What is stress concentration factor Kt?

Kt is the ratio of maximum local stress to nominal stress at a geometric discontinuity. Kt = σ_max / σ_nom. It depends only on geometry, not material. A circular hole in a wide plate under tension has Kt ≈ 3.0.

What causes stress concentrations?

Any abrupt change in geometry: holes, notches, fillets, keyways, threads, grooves, changes in cross-section. The stress flow lines crowd together at these features, increasing local stress.

How does Kt affect fatigue life?

Stress concentrations dramatically reduce fatigue life because fatigue cracks initiate at the point of highest stress. The fatigue notch factor Kf ≤ Kt accounts for material sensitivity: Kf = 1 + q(Kt-1), where q is the notch sensitivity factor.

How can stress concentrations be reduced?

Use generous fillet radii, avoid sharp corners, use gradual transitions, add relief grooves near shoulders, polish surfaces at critical points, and use shot peening to introduce beneficial compressive residual stress.

What is Peterson's Stress Concentration Factors?

Peterson's is the definitive reference book containing charts and equations for Kt values for hundreds of geometric configurations. It provides Kt as a function of geometric ratios (r/d, D/d, etc.) for tension, bending, and torsion loading.

Ferramenta de Engenharia Gratuita

Calculadora do Fator de Concentração de Tensão

Consulte Kt para geometrias comuns — furo em chapa, raiz de ombro, entalhe em U — usando dados simplificados dos gráficos de Peterson’s.

Gráficos de Peterson’sConsulta de Kt#173

Resultados

Fator de Concentração de Tensão Kt

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Tensão Local Máxima σ_max

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Relação Geométrica

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Fator de Concentração de Tensão

Valores Típicos de Kt

Geometria	Intervalo de Kt
Furo central em chapa larga	~3,0 (d/W pequeno)
Raiz de ombro (D/d=2, r/d=0,1)	~1,8–2,5
Entalhe em U	~1,5–3,5
Rebaixo circunferencial	~1,5–3,0

⚠️ Nota: Estes são valores aproximados de equações simplificadas de ajuste de curvas. Para valores precisos, consulte Peterson’s Stress Concentration Factors ou realize uma análise por elementos finitos (FEA). Kt é apenas para análise elástica.