Average axial, average direct-shear and elastic bending stress
Evaluate one documented section and one internal resultant. The worksheet reports an average axial/direct-shear value or a nominal extreme-fiber elastic bending value—never a local peak or design acceptance.
4. Result
Method and applicability
Average axial normal stress
σavg = N/A
- Internal axial resultant through the section centroid.
- Uniform average sufficiently away from load introduction and discontinuities.
- Not eccentric bending or a local notch/thread stress.
Average direct-shear stress
τavg = V/A
- Reports only the sectional average.
- The real distribution generally is not uniform.
- Not the beam formula VQ/(It), bearing stress or torsional shear.
Nominal elastic bending stress
σnom = M/W = Mc/I
- Linearly elastic simple flexure and correct neutral axis.
- W = I/c for the stated axis and extreme fiber.
- Not plastic, composite, curved-beam or local peak stress.
Dimensional identities used: N/mm² = MPa; N·mm/mm³ = MPa. The sign is preserved from the documented internal-force convention. Strength, allowables, partial/safety factors and acceptance criteria are deliberately absent.
Sources and classification
- University of Illinois Mechanics Reference — Stress: distinguishes point stress from sectional averages; states the centric/far-field conditions for uniform axial average and that direct-shear distribution cannot generally be assumed uniform.
- University of Illinois Mechanics Reference — Bending: linearly elastic flexural relation σ = −My/I, maximum magnitude |M|/S and S = I/c.
- NIST SP 811 Appendix B: exact inch/pound-force basis and published stress conversion factors.
Classification: these are bounded general-mechanics relationships, not formulas attributed to ISO, ASME, ASTM, EN or another design standard. Any actual allowable, resistance, load combination, stress concentration, fatigue method or acceptance rule requires its controlled governing source.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
