Crack Paths 2012

1. Registration, generation, calculation:

σij(t), εij(t), (i,j=x, y, z)

2. Determination of the critical plane position

3. Calculation of the equivalent history σeq(t)

4. Cycle and half-cycle counting (rain flow)

5. Calculation of the damage degree S(TO)

6. Calculation of the fatigue life TCAL

Figure 1. Algorithm for determination of the fatigue life of materials under multiaxial

service loadings.

The aim of the paper is comparison of the variance method and the method of

damage accumulation for determination of the critical plane position with the results of

experiments.

E X P E R I M E N T S

Specimens of round sections were tested (see Fig. 2). Those were cut from the sheets

16 m m thick, according to the rolling direction. The specimen surface have been

obtained by turning followed using conventional polishing with progressively finer

emery papers. A final average roughness 0.16 μ mhas been measured. Diameter of the

specimens was d = 8 m mfor pseudo-random loading. Somemechanical properties of

the tested steel are given in Table 1. The tests were performed, in the high cycle fatigue

regime (HCF) under variable amplitude and pseudo-random bending with torsion

loading, at Opole University of Technology [6]. The fatigue stands was used to carry

out fatigue tests. The stand MZGS-200PL(pseudo-random loading), with the

dominating frequency 28.8 Hz for bending and 30 Hz for torsion, is applied for fatigue

tests of specimens made of structural materials subjected to non-proportional

combinations of the bending momentM Band the torsional momentMT.

Figure 2. Shape and dimensions of specimen, dimensions in mm.

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