1,721,054 research outputs found
Fracture behaviour of nanobeams through Two-Phase Local/Nonlocal Stress-Driven model
Full text linkThe aim of the present work is to employ the two-phase local/nonlocal Stress-Driven integral Model (SDM) to analyse the size-dependent Mode I fracture behaviour of Bernoulli-Euler cracked nanobeams, in terms of energy release rate, stress intensity factor and nonlocal stress field near the crack tip. Both edge- and centrally-cracked nanobeams, subjected to concentrated forces, are examined. The edge-cracked nanobeam is modelled as a pair of cantilever nanobeams, whereas the centrally-cracked nanobeam as a pair of double-clamped nanobeams with internal discontinuity due to concentrated loads. Moreover, a comparison with the results obtained from a gradient elasticity theory based model, available in the literature, is performed. From the present study, it is observed that the energy release rate decreases by increasing the nonlocality, showing the superior fracture performance of nanobeams with respect to large-scale beams
Nanobeams with internal discontinuities: A local/nonlocal approach
Full text linkThe aim of the present work is to extend the two-phase local/nonlocal stress-driven integral model (SDM) to the case of nanobeams with internal discontinuities: as a matter of fact, the original formulation avoids the presence of any discontinuities. Consequently, here, for the first time, the problem of an internal discontinuity is addressed by using a convex combination of both local and nonlocal phases of the model by introducing a mixture parameter. The novel formulation here proposed was validated by considering six case studies involving different uncracked nano-beams by varying the constrains and the loading configurations, and the effect of nonlocality on the displacement field is discussed. Moreover, a centrally-cracked nanobeam, subjected to concentrated forces at the crack half-length, was studied. The size-dependent Mode I fracture behaviour of the cracked nanobeam was analysed in terms of crack opening displacement, energy release rate, and stress intensity factor, showing the strong dependency of the above fracture properties on both dimensionless characteristic length and mixture parameter values
Computational approach to fatigue behaviour of randomly or unidirectional fibre reinforced materials
No full textThe reinforcement of materials by means of fibres has been recognised to be a simple and effective way to enhance the mechanical properties. Usually the tensile strength, the wear resistance, the durability, the fracture and fatigue resistance are the main mechanical characteristics that can be improved by such a reinforcing technique. Therefore, fibrereinforced composite (FRC) materials are widely used in highly stressed structural applications, and suitable mechanical models are being developed. The present paper extends a previous mechanical-based homogenisation approach proposed by the authors for the mesoscopic description of fibre-reinforced materials under cycling loading, by taking into account the fatigue matrix degrading effects and fatigue fibre-matrix debonding. In particular, fatigue loading are responsible for the degradation of the fibre-matrix interface and, consequently, the reduction of the bearing capacity of such materials. By analyzing the debonding phenomenon through fracture mechanics, the detaching process can be quantified by means of classical fatigue laws. By also taking into account the degrading effects on the matrix material, a global damage parameter (d) for the composite being examined can be defined. The developed mechanical model, implemented in a FE code, is used to simulate the static and fatigue behaviour of FRC materials and the results are compared with literature data
A novel methodology for fatigue assessment of high strength steels with non-metallic inclusions
No full textIn the present paper, the multiaxial critical plane-based criterion proposed by Carpinteri et al. is employed in conjunction with the varea-parameter model by Murakami and Yanase for the fatigue assessment of high strength steels, where the influence of non-metallic inclusions on fatigue life is taken into account. An experimental campaign, available in the literature and performed on AISI 4140 steel specimens, is analysed to evaluate the criterion accuracy. The obtained results in terms of fatigue lifetime are compared with those experimentally obtained, showing a quite satisfactory agreement
Fracture analysis of nanobeams based on the stress-driven non-local theory of elasticity
No full textMode I fracture behavior of edge- and centrally-cracked nanobeams is analyzed by employing both stress-driven non-local theory of elasticity and Bernoulli–Euler beam theory. The present formulation implements the size-dependency experimentally observed at material micro- and nano-scale, by assuming a non-local constitutive law, that relates the strain to the stress in each material point of the body, through an integral convolution and a kernel. It is observed that the energy release rate decreases by increasing the nonlocality, showing the superior fracture performance of nanobeams with respect to large-scale beams
A novel procedure for the fatigue behaviour assessment of AM metals with defects
No full textThe effect of defects on fatigue performance of AM metals is nowadays the focus of several technical papers, and the Kitagawa-Takahashi diagram is usually employed in order to establish a relationship between fatigue limit and defect size. In such a context, the present paper aims to investigate the defect effect on the fatigue limits of an AM aluminium alloy by exploiting a novel analytical procedure. Such a procedure is based on the joint application of: (i) the Kitagawa-Takahashi diagram, formulated by employing the modified El-Haddad model, for fatigue limit calculations; (ii) the fatigue criterion by Carpinteri et al., based on the critical plane approach, for fatigue strength assessment and lifetime estimation
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
Fatigue life assessment of DCI smooth specimens
No full textDuctile cast iron (DCI) structural components are commonly employed in a wide range of industrial applications. The increasing use of DCI is justified by the good combination of mechanical and technological properties. Another advantage, not negligible, is the low production cost. The goal of the present paper is to estimate the lifetime of ductile cast iron smooth specimens under multiaxial fatigue loading, by using the multiaxial critical plane-based criterion proposed by Carpinteri and others. The obtained results in terms of fatigue life are quite satisfactory, because they fall into the scatter band 3 in almost all loading conditions examined. Finally, the accuracy of the criterion is compared with that obtained by using two stress invariant-based criteria
Fracture analysis of nanobeams based on the stress-driven non-local theory of elasticity
No full textMode I fracture behavior of edge- and centrally-cracked nanobeams is analyzed by employing both stress-driven non-local theory of elasticity and Bernoulli–Euler beam theory. The present formulation implements the size-dependency experimentally observed at material micro- and nano-scale, by assuming a non-local constitutive law, that relates the strain to the stress in each material point of the body, through an integral convolution and a kernel. It is observed that the energy release rate decreases by increasing the nonlocality, showing the superior fracture performance of nanobeams with respect to large-scale beams
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