Transient Temperature Distribution and Thermo-Elastic Stress in Gun Tubes

The objective of this thesis is to predict the transient temperature distribution and thermo-elastic stress in gun tubes. Necessary background about the design of gun tubes and the  corresponding constraints and physical phenomena is discussed; general theories of heat transfer  in gun tubes and test reports on the specific weapon systems are considered in this thesis. A  modeling and simulation method is developed and implemented using commercially available  ballistics software and ANSYS FEA simulation software. The capability of predicting the transient  temperature distribution of an AR–15 rifle is validated by four experiments with different firing  schedules. For these experiments, an FLIR E8-XT thermal camera is used to record temperatures.  The predicted model is validated by comparing simulated thermo-elastic stresses in an M4A1  Carbine barrel with the tested data published in the literature. Overall, the percent error of  experimented and simulated temperatures is less than 10%; while the error increases as the number  of cartridges fired increases. The maximum percent error occurring to the AR–15 barrel is 12.3%  at 0.2032 meters. This suggests that the effect of heat transferred from the gas port should not be  neglected. The simulated rupture of the M4A1 Carbine barrel occurs at 548 rounds, 0.092 meters  from the breech, at a temperature of 1090 K. The resulting percent errors from published  experiments are 7.4% in the number of rounds until failure and 9.7% in location and temperature  at failure. Additional simulations have been performed to provide insight into the effects of cyclic  rate of fire and cooling time between bursts on the temperature distribution of an M4A1 Carbine  barrel. The simulation results suggest that the cooling time between bursts has a greater impact on  the barrel’s temperature distribution.