Critical Fracture Processes in Army Cannons: A Review
Abstract
Fast fracture in cannons can well be 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 thermomechanical 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2003
- Accession Number
- ADA414671
Entities
People
- Edward Troiano
- John H. Underwood
Organizations
- United States Army Armament Research, Development and Engineering Center