Chair: evidence to a testable design

Connected engineering example. Calculations are reproducible; no physical chair or treatment has been validated. This supplements the incomplete answer Q4114 without relabeling it as verified.

What can be established now

For an assumed 100 kg static occupant: force = 980.665 N; an ideal equal four-leg split gives 245.166 N per leg.

A separate ideal beam example (450 mm span, 450 mm width, 20 mm thickness, center load) gives bending moment 110.325 N m and stress 3.677 MPa. This is a demand calculation, not a material capacity or safety result.

Static occupant only, conventional standard gravity, separate ideal support and beam models. The full seat width is assumed to act as one rectangular beam. Not a plate/joint/contact model; no chair self-weight, impact, fatigue, grain defects, eccentricity or backrest forces.

F = m g
R = F/4 (four equal ideal support reactions)
M = F L/4 (separate simply-supported center-load beam idealization)
I = b t^3/12
stress = M(t/2)/I

Whole process and next evidence

Step / status	Next action
Requirements and use provisional	Confirm intended use, occupant range, geometry and applicable seating standard.
Load accounting calculated	Compare static, eccentric, impact and repeated-load cases; only static example computed here.
Materials and joints missing design inputs	Select actual species/grade or panel specification, orientation, moisture, connections and published design properties.
Optional ionization energy threshold calculated; treatment benefit unmeasured	Independent treated/untreated comparison; it does not gate conventional chair development.
Fabrication and inspection not executed	Produce reviewed drawings and joint details before fabrication; record dimensions and defects.
Whole-chair validation not performed	Qualified review and suitable strength, stability, fatigue and durability tests. Obtain applicable standard; no certification claimed.

Ionization is a separate branch

1 MHz is below argon’s single-photon threshold. 4 × 10¹⁵ Hz is energetically above it; yield remains unknown. Neither establishes treatment benefit. Saved run 24 · Saved run 25. These are saved simulation records, not physical measurements.

Evidence provenance

USDA Wood Handbook, Chapter 5 (2021)
Reviewed abstract: wood properties vary, including with moisture and growth features such as knots and grain slope. This reference supports material variability, not an allowable stress for the proposed chair. No specimen grade, allowable strength or stiffness has been established.

NIST ASD: neutral argon ionization energy
Neutral ground-state argon first ionization energy is 15.7596119 ± 0.0000005 eV. The condition hf >= ionization energy is only single-photon energetic eligibility; it does not establish yield, surface-treatment benefit or chair performance.

BIFMA standards overview: candidate selection reference; obtain the applicable full standard before defining compliance tests.

Download the structured evidence and calculation packet