Deutsches Institut fur Normung e. V.

Calculation of load capacity of shafts and axles - Part 1: General
 N 743-1

Annotation

This standard applies to the calculation and verification of the safety of axles and shafts against:

- fatigue failure (endurance failure) if the fatigue strength is exceeded;

- permanent deformation (or incipient cracking or overload breakage).

The calculation of the factor of safety against fatigue failure is based on constant equivalent damaging stress amplitudes. These result from the agreed loadings or are to be determined by appropriate failure theories. For the calculation of the factor of safety against permanent deformation, the maximum possible stress is used. This is obtained by using the agreed or determined maximum load (see [1]).

The scope of this standard is limited to steel. Welded components are to be considered separately, and this standard does not apply to them.

To calculate the fatigue strength it is assumed that the amplitudes of the individual types of loading (tension/compression, bending, torsion) occur at the same point in time.

Residual stresses are not explicitly considered in the calculation. In the case of hard surfaces, they are globally taken into account by the sensitivity factor n and the influence factor for surface conditioning KV.

The change in fatigue strength due to residual stress caused by local deformation has not yet been sufficiently investigated, so that this influence cannot yet be calculated. For boundary cases (components the failure of which results in heavy consequential damage), experimental studies or, alternatively, monitoring within the scope of inspections, may be required, in particular when overloading causes residual tensile stresses. As to the current situation regarding ductile materials, it has not yet been established that local plastic deformation and thus, residual stresses, have an essential influence on fatigue strength.