Low Cycle Fatigue
Low Cycle Fatigue (LCF) describes the service environment of many critical (and primarily metal) components: low frequency, large loads/strains. The LCF environment is typical of turbine blades (heat-up/cool down cycling) and other power generation equipment subject to thermal and/or mechanical cycling (ie. pressure vessels, piping, etc.) LCF typically involves large deformations, thereby accumulating damage on the specimen. LCF research is essential for the understanding of failure (in metals), for design and engineering purposes.
High Cycle Fatigue
High Cycle Fatigue (HCF) results from vibratory stress cycles at frequencies which can reach thousands of cycles per second and can be induced from various mechanical sources. It is typical in aircraft gas turbine engines and has led to the premature failure of major engine components (fans, compressors, turbines). While LCF involves bulk plasticity where stress levels are usually above the yield strength of the material, HCF is predominantly elastic, and stress levels are below the yield strength of the material.