Fatigue of Welded structures | Online Calculator

Fatigue Calculators

Fatigue Calculation of a Welded Structures

This calculation determines the cyclic strength of welded structures. The calculation is performed for the most common types of welded joints and product loading conditions.

To perform calculations, the maximum σmax and minimum σmin tensile (compressive) cyclic stresses, as well as the material category should be specified.

The calculation of the number of allowable loading cycles has been performed in two ways, namely, Ncrack according to the limit state criterion (formation of a fatigue crack 2-3 mm deep) and Nstress according to the maximum allowable stresses.

The fatigue strength of welded joint σR and cycle asymmetry coefficient Rσ are also calculated.

INITIAL DATA

σmax - Maximum tensile (compressive) stress of loading cycle;

σmin - Minimum tensile (compressive) stress of loading cycle.

RESULTS DATA

Rσ - Cycle asymmetry coefficient;

σR - Fatigue strength;

Ncrack - Number of loading cycles to fatigue crack formation;

Nstress - Number of loading cycles according to the criterion of permissible stresses.

Maximum stress (σmax)

Minimum stress (σmin)

Low carbon steel

Low alloy steel

High strength steel

Cycle asymmetry coefficient (Rσ)

Fatigue strength (σR)

Number of cycles (Ncrack)

Number of cycles (Nstress)

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BASIC FORMULAS

Calculation performed for most common types of welds.

Cycle asymmetry coefficient:

Rσ = σmax / σmin;

Number of loading cycles Nstress:

σmax = σR*e A / [Nstress + B];

σR - fatigue strength, determined from diagrams;

A, B - coefficients, depending on the ratio of σmax / σmin;

Number of loading cycles Ncrack:

σmaxm*Ncrack = σRm*NG;

NG = 2*106 - base number of cycles to failure;

Exponent m is defined through parameters A, B, σR.

INITIAL DATA

σmax - Maximum tensile (compressive) stress of loading cycle;

σmin - Minimum tensile (compressive) stress of loading cycle.

RESULTS DATA

Rσ - Cycle asymmetry coefficient;

σR - Fatigue strength;

Ncrack - Number of loading cycles to fatigue crack formation;

Nstress - Number of loading cycles according to the criterion of permissible stresses.

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