Fatigue life is the number of loading cycles that a structure or component sustains before failure occurs. Because fatigue failure can occur at very low stresses with little warning, this mode of failure is often overlooked in the design and the consequences are frequently catastrophic. T.R. Gurney, in his book Fatigue of Welded Structures, estimated that 90% of the failure which occur in engineering components can be attributed to fatigue.
FatiguePlus and SFAT are two separate design code compliance software packages. In a general sense, FatiguePlus is mechanical engineering oriented while SFAT focuses on structural engineering. Fatigue involves complex phenomena and mechanism, and the design codes constantly change as researches, practices and experiences evolve. Using FatiguePlus and SFAT the user can minimize risk of failure from cyclic loading and ensure design code compliance by applying automated fatigue life analysis, making the complicated tasks easy. In addition, FatiguePlus provides a generic fatigue life analysis module that incorporate Basquin model, Basquin-Coffin-Manson model, Kandil-Brown-Miller model, Socie-Fatemi model and Matake Criterion.
FatiguePlus and SFAT can handle cyclic loading from as simple as a single stress value, to component stresses of large number of nodes/elements in large number of loading steps generated by ANSYS. Stress history files generated by other FEA packages can also be imported and processed. Data input can be generated by manual entry, by importing ANSYS .rst files, or by importing stress history files. The loading can be of constant amplitude or variable amplitude, proportional or non-proportional. For non-proportional loading conditions, the programs scan for critical plane that generates the highest fatigue damage ratio, thanks to the multiaxial capability of the programs.
FatiguePlus and SFAT calculate fatigue damage ratios for each loading cycle, sums cumulative damage ratios using Miner’s Rule, and counts the number of loading cycles using rainflow counting algorithm following ASTM 1049 procedure. In addition to reporting calculations, the graphical charts of stress range time history, stress range histogram and fatigue damage ratios are also generated.
FatiguePlus is a fatigue life analysis software for pressure vessels, boilers, heat exchangers, mechanical components at elevated temperatures, as well as other structures subjected to cyclic loading. For thermal transient loading, FatiguePlus calculates fatigue life at each loading step based on material properties at temperature.
FatiguePlus consists of different modules for different design codes, including the following:
- Generic Fatigue Life Analysis Module, which contains most popular fatigue models including Basquin’s equation, Basquin-Coffin-Manson model, Kandil-Brown-Miller criterion with Wang-Brown modification, and Socie-Fatemi criterion. Mean stress can be considered using Soderberg, Goodman, Gerber, Morrow, Smith-Watson-Topper, or Manson-Halford criterion where applicable.
- EN 12952-3, Water-tube boilers and auxiliary installations — Part 3: Design and calculation for pressure parts of the boiler.
- EN 13445-3, Unfired pressure vessels Part 3: Design.
- ASME Section VIII, Rules for Construction of Pressure Vessels Division 2 — Alternative Rules.
- ASME Section VIII, Rules for Construction of Pressure Vessels Division 3 — Alternative Rules for Construction of High Pressure Vessels.
- ASME Section III — Rules for Construction of Nuclear Facility Components — Appendices.
The user can select a material from ASME Secion II Part D Properties, EN 10028 flat products, EN 10216 seamless tubes, EN 10217 welded tubes, EN 10213 castings, EN 10222 forgings, EN 10269 fasteners, or EN 10273 weldable bars. The Generic Fatigue Life Analysis Module also contains a material database with common metals such as ASTM A36, SAE-AISI 1035 etc. in which the user can edit material, add material or delete material; the user can also export or import the material database.
SFAT is a fatigue life analysis software for steel structures, components, as well as welded and bolted connections in bridges, cranes, offshore platforms, offshore wind structures, and other structures subjected to cyclic loading.
SFAT consists of different modules for different design codes, including the following:
- ANSI/AISC 360, Specification for Structural Steel Buildings.
- ASME BTH-1, Design of Below-the-Hook Lifting Devices.
- EN 1993-1-9, Design of steel structures – Part 1-9: Fatigue.
- DNVGL-RP-C203, Fatigue design of offshore steel structures.
- API-2A-WSD, API Recommended Practice 2A-WSD: Planning, Designing, and Constructing Fixed Offshore Platforms — Working Stress Design.
- ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures.