Papers by Gabriella Epasto
Finite element analysis of foam-filled honeycomb structures under impact loading and crashworthiness design
International Journal of Crashworthiness, 2016
Thermographic method for very high cycle fatigue design in transportation engineering
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2014
ABSTRACT With the increasing progress of the technological development in the transport industry,... more ABSTRACT With the increasing progress of the technological development in the transport industry, the required fatigue life has increased, so it is very important to determine a safe fatigue strength for 109 cycles. Nowadays, the very high cycle fatigue constitutes one of the main fatigue design criteria for applications in transport industry. In this paper, the infrared thermography and an energetic approach were applied to investigate a tool steel in very high cycle fatigue regime. The traditional energetic approach was developed in order to extend it in very high cycle fatigue regime and to predict the S-N curves. The failure mechanism of the investigated steel was evaluated by means of scanning electron and optical microscopies in order to assess if the nature of microstructure and the metallurgical defects, in terms of inclusions and pores, can influence the crack initiation.
Journal of Sandwich Structures
Il metodo dell’impact-echo per la valutazione dello stato di degrado di strutture in cap”
Analisi Del Comportamento Ad Impatto DI Differenti Tipologie DI Panelli Sandwich
Impieghi della tomografia industriale a fuoco variabile in vari settori dell’ingegneria meccanica
Indagine sperimentale su strutture sandwich per applicazioni navali
Indagine sperimentale del comportamento meccanico di compositi sandwich in alluminio
Mechanical Behaviour of Glass Fiber Reinforced Aluminium Honeycomb Sandwiches
Investigation of very high cycle fatigue by thermographyc method
Low velocity impact response of glass fiber reinforced aluminium foam sandwich
Computed Tomography analysis of damage in composites subjected to impact loading
Low-velocity impact strength of sandwich materials
L e procedure per il controllo delle strutture in calcestruzzo precompresso sono considerevolment... more L e procedure per il controllo delle strutture in calcestruzzo precompresso sono considerevolmente differenti da quelle utilizzate per le strutture in c.a. convenzionali. In generale, vi è una ridotta evidenza esterna dei danni o del deterioramento della struttura. La fuoriuscita occasionale di qualche cavo dagli ancoraggi o dalla superficie di travi o di lastre potrebbe non essere sufficiente a identificare un danneggiamento in atto. Le strutture in calcestruzzo armato precompresso sono strutture critiche per quanto riguarda l'applicabilità delle tecniche di indagine convenzionali, nel senso che le informazioni ottenute con queste ultime sono insufficienti a dare un quadro conoscitivo adeguato sulle reali condizioni di degrado. Da qui è nata l'esigenza di studiare e di sperimentare specifiche e innovative tecnologie di indagine non convenzionali. Dal momento che le strutture in c.a.p. possono raggiungere uno stato strutturale critico (precedente al collasso) senza l'apparizione di fessurazioni evidenti o deflessioni, è stato fondamentale sviluppare dei metodi di indagine che potessero determinare il reale stato di degrado di questa tipologia di strutture.
The use of sandwich structures combines low weight with high energy absorbing capacity, so they a... more The use of sandwich structures combines low weight with high energy absorbing capacity, so they are suitable for applications in the transport industry (automotive, aerospace, shipbuilding industry), where the "lightweight design" philosophy and the safety of vehicles are very important aspects. The goal of this paper was the analysis of the bending and the low -velocity impact response of aluminium foam sandwiches reinforced by the outer skins made of glass fibre reinforced epoxy matrix. The results were compared with those obtained for aluminium foam sandwiches without glass fibre skins. An analytical model for the peak load prediction under low velocity impact was developed and the predicted values are in good agreement with the experimental measurements. The impact response of the sandwiches was investigated using a theoretical approach, based on the energy balance model and the model parameters were obtained by the tomographic analyses of the impacted panels.
Internal damage investigation of composites subjected to low-velocity impact
ABSTRACT The application of composite materials for lightweight structures in the transportation ... more ABSTRACT The application of composite materials for lightweight structures in the transportation engineering requires a better understanding of their impact response. The aim of this paper was the experimental investigation of different types of composites (laminated composites, PVC foam sandwiches, aluminium foam and honeycomb sandwiches, laminated wood) subjected to low-velocity impact tests and the analysis of their collapse modes as well as the study of their structural response in terms of energy absorption capacity. The failure mode and the internal damage of the impacted composites have been investigated using two experimental techniques: three-dimensional (3D) computed tomography and IR thermography.
