A series of elastic-perfectly plastic strips (originally 30 strips were used) that model the region both ahead and behind the crack tip is used to keep track of the plasticity produced at the crack tip.
This profile of the crack is used to calculate the stress intensity factor level
The rate of crack growth is then calculated from Fastran was written in the 1980s by James C. Newman while at NASA and is an acronym derived from NASA FATIGUE CRACK GROWTH STRUCTURAL ANALYSIS.
[3] It was assumed this was due to plasticity at the crack tip preventing the fracture surfaces from fully closing.
A similar program CORPUS was also developed around the same time by A. U. de Koning.
This in combination with a load factor is used to supply the far-field stress of the given geometry.
In addition the model is able to predict retardation due to overloads which increase the plastic material in the wake of the crack.
is used to adjust the flow stress to the degree of restraint experienced at the crack tip.
This value reflects the stress state at the crack tip and typically lies between a value of
The parameter is also used as an adjustment variable to correct the rate of crack to match test data.
Plasticity will be greater in regions of plane stress but Fastran only models the crack as a 2d cross section.
Fastran has been used in the research community and for maintaining the safe life of aircraft as the C-130 used by the USAF, RAF and RAAF.