Explicit_Dynamics_Chapter 8_Analysis_Settings
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ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights ebruary 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Maximum Part Scaling
– Limits the ratio of scaled mass / physical mass that can be applied to an individual body.
• If this ratio is exceeded, the simulation will stop with an error message.
8-2
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Solve Initiation
– Resume From Cycle
• Specifies the cycle (time step) from which to start the Solve.
8-4
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
Training Manual
• Example energy conservation graph for model with symmetry plane and erosion
– Default (cycle 0) is to start at the beginning ( ( y ) g g (time zero). )
Training Manual
• When resuming a simulation, changes to analysis settings will be respected where possible.
– Limits the ratio of scaled mass / physical mass that can be applied to each element in the model.
• If this ratio is exceeded, the simulation will stop with an error message.
• Solve Termination
– Maximum Number of Cycles
• Specifies the maximum number of cycles (time increments) allowed for the simulation.
– The simulation will stop once the specified value is reached. – Enter a large number (default) to ensure simulation runs to the End Time. Time
– Solution stops if the energy error exceeds the Maximum Energy Error (expressed as a fraction)
Training Manual
Reference Energ = Internal Energ + Kinetic Energy + Ho rglass Energ Energy Energy Energ Hourglass Energy Current Energy = Internal Energy + Kinetic Energy + Hourglass Energy Work Done = Work done by constraints + Work done by loads + Work done by body forces + Energy removed from system by element erosion + Work done by contact penalty forces
– Initial Time Step
• If left on Program Controlled (recommended) the initial time step (recommended), will be automatically set to ½ the smallest initial element stability time step
– e.g. you often wish to resume a simulation with an extended End Time.
• Changes to any other features in the model (geometry suppression, connections, loads, etc….) will not be respected. • List of cycles from which to resume will only be populated if a previous solve has been executed and restart files generated.
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-3
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Maximum Energy Error
• Update Frequency
– The frequency (in cycles) that mass scaling is performed.
• A value of zero (default) means mass scaling is only done once, at the start of the simulation
Chapter 8 Explicit Dynamics: Analysis Settings
Introduction to ANSYS Explicit Dynamics
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-1
– Maximum Time Step
• Solver will use the minimum of this value or the computed stability time step • Program Controlled is recommended
– Time Step Safety Factor
• Minimum CFL Time Step
– Minimum CFL time step to be obtain with mass scaling
• Should be larger that the observed CFL time step
Training Manual
• Maximum Element Scaling.
• Reference Energy Cycle
– Defines the cycle at which the solver calculates the reference energy
• Usually the start cycle (default)
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
• Specifies directory where project data will be stored
Training Manual
• End Time is the only required input
– All other options have defaults
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
• Safety factor is applied to the computed stability time step
– Default (0.9) should work for most simulations
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
Training Manual
– Minimum Time Step
• If the time drops below this value the simulation will stop • If left on Program Controlled (recommended), the value will be set to 1/10th the Initial Time Step
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-5
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Time Step Controls
8-6
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Automatic Mass Scaling
– Masses in smaller elements are scaled up to increase the time step used in the simulation – Additional input is required for this option
• C ti ! M Caution! Mass scaling i t d li introduces additional mass i t th dditi l into the system to increase the CFL time step. Introducing too much mass can lead to unphysical result.
– End Time (no default)
• Defines the timescale that you want the simulation to run. • Enter a reasonable estimate for this parameter since it controls the length of time the simulation will take to run. • Used in other pre-processing objects (such as tabular loads) and also to define the scale for Chart output of results objects.
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Analysis Settings
• Analysis Settings are grouped in six categories
– Step Controls – Solver Controls – Damping Controls – Erosion Controls – Output Controls – Analysis Data Management
Explicit Dynamics: Analysis Settings
Step Controls
• Maximum Part Scaling
– Limits the ratio of scaled mass / physical mass that can be applied to an individual body.
• If this ratio is exceeded, the simulation will stop with an error message.
8-2
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Solve Initiation
– Resume From Cycle
• Specifies the cycle (time step) from which to start the Solve.
8-4
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
Training Manual
• Example energy conservation graph for model with symmetry plane and erosion
– Default (cycle 0) is to start at the beginning ( ( y ) g g (time zero). )
Training Manual
• When resuming a simulation, changes to analysis settings will be respected where possible.
– Limits the ratio of scaled mass / physical mass that can be applied to each element in the model.
• If this ratio is exceeded, the simulation will stop with an error message.
• Solve Termination
– Maximum Number of Cycles
• Specifies the maximum number of cycles (time increments) allowed for the simulation.
– The simulation will stop once the specified value is reached. – Enter a large number (default) to ensure simulation runs to the End Time. Time
– Solution stops if the energy error exceeds the Maximum Energy Error (expressed as a fraction)
Training Manual
Reference Energ = Internal Energ + Kinetic Energy + Ho rglass Energ Energy Energy Energ Hourglass Energy Current Energy = Internal Energy + Kinetic Energy + Hourglass Energy Work Done = Work done by constraints + Work done by loads + Work done by body forces + Energy removed from system by element erosion + Work done by contact penalty forces
– Initial Time Step
• If left on Program Controlled (recommended) the initial time step (recommended), will be automatically set to ½ the smallest initial element stability time step
– e.g. you often wish to resume a simulation with an extended End Time.
• Changes to any other features in the model (geometry suppression, connections, loads, etc….) will not be respected. • List of cycles from which to resume will only be populated if a previous solve has been executed and restart files generated.
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-3
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Maximum Energy Error
• Update Frequency
– The frequency (in cycles) that mass scaling is performed.
• A value of zero (default) means mass scaling is only done once, at the start of the simulation
Chapter 8 Explicit Dynamics: Analysis Settings
Introduction to ANSYS Explicit Dynamics
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-1
– Maximum Time Step
• Solver will use the minimum of this value or the computed stability time step • Program Controlled is recommended
– Time Step Safety Factor
• Minimum CFL Time Step
– Minimum CFL time step to be obtain with mass scaling
• Should be larger that the observed CFL time step
Training Manual
• Maximum Element Scaling.
• Reference Energy Cycle
– Defines the cycle at which the solver calculates the reference energy
• Usually the start cycle (default)
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
• Specifies directory where project data will be stored
Training Manual
• End Time is the only required input
– All other options have defaults
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
• Safety factor is applied to the computed stability time step
– Default (0.9) should work for most simulations
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
Training Manual
– Minimum Time Step
• If the time drops below this value the simulation will stop • If left on Program Controlled (recommended), the value will be set to 1/10th the Initial Time Step
ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved.
8-5
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Time Step Controls
8-6
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Step Controls
• Automatic Mass Scaling
– Masses in smaller elements are scaled up to increase the time step used in the simulation – Additional input is required for this option
• C ti ! M Caution! Mass scaling i t d li introduces additional mass i t th dditi l into the system to increase the CFL time step. Introducing too much mass can lead to unphysical result.
– End Time (no default)
• Defines the timescale that you want the simulation to run. • Enter a reasonable estimate for this parameter since it controls the length of time the simulation will take to run. • Used in other pre-processing objects (such as tabular loads) and also to define the scale for Chart output of results objects.
Release 12.1 February 2010
Explicit Dynamics: Analysis Settings
Analysis Settings
• Analysis Settings are grouped in six categories
– Step Controls – Solver Controls – Damping Controls – Erosion Controls – Output Controls – Analysis Data Management