1,721,290 research outputs found
Fretting-fatigue analysis of shot-peened aluminium and titanium test specimens
Full text linkIn the last decades, many alleviation measures were proposed in order to improve the life of fretting fatigue-affected components. In such a context, the shot peening treatment is worth noting. Therefore, in the present paper, the fatigue life of shot-peened aluminium and titanium alloy specimens, subject to fretting fatigue under partial slip regime, is assessed by means of the Carpinteri et al. criterion for fretting fatigue. First, according to the superposition principle, the relaxed residual stresses (due to the shot peening treatment) are combined with the stress components due to fretting fatigue loading. Then fretting fatigue assessment is performed. In such a context, a novel theoretical law for the relaxed residual stress field is here proposed, the implementation of which shows very promising results in terms of fretting fatigue life estimation of the shot-peened specimens examined
Fretting fatigue and shot peening: a multiaxial fatigue criterion including residual stress relaxation
No full textFretting fatigue damage is a typical material damage arising in mechanical components. In such a damage condition, surface cracks can initiate at the surface contact zone, and under a fluctuating loading they can grow up to the complete failure of the component, resulting in a catastrophic failure. In order to prevent/mitigate fretting fatigue damage, shot peening is widely used in mechanical components. The improvement due to shot peening is related to different factors, but the main one is the compressive residual stress field produced by such a treatment in a region near the contact surface. Unfortunately, both the uncertainty in measurements and stability (relaxation) of residual stress field, make shot peening effects difficult to be included in models aimed to the estimation of fatigue life. Due to this lack in the literature, especially relatively to the fretting fatigue field, in the present paper a new fretting fatigue model, that is able to consider shot peening residual stress and its relaxation, is presented. A 3D elastic-plastic finite element model, which incorporates the shot peening residual stress and its relaxations, is employed. The results obtained, in terms of stress field, are used as input data of a multiaxial stress-based criterion to estimate both fatigue lifetime and crack initiation direction
Fretting fatigue of 7050-T7451 Al alloy: the influence of bulk mean stress
No full textFretting fatigue is a combination of fatigue and micro-sliding due to fretting. The aim of the present work is to estimate crack initiation direction, endurance strength and lifetime of aluminium 7050-T7451 alloy specimens. The experimental campaign examined is devoted to investigate the role of the mean bulk stress on fretting fatigue behaviour. The above estimations are performed by using the Carpinteri et al. criterion for fretting fatigue. In such a context, the accuracy of the criterion is verified
Lifetime estimation of mechanical assemblies under constant amplitude fretting fatigue loading
No full textIn 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
In un contesto più ampio
No full textIl volume contiene una serie d isaggi sulla teoria e la pratica dei Piani per la salute, strumenti di promozione della salute attuati nella regione Emilia-Romagna
Il caso di Imola
No full textIl capitolo descrive l'esempio di attuazione del Piano per la salute nella realtà di Imola e ne sottolinea la ampia partecipazione e l'innovativa struttura democratica utilizzata
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Fracture behaviour of cracked nanobeams by means of the stress-driven non-local model
No full textIn the present paper, the Mixed Mode fracture behaviour of nanobeams under static loading is investigated by using the stress-driven nonlocal theory of elasticity, according to the Bernoulli-Euler beam theory. More precisely, an edge-cracked nanobeam is examined. Such a cracked nanobeam is modelled by using a modification of the classical cracked-beam theory, consisting in dividing the nanobeam into two beam segments connected through a massless elastic rotational spring located at the cracked cross-section. The deflection is obtained for different values of both relative crack depth and crack orientation. Further, the dimensionless transversal displacement along the beam length is determined considering a crack length equal to half of the beam height and characterised by different orientations
The RED criterion for fatigue life assessment of metals under non-proportional loading
No full textIn the present paper, a novel criterion for fatigue life assessment of engineering components under multiaxial low-cycle fatigue regime is proposed. The criterion, named Refined Equivalent Deformation (RED) criterion, allows to take into account, when the load is non-proportional, the fatigue strength decrease experimentally observed for those metals sensitive to non-proportionality. The criterion is applied to two different metals (304 stainless steel and 6061 aluminum alloy) characterised by different non-proportional sensitivities. The accuracy of such a criterion is compared with those of other criteria available in the literature
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