In plane compressive response and crushing of foam filled aluminum honeycombs
Journal of Composite Materials, 2014
ABSTRACT In this paper, the influence of foam filling of aluminum honeycomb core on its in-plane ... more ABSTRACT In this paper, the influence of foam filling of aluminum honeycomb core on its in-plane crushing properties is investigated. An aluminum honeycomb core and a polyurethane foam with densities of 65, 90, and 145 kg/m3 were used to produce foam filled honeycomb panels, and then experimental quasi-static compression tests were performed. Moreover, finite element model, based on the conducted tests, was developed. In the finite element analyses, three different polyurethane foams were used to fill three different honeycomb cores. The effects of foam filling of aluminum honeycomb core on its in-plane mechanical properties (such as mean crushing strength, absorbed energy, and specific absorbed energy) were analyzed experimentally and numerically. The results showed that the foam filling of honeycomb core can increase the in plane crushing strength up to 208 times, and its specific absorbed energy up to 20 times. However, it was found that the effect of foam filling decreases in heavier honeycombs, producing an increment of the above mentioned properties only up to 36 and 6 times, respectively.
Metals, 2011
The structures realized using sandwich technologies combine low weight with high energy absorbing... more The structures realized using sandwich technologies combine low weight with high energy absorbing capacity, so they are suitable for applications in the transport industry (automotive, aerospace, shipbuilding industry) where the "lightweight design" philosophy and the safety of vehicles are very important aspects. While sandwich structures with polymeric foams have been applied for many years, currently there is a considerable and growing interest in the use of sandwiches with aluminum foam core. The aim of this paper was the analysis of low-velocity impact response of AFS (aluminum foam sandwiches) panels and the investigation of their collapse modes. Low velocity impact tests were carried out by a drop test machine and a theoretical approach, based on the energy balance model, has been applied to investigate their impact behavior. The failure mode and the internal damage of the impacted AFS have also been investigated by a Computed Tomography (CT) system.
Total hip arthroplasty by using a cementless ultrashort stem: A subject-specific finite element analysis for a young patient clinical case
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2013
In this article, a subject-specific finite element analysis has been developed to study a clinica... more In this article, a subject-specific finite element analysis has been developed to study a clinical case of a surgically misaligned hip prosthesis with an ultrashort stem. It was set out to study the strain energy density pattern, comparing the results obtained with computed tomography images. The authors developed two other numerical models: the first one analyzes the stress and strain distributions in the healthy femur (without prosthesis) and the second one analyzes the same boneimplant biomechanical system of the clinical case but assuming the prosthesis in the proper position. The misaligned prosthesis produced an overload at the proximal posterior plane of the femur, as confirmed by computed tomography images, which detect the formation of new bone. The numerical model of the correctly positioned prosthesis demonstrated that the bone is not overloaded and that the position of neutral axis does not significantly shift from the physiological condition.
Marine Structures, 2013
The use of lightweight aluminium sandwiches in the shipbuilding industry represents an attractive... more The use of lightweight aluminium sandwiches in the shipbuilding industry represents an attractive and interesting solution to the increasing environmental demands. The aim of this paper was the comparison of static and low-velocity impact response of two aluminium sandwich typologies: foam and honeycomb sandwiches. The parameters which influence the static and dynamic response of the investigated aluminium sandwiches and their capacity of energy absorption were analysed. Quasistatic indentation tests were carried out and the effect of indenter shape has been investigated. The indentation resistance depends on the nose geometry and is strongly influenced by the cell diameter and by the skincore adhesion for the honeycomb and aluminium foam sandwich panels, respectively. The static bending tests, performed at different support span distances on sandwich panels with the same nominal size, produced various collapse modes and simplified theoretical models were applied to explain the observed collapse modes. The capacity of energy dissipation under bending loading is affected by the collapse mechanism and also by the face-core bonding and the cell size for foam and honeycomb panels, respectively. A series of low-velocity impact tests were, also, carried out and a different collapse mechanism was observed for the two typologies of aluminium sandwiches: the collapse of honeycomb sandwiches occurred for the buckling of the cells and is strongly influenced by the cell size, whereas the aluminium foam sandwiches collapsed for the foam crushing and their energy absorbing capacity depends by the foam quality. It is assumed that a metal foam has good quality if it Marine Structures 30 (2013) 74-96 has many cells of similar size without relevant defects. A clear influence of cell size distribution and morphological parameters on foam properties has not yet been established because it has not yet been possible to control these parameters in foam making. The impact response of the honeycomb and foam sandwiches was investigated using a theoretical approach, based on the energy balance model and the model parameters were obtained by the tomographic analyses of the impacted panels. The present study is a step towards the application of aluminium sandwich structures in the shipbuilding. Nomenclature b sample width (mm) c core thickness (mm) d honeycomb cell size (mm) m impact mass (kg) n parameter of the Meyer contact law t face thickness (mm) w i impactor displacement (m) w b sandwich deflection (m) v impact velocity (ms À1 ) CT Computed Tomography E absorbed energy (J) E b bending energy dissipation (J) E c contact energy dissipation (J) E m membrane energy dissipation (J) E s shear energy dissipation (J)
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Papers by Gabriella Epasto