Gear Load-Carrying Capacity Design, Calculation And Application in Mechanical Transmission

1. Basic Design Process for Gear Load-Carrying Capacity

2. Core Calculation Methods

2.1 Tooth Surface Contact Fatigue Strength Calculation (per ISO 6336 Standard)

• σH is the calculated contact stress (MPa)

• ZH denotes the zone factor, ZE the elastic coefficient of materials, Zε the contact ratio factor, and Zβ the helix angle factor

• Ft represents the tangential force at the transverse pitch circle (N)

• b is the face width (mm), d1 the pitch circle diameter of the pinion (mm), and u the gear ratio (u=z2/z1)

• σHP is the allowable contact stress (MPa), calculated as:σHP = σHlim × ZN × ZL × Zv × ZR × ZW × ZX / SHmin(σHlim = contact fatigue limit of test gears; ZN = life factor; ZL = lubricant factor; Zv = speed factor; ZR = surface roughness factor; ZW = work hardening factor; ZX = size factor; SHmin = minimum safety factor)

2.2 Tooth Root Bending Fatigue Strength Calculation

• σF is the calculated bending stress (MPa)

• mn is the normal module (mm)

• YF = form factor, YS = stress correction factor, Yβ = helix angle factor, YB = face width factor

• σFP is the allowable bending stress (MPa), calculated as:σFP = σFlim × YN × YδrelT × YRrelT × YX / SFmin(σFlim = bending fatigue limit of test gears; YN = life factor; YδrelT = relative tooth root fillet sensitivity factor; YRrelT = relative surface condition factor; YX = size factor; SFmin = minimum safety factor)

3. Load-Carrying Capacity Verification

3.1 Basic Verification Conditions

• Contact fatigue strength: σH ≤ σHP

• Bending fatigue strength: σF ≤ σFP

3.2 Special Working Condition Verification

3.3 Influence of Key Factors

• Geometric parameters: Module significantly enhances bending strength; number of teeth affects curvature radius and form factor (pinion z1 ≥ 17-20 is recommended); face width linearly improves both strengths (face width factor ψ_d = 0.8-1.4); helix angle increases contact length (β = 8°-15°); profile shift coefficient optimizes contact path.

• Materials and processes: Carburizing and quenching (for high loads), induction hardening (for medium loads), and quenching and tempering (for general loads) are common heat treatments; shot peening enhances fatigue limit, surface coating improves wear resistance, and grinding/polishing reduces roughness.

4. Design Applications and Standards

4.1 Advanced Design Methods