NEi Software Nastran Finite Element Analysis

Nastran Finite Element Analysis and Simulation Software

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NEi Nastran Fatigue


Fatigue capability allows users to investigate the durability of a part under repeated loading. Understanding how a component behaves under repeated loading is important, because 70-80% of all mechanical failures are caused by fatigue in service due to a cyclic load with a magnitude lower than their design load. NEi Nastran Fatigue features uniaxial and multiaxial fatigue models, allowing it to cope with stress histories coming from real world, complex, load inputs.

  • Rotating machine components
  • Aircraft structures
  • Electronic assemblies
  • Offshore structures
  • Bolted joints
  • Bridges
  • Wind turbines

Fatigue Applications

NEi Nastran’s multiaxial fatigue is capable of calculating fatigue life based on stress-life (S-N) theory and strain-life (E-N) theory. Both the stress-life and strain-life methods allow users to input multiple time history loads (either from test data or design data) to a static analysis along with material stress vs. cycle or strain vs. cycle information to extract life expectancy and accumulated damage. These results can be viewed as a contour plot for easy visualization of critical areas with respect to fatigue, based on damage level or cycles / life to failure.

Rollover each image to see a closeup. Piston rod

Strain-life material input
Meshed piston rod
Gauge Data Rainflow Matrix
  Damage Matrix

User Input

  • Load-time history
  • S-N (stress vs. number of cycles) or E-N (strain vs. number
    of cycles) material information


  • Accumulated damage contour plots
  • Life contour plots
  • Rainflow matrix
  • Damage matrix

Stress-life material input

Stress-life material input

Strain-life material input

Strain-life material input

Random Vibration Fatigue

Random vibration fatigue (or spectral fatigue assessment) is an extension of NEi Nastran’s random response solution. Vibration fatigue allows users to simulate vibration shake tests that would have an input PSD. This would be applicable to dynamic analyses that have random inputs such as road vibration, wave cycles, wind loads, or engine vibration.

Vibration fatigue within NEi Nastran is capable of stress-life and strain-life theory, along with Steinberg’s three band method, and is used to calculate damage and life.

Damage accumulation plot

Damage accumulation plot from a 0.8g RMS for 84.7 minutes

Advanced Fatigue Analysis

NEi Software also offers advanced fatigue capabilities to build upon those found in NEi Nastran including:

  • Nominal and elastic stress methods
  • Local strain approach
  • Nonlinear material using Neuber's rule
  • Haigh diagram
  • Woehler and hysteresis curve generation
  • Failure probability and multiple material hypotheses for creating cyclic material properties
  • Fatigue properties material database


PDFNEi Nastran Fatigue

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