A mechanical model for fatigue crack propagation.

Abstract

A MECHANICAL MODEL OF FATIGUE CRACK PROPAGATION IS PROPOSED. IT HYPOTHESIZES THAT DAMAGE DUE TO STRAIN CYCLING OF THE MATERIAL AT A CRACK TIP CAUSES PROPAGATION. MASON-COFFIN'S STRAIN CYCLE FATIGUE LAW WAS USED AS FAILURE CRITERION AND MINER'S LAW WAS USED FOR DAMAGE ACCUMULATION. THE PROPOSED THEORY CORRELATES SURPRISINGLY WELL WITH DATA FOR 2024-T351 A1 AND 4340 FULLY ANNEALED STEEL. STRAINS AT A CRACK TIP WERE MEASURED BY THE MOIRE OPTICAL INTERFERENCE METHOD. THE STRAIN AT A CRACK TIP WAS PROPORTIONAL TO DELTA K SQUARE. THE RESULTS OF STRAIN MEASUREMENTS WERE USED TO CALCULATE CRACK PROPAGATION RATE. /AUTHOR/