Linear Dynamic Analysis

EIGENVALUE ANALYSIS

• Natural frequencies and mode shapes
• Modal stresses and strain energy computation
• Eigenvalue extraction algorithms
  • Conventional subspace iteration
  • Accelerated subspace iteration
  • Lanczos Method
  • Inverse iteration
  • Guyan reduction
• Extraction of zero frequencies (rigid body modes) and coincident frequencies
• Component mode synthesis to evaluate natural frequencies and mode shapes for:
  • Normal structures, given the mode shapes of the substructures or components
  • Cyclicsymmetric structures, given the mode shapes of one sector

Bending Mode of an Impeller

MODAL DYNAMIC ANALYSIS

• Viscous, structural, proportional and material damping
• Capabilities to handle rigid body modes
• Transient Dynamic Analysis
  • Time dependent ground excitations, nodal forces, and pressure loading
  • Nonzero initial displacements
  • Time dependent loads using time functions and arrival times
  • Time history and snapshot output for displacements, velocities, accelerations, stresses, reactions, and beam end forces
  • Generation of floor response spectra
• Frequency response analysis
  • Frequency dependent harmonic ground excitations, nodal force, and pressure loading
  • Amplitude and phase spectrum input
  • Point-to-point transfer function calculation
• Amplitude and phase spectra output for displacements, velocities, accelerations, reactions, and beam end forces
• Random Vibration Analysis
  • Stationary nodal forces, ground excitations, and pressure loading
  • Non-Stationary inputs
  • Auto PSD and complex cross PSD input
  • Numerical or exact integration of the PSDs to compute the covariance matrices
  • Auto PSD output for displacements, velocities, accelerations, stresses, reactions, and beam end forces
  • RMS responses for displacements, velocities, accelerations, stresses, reactions, and beam end forces
• Shock (response) spectrum analysis
  • Multi directional displacement, velocity or acceleration spectra input
  • Modal combination rules
    • Absolute sum
    • Square root of sum of squares or RMS sum
    • Peak RMS or NRL sum
    • Complete quadratic combination (CQC) sum
  • Direction combination by RMS or absolute sum
  • Automated mode selection and spectra computation by U.S. Navy DDAM method
  • Missing mass correction

NISA DYSPAN (Dynamic Spectrum Analyzer)

• Response spectrum generation
• PSD generation
• Spectrum compatible time history generation
• FFT generation

DIRECT TRANSIENT DYNAMIC ANALYSIS

• Newmark-Beta method for implicit time integration
• Lumped and consistent mass formulation
• Discrete damper elements and proportional (Raleigh) damping
• Nonzero initial conditions
• Time dependent boundary conditions
• Forces due to moving frames of references
  • Centrifugal forces
  • Coriolis forces
  • Linear and angular forces
  • Time dependent concentrated and distributed loading Absolute motion of unconstrained structures