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.
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Fator de segurança estático (rolamento)
O fator de segurança estático de um rolamento é s_0 = C_0 ÷ P_0, a partir da capacidade de carga estática C_0 (tabelada) e da carga estática equivalente P_0. Ele compara a capacidade do rolamento de resistir à deformação permanente (indentação das pistas) com a carga estática equivalente que ele realmente sofre. A capacidade estática C_0 é, por definição, a carga que causa uma deformação permanente total de 0,0001 do diâmetro do corpo rolante no contato mais carregado — um valor pequeno, considerado o limite aceitável (acima disso, as marcas geram ruído e vibração ao girar). O fator s_0 indica a margem: as normas e os fabricantes recomendam valores mínimos conforme a aplicação — tipicamente s_0 ≥ 1 a 1,5 para operação normal e silenciosa, menor (0,5-1) para baixa rotação e pouca exigência, e maior (≥2-3) para choques fortes ou alta precisão. Esta verificação é complementar à de vida (fadiga): um rolamento pode ter vida L10 de sobra, mas falhar por deformação estática sob uma sobrecarga de pico se s_0 for insuficiente. Ambas as verificações — dinâmica (vida) e estática (s_0) — devem ser atendidas. Informe a capacidade estática e a carga estática equivalente.
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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.
Bearing Speed Factor
Calculate a bearing's speed factor, A = n·d_m, from the rotation n (rpm) and the bearing mean diameter d_m (mm, = (D + d)/2, the average of outer and inner diameters). The n·d_m factor (often in mm·rpm, or m/min times the perimeter) is the key indicator of a bearing's SPEED DUTY, and governs several application limits. It sets the operating LIMIT SPEED: each bearing (and each lubrication type) has a maximum n·d_m above which friction heating, centrifugal force on the rolling elements and dynamic effects make operation unfeasible — grease lubrication tolerates lower values, oil higher, and special systems (oil jet, mist) the highest (high-speed bearings, like turbine and machine-tool spindle bearings, reach n·d_m in the millions). The speed factor also influences the bearing type choice (balls take more speed than rollers), the lubricant and the internal clearance (fast bearings may need larger clearance to accommodate thermal expansion). Comparing the application's n·d_m with the bearing limit is an essential check in medium- and high-speed rotating machines. Enter the rotation and the mean diameter.
Reliability-Adjusted Life (Bearing)
Calculate a bearing's adjusted life for a reliability other than 90%, L_na = a_1·L10, from the reliability factor a_1 (dimensionless) and the nominal life L10 (in millions of revolutions). The standard L10 life corresponds to 90% reliability (10% failures). But many CRITICAL applications — where a bearing failure is unacceptable (turbines, aerospace, medical equipment, continuous-process machines) — require HIGHER reliabilities (95%, 99%, 99.9%). Since demanding higher reliability means accepting FEWER failures, the corresponding life is SHORTER: a_1 is below 1 for reliabilities above 90%. Typical values: a_1 = 1.0 for 90% (L10), 0.64 for 95% (L5), 0.21 for 99% (L1), 0.093 for 99.9% (L0.1). For example, to ensure 99% of bearings survive (instead of 90%), the design life drops to about 21% of L10. This is one of the 'modified life' corrections in the standards (ISO 281), which also include factors for material and lubricant quality and contamination (the more sophisticated a_ISO factor). Adjusting life for required reliability is essential in critical designs: simply using L10 (90%) would be too risky for a turbine, and too conservative for a household fan. Enter the reliability factor and the L10 life.
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.