FATIGUE DEGRADATION STRATEGIES TO SIMULATE CRACK PROPAGATION USING PERIDYNAMIC BASED COMPUTATIONAL METHODS

Abstract

THE AIM OF THIS PAPER IS TO DEVELOP NEW COMPUTATIONAL TOOLS TO STUDY FATIGUE CRACK PROPAGATION IN STRUCTURAL MATERIALS. IN PARTICULAR WE COMPARE THE PERFORMANCE OF DIFFERENT DEGRADATION STRATEGIES TO STUDY FATIGUE CRACK PROPAGATION PHENOMENA ADOPTING PERIDYNAMIC BASED COMPUTATIONAL METHODS. THREE FATIGUE DEGRADATION LAWS ARE PROPOSED. THE FIRST AND THE THIRD LAWS SIMULATE THE DEGRADATION PROCESS REDUCING THE MATERIAL STIFFNESS AS THE NUMBER OF LOAD CYCLES INCREASES, WHILE THE SECOND FATIGUE LAW REDUCES THE FAILURE STRETCH AS THE NUMBER OF LOAD CYCLES INCREASES. INITIALLY A SIMPLE CYLINDER MODEL IS USED TO COMPARE THE COMPUTATIONAL PERFORMANCE OF THE THREE FATIGUE LAWS. THEN THE FATIGUE DEGRADATION STRATEGIES ARE IMPLEMENTED IN A PERIDYNAMIC FRAMEWORK TO STUDY FATIGUE CRACK PROPAGATION PHENOMENA. THE RESULTS OBTAINED USING THE CYLINDER MODEL ALLOW A COMPARISON ON THE ROBUSTNESS OF THE THREE DEGRADATION STRATEGIES WITH RESPECT TO VARIATIONS OF TWO DISCRETIZATION PARAMETERS: GRID SPACING AND NUMBER OF CYCLES PER LOAD INCREMENT. THE FINDINGS OF THE CYLINDER MODEL ARE CONFIRMED THEN BY PERIDYNAMIC BASED SIMULATIONS. BOTH CYLINDER MODEL AND PERIDYNAMIC SIMULATIONS SHOW THAT THE THIRD PROPOSED DEGRADATION LAW IS UNIQUE IN ITS COMBINATION OF HIGH ACCURACY, HIGH STABILITY AND LOW COMPUTATIONAL COST. THE SECOND AND THE THIRD FATIGUE DEGRADATION LAWS ARE ORIGINAL. FATIGUE CRACK PROPAGATION PHENOMENA ARE STUDIED USING A PERIDYNAMIC APPROACH, VERY FEW PAPERS ADOPT THIS METHOD.