Properties


Mass Properties	Open the Mass Properties Management form by selecting it from the MSC SuperModel main menu. Set the Action to Show and Object to Mass Prop Region.
Mass Properties Region	Select the Mass Properties Region which is to be displayed.
Region Definition	Select the Region Definition button to bring up a subform which displays the group from which the region is created.
Mass Factors	Use the Mass Factors scroll frame to view the Mass Factors. The date and time the factor was created or changed are displayed

Requirements

Before using the Mass Properties Management function, the finite elements to which mass factors are applied must be grouped into regions that share factors. Material density for all elements with factors must also be defined.

Before customizing the Mass Properties Management function, the user must program forms and algorithms for parameter lists. A separate function is required for each type of mass factor.

Description of Mass Properties Management Forms

A number of forms are used in the Mass Properties Management function. All of these forms are accessed from the MSC SuperModel main menu.

Creating a Mass Properties Region Using Selected Entities

Creating A Mass Properties Region Using Groups

This is a user-customized form.

Subforms for Selecting a Custom Algorithm, List, and Assignment Type

The following are examples of subforms using the ability to assign factors by customized parameter list calculations.

Defining a Mass Properties Region

Deleting a Mass Properties Region

Deleting Mass Factors

Applying Mass Factors

Example of Usage

The following example illustrates the basic usage of the Mass Properties Management function. Figure 3‑3 represents a section of a wing structure, that is constructed utilizing three spars. The elements of the wing have been grouped based on the structural components modeled. This example concentrates on spar number 3 (Figure 3‑4 and Figure 3‑5), that has been grouped as spar3. The spar has been further broken down into upper and lower spar caps (Figure 3‑6), grouped as spar3.capu and spar3.capl, a spar web (Figure 3‑7), grouped as spar3.web, and the effective portions of the upper and lower skins (Figure 3‑8), grouped as spar3.skinu and spar3.skinl. The remaining spars are similarly grouped.

The goal of this example is to apply mass factors to these groups.

Figure 3‑3 Three Spar Wing Structure

Figure 3‑4 Spar Number 3

Figure 3‑5 Spar Number 3

Figure 3‑6 Spar 3 Upper and Lower Caps

Figure 3‑7 Spar 3 Web

Figure 3‑8 Spar 3 Upper and Lower Effective Skins

Create the Mass Properties Regions

1. Open the Mass Properties Management from the MSC SuperModel main menu.

2. Set the Action to Create, Object to Mass Prop Region, and Method to By Groups.

3. Select the spar3.capu group in the Group frame.

4. Enter Spar3 Upper Cap in the Description listbox.

5. For each mass factor type, select the Enter Value option and enter the value of the factor in the databoxes in the Mass Factors scroll frame. The date and time the factor was entered are recorded automatically.

6. Select Accept to create the spar3.capu Mass Properties Region.

7. Repeat steps 3 through 6 to create four more Mass Properties Regions from the remaining groups of spar3 (spar3.capl, spar3.web, spar3.skinl and spar3.skinu).

Modify Existing Mass Properties Regions

1. Open the Mass Properties Management from the MSC SuperModel main menu.

2. Set the Action to Modify, Object to Mass Prop Region, and Method to By Groups.

3. Select the spar3.web Mass Properties Region in the region selection frame.

4. Use the Mass Factors scroll frame to change the Mass Factors. For each mass factor to be changed, select the Enter Value option and enter the new value of the factor in the databox. The date and time the factor was modified and recorded automatically.

5. Select Accept to modify the spar3.web Mass Properties Region.

Mass Properties Management Customization

Users can integrate their own custom method for calculating mass factors into MSC SuperModel, and then store that data in their database. This section describes the use of a registration class to transfer data between the custom class and existing routines. The user data documentation should be referred to for information about storing data in the database. Forms used to enter the custom data can be registered using the user Action-Object-Method (AOM) server.

Information about algorithms available, types of factors calculated by those algorithms, instances of calculated factors, and the factor values themselves must be passed back and forth between the forms for defining the Mass Properties regions and the classes defined to manage the factor calculation algorithms. A Registry Class was set up as an intermediary between the forms and the algorithms to allow flexibility in the number of algorithms available in any given MSC SuperModel installation. Algorithms and their available assignment types must be registered with this class so they can be displayed as available means of assigning factors. This class is also used to get the current status of available factor lists and the factor values themselves.

To start the data transfer process, two calls to the registry class are made when the Algorithm Class is initialized, one to register the name and class of the algorithm, and the other to register the types of factors available for that algorithm.

Figure 3‑9 Transfer of Algorithm Name

Figure 3‑10 Transfer of Factor Assignment Types

Figure 3‑11 Transfer of the List of Available Algorithm Names

Figure 3‑12 Transfer of Mass Factor Value

Outline of a User Data Management Class for an Algorithm

The following example serves as a skeleton for a class a user would need to set up to define a new algorithm. The functions listed are required and should perform the functions listed by the comment portions of the code:

#include massprop_appstrings.p

#DEFINE CLASSNAME         user_algname

#DEFINE CLASSNAME_QUOTED "user_algname"

CLASS CLASSNAME

/*

* The algorithm data management class handles all work

* involved in storing and retrieving data associated with

* an algorithm and its associated parameter lists.  It:

*   - registers its availability and associated factor

*     types in a registry class

*   - interacts with the GUI used to set up the parameter

*     lists to store and retrieve list instances

*   - calculates and stores mass factors at the request of

*     the mass region, via a "registry class"

*   - gives a list of available parameter lists, at the

*     request of the mass region via a "registry class"

*   - provides mass factors as requested

*/

FUNCTION init()

/*

* Purpose:

*   - Register algorithm in registry class:

*   - Register types of factors in registry class

*   - Create user data templates, if they don’t exist

* Input:

*   (none)

* Output:

*   (none)

* Side Effects:

*   - Lets mass region GUI know that a new algorithm is

*   available, and will thus appear on the list of available

*   algorithms.

*   - Sets up templates for later data storage

* External Dependencies:

*   Need user data functions to store data

*   Need registry class to keep track of available

*   algorithms.

* General Description:

*   To be called in the init.pcl when starting up PATRAN,

*   or any other customized PATRAN initialization

*/

REGISTER_CLASSNAME.register_alg( @

/* algorithm name STRING */        algorithm_name, @

/* current class name STRING */    CLASSNAME_QUOTED)

REGISTER_CLASSNAME.register_asg( @

/* algorithm name STRING */        algorithm_name,@

/* factor types STRING ARRAY */    fact_types,@

/* number factor types INTEGER */  num_types)

IF( !template exists) ud_create_template(...)

END FUNCTION /* init */

/*

* A series of routines will follow here to manage the

* data, as needed by the GUI and the various templates

* associated with the algorithm.  At minimum, this

* will include store,delete, and get functions for the

* parameter list.

*/

FUNCTION store_data

END FUNCTION /* store_data */

FUNCTION delete_data

END FUNCTION /* delete_data */

FUNCTION get_data

END FUNCTION /* get_data */

FUNCTION calculate_factors ()

/*

* Purpose:

*   - Needed only if it is necessary to be able to

*     initiate factor calculation from the mass region

*     form.

*   - Calculate massproperty factors

*   - Store factors in the parameter list used to

*     calculate them

* Input:

*   (none)

* Output:

*   (none)

* Side Effects:

*   - Modifies parameter list instance

* External Dependencies:

*   - Called by mass region class

*   - Calls routine in mass region class to get current

*     instance

* General Description:

* The calc factors function is called by the Mass Properties

* region when a factor is needed, using

* ui_exec_function(smdl_algname,"calculate_factors").

* It calls back to the Mass Properties region to get the

* name of the instance for which the factor is to be

* calculated, and then calls the algorithm to calculate

* the factors.  It stores the factors in the parameter

* list once they are calculated.

*/

smdl_mass_region.give_current_instance(current_instance)

/*

*  Calculate factors using whatever functions are needed.

*  This can be done here or another call can be made.

*/

/*

*  Store factors in the parameter list.  As with

*  calculation, this can be done here or in another

*  function, e.g. the calculation function.

*  The class that calls this function can then get the

*  factor through the registry class and the send_factor

*  function in this class.

*/

END FUNCTION /* calculate_factors */

FUNCTION send_factor ()

/*

* Purpose:

*   - Provide Mass Properties factors to registry class

* Input:

*   (none)

* Output:

*   (none)

* Side Effects:

*   (none)

* External Dependencies:

*   Called by registry class.  Uses functions in that class:

*   give_param_list -- gets instance name for which factors

*                      are needed

*   receive_factors -- sends factors back to registry class

* General Description:

*   Factors will be given to the Mass Properties region

*   via a call to the registry function.  The mass region

*   will make a call like:

*     ui_exec_function(ALG_CLASS,send_factor)

*   This class then gets the param list name from the

*   registry class, retrieves factors for that list, and

*   sends the factors back to the regisrty class.

*   The registry class then provides the factor to the

*   requesting function.

*/

  REGISTER_CLASSNAME.give_param_list(instance)

/*

   * from the specified instance, get the factors

*/

    ud_get_instance(template,instance,r_data,s_data)

    factor=r_data

    date=s_data(n)

  REGISTER_CLASSNAME.receive_factors(factor_array,date)

END FUNCTION /* send_factor */

FUNCTION give_lists ()

/*

* Purpose:

*   - Provide to registry class a list of available instances

*     for algorithm

* Input:

*   (none)

* Output:

*   (none)

* Side Effects:

*   - Registers list of parameter list instances

* External Dependencies:

*   Called by registry class

* General Description:

* This function gets a list of the current instances and

* registers it in the registry class.  It is called by

* the registry class when a request is made to it for

* a list.

*/

  ud_get_all_instances(template, list, num)

  REGISTER_CLASSNAME.register_lst(algname, list, num)

 END FUNCTION/* give_lists*/

END CLASS /* smdl_algname */

Mass Factor Customization

The number and names of the mass factors displayed in the Mass Properties Management forms are set by calls to the function smdl_uil_massprop_setup. Users may customize the mass factors by writing their own function of the same name and reading it in so that it replaces the standard function. The text of the standard function follows as a template for customization:

FUNCTION  smdl_uil_massprop_setup(num_props,names)

$  Purpose:

$    Establish the number and names of mass factors

$  Input:

$    <none>

$  Output:

   /* Number of mass factors */      INTEGER num_props

   /* Names of the mass factors */   STRING  names[]()

$  Side Effects:

$  External Dependencies:

$  General Description:

$  Notes:

$    Mass factor names must be 32 characters or fewer

  INTEGER retval = 0

  write("Initializing Mass Factor variables")

/*

  *  Change this number to increase the number of factors

  *  The maximum number of factors is 10

*/

  num_props = 3

  IF ( num_props <= 0 ) THEN

     retval = -1

  ELSE

     sys_allocate_array(names,1,num_props)

/*

     *  The number of names should correlate with num_props

*/

     names(1) = "- Factor #1 -"

     names(2) = "- Factor #2 -"

     names(3) = "- Factor #3 -"

  END IF

RETURN retval

END FUNCTION