REACTION RATE ENGINEERING MODELS OF FATIGUE CRACK GROWTH

EXPLORE TO WHAT EXTENT THE EXISTING MICRO REACTION RATE KINETIC THEORY OF THERMALLY ACTIVATED FRACTURE CAN BE USED TO RELATE THE PARAMETERS OF PROBABILISTIC MACRO ENGINEERING MODELS OF CUMULATIVE DAMAGE (FATIGUE, FATIGUE CRACK GROWTH) TO THE USUAL PARAMETERS OF ENGINEERING SIGNIFICANCE SO THAT ACCURATE PREDICTION OF CRACK GROWTH CAN BE ACHIEVEDWITH MINIMUM TESTING FOR A SPECIFIC SET OF ENGINEERING CONDITIONS. FIRST, A DETERMINISTIC MACRO MODEL OF DAMAGE ACCUMULATION FOR FATIGUE CRACK GROWTH (FCG) WILL BE CONSTRUCTED FROM THE MICRO THEORY. SECOND, IDENTIFY THE PARAMETERS IN THE MACRO MODEL WITH PHYSICAL AND MATERIALS PROPERTIES OF ENGINEERING SIGNIFICANCE TO SEE WHICH MUST BE ESTIMATED BY TESTING AND WHICH CAN BE ESTIMATED FROM KNOWN MATERIAL PROPERTIES. THIRD, FOUR SETS OF EXISTING DATA ON FCG WILL BE USED TO EXPLORE THE PARAMETER ESTIMATION PROBLEM IN ORDER TO DETERMINE THE MINIMUM AMOUNT OF TESTING NEEDED TO CHARACTERIZE A COMPONENT FOR PREDICTION PURPOSES. FOURTH, DETERMINE HOW VARIABILITY IS TO BE INCLUDED IN THE DETERMINISTIC ENGINEERING MODEL SO THAT THE INHERENT PROBABILISTITY DISTRIBUTIONS PRESENT IN THE PHENOMENON CAN BE INCLUDED, AND REPEAT THE FIRST, AND THIRD ITEMS ABOVE.