1,721,012 research outputs found
Influence of fretting fatigue parameters on fatigue life and crack orientation
No full textCoupled metallic structural components, subjected to vibrations or small oscillatory movements, are prone to fretting, which can significantly affect their fatigue behaviour. Despite the numerous efforts in recent decades to investigate the influence of fretting parameters (such as fretting loading, friction coefficient, relative slip amplitude, contact geometry, surface finishing, different materials, testing environment) on the fatigue behaviour of the analysed components, research in this field is still open. In the present paper, experimental tests available in the literature, carried out on Al-4Cu specimens in partial slip regime with cylindrical fretting pads, are simulated through an analytical methodology proposed by the present authors. Satisfactory results in terms of both crack orientation and fatigue life are obtained by employing such a methodology. Then, a parametric study on the fretting parameters used as input data for this analytical methodology is performed in the present research work, in order to evaluate their influence on the fatigue life and crack orientation of fretting-affected structural components
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
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
Fatigue behaviour assessment of ductile cast iron smooth specimens
Full text linkIn the present paper, the fatigue behaviour of two Ductile Cast Irons (DCIs) is analyzed. Both infinite and finite life fatigue tests are simulated by employing the Carpinteri et al. criterion. Such tests, found in the literature, are related to DCI smooth specimens subjected to proportional and non-proportional constant amplitude cyclic loadings. The theoretical results are compared with the experimental ones in terms of both fatigue endurance and fatigue life
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
Total life approach analysis of ductile cast iron smooth specimens
No full textDuctile cast irons (DCIs) offer an interesting combination of good castability and high mechanical properties, with acceptable costs. DCI structural components are widely used in important applications like automotive components (e.g. crankshafts and truck axles), wind turbines components and pipelines components (e.g., valves, fit-tings and pipes). In this paper, several sets of fatigue tests, available in the literature, are simulated by using a total life approach, and the fatigue lifetime is computed. The examined ductile cast iron EN-GJS-400-18 specimens were alternatively subjected to tensile and torsional loading, and to in-phase and out-of-phase combined bending and torsion. The obtained results are compared with experimental ones, and a quite good accuracy of the criterion used is observed for the simulated tests
A Novel Damage Parameter for Fatigue Life Assessment under Non-Proportional Loading
No full textAs is well-known, the loading non-proportionality has a significant influence on fatigue process, since the rotation of principal stress/strain axes can lead to additional cyclic hardening. In order to accurately reflect the effect of additional cyclic hardening on the predicted lifetime, Vantadori has recently formulated a strain-based fatigue criterion which implements a novel strain factor (function of material constants and degree of non-proportionality) in the damage parameter relationship. By considering some experimental data available in the literature, the goal of the present paper is to discuss the accuracy of the present criterion in estimating fatigue lifetime of metallic components, especially under non-proportional loading
Effect of the porosity on the fatigue strength of metals
No full textIn the present paper, a procedure for fatigue strength assessment of metals containing solidification defects is employed to analyze the fatigue behavior of a ductile cast iron (DCI) characterized by a relevant micro-shrinkage porosity. The procedure implements (i) a statistical method deriving from extreme value theory, (ii) the (Formula presented.) -parameter model, and (iii) the multiaxial critical plane-based criterion by Carpinteri et al. According to the above statistical method, both the distribution of defects and the return period are determined. More precisely, the return period is computed by also exploiting a relationship here proposed to optimize the accuracy of the procedure in terms of fatigue strength estimation. The great potential of the present procedure is that the defect content analysis (performed by means of a statistical method deriving from extreme value theory) can be easily performed using machine learning techniques
A novel procedure for damage evaluation of fillet-welded joints
Full text linkIn the present paper, a novel procedure for fatigue resistance assessment of fillet-welded joints under complex random loading is proposed. It consists of two consecutive steps: (1) computation of the stress tensor at the verification point; (2) evaluation of damage and, consequently, fatigue life. The procedure exploits the multiaxial critical plane-based criterion by Carpinteri et al. for random loading. A case study, represented by a mechanical component of an arm sprayer used in agriculture, is examined in order to assess such a procedure. A comparison between experimental and numerical results in terms of crack nucleation location is performed
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