0000000000785180
AUTHOR
T. Lagoda
Fatigue life estimation for 30CrNiMo8 steel under in- and out-of-phase combined bending and torsion with variable amplitudes
Fatigue life successively calculated according to three criteria of multiaxial fatigue for randomly varying loading is compared with fatigue life obtained by Sanetra and Zenner in testing cylindrical specimens of 30CrNiMo8 steel by in- and out-of-phase bending and torsion with variable amplitudes. The position of the plane of fatigue fracture is determined using the variance method. The histories of equivalent stresses are schematically represented by the Monte Carlo method. Fatigue damage was computed using the Palmgren-Miner hypothesis. The most realistic estimates of fatigue life in the scatter band of the results with a factor of 3 are obtained on the basis of the criterion of maximum t…
The influence of alternate block loading on the fatigue lifetime
The paper presents the results of fatigue tests of cylinder specimens made of duralumin PA6 under alternate block loading for bending and torsion. Each block contains n and n cycles with sinusoidal course. Based on the fatigue curves amplitudes suitable for 105, 3·105 and 106 number of cycles to failure were determined. The loading was applied in alternate two-amplitudes blocks by 104, 3·104 or 105 each one (10% of the fatigue life for the given loading level) until failure of the specimen (fig.1).
Comparison of different methods for presenting variable amplitude loading fatigue results
This paper discusses eight methods for presenting fatigue test results for variable amplitude loading and their comparison with constant amplitude loading. While the maximum amplitude method compares constant and variable amplitude loading results by the Woehler and Gassner curves, all other seven methods try to transform the variable amplitude results into the Woehler curve by applying different equations. The advantage of the maximum amplitude method is the direct comparison of the maximum amplitude of the spectrum with the yield strength and with the high-cycle fatigue strength, which is an important step in structural design. Among the other methods, the best results were obtained by fo…
Spectral analysis of the criteria for multiaxial Random Fatigue
In the paper the spectral analysis of several fatigue criteria under simple and complex states of stress has been done and limitations appearing while formulating new criteria for multiaxial random loadings have been shown. The presented analysis includes determination, with digital simulation, of probability density function and power spectral density function of the equivalent stress according to three special linear criteria of multiaxial random fatigue and six nonlinear criteria. Calculations were carried out for four kinds of random stress state. It has been shown that mathematical models for the criteria of multiaxial random fatigue formulated as nonlinear combinations of stress state…