Where does the greatest stress on a rotating propeller occur?

The greatest stress on a rotating propeller occurs at the root. This is primarily due to the fact that the root is where the propeller blade connects to the hub, and it is subjected to both bending and twisting forces during operation. As the propeller rotates, the aerodynamic load increases from the tip towards the root, leading to higher shear and bending moments concentrated at this juncture.

Additionally, within the root area, the material must bear not only the forces generated from lift and drag but also those associated with the rotational dynamics of the propeller, representing the point of maximum load distribution. This combined stress results in the root experiencing significantly greater stress levels compared to the other sections of the blade.

In contrast, while the tip may experience high shear due to the high speed of the outermost section, the root remains the most critical area for stress considerations due to its structural and connection role.