| This research project focused on the creep and creep crack growth characteristics of two aluminum-copper alloys, 2519-T87 and its chemical variant, C415-T8 at 135{dollar}spcirc{dollar}C and 150{dollar}spcirc{dollar}C. Both aluminum C415 and 2519 displayed creep-brittle properties at both test temperatures, having a total creep strain to failure only on the order of 3.5%. Creep deformation tests revealed that C415 has a greater resistance to creep deformation than 2519 for a given temperature and stress level. The {dollar}theta{dollar}-projection analysis was successfully used to fit creep deformation data and is a viable technique for extending creep data obtained within a laboratory time frame (less than 5000 hours) to long term exposure conditions. For both alloys and test temperatures, creep crack growth rates were shown to best correlate with the stress intensity factor, K, with a transition time, t{dollar}rmsb{lcub}g{rcub},{dollar} applied to the data. The transition time removed the data which was obtained under transient crack growth conditions and allowed the data obtained under steady-state conditions to be studied and correlated with K. Even though aluminum C415 showed a greater resistance to creep deformation than aluminum 2519, the creep crack growth rates were greater in C415 than 2519 for equivalent levels of K and the same test temperature. Finally, a model for incubation time is proposed based on continuous void nucleation within the creep zone ahead of the crack tip. |
