Fatigue, Fracture & Durability

Advanced Methods for Predicting Durability and Damage Tolerance

When a structure is subjected to cyclic loads due to dynamic motion or repetitive static loading, durability and damage tolerance are a concern. ATA’s fatigue analysis experience is not limited to a single industry but spans across multiple industries, such as themed entertainment structures, industrial equipment, and aerospace structures.

We typically evaluate structural endurance of metals and composites by using CAE methods to predict stress or strain and then applying industry standards to interpret the data and predict the resulting finite fatigue life or damage, or safety factor on infinite life (endurance limit method). In addition, we can efficiently perform fatigue life or damage predictions in Siemens Simcenter 3D or fe-safe durability software using static or transient event data. Stress analysis results are also the foundation for further specialized analyses such as damage tolerance and crack growth.

Standards Experience

ATA staff have expertise in the application and interpretation of fatigue requirements for metallic welded, unwelded, and bolted structures subjected to cyclic loading. Some of the fatigue standards that ATA has extensive experience in applying are the following:

  • AISC 360 Steel Construction Design Manual
  • Aluminum Design Manual
  • AWS D1.1 and D1.3
  • BS 7608
  • DIN 15018-1, -2, and -3
  • DNV-RP-C203 Fatigue Design of Offshore Steel Structures
  • EN 1993-1-9 Eurocode 3: Design of steel structure
  • FKM Guideline: Analytical Strength Assessment of Components Made of Steel, Cast Iron, and Aluminum Materials in Mechanical Engineering
  • GB 50017 Code for Design of Steel Structures (China)

Fracture

Whereas durability analysis focuses on crack initiation, damage tolerance analysis demonstrates that under an assumed flaw size, the metallic structure can tolerate additional load cycles without catastrophic failure. ATA uses NASGRO to perform fatigue crack growth analyses based on linear elastic fracture mechanics. These types of analyses are most commonly performed for the following reasons: (1) to determine residual strength in metallic aerospace structures, (2) to develop recommended inspection cycles for themed entertainment and aircraft structures, and (3) to determine repair urgency when new cracks have been discovered in an existing system. ATA also performs nonlinear crack growth analysis when necessary; this is applicable when the metal is very ductile. Damage tolerance and crack growth of composites and other nonmetallics must be evaluated empirically in most cases, and ATA is familiar with such test planning and oversight.

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