Dynamic Modal Superposition

DJHEC has extended their Finite Element Analysis (FEA) capabilities to include dynamic modal superposition. Dynamic modal superposition is used to analyze transient linear dynamic problems using modal superposition. The method performs a frequency extraction and couples the frequency modes with the structure’s input over time. The required input of the analysis is test data in the form of displacement, acceleration, or applied force. The output of the analysis DJHEC typically produces is either high strain areas or coupling results with a fatigue life software to predict hours to failure.

This method is appropriate and best suited for structures prone to vibration issues such as a vehicle cab during a rough transport operation. One of the largest benefits of this method is observed when comparing the computational costs and run time to a dynamic simulation.

Advantages of this method of simulation include:

  • Faster than almost all current forms of Dynamic FEA and less time consuming to review results
  • Faster than many non-linear simulations
  • Readily applied in fatigue life software to predict life or number of repeats to failure
  • Capable of simulating loading not well defined by static analysis similar to rough transport operations
  • Utilizes exact incrementation
  • Results are simple and quick to review because there is only 1 plot needed (Life)
  • Aids in understanding the critical modes of a system
  • Easily generate a strain time history at locations of interest


Utilizing Fatigue Life Software to Perform Linear Superposition of Excitation Frequencies

Accelerometer Test Data vs. Finite Element Model Simulation Results