I have been trying to evaluate the stress on aluminium propeller:
Diameter: 78", 2600RPM
Have fed load numbers from here, applied distributed mass model onto the blades.
Static Thrust (2600 rpm): MT 2-blade, 83" composite, 920 pounds MT 3-blade, 80" composite, 900 pounds McCauley 2-blade, 82" aluminium, 860 pounds McCauley 3-blade, 78" aluminium, 825 pounds
The results are rather scary - 30 MPa out of 55 max, for 6061 class Aluminium (the visual deformation is increased 20x for better representation), resulting in +-1cm vertical bending.
Is this normal?
Is there any info on industry's practice for safety margin (numbers show its less that 50%)? Or any kind of test procedures applicable to manufacturers?
Finally, a combined non-Linear analysis (incl. torque) - over-stressed by 250%: (notice that everything not in blue will bend and likely crack, with only the blade tips surviving the torture)