nastran manual
This section describes all options of the Dynamic Loads menu.
There are two ways to enter the conditions for dynamic analysis:
- First, when the conditions are dependent on the frequency. In this case the user has to use frequency dependent dynamic loads. Only loads with its' names including 'Freq' can be used in this case.
- Second, when the conditions are time dependent. In this case the user has to use time dependent dynamic loads. Only loads with its' names including 'Time' can be used in this case.
It is important not to confuse these two forms of loads introduction with an analysis formulation (modal or direct).
MENU SEQUENCE:
Defines a frequency dependent dynamic load of the form:
This type is used in transient response problems, where:
f= independent variable, it is a frequency.
i= imaginary unit.
A= Scale factor
Ft= Frequency delay
= Phase lead
C(f) and D(f) are functions defined by tables of interpolation. Tables have to be created before assigning this condition and associated to the condition using statements “Table Interpolation Values C[f]” or “Table Interpolation Values D[f]”.
The user has to define these tables using the following menu sequence: Materials->Tables. More information about table creation can be found in the chapter Tables of this manual.
Finally, the user has to select in which degree of freedom he wants the load to act.
This condition can be assigned over points, lines and surfaces and has effect over nodes of the mesh.
MENU SEQUENCE:
Defines a frequency dependent dynamic load of the form:
For use in frequency response problems, where:
f= independent variable, it is a frequency.
i= imaginary unit.
A= Scale factor
Ft= Frequency delay
= Phase lead
B(f) and (f) are functions defined by tables of interpolation.
Tables have to be created before assigning this condition and associated to the
condition using statements “Table Interpolation Values B[f]” or “Table
Interpolation Values
[f]”.
The user has to define these tables using the following menu sequence: Materials->Tables. More information about table creation can be found in the chapter Tables of this manual
This condition can be assigned over points, lines and surfaces and has effect over nodes of the mesh.
MENU SEQUENCE:
Defines a time dependent dynamic load of the form:
This condition is used in transient response problems, where:
t= independent variable, it is a time.
A= Scale factor
= Time delay
F(t-) is a function defined by table of interpolation. Table has
to be created before assigning this condition and associated to the condition
using statements “Table Interpolation Values F(t-
)”.
The user has to define these tables using the following menu sequence: Materials->Tables. More information about table creation can be found in the chapter Tables of this manual.
This condition can be assigned over points, lines and surfaces and affects nodes of the mesh.
MENU SEQUENCE:
Defines a time dependent dynamic load of the form:
For use in transient response problems, where:
t= independent variable, it is a time.
A= Scale factor
= time delay
T1=Inferior time limit
T2=Superior time limit
F= frequency in cycles per unit time
P= Phase angle (in degrees)
C= Exponential coefficient
B= Growth coefficient.
It is not necessary to define any interpolation table for this load.
This condition can be assigned over points, lines and surfaces, and affects nodes of the mesh.
Defines a time dependent dynamic load of the form:
This condition is used in transient response problems. The definitions of the parameters of this load are equal to Time Dynamic Type 2.
Defines a frequency dependent dynamic pressure for frequency response problems use.
This load is very similar to “Freq Dynamic Type 1” with some changes in parameters:
A=scale factor was changed to a vector that the user has to introduce using statements: X-Pressure, Y-Pressure, and Z-Pressure.
Ft= Frequency delay is equal to zero.
= Phase lead is equal to zero.
C(f) and D(f) are functions defined by tables of interpolation. Tables have to be created before assigning this condition and associated to the condition using statements “Table Interpolation Values C[f]” or “Table Interpolation Values D[f]”.
In conclusion, the final aspect of the load is as follows:
If lines are used, it is possible to select in which coordinate system (BASIC, ELEMENT) and which type of load (NORMAL, PROJECTED) will be applied to line of geometry. Descriptions of these statements are explained with more details in static loads that can be applied to lines. See these chapters for more information.
This load can be assigned over lines and affects elements of the mesh.
This load is only available for MSC/NASTRAN and NE/NASTRAN codes.
Defines a frequency dependent dynamic pressure for use in frequency response problems.
This load is very similar to “Freq Dynamic Type2” with some changes in parameters:
A=scale factor was changed to a vector that the user has to introduce using statements: X-Pressure, Y-Pressure, and Z-Pressure.
Ft= Frequency delay is equal to zero.
= Phase lead is equal to zero.
B(f) and (f) are
functions defined by tables of interpolation. Tables have to be created before
assigning this condition and associated to the condition using statements
“Table Interpolation Values B[f]” or
“Table Interpolation Values h[f]”.
In conclusion, the final aspect of the load is like this:
If lines are used, it is possible to select in which coordinate system (BASIC, ELEMENT) and which type of load (NORMAL, PROJECTED) will be applied to line of geometry. Descriptions of these statements are explained with more details in static loads that can be applied to lines. See these chapters for more information.
This load can be assigned over lines and affects elements of the mesh.
This load is only available for MSC/NASTRAN and NE/NASTRAN codes.
Defines a time dependent dynamic pressure for use in transient response problems.
This load is very similar to “Time Dynamic Type 1” with some changes in parameters:
A=scale factor was changed to a vector that the user has to introduce using statements: X-Pressure, Y-Pressure, and Z-Pressure.
= Time delay is equal to zero.
F(t-) is a functions defined by table of interpolation. Table has
to be created before assigning this condition and associated to the condition
using statements “Table Interpolation Values F(t-
)”.
The user has to define these tables using the following menu sequence: Materials->Tables. More information about table creation can be found in chapter Tables of this manual.
In conclusion, the final aspect of the load is like this:
If lines are used, it is possible to select in which coordinate system (BASIC, ELEMENT) and which type of load (NORMAL, PROJECTED) will be applied to a line of geometry. Descriptions of these statements are explained with more details in static loads that can be applied to lines. See these chapters for more information.
This load can be assigned over lines and affects elements of the mesh.
This load is only available for MSC/NASTRAN and NE/NASTRAN codes.
Defines a time dependent dynamic pressure for use in transient response problems.
This load is very similar to “Time Dynamic Type 2” with some changes in parameters:
A=scale factor was changed to a vector that has to be introduced using statements: X-Pressure, Y-Pressure, and Z-Pressure.
= Time delay
T1=Inferior time limit
T2=Superior time limit
F= frequency in cycles per unit time
P= Phase angle (in degrees)
C= Exponential coefficient
B= Growth coefficient.
In this load is not necessary to define any interpolation table.
In conclusion, the final aspect of the load is as follows:
If lines are used, it is possible to select in which coordinate system (BASIC, ELEMENT) and which type of load (NORMAL, PROJECTED) will be applied to line of geometry. Descriptions of these statements are explained with more details in static loads that can be applied to lines. See these chapters for more information.
This load can be assigned over lines and affects elements of the mesh.
This load is only available for MSC/NASTRAN and NE/NASTRAN codes.
Defines values for the initial conditions of coordinates used in transient analysis. Both displacement and velocity values may be specified at independent (global) coordinates of the structural model.
Initial conditions may be used only in direct formulation.
This condition can be assigned over points, lines and surfaces and affects nodes.