Plain Bearings (`plain-bearings`)

Check	IND	US	EU	ISO
Sommerfeld / film factor screening	implemented	—	—	—
Minimum film thickness	implemented	—	—	—
Thrust unit load	implemented	—	—	—

Purpose

Screen hydrodynamic journal and thrust pad bearings (ISO 7902 / ISO 12130 / ISO 12131 screening) with Sommerfeld number, minimum film thickness, power loss, and temperature rise. Supports preliminary bearing design before detailed Reynolds equation solution.

Physics & theory

In a journal bearing, rotating shaft (journal) separates from the bushing by a lubricant film when sufficient speed generates hydrodynamic pressure. The Sommerfeld number $S = (μ n / p) (r / c)^{2}$ characterizes operation, where $μ$ is viscosity, $n$ is speed, $p$ is unit load, $r$ is radius, and $c$ is radial clearance.

Minimum film thickness $h_{m i n}$ occurs near the maximum pressure arc; it must exceed composite surface roughness to avoid boundary contact. Eccentricity ratio $ε$ is interpolated from Raimondi–Boyd $ε (S)$ charts (full journal, $L / D \approx 1$ screening). Power loss is viscous shear in the film. Outlet temperature uses a light 2–3 pass ΔT ↔ viscosity iteration (Walther screening scale on the user viscosity); short-bearing / single-zone limits remain.

Governing equations

S = \frac{μ n}{p} (\frac{r}{c})^{2}, p = \frac{W}{2 r L}

h_{m i n} = c (1 - ε)

Numerical method

Sommerfeld + Raimondi–Boyd $ε (S)$ , iterative mean-film temperature viscosity. Inputs: diameter, length, clearance, load, speed, viscosity, ambient temperature. Outputs: $S$ , $h_{m i n}$ , eccentricity, power loss, specific load, outlet T, shaft/housing fit recommendation.

Inputs

Parameter	Description
Journal / pad diameter, length	Bearing geometry
Radial clearance $c$	Assembly clearance
`load`, `speed`	Operating W and rpm
Oil viscosity $μ$	At ambient / stated reference temperature (or from oil catalog)
Oil catalog	~25 ISO VG mineral/PAO/ester grades → ν(T)
Bushing material	~12 materials with specific-load / PV / temp limits
Ambient temperature	For ΔT iteration and outlet T
Bearing type	Journal / thrust pad / tilting pad

Outputs

Sommerfeld number, eccentricity ratio, minimum film thickness, film parameter / specific load, power loss, outlet temperature
Live Design Summary rail (S, $h_{m i n}$ , specific load, outlet T, status)
Deterministic plain advisor (L/D, clearance, viscosity, pad count rationale + alternatives)
Sectioned PDF / Excel (Design Summary, film factors, recommendation)
Status banner with ε, film ratio, load-limit highlights

Design codes & checks

ISO 7902 — Hydrodynamic plain journal screening
ISO 12130 / 12131 — Tilting-pad / thrust pad screening
Specific load and temperature screening limits

Assumptions & limitations

Full journal, steady-state; oil catalog + Walther ν(T); light ΔT ↔ viscosity iteration (not full flow heat balance).
Raimondi–Boyd ε(S) interpolated for L/D ∈ {0.25…1.5} — still not full finite-length Reynolds solution.
No dynamic instability (oil whirl/whip) analysis.
No MITCalc-IV-class sliding material + oil flow database.

Design workflow

Validate / Calculate: Forward ISO 7902/12130 screening with mode-aware Calculate label.
Auto-design: Available via design workflow where wired.

References

Hamrock, B. J., Schmid, S. R., & Jacobson, B. O. Fundamentals of Fluid Film Lubrication, 2nd ed. CRC Press.
Shigley, J. E., & Budynas, R. G. Mechanical Engineering Design, 11th ed., Ch. 12.
ISO 7902-1:2020. Calculation of plain bearings — Hydrodynamic plain journal bearings.
Bassani, R., & Piccigallo, B. Hydrostatic Lubrication. Elsevier.
PhyCalcPro verification benchmarks in src/data/verification/ (plain-bearings-indicative-*.json).

Plain Bearings

Assumptions

Limitations

Engineering checks