0000000000236015
AUTHOR
Salvatore Fragapane
Experimental and numerical analysis of aluminum-aluminum bolted joints subject to an indentation process
Abstract The increasing interest of the industry (especially automotive, aviation and marine) in the fastener joints (riveted, bolted, etc.) between metallic materials, has re-opened the study on the possibility to improve the performance of the drilled structure using plastic deformation processes. Indentation process, performed before the drilling operation, creates circumferential compression stresses around the hole which increase significantly the mechanical performance of the drilled structures. In this paper, static and the fatigue performances of aluminum–aluminum (AW 6082-T6) single-lap bolted joints are studied. In particular, the study compares the mechanical strength of only dri…
Stiffness and Reinforcement Effect of electrical Resistance Strain Gauges
: The increasing use of low-modulus materials, on which the reinforcement effect of the electrical resistance strain gauge is not negligible, has re-opened the research interest into this issue. This study deals with the evaluation of stiffness, and of the strain gauge Young's modulus involved in the estimation of both the global and the local reinforcement effect; the relationship between the strain gauge stiffness and the local reinforcement effect is also analysed. In particular, the experimental technique used to determine the stiffness of some commercial strain gauges is described. The results show that the strain gauge stiffness alone does not permit an accurate evaluation of the loc…
The Reinforcement Effect of Strain Gauges Embedded in Low Modulus Materials
The reinforcement effect of electrical resistance strain gauges is well-described in the literature, especially for strain gauges installed on surface. This paper considers the local reinforcement effect of strain gauges embedded within low Young modulus materials. In particular, by using a simple theoretical model, already used for strain gauges installed on the surface, it proposes a simple formula that allows the user to evaluate the local reinforcement effect of a generic strain gauge embedded on plastics, polymer composites, etc. The theoretical analysis has been integrated by numerical and experimental analyses, which confirmed the reliability of the proposed model.
Materiali Compositi Ibridi Resistenti al Fuoco
La sempre crescente richiesta nell’ambito della progettazione strutturale aeronautica/aerospaziale di materiali aventi elevate perfomance meccaniche, ha determinato negli ultimi decenni la diffusione dei materiali compositi a matrice polimerica (Polymer Matrix Composites, PMCs) rinforzati prevalentemente con fibre di carbonio (Carbon Fiber Reinforced Plastic, CFRP). Le principali limitazioni nell’uso di tali compositi sono dovute all’elevata sensibilità agli agenti ambientali ed alle basse temperature di esercizio; inoltre, tali materiali mal sopportano l’esposizione al fuoco e ciò per via della facile incendiabilità non solo della matrice ma anche delle fibre. Al fine di mettere a punto un…
SVILUPPO DI COMPOSITI STRUTTURALI IBRIDI PER APPLICAZONI AERONAUTICHE
La sempre crescente richiesta nell’ambito della progettazione strutturale aeronautica/aerospaziale di materiali aventi elevate perfomance meccaniche, ha determinato negli ultimi decenni la diffusione dei materiali compositi a matrice polimerica (Polymer Matrix Composites, PMCs) rinforzati prevalentemente con fibre di vetro, aramide e di carbonio (Fiber Reinforced Plastic, FRP). Le principali limitazioni nell’uso di tali compositi sono dovute all’elevata sensibilità agli agenti ambientali ed alle basse temperature di esercizio; inoltre, tali materiali mal sopportano l’esposizione al fuoco e ciò per via della facile incendiabilità non solo della matrice ma anche delle fibre (aramide e carboni…
STUDIO DI UN’APPLICAZIONE IN CAMPO AERONAUTICO DI COMPOSITI STRUTTALI IBRIDI RESISTENTI AL FUOCO
In the aeronautical/aerospace structural design the increasing demands of materials having high mechanical performance, has led to the a wide use of Polymeric Matrix Composites (PMCs) mainly reinforced by carbon fibers (Carbon Fiber Reinforced Plastics, CFRP). The main drawbacks in the use of such composites are due to high sensitivity to environmental features and low working temperatures; moreover, these materials do not tolerate the fire exposure because of the inflammability of both the matrix and the fibers. In order to develop a composite that combines the structural performance of CFRP with a good strength to high temperatures and fire, in the present work the use of a hybrid composi…
The Reinforcement Effect of Strain Gauges Embedded in Low Modulus Material
The reinforcement effect of electrical resistance strain gauges is well-described in the literature, especially for strain gauges installed on surface. This paper considers the local reinforcement effect of strain gauges embedded within low Young modulus materials. In particular, by using a simple theoretical model, already used for strain gauges installed on the surface, it proposes a simple formula that allows the user to evaluate the local reinforcement effect of a generic strain gauge embedded on plastics, polymer composites, etc. The theoretical analysis has been integrated by numerical and experimental analyses, which confirmed the reliability of the proposed model.
L’EFFETTO RINFORZANTE DEGLI ESTENSIMETRI INGLOBATI
L’effetto rinforzante degli estensimetri elettrici a resistenza è ben documentato nella letteratura tecnica soprattutto per ciò che riguarda gli estensimetri installati in superficie. Questa memoria riguarda l’effetto rinforzante locale degli estensimetri inglobati all’interno dei materiali. In particolare si estende agli estensimetri inglobati un semplice modello già utilizzato per gli estensimetri installati in superficie. Il modello - che si basa sulle seguenti ipotesi: influenza dell’adesivo trascurabile, modulo di Young dell’estensimetro costante, distribuzione esponenziale delle tensione tangenziali e spessore della struttura uguale a quello dell’estensimetro – conduce ad una semplice…
ANALISI DELL’EFFETTO RINFORZANTE DEGLI ESTENSIMETRI INGLOBATI IN MATERIALI A BASSO MODULO
L’effetto rinforzante degli estensimetri elettrici a resistenza è ben documentato nella letteratura tecnica soprattutto per ciò che riguarda gli estensimetri installati in superficie. Questa memoria riguarda l’effetto rinforzante locale degli estensimetri inglobati all’interno dei materiali. In particolare si estende agli estensimetