# Fatigue strength of welded components

## Values for calculation

$e_n$ $\mathrm{mm}$
$T^*$ $\mathrm{°C}$
$Δσ_{eq}$ $\mathrm{MPa}$
$m_1$
$C_1$
$m_2$
$C_2$
$Δσ_D$ $\mathrm{MPa}$
$Δσ_{Cut}$ $\mathrm{MPa}$

## Calculation

### Thickness correction factor in welded components

$\text{if }\ e_n> 150$
$$f_{ew}=\left(\cfrac{25}{150}\right)^{0.25}$$
$\text{else if }\ e_n\le 25$
$$f_{ew}=1$$
$\text{else}$
$$f_{ew}=\left(\cfrac{25}{e_n}\right)^{0.25}$$

### Temperature correction factor

$\text{if }\ T^*\le 100$
$$f_{t^*}=1$$
$\text{else if }\ \text{type }$$\text{of }$$\text{material}=\text{ferritic material}$
$$f_{t^*}=1.03-1.5\cdot 10^{-4}\cdot T^*-1.5\cdot 10^{-6}\cdot {T^*}^2$$
$\text{else if }\ \text{type }$$\text{of }$$\text{material}=\text{austenitic material}$
$$f_{t^*}=1.043-4.3\cdot 10^{-4}\cdot T^*$$
$\text{else}$
$$f_{t^*}=1$$

### Overall correction factor applied to welded components

$$f_w=f_{ew}\cdot f_{t^*}$$

### Allowable number of cycles obtained from the fatigue design curves

$\text{if }\ \cfrac{Δσ_{eq}}{f_w}\geq Δσ_D$
$$N=\cfrac{C_1}{\left(\cfrac{Δσ_{eq}}{f_w}\right)^{m_1}}$$
$\text{else if }\ Δσ_{Cut}< \cfrac{Δσ_{eq}}{f_w}< Δσ_D$
$$N=\cfrac{C_2}{\left(\cfrac{Δσ_{eq}}{f_w}\right)^{m_2}}$$
$\text{else}$
$$N={INF}$$