Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress
Abstract
Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models of breech components, over the following ranges of key parameters: 380 to 745 MPa cyclic internal pressure; 100 to 160-mm bore diameter cannon pressure vessels; 1040 to 1170 MPa yield strength A723 steel; no residual stress; shot-peen residual stress; overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot-peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength, and initial defect size. The fatigue life model includes six test conditions in a stress versus life plot with an correlation of 0.94. The model shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2000
- Accession Number
- ADA379634
Entities
People
- John H. Underwood
- Michael J. Glennon
Organizations
- United States Army Armament Research, Development and Engineering Center