Shafts

Shaft Design

Stress, fatigue safety factor, deflection and critical speed of a stepped shaft on two bearings carrying gears, pulleys or couplings: the radial loads in two planes give the shear and bending-moment diagrams, the applied torques give the torque diagram, and at every step and every load station the rotating shaft's fully reversed bending and steady torsion are checked by the distortion-energy Goodman criterion with Marin's endurance-limit factors and the entered fatigue stress-concentration factors, and by the von Mises static criterion against yield. The deflection curve is integrated numerically through the varying stiffness, giving the slopes at the bearings for the bearing check and the first critical speed by Rayleigh's method from the station masses and the shaft's own mass. Charts of the diagrams and the deflection, and a drawing of the shaft.

1 worked example reproduced, listed on the tool page.

Interference and Press Fit

Contact pressure, stresses and holding capacity of a hub shrunk or pressed on a solid or hollow shaft by Lamé's thick-cylinder solution: the pressure from the diametral interference and the two materials' moduli, the radial and hoop stresses through both parts, von Mises and Tresca at the hub bore and the shaft surface against yield with a design factor, the elastic limit of the interference, the holding torque and axial force by friction, the press force, the heating or cooling for a shrink assembly, the loosening of the fit with speed and the release speed, and the effect of an external pressure and a transmitted torque. The interference is entered with a tolerance on each part and a surface-finish loss, so the loose, nominal and tight fits are all reported.

1 worked example reproduced, listed on the tool page.

Other Mechanical Design sections

Gears · Bearings · Springs · Fasteners and Power Screws · Pressure Vessels · Tolerances · Mass Properties · Vibration · Acoustics · Brakes, Clutches and Belts · Machining and Manufacturing · Lubrication and Wear