Linear Elastic Fracture Mechanics (LEFM)

Linear Elastic Fracture Mechanics

LEFM can be used to predict cracking behavior and life of structures.

Lambda has developed linear elastic fracture mechanics (LEFM) computer codes to predict the fatigue crack growth behavior of structures with a variety of damage and loading geometries. LEFM codes are routinely used to solve crack growth behavior under complex load history and residual stress distribution from processes such as LPB and shot peening.

The field of LEFM deals with the fundamental understanding of cracking of structures leading to final failure. LEFM can be used to predict cracking behavior and life from the known geometry of the structure and the loading conditions.

Lambda's solutions to problems are frequently obtained by adopting a systems approach to include stress solutions from finite element analysis (FEA), with the knowledge of residual stresses from x-ray diffraction analysis, and LEFM codes.

Validation of such predictions is always obtained through in-house fatigue tests of laboratory specimens, specially designed simulation specimens, and actual components.

Unified Fatigue Design Method (UFDM)

Unified fatigue design method (UFDM) (patent pending) is a design methodology developed at Lambda Research and Engineering to precisely identify the possible minimum, optimum and maximum compressive residual stresses necessary to mitigate a specific damage problem in a structure. The UFDM covers the entire high cycle fatigue (HCF) and low cycle fatigue (LCF) regimes.

"Safe" regions are predicted using known fatigue models and material constants. The presence of pre-existing notches, foreign object damage (FOD), fretting damage, corrosion pitting damage, etc., is included in the solution.

By adopting a systems approach to include stress and part distortion analyses from FEA, knowledge of actual residual stresses in components from x-ray diffraction analysis, and crack growth analysis from LEFM codes, UFDM solutions obtained are very powerful.