ANSYS mechanical FEM Finite Element Model History of engineering & technology LEFM STBF Single Tooth Bending Fatigue Taguchi method Technology: general issues U-notch XFEM critical load critical plane design flaws fatigue crack growth fatigue failure fatigue life fatigue life prediction finite element method fracture gears hinge kit system lead crowning modifications material characterization mechanical system mesh density meshing errors metal casting mixed mode stress intensity factors mold design