---
type: concept
title: "Midas NFX Fatigue Analysis"
created: 2026-06-02
updated: 2026-06-02
address: c-000181
aliases:
  - NFX fatigue analysis
tags:
  - concept
  - finite-element-method
  - midas-nfx
  - fatigue
  - verification
status: current
related:
  - "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
  - "[[midas NFX]]"
  - "[[Finite Element Modeling and Convergence Checks]]"
  - "[[Abaqus Progressive Damage and Failure]]"
  - "[[Midas FEA Fatigue Analysis]]"
sources:
  - "[[Midas-NFX-Analysis-Manual|Midas NFX Analysis Manual]]"
---

# Midas NFX Fatigue Analysis

## Definition

NFX fatigue analysis estimates fatigue damage and life from finite element stress or strain histories. The manual covers stress-life, strain-life, and random vibration fatigue approaches.

## Stress-Life Method

The stress-life method uses S-N curves and is positioned for relatively low stress levels where elastic behavior dominates. The manual describes stress amplitude, mean stress, rainflow counting for variable-amplitude histories, S-N curve correction factors, Miner cumulative damage, and life as inverse damage.

## Mean-Stress Corrections

The source includes Goodman, Gerber, Soderberg, Morrow, and Smith-Watson-Topper style mean-stress correction ideas. This matters for solver verification because identical FE stress histories can produce different fatigue lives depending on correction method.

## Strain-Life Method

The strain-life method is positioned for higher stress/strain concentration regions where plastic strain can control life. The manual includes elastic/plastic strain decomposition, cyclic strength/hardening parameters, and Neuber-rule based recovery from linear elastic results.

## Random Vibration Fatigue

For complex load histories, the manual also treats frequency-domain random vibration fatigue. That workflow connects modal/frequency response outputs to fatigue damage rather than relying on explicit time histories.

## Solver Development Use

For a custom solver, fatigue is primarily a postprocessing harness problem. The FE solver must first produce trusted stress/strain histories at documented locations; only then should rainflow counting, S-N/E-N interpolation, mean-stress correction, Miner damage, and random-response fatigue be tested.

## Connections

- [[Finite Element Modeling and Convergence Checks]] connects fatigue accuracy to stress recovery and mesh quality.
- [[Abaqus Progressive Damage and Failure]] provides a broader damage/failure comparison.
- [[Midas FEA Fatigue Analysis]] is the sibling MIDAS fatigue reference.