Papers by Author: Franco Furgiuele

Abstract: The Navier-Stokes equation is currentlyconsidered for modelling of squeeze-film damping in MEMS devices, also when the fluid flow associated to it is rarefied.In order to include rarefaction effects in such equation, a common approach consists of replacing the ordinary fluid viscosity with a scaled quantity, known as effective viscosity.The literature offers different expressions for the effective viscosity as a function of the Knudsen number (K_n). Such expressions were shown to work well whenK_n<1, but theyresulted to be lessaccurate in case ofK_n>1. In this paper a new expression is proposed to evaluate the effective viscosity for 1<K_n<40with increased reliability. Such anexpression was derivedfrom an optimized numerical-experimental procedure,developed in MATLAB^® environment, using a finite element code and experimental data extracted from the literature. A comparison is finally reported and discussed between the results, in terms of damping coefficient, obtained considering previously reported effective viscosity expressions and the novel one,with reference to different squeeze film damping layouts, for which experimental data are already available.

Abstract: Aluminum (Al) and Magnesium (Mg) alloys are nowadays widely employed in order to produce lightweight automotive and aeronautical components and to gain fuel saving and reduced emissions. However, the joining of Al and Mg alloys poses well known technical problems and the application of conventional joining techniques, e.g. welding, may be ineffective. On the other hand, adhesive bonding may be considered as a candidate replacement of the traditional techniques and for this reason it has been recently proposed as an alternative technology for Al/Mg joints. In particular, it has been demonstrated that adhesive bonding, in conjunction with state-of-the-art surface treatments, can provide Al/Mg joint with enhanced strength. However, in order to evaluate the potential of adhesive bonding to outperform the conventional joining techniques a systematic comparative analysis is needed. Therefore, the aim of this work is to supplement the existing studies on Al/Mg bonding providing a comparative analysis between Al/Mg joints prepared using gas metal arc (MIG) welding, riveting and adhesive bonding. Probably, the use of adhesive bonding as complementary joining process will be the industrial answer to the hybrid joints performance needs.

Abstract: This paper deals with the application of Cohesive Zone Model (CZM) concepts to study mode I fracture in adhesive bonded joints. In particular, an intrinsic piece-wise linear cohesive surface relation is used in order to model fracture in a pre-cracked bonded Double Cantilever Beam (DCB) specimen. Finite element implementation of the CZM is accomplished by means of the user element (UEL) feature available in the FE commercial code ABAQUS. The sensitivity of the cohesive zone parameters (i.e. fracture strength and critical energy release rate) in predicting the overall mechanical response is first examined; subsequently, cohesive parameters are tuned comparing numerical simulations of the load-displacement curve with experimental results retrieved from literature.

Abstract: The aim of the present paper is to evaluate the interfacial fracture toughness of an Al/Epoxy adhesive system with a crack lying at the interface. A cracked lap shear specimen loaded in four point bending is adopted and the fracture toughness is pointed out in terms of the critical complex stress intensity factor. To this aim numerical analyses of the fracture specimen have been carried out using a commercial finite element code. In addition, fracture surfaces are analyzed and the locus of failure is discussed.