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摩擦学·摩擦磨损润滑
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摩擦学·摩擦磨损润滑
12
engines
静摩擦与动摩擦(库仑摩擦)
Static vs kinetic friction (Coulomb)
静μs>动μk · F=μN · 摩擦锥 · 临界拉动
F_max,static = μs·N, f_kinetic = μk·N with μs > μk; plus the friction cone and angle of repose tan θ = μs
斯特里贝克曲线 —— 摩擦系数与 Hersey 数
Stribeck curve — friction vs Hersey number
摩擦μ vs Hersey数ηN/P · 边界→混合→流体润滑
How the coefficient of friction changes with viscosity × speed ÷ load across three lubrication regimes
阿查德粘着磨损定律
Archard adhesive wear law
磨损体积V=k·W·L/H · 载荷/滑距/硬度
Estimating worn volume, wear depth and lifetime from the wear coefficient, load, sliding distance and hardness
润滑状态 —— 膜厚比 λ
Lubrication regimes — film parameter λ
边界/混合/流体/弹流 · 膜厚比λ=h/σ
Classifying a contact by λ = h_min / σ, the minimum film thickness over the combined surface roughness
赫兹接触应力(球—平面)
Hertzian contact stress (sphere on flat)
球/柱接触 · 最大压力p0 · 接触半径a
Contact radius, peak pressure and pressure distribution of an elastic contact under normal load
滚动阻力(F = Crr·N)
Rolling resistance (F = Crr·N)
F=Crr·N · 滚动≪滑动 · 轮胎能耗
Why rolling is far cheaper than sliding: hysteresis loss and the coefficient Crr
润滑油黏度—温度曲线与黏度指数
Lubricant viscosity vs temperature & viscosity index
μ随温降 Walther/Arrhenius · 粘度指数VI
Viscosity drops sharply with temperature; the Viscosity Index (VI) measures how flat the curve is — multigrade oils are flatter
弹流润滑最小油膜厚度 —— Dowson–Hamrock 标度
EHL minimum film thickness — Dowson–Hamrock scaling
弹流最小膜厚 · Dowson-Hamrock标度
How a fluid film ~0.1–1 µm thick separates loaded gear and bearing contacts, and why speed rules
黏滑振动(stick-slip)
Stick-slip oscillation
μs>μk+柔度→粘滑振荡 · 锯齿运动
μs > μk with a compliant (spring) drive ⇒ sawtooth 'stick-build-slip-jump' motion
轴承摩擦力矩与功率损耗
Bearing friction torque & power loss
T=μ·W·r · 滑动/滚动轴承摩擦力矩
Friction torque T = μ·W·r, power loss P = T·ω; rolling bearings have tiny μ, plain bearings an order of magnitude higher
滑动轴承 PV 极限
Plain bearing PV limit
压力×速度PV极限 · 滑动轴承选材
Computing bearing pressure P and sliding velocity V from load and speed, and checking P·V against the material PV limit
表面粗糙度 Ra / Rq / Rz
Surface roughness Ra / Rq / Rz
Ra/Rq(RMS)/Rz · 由轮廓算粗糙度参数
Computing the arithmetic average Ra, the RMS Rq and the five-length peak-to-valley Rz from a sampled profile