static and dynamic response of titanium alloy produced by electron beam melting

Abstract The suitability of Titanium alloys for many specialized applications requiring excellent performances at both static and dynamic strain rates, benefits of modern manufacturing technologies like the additive manufacturing, oriented toward the obtainment of complicated component shapes. The EBM methodology for the production of Ti6Al4V components is based on the localized melting of alloy powders by way of guided electron beams scanning the powder volume by successive planar trajectories; for this reason, the whole production process may confer a certain degree of anisotropy to the components. The material behavior of the EBM alloy may be orientation-dependent in terms of stress-strain elastoplastic response as well as in terms of damage sensitivity and ductile fracture under given triaxiality histories. The static and dynamic behavior of a sintered Ti6Al4V alloy is investigated here by way of quasistatic tension-torsion tests and dynamic tensile Hopkinson bar (SHTB) tests. The outcome of the latter experiments, compared to similar tests results from the literature concerning Ti alloy obtained by classical metallurgical techniques, gives some indications about how the technological process may affect the final performance of the material and the component

Twin-waves propagation phenomena in magnetically-coupled structures

The use of magnetic dipoles embedding in an elastic support introduces long-range interaction forces. This is a completely new paradigm in structural mechanics, classically based on local short-range particle interaction. The features of long-range forces produce very new mechanical coupling effects. This paper examines the case in which two identical rod-like structures, each with a dipole distribution embedded, vibrate side by side. Waves generated in one of the rods propagate also in the second and vice versa creating a new effect we name twin-waves. The present investigation unveils the existence of an infinite number of propagation modes even in one-dimensional infinite structures, a new and unus al behaviour in classical waveguides. The physics behind this phenomenon is further investigated also by numerical simulations

Lagrange and H(curl⁡,B)H(\operatorname{curl},{\cal B}) based Finite Element formulations for the relaxed micromorphic model

Modeling the unusual mechanical properties of metamaterials is a challenging topic for the mechanics community and enriched continuum theories are promising computational tools for such materials. The so-called relaxed micromorphic model has shown many advantages in this field. In this contribution, we present the significant aspects related to the relaxed micromorphic model realization with the finite element method. The variational problem is derived and different FEM-formulations for the two-dimensional case are presented. These are a nodal standard formulation $H^1({\cal B}) \times H^1({\cal B})$ and a nodal-edge formulation $H^1({\cal B}) \times H(\operatorname{curl}, {\cal B})$, where the latter employs the N\'ed\'elec space. However, the implementation of higher-order N\'ed\'elec elements is not trivial and requires some technicalities which are demonstrated. We discuss the convergence behavior of Lagrange-type and tangential-conforming finite element discretizations. Moreover, we analyze the characteristic length effect on the different components of the model and reveal how the size-effect property is captured via this characteristic length

Towards the conception of complex engineering meta-structures: relaxed-micromorphic modelling of mechanical diodes

In this paper we show that an enriched continuum model of the micromorphic type (Relaxed Micromorphic Model) can be safely used to model metamaterials' response in view of their use for meta-structural design. We focus on the fact that the reduced model's structure, coupled with the introduction of well-posed interface conditions, allows us to easily test different combinations of metamaterials' and classical-materials bricks, so that we can eventually end-up with the conception of a meta-structure acting as a mechanical diode for low/medium frequencies and as a total screen for higher frequencies. Thanks to the reduced model's structure, we are also able to optimize this meta-structure so that the diode-behaviour is enhanced for both "pressure" and "shear" incident waves and for all possible angles of incidence.Comment: 19 pages, 18 figures (43 pictures). arXiv admin note: substantial text overlap with arXiv:2007.1494

Identification of aroma compounds of Vitis vinifera L. flowers by SPME GC-MS analysis

Using a gas chromatographic method (GC-MSanalysis), it was possible to determine the volatile constituent of an odorous flower from Vitis vinifera varieties growing in Sicily. More than 50 compounds were identified and the technique allowed us to determine that sesquiterpenes, as well as monoterpenes such as limonene and cymene, were the principal components. The odour-profiles allowed us to distinguish between variety groups or even single varieties.