Critical Fracture Processes in Army Cannons: A Review

Abstract

Fast fracture in cannons can be well described using elastic-plastic fracture toughness, in combination with comparisons of cannon section size relative to the size required to maintain plane strain fracture. Fatigue fracture of cannon tubes is modeled from results of full-size fatigue tests that simulate cannon firing. These tests are also the basis of fatigue-intensity-factor modeling of fatigue life, which incorporates material strength, initial crack size and Bauschinger-modified autofrettage residual stress into life predictions. Environment-assisted fracture in the thermally damaged near-bore region of fired cannons is shown to be controlled by hydrogen. High strength cannon steels are susceptible to hydrogen; cannon propellant gases provide the hydrogen; and the source of sustained tensile stress is the near-bore thermal damage and compressive yielding. A thermo-mechanical model predicts tensile residual stress of similar depth to that of observed hydrogen cracks. Coating fracture in the thermal-damage region of fired cannons is characterized and modeled. The Evans/Hutchinson slip zone concept is extended to calculate in-situ coating fracture strength from observed crack spacing and hardness in the damaged region.

Structural Integrity Analysis of a Battle Tank Gun Barrel during Service

“…Under such conditions, a prior assessment of structural integrity, before the actual component is exposed to such hostile environment, becomes an indispensable task for the designer. Fast fracture in cannons and gun barrels are well reported in literature due to their large section size under planestrain conditions 1 . In some cases, due to high instantaneous operating stress-temperature pulse, chances of elastic-plastic fracture or plastic collapse are not ruled out.…”

Severe Thermal and Pressure Transients and the Survival of Internally Coated Tubes with Interface Defects

“…Using this information, Underwood and co-workers [1,[3][4][5][6][7][8][9]] developed a thermomechanical model which used the finite difference method to first evaluate the transient temperature distributions as a function of the depth for a coated steel plate; the temperature calculations were done using boundary condition measurements from bore locations where the heat transfer was the most severe. For the model, linearly temperature dependent material properties were used to account for the wide temperature range that the coating and steel substrate experienced.…”

Stress intensity factors calculation for surface crack in cylinders under longitudinal gradient pressure using general point load weight function

“…As an example, the fracture surface of the cylinder under two‐dimensional mechanical and thermal loadings is presented in Fig. . Due to two‐dimensional stress fields on crack faces, the pattern of crack growth is not the same commonly case, and the fracture surface does not remain in semi‐elliptical shape, because the critical points of initial or propagating crack may not be the deepest and surface points, as commonly the case.…”

“…1 Surface fracture of a cylinder under longitudinal mechanical and thermal loading. 10 cracks in thick-walled cylinder with outer radius to inner radius ratio of 1.25 under longitudinal gradient internal pressure is derived.…”