Equivalent Static Load (Bearing)
Calculate a bearing's equivalent static load, P_0 = X_0·F_r + Y_0·F_a, from the radial load F_r (N), the axial load F_a (N) and the static factors X_0 and Y_0 (tabulated by the maker). Unlike the equivalent dynamic load (related to FATIGUE under rotation), the equivalent static load is used to check the bearing under loads with the bearing STOPPED or turning very slowly, or under PEAK loads (shocks, momentary overloads). The risk here is not fatigue but PERMANENT DEFORMATION (indentation) of the races by the rolling elements: an excessive static load 'dents' permanent marks (brinelling) into the races, which then cause noise, vibration and early failure when the bearing turns again. The equivalent static load is the pure radial load that would cause the same maximum permanent deformation (at the most-loaded contact) as the real radial-axial combination. It is compared with the bearing's static load rating C0 (also tabulated) via the static safety factor s0 = C0/P0. This check is especially important in bearings carrying loads with the machine stopped (shafts of equipment parked under load) or subject to shocks. Enter the radial load, axial load and the static factors X0 and Y0.
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Carga estática equivalente (rolamento)
A carga estática equivalente de um rolamento é P_0 = X_0·F_r + Y_0·F_a, a partir da carga radial F_r, da carga axial F_a e dos fatores estáticos X_0 e Y_0 (tabelados). Diferente da carga dinâmica equivalente (que se relaciona à fadiga sob rotação), a carga estática equivalente é usada para verificar o rolamento parado ou girando muito devagar, ou sob cargas de pico (choques, sobrecargas momentâneas). O risco nesse caso não é a fadiga, mas a deformação permanente (indentação) das pistas pelos corpos rolantes: uma carga estática excessiva 'amassa' marcas permanentes (brinelling) nas pistas, que depois geram ruído, vibração e falha prematura quando o rolamento volta a girar. A carga estática equivalente é a carga radial pura que causaria a mesma deformação permanente máxima que a combinação real. Ela é comparada com a capacidade de carga estática C0 do rolamento (também tabelada) pelo fator de segurança estático s0 = C0/P0. Essa verificação é especialmente importante em rolamentos que sustentam cargas com a máquina parada (eixos de equipamentos estacionados sob carga), ou que sofrem choques. Informe a carga radial, a carga axial e os fatores estáticos X0 e Y0.
Related Tools
Static Safety Factor (Bearing)
Calculate a bearing's static safety factor, s_0 = C_0 ÷ P_0, from the static load rating C_0 (N, tabulated by the maker) and the equivalent static load P_0 (N). The static safety factor compares the bearing's ability to resist PERMANENT DEFORMATION (race indentation) with the equivalent static load it actually carries. The static rating C_0 is, by definition, the load causing a total permanent deformation of 0.0001 of the rolling-element diameter at the most-loaded contact — a small value, taken as the acceptable limit (above it, the marks cause noise and vibration when turning). The factor s_0 shows the margin: codes and makers recommend MINIMUM s_0 values per application and smoothness requirements — typically s_0 ≥ 1-1.5 for normal, quiet operation, possibly lower (0.5-1) for low-speed, undemanding applications, and higher (≥2-3) for heavy shocks or high precision. This check is COMPLEMENTARY to the life (fatigue) check: a bearing may have ample L10 life but fail by static deformation under a peak overload if s_0 is insufficient. Both checks — dynamic (life) and static (s_0) — must be met. Enter the static rating and the equivalent static load.
Equivalent Dynamic Load (Bearing)
Calculate a bearing's equivalent dynamic load under combined loading, P = X·F_r + Y·F_a, from the radial load F_r (N), the axial load F_a (N) and the factors X and Y (dimensionless, tabulated by the maker per bearing type and the F_a/F_r ratio). Most bearings actually carry RADIAL (perpendicular to shaft) and AXIAL (along shaft) loads at once, but catalog life and capacity formulas are defined for an equivalent pure radial load. The equivalent dynamic load is that fictitious radial load that would give the SAME bearing life as the real load combination. The X and Y factors depend on the bearing type (deep-groove ball, angular contact, self-aligning, tapered roller) and the axial-to-radial ratio — for mainly radial loads, X≈1 and Y≈0 (axial negligible); when axial grows past a limit (the e factor), Y starts to contribute. Computing P correctly is the first step in any bearing design, since P enters the life formula L10 = (C/P)^p and the capacity check. Wrong factors (or ignoring axial load) give an incorrect life estimate. Enter the radial load, axial load and the X and Y factors.
Cubic Mean Load (Bearing)
Calculate the equivalent mean load of a bearing under a cycle with two different loads, P_m = ∛(P₁³·U₁ + P₂³·U₂), from the loads P₁ and P₂ (N) and the time (or revolution) fractions during which they act U₁ and U₂ (with U₁ + U₂ = 1). Many bearings do not work under CONSTANT load: the load varies over the operating cycle (a press loading and unloading, a motor accelerating and decelerating, a machine with different work phases). To compute life in this case, the variable cycle is replaced by an equivalent CONSTANT load causing the same fatigue damage — the mean load. But the mean is NOT arithmetic: since fatigue damage is proportional to load CUBED (the life exponent p=3), the mean load is a time-fraction-weighted mean, but with the loads cubed (then cube-rooted) — the so-called cubic mean or 'fatigue-weighted mean'. This makes HIGH loads weigh disproportionately more (a double load causes 8× more damage), so even a small fraction of time at high load dominates the result. This formula (here for two load levels; it generalizes to several) is essential to size bearings in variable-load machines, avoiding underestimating the damage. Enter the two loads and their time fractions.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.