Fatigue strength of severely notched specimens made of Ti–6Al–4V under multiaxial loading

Abstract

The present paper deals with multiaxial fatigue behaviour of severely notched components made of titanium grade 5 alloy (Ti-6Al-4V). The experimental tests have been carried out under combined Mode I and Mode III loadings, both in phase and out of phase. Cylindrical specimens weakened by circumferential notches have been employed. Different nominal load ratios have been applied in the tests (R = -1, 0 and 0.5). The specimens had a notch-tip radius smaller than 0.1 mm, a notch depth equal to 6 mm and an opening angle of 90. The results obtained by multiaxial fatigue testing are depicted in comparison with data from pure modes of loading on smooth and notched samples, characterized by a load ratio in the range -3 ≤ R ≤ 0.5. A large bulk of new fatigue data (more than 160) is summarized in the manuscript. The data are first plotted in terms of the nominal stress amplitudes, and then they are reanalysed by means of the local energy measured in the control volumes surrounding the notch tip. The dependence of the size of the control radius as a function of the loading mode is analysed. A very different behaviour is found for tension and torsion, corresponding to a different notch sensitivity

Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach

“…6b shows a comparison between the averaged SED-based scatter-band calibrated previously by Berto el al. [24] on about 160 uniaxial and multiaxial experimental data obtained from sharp V-notched Ti-6Al-4V specimens and the new fatigue results relevant to pure bending loading, obtained in the present contribution and expressed in terms of total fatigue life. It can be observed from Fig.…”

“…The control radius R0 for fatigue strength assessment of notched components made of titanium grade 5 alloy has been previously estimated by Berto et al [24] by equating the averaged SED in two situations, i.e. the fatigue limit (or the highcycle fatigue strength) of un-notched and notched specimens, respectively.…”

Local strain energy density for the fatigue assessment of hot dip galvanized welded joints: some recent outcomes

“…Also fatigue data obtained for very thin welded joints have been successfully summarized in terms of the SED ( [31]). Recently, the SED approach has been extended to the fatigue assessment of notched specimens made of Ti-6Al-4V under multiaxial loading [32] and to high temperature fatigue data of different alloys [33]- [35]. A new method to rapidly evaluate the SED value from the singular peak stress determined by means of numerical model has been presented by Meneghetti et al [36].…”

Experimental and FE Modeling of Mixed-Mode Crack Initiation Angle in High Density Polyethylene

“…Moreover, it has been successfully employed for the fatigue strength of welded joints [33][34] and notched components [35,36]. As shown by Lazzarin et al [37], the SED can be easily evaluated numerically through finite element analysis by using coarse meshes, and it allows automatically to take into account higher order terms and three-dimensional effects [38,39].…”