NASGRO

NASGRO is a crack growth model and accompanying software framework developed by NASA and the Southwest Research Institute for predicting fatigue crack growth in metallic structures under variable-amplitude loading and environmental conditions. It generalizes the Paris law by including a fatigue threshold, a power-law growth regime, and mechanisms to account for overload retardation and environmental effects such as corrosion and hydrogen embrittlement. The NASGRO formulation expresses the crack growth rate as a function of stress intensity factors, load ratio, and other factors, enabling more accurate life prediction across complex loading spectra than simpler models.

Development in the 1990s as part of NASA’s damage-tolerance research has led NASGRO to become widely used in aerospace and related industries. Its parameters are material-specific and must be calibrated from experimental data, often involving fitting growth-rate versus ΔK measurements under representative loading.

NASGRO is implemented in software tools and is used to perform damage-tolerance analyses, assess remaining life of critical components, and support certification and safety assessments for metallic structures.

Materials commonly analyzed with NASGRO include aluminum alloys, steels, and titanium alloys, among others.

While versatile, the model requires quality data and careful validation for each material and service environment.

NASGRO remains part of the broader set of fracture-mechanics methods and is often discussed alongside Paris, Forman, and other crack-growth models.