Training Manual 001419

1
3.4 Dynamics Enhancements

• Mode Superposition method allows non-proportional
  damping
• Block Lanczos solver enhancements
• Full harmonic analysis allows prestress effects

2
Dynamics Enhancements Q-R Damp Mode
Superposition

• Non-proportional damping available with mode
  superposition method at 5.7
• Modal analysis carried out using Q-R damped
  eigensolver
• Allows all types of damping including element
  damping
• Extremely fast compared to full method

Only applicable in a full or reduced harmonic
Element damping valid at 5.7
Frequency dependent damping valid
Alpha damping valid
Material damping valid
Beta damping valid
3
Dynamics Enhancements Q-R Damp Mode
Superposition

• Applications
• Models where a spring-damper component needs to
  be represented by a single stiffness and damping
  constant.
• For example
• components of an automobile suspension system
• dashpot mechanism on a door
• simplified bearings on a rotor shaft
• dampers used in a nuclear piping assembly

4
Dynamics Enhancements Q-R Damp Mode
Superposition

• Procedure
• Modal analysis
• MODOPT, qrdamp
• Define damping
• ALPHAD BETAD MP,DAMP (as before)
• New element damping is also allowed, via
  COMBIN7, COMBIN14, COMBIN37, COMBIN40, CONT178
  etc.
• Mode superposition
• Transient analysis TRNOPT,msup
• Harmonic analysis HROPT,msup
• All damping must be specified in the modal
  analysis step

5
Dynamics Enhancements Q-R Damp Mode
Superposition

• Limitations
• Damping specified during mode superposition is
  ignored.
• QR damping does not support DMPRAT and MDAMP.
• Gap conditions (GP) are not supported.

6
Dynamics Enhancements Q-R Damp Mode
Superposition
Benchmark Results
FY 200
SOLID92s
COMBIN40
FZ 1000

• Elements SOLID92 and COMBIN40
• DOFs 5531
• Damping Rayleigh, material, and element

COMBIN40
7
Dynamics Enhancements Q-R Damp Mode
Superposition
8
Dynamics Enhancements Block Lanczos Enhancements

• Improved memory management
• Automatic supplemental memory allocation
• Intelligent choice of workspace
• Minimum memory mode
• Example
• 1.4 million DOF problem, 10 modes, Compaq Alpha
• platform (1 cpu)
• Required only 870 MB (-m 870) of memory.
  (5.6 required -m 2580)
• 8093 cpu sec, 11723 wall-clock sec