Based on your analysis type, Mechanical enables you to begin your analysis with an initial specification using one of the object types described below. Initial specifications include Initial Conditions, links to an existing solved or associated environment, or an Initial Temperature. These objects are all default objects (included with) of the individual analysis types.
| Analysis Type | Object | Description |
|---|---|---|
|
Initial Conditions folder |
By default, a transient analysis is at rest. However, you can define velocity as an initial condition by inserting a Velocity object under the Initial Conditions folder. | |
|
Initial Conditions folder: Pre-Stress object |
Because an Explicit Dynamics analysis is better suited for short duration events, preceding it with an implicit analysis may produce a more efficient simulation especially for cases in which a generally slower (or rate-independent) phenomenon is followed by a much faster event, such as the collision of a pressurized container. For an Explicit Dynamics system, the Initial Conditions folder includes a Pre-Stress object to control the transfer of data from an implicit static or transient structural analysis to the explicit dynamics analysis. Transferable data include the displacements, or the more complete Material State (displacements, velocities, stresses, strains, and temperature). See Recommended Guidelines for Pre-Stress Explicit Dynamics for more information. An explicit dynamics analysis is at rest by default. However, for Explicit Dynamics and LS-DYNA systems, you can define velocity or angular velocity as initial conditions by inserting a Velocity object, a Drop Height object, or an Angular Velocity object under the Initial Conditions folder. If initial velocity, drop height, or angular velocity are defined in an LS-DYNA Restart, they override the velocities calculated at the end of the previous calculation. | |
|
Random Vibration, Response Spectrum, Harmonic Response MSUP (Mode-Superposition) linked, or Transient (MSUP) linked |
Initial Conditions folder: Modal object |
A Random Vibration, Response Spectrum, Harmonic (Mode-Superposition - MSUP) linked or a Transient (MSUP) linked analysis must use the mode shapes derived in a Modal analysis. |
|
Pre-Stress object |
You can use the physics settings and results of an upstream Coupled Field Static analysis in downstream Coupled Field Harmonic and Coupled Field Modal analyses. Also see the Prestressed Coupled Field Harmonic Analysis and Prestressed Coupled Field Modal Analysis sections. | |
|
Pre-Stress object |
An Eigenvalue Buckling analysis must use the stress-stiffening effects of a static structural analysis. See the Eigenvalue Buckling Analysis section for details. | |
|
Harmonic Response (Full) |
Pre-Stress object |
A Harmonic Response () analysis linked to a Static Structural analysis can use the stress results to account for stress-stiffening effect. Also see the Harmonic Response (Full) Analysis Using Pre-Stressed Structural System section. |
|
Pre-Stress object |
A Modal analysis can use the stress results from a Static Structural analysis to account for stress-stiffening effect. See the Modal Analysis section for details. | |
|
Initial Temperature object |
For a Steady-State Thermal analysis, you have the ability to specify an initial temperature. | |
|
Pre-Stress object |
For a Substructure Generation analysis, an upstream Static Structural analysis (only) can be used to create pre-stress effects. | |
|
Initial Temperature object |
For a Transient Thermal analysis, the initial temperature distribution should be specified. |
Note: When available in the Outline, you can apply temperatures from a Steady-State Thermal or a Transient Thermal analysis to a Static Structural, Transient Structural, or Electric analysis as a Imported Body Temperature load using the context (right-click) menu option Import Load that is available on the Environment object of the structural or electric analysis. The option provides a menu you can use to select the desired analysis you wish to link to. You can also perform this linking by dragging and dropping the Solution object of the Steady-State Thermal or a Transient Thermal analysis onto the Environment object of the structural or electric analysis. You can also apply Heat Generation from an Electric analysis to a Steady-State Thermal or Transient Thermal analysis using these methods.
Requirements/Usage
Depending upon the analysis type, an appropriate object is automatically added to the Outline enabling you to set an initial analysis specification:
For a Transient Structural analysis, use the Initial Conditions object to insert Velocity. For an Explicit Dynamics analysis, use the Initial Conditions object to insert Velocity, Angular Velocity, and Drop Height. These values can be scoped to specific parts of the geometry.
For a Harmonic Response, Modal, Eigenvalue Buckling, Substructure Generation, or Explicit Dynamics analysis, use the Details view of the Pre-Stress object to define the associated Pre-Stress Environment. For an Explicit Dynamics analysis, use the Details view of this object to select either Material State (displacements, velocities, strains and stresses) or Displacements only modes, as well as the analysis time from the implicit analysis which to obtain the initial condition. For Displacements only, a Time Step Factor may be specified to convert nodal DOF displacements in the implicit solution into constant velocities for the explicit analysis according to the following expression:
Velocity = Implicit displacement/(Initial explicit time step x time step factor)
Note: The Displacements only mode is applicable only to results from a linear, static structural analysis.
For a Random Vibration or Response Spectrum analysis, you must point to a modal analysis using the drop-down list of the Modal Environment field in the Details view.
For the Steady-State and Transient Thermal analyses, use the Details of the Initial Temperature object to scope the initial temperature value. For a Transient Thermal analysis that has a non-uniform temperature, you need to define an associated Initial Temperature Environment.
The Details view of the Modal (Initial Conditions) object for linked Mode-Superposition Harmonic and Mode-Superposition Transient analyses displays the name of the pre-stress analysis system in the Pre-Stress Environment field, otherwise the field indicates None or None Available.