This study offers a thorough analysis using finite element methods (FEA) to examine how fatigue cracks grow in three different materials: Structural steel , Titanium alloy (Ti Grade 2), and epoxy/aramid-based printed circuit board (PCB) laminates. Using ANSYS Workbench, we ran simulations under both static and repeated loading to understand how these materials fracture. The approach was based on Linear Elastic Fracture Mechanics (LEFM), employing the Maximum Circumferential Stress Criterion to predict where cracks might start and how they could spread. Also, the Equivalent Domain Integral (EDI) method helped us calculate the Stress Intensity Factors (SIFs) when cracks are under mixed loading modes. We modeled the growth of fatigue cracks using the Paris Law, relying on material-specific constants (C and m) drawn from previous studies and experimental tests. For example, titanium Grade 2 showed Paris Law constants with C values between 1.8 × 10⁻¹⁰ and 7.9 × 10⁻¹² m/cycle, and m values from 2.4 to 4.3, reflecting differences caused by manufacturing processes and microstructure. While detailed Paris Law constants for epoxy/aramid laminates are scarce, similar composite materials have shown that the Paris Law can still be relevant under certain conditions. In assessing the materials' performance, we looked at various mechanical responses such as total deformation, directional deformation, equivalent (von Mises) stress, and maximum principal stress. These metrics help evaluate the structural integrity under fatigue. To ensure our simulation methods were accurate, we compared results from standard benchmark tests including Single Edge Notched (SEN) plates, Modified Compact Tension (CT) specimens, and plates with edge cracks or central holes. These tests were performed on SAE 1020 steel and aluminum alloys, with results checked against established data. The findings emphasized notable differences in how quickly cracks grew, the SIF values, and failure modes across the materials. These differences emphasize why choosing the right material is critical for safety-critical applications. The validated FEA approach we've used provides a dependable way to predict fatigue behavior in various material systems, helping improve the design of more durable and reliable structural parts
Keywords:-
Crack propagation, Structural steel, Finite Element Method (FEM), Linear Elastic Fracture Mechanics (LEFM), Stress Intensity Factor (SIF), J-integral, Maximum circumferential stress criterion, Fracture toughness, Material comparison, Mixed-mode loading