All replica tests were conducted on MTS 809 type axial tension and torsion fatigue testing machine following ASTM E647-11 Standard Test Method for Measurement of Fatigue Crack Growth Rates
Calculate time to failure: Using the initial and final flaw sizes, pressure cycles counted over a period of time, and calculated crack growth rate
, a remaining life or time to failure (TTF) can be calculated.
Increasing either B2 or m2 increases model crack growth rate
predictions as well as the transition crack length.
In order to determine the crack growth rate
using thermographic mapping of the material undergoing fatigue, we applied a specific procedure, which was described extensively in previous work .
The crack growth rate
(da/dN) as a function of amplitude of stress intensity factor ([Delta]K) for steel 42 CD 4 is given in Figure 10.
The morphology of fatigue fracture surface (caused by constant cycle loading) is strictly related to crack growth rate
Initial measurements indicate a crack growth rate
at the early stages of impact-fatigue in excess of 2.
The dependences of crack growth rate
versus the stress intensity factor range were determined (Fig 8) by testing requirements and the specified calculation technique (according to ASTM E 647-00).
Threshold fatigue crack growth: The best threshold fatigue crack growth rate
proves the material performance.
Some of the most common tests performed on aircraft include low cycle fatigue, thermo-mechanical fatigue, fracture mechanics, creek crack growth rate
, impact testing, high strain rate, drop weight impact, and stress and creek rupture.
Taking one micrometer as the final crack length in the flexure, this one micrometer, over a 10 year period, translates to an average crack growth rate
of one atomic distance per day.
The spacing of fatigue striations is usually very uniform and can be used to calculate the crack growth rate
if the cyclic stress frequency is known.