A B S T R A C T The myriad applicability of the frequency-domain critical plane criterion is outlined in order to evaluate and track the progression of fatigue damage in metallic structures subjected to high-cycle multiaxial random vibrations. The fatigue assessment using the given criterion is performed according to the following stages: (i) critical plane definition, (ii) power spectral density evaluation of an equivalent normal stress and (iii) computation of the damage precursor and fatigue life. The frequency-domain critical plane criterion is validated using experimental results related to (a) AISI 1095 steel cantilever beams under nonlinear base vibration, (b) 18G2A steel and (c) 10HNAP steel round specimens under random non-proportional combined flexural and torsional loads.Keywords damage precursor; frequency domain; high-cycle fatigue; multiaxial loading; random loading; vibration fatigue. Z ' = rotated frame Puvw = reference system related to the critical plane S eq (ω) = equivalent PSD function s xyz (t) = stress vector in PXYZT = time interval of observation T cal = fatigue life determined through calculations T exp = fatigue life through experiments α n = nth bandwidth parameter, with n = 1,2,3, … γ = rotation about the w axiŝ 1;2 and3 = rotation about the X ' axis λ n = nth spectral moment, with n = 1,2,3, … σ af = fatigue limit for fully reversed normal stress (R = À 1) σ 2 6';6' = variance of s 6 ' t ð Þ σ 2 6};6} = variance of s 6 } t ð Þ τ af = fatigue limit for fully reversed shear stress (R = À 1) ω = pulsation Correspondence: S. Vantadori.

The goal of the present paper is to discuss the reliability of a strain-based multiaxial Low-Cycle Fatigue (LCF) criterion, recently proposed by some of the present authors, in estimating the fatigue lifetime of metallic structural components weakened by sharp notches. Such a criterion, based on the critical plane approach, is formulated according to the control volume concept related to the Strain Energy Density (SED) criterion: a material point located at a certain distance from the notch tip is assumed to be the verification point where to perform the fatigue assessment. The above distance is assumed to be a function of both the biaxiality ratio (applied shear stress amplitude over normal stress amplitude)  phase angle between transversal normal strain t  and axial normal strain z  ur  , ut  , uz  direction cosines of u -axis vr  , vt  , vz  direction cosines of v -axis wr  , wt  , wz  direction cosines of w -axis  phase angle between shear strain zt  and axial normal strain z  a  Manson-Coffin shear strain amplitude zt  shear strain  angle between the averaged principal strain direction 1 and the normal w to the critical plane

The present paper is devoted to the assessment of synergy due to the combined use of metallic and synthetic fibres in concrete matrix. Such an evaluation is performed both at first cracking stage by computing fracture toughness, and at post-peak stage by determining two toughness indexes. The results from experimental three-point bending tests on concrete specimens reinforced with copper-coated steel fibres and polypropylene fibres are employed for such computations. The novelty of this research work is that the Mixed Mode loading effect occurring at crack tip is taken into account when computing fracture toughness. Plain concrete specimens and specimens reinforced with only one type of fibres are experimentally and analytically examined for comparison.

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Nowadays, research on sustainable buildings is devoted to materials which offer advantages in terms of recyclability, low 3

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In the present paper, a new analytical methodology to estimate both crack path and lifetime of metallic structural components under fretting fatigue elastic partial slip loading condition is proposed. Such a methodology consists in the joint application of (a) the criterion by Carpinteri et al for metallic structures under multiaxial constant amplitude fatigue loading in high‐cycle fatigue regime, (b) the critical direction method by Araújo et al, and (c) the critical distance method by Taylor, in the form of the line method. The accuracy of the above methodology is evaluated through experimental tests available in the literature, performed employing two cylindrical fretting pads pressed with a constant normal load against a dog‐bone type test specimen subjected to a cyclic axial load. All these components are made of Al 7075‐T651 aluminium alloy.