Issue 38

A. Niesłony, Frattura ed Integrità Strutturale, 38 (2016) 177-183; DOI: 10.3221/IGF-ESIS.38.24 182 the Eq. (8) for PSD of EMS simplify to following expression (18) As we can see cross power spectrum is not present. This function is the only one which includes information about correlation (phase shift for one harmonic component) what can be treat as a proof of the omission of phase shift effect. Figure 2: SN curves uniaxial and biaxial data presented by Cláudio et al. [13]. R EMARKS AND FINAL CONCLUSIONS 1. It is not recommended to use the EMS criterion in a case where the shear stresses dominate, and the ratio of fatigue limits is different from the square root of three. 2. Abnormal behaviour of EMS criterion it can be observed in comparison to experimental results under biaxial tension- compression. For example uniaxial and in-phase biaxial loading give the same equivalent amplitude according this criterion but the test results showing shortening of the fatigue life, see Fig. 2. 3. The impact of non-parallelism of fatigue characteristics on calculated life is significant and depends on loading level. 4. Correlation between normal and shear stress components are neglected. Therefore, this criterion can be used for materials that do not show sensitivity to the phase shift between these components. R EFERENCES [1] Karolczuk, A., Macha, E., A review of critical plane orientations in multiaxial fatigue failure criteria of metallic materials, Int J Fract., 134 (2005) 267–304. doi:10.1007/s10704-005-1088-2. [2] Wang, Y., Susmel, L., The Modified Manson–Coffin Curve Method to estimate fatigue lifetime under complex constant and variable amplitude multiaxial fatigue loading, Int. J. Fatigue., 83 (2016) 135–149. doi:10.1016/j.ijfatigue.2015.10.005. [3] Ince, A., Glinka, G., A generalized fatigue damage parameter for multiaxial fatigue life prediction under proportional and non-proportional loadings, Int. J. Fatigue. 62 (2014) 34–41. doi:10.1016/j.ijfatigue.2013.10.007. [4] Pitoiset, X., Preumont, A., Spectral methods for multiaxial random fatigue analysis of metallic structures, Int. J. Fatigue. 22 (2000) 541–550. doi:10.1016/S0142-1123(00)00038-4. [5] Niesłony, A., Comparison of some selected multiaxial fatigue failure criteria dedicated for spectral method, J. Theor. Appl. Mech., 48 (2010) 233–254. [6] de la Fuente, E., An efficient procedure to obtain exact solutions in random vibration analysis of linear structures, Engineering Structures, 30 (2008) 2981–2990. doi:10.1016/j.engstruct.2008.04.015. [7] Huber, M.T., Specific work of strain as a measure of material effort, Archives of Mechanics, 56 (2004) 173–190. [8] v Mises, R., Mechanik der festen Körper im plastisch- deformablen Zustand, Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse, 1913 (1913) 582–592. EMS xx xx xy xy G f G f G f , , ( ) ( ) 3 ( )   10 4 10 5 10 6 10 7 10 8 10 2 N , cycles σ xx,a , σ EMS,a , MPa uniaxial: data uniaxial: fit biaxial δ = 0 ◦ : data biaxial δ = 0 ◦ : fit biaxial δ = 90 ◦ : data biaxial δ = 90 ◦ : fit biaxial δ = 180 ◦ : data biaxial δ = 180 ◦ : fit