Elevated temperature fatigue for AISI 4340 steel

One of the most important considerations for the design and development of large caliber cannon tubes is the effects of material fatigue. Fatigue of cannon tube material results from the cyclic hoop stresses that result from the high pressure inside the cannon tube during firing. Extensive research has been conducted regarding the effect of stress level on the fatigue life of a variety of engineering materials; however, little research has been conducted for elevated temperature fatigue life of steel alloys used in large caliber cannon tubes.;Data gathered from stress and temperature testing on AISI 4340 steel was used to develop an elevated temperature fatigue prediction model for AISI 4340 steel. The similarities of AISI 4340 steel to the A723 steel used in large caliber cannon tubes allows this model to be used as a predictor for determining remaining life of a larger caliber cannon tube based on the conditions of cannon tube during firing. The usage of such data in a Fatigue Odometer System (FOS) along with the Palmgren-Miner rule for fatigue life determination will allow for a better assessment of remaining tube life. An anticipated increase in tube life will decrease the operating costs of the cannon tubes without sacrificing the safety of the individuals using the cannon tubes.