Press fit (interference fit)
Contact pressure, transmissible force and torque, and the tangential/radial/equivalent stresses in an interference fit, from Lamé’s equations in the elastic regime.
Stresses
Interference δ is typically δ/d ≈ 0.001 and should be corrected for surface roughness. Assumes stresses stay below the elastic limit. If the entered geometry is physically invalid (interface diameter or outer diameter smaller than the bore, or a negative bore), the legacy source silently discards all three diameters and substitutes its own default set (dᵢ=20 mm, d=23 mm, dₒ=80 mm) rather than rejecting the input — preserved exactly. There is no separate output showing the diameters actually used, so an invalid combination is not obviously flagged in the results. Separately, entering dₒ=0 is a supported special case (unlike the reset above) — the legacy source treats it as an effectively infinite outer diameter (a very thick outer part with no defined outer boundary), substituting a large finite stand-in value rather than 0 itself; this is not indicated in the field label.
Method & references
- Lamé’s equations for thick-walled cylinders (elastic regime).
- Default values represent a bronze bush in a steel flange.
The computation is a literal port of the original client-side JavaScript from /calculators/e3_8.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.