Home
Create Analysis
Create an analysis for your project.
Fatigue
Fatigue analysis is intended for predicting life of structures under cyclic loading.
Fatigue Theory
Background information on Fatigue analysis in SimSolid.
Endurance Limit Modifying Factors
Account for factors that can affect fatigue strength of a structure.

Welcome
What's New
View new features for SimSolid 2024.1.
Get Started
Learn the basics and discover the workspace.
Tutorials
Discover SimSolid functionality with interactive tutorials.
Interface with External Products
Interfaces that support SimSolid output file format.
Geometry
Information about treatment and properties of geometric entities in SimSolid.
Assembly
Summary of available functionality for defining the properties and behavior of parts in the model.
Connections
Connections are used to define the association of different regions of interest between parts in an assembly.
Create Analysis
Create an analysis for your project.
- Structural
- Modal
- Dynamics
  Evaluate your design in real-time using SimSolid dynamics analysis.
- Thermal
  Thermal analysis predicts how thermal effects propagate through the model. Steady state and thermal transient analyses are supported.
- Fatigue
  Fatigue analysis is intended for predicting life of structures under cyclic loading.
  - Fatigue Theory
    Background information on Fatigue analysis in SimSolid.
    - Fatigue Assessment Methods
      In SimSolid, uniaxial and multiaxial fatigue analysis using SN (stress-life) and EN (strain-life) approach is supported.
    - Stress-life (SN) Approach
      The stress-life method works well in predicting fatigue life when the stress level in the structure falls mostly in the elastic range.
    - Strain-life (EN) Approach
      The EN Approach uses plastic-elastic strain results to perform strain-life analysis.
    - Spot Weld Fatigue Analysis
      Allows for the study of fatigue performance of spot welds in structures.
    - Seam Weld Fatigue
      The seam weld fatigue implemented in SimSolid is based on linearization of stress in the conjunction with Volvo method and following that it predicts fatigue damage and life. Linearized stress decomposes a through-thickness elastic stress field into equivalent membrane and bending.
    - Random Response Fatigue Analysis
      The study of fatigue life of structures under random loading.
    - Rainflow Cycle Counting
      Use cycle counting to extract discrete simple "equivalent" constant amplitude cycles from a random loading sequence.
    - Mean Stress Correction
      Use mean stress correction to account for the effect of non-zero mean stresses.
    - Damage Accumulation Model
      Palmgren-Miner's linear damage summation rule is used.
    - Endurance Limit Modifying Factors
      Account for factors that can affect fatigue strength of a structure.
    - Scatter in Fatigue Material Data
      Handle scatter in fatigue test results.
  - Import Loadcase-channel Map
    Import a loadcase-channel map file to import all the channels defined in the file and create appropriate events.
  - Import Channels
    Import channels which define load amplitude changes in time.
  - Review Channels
    Review channels in a group.
  - Create Event
    Create an event consisting of channels and loadcases.
  - Import Sequences
    Import a file to automatically create load case sequences.
  - Create Sequence
    Create a sequence with load cases for the fatigue analysis.
Boundary Conditions
Boundary Conditions available for SimSolid.
Post Processing
Run analyses and view a variety of results in SimSolid.
Design Study
Design studies allow you to quickly evaluate and compare the structural performance from different design scenarios.
Verification Problems
Solved verification models.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding

Endurance Limit Modifying Factors

Account for factors that can affect fatigue strength of a structure.

Surface Condition (Finish and Treatment)

Surface condition is an extremely important factor influencing fatigue strength, as fatigue failures nucleate at the surface. Surface finish and treatment factors are considered to correct the fatigue analysis results.

Surface finish correction factor C_finish is used to characterize the roughness of the surface. It's presented on diagrams that categorize finish by means of qualitative terms such as polished, machined or forged.

Figure 1. Surface finish correction factor for steels*

(*Source: Yung-Li Lee, Jwo. Pan, Richard B. Hathaway and Mark E. Barekey. Fatigue testing and analysis: Theory and practice, Elsevier, 2005)

Surface treatment can improve the fatigue strength of components. NITRIDED, SHOT-PEENED, COLD-ROLLED are considered for surface treatment correction. You can also input a value to specify the surface treatment factor C_treat.

In general cases, the total correction factor is C_sur= C_treat* C_finish.

If treatment type is NITRIDED, then the total correction is C_sur= 2.0 * C_finish (C_treat= 2.0).

If treatment type is SHOT-PEENED or COLD-ROLLED, then the total correction is C_sur = 1.0. It means you will ignore the effect of surface finish.

The fatigue endurance limit FL is modified by C_sur as: FL' = FL * C_sur. For two segment SN curve, the stress at the transition point is also modified by multiplying by C_sur.

Fatigue Strength Reduction Factor

In addition to the factors mentioned above, there are various other factors that could affect the fatigue strength of a structure, such as notch effect, size effect, and loading type. Fatigue strength reduction factor K_f is introduced to account for the combined effect of all such corrections. The fatigue endurance limit FL will be modified by K_f as: FL' = FL / K_f.

If both C_sur and Kf are specified, the fatigue endurance limit FL will be modified as: FL' = FL * C_sur/ K_f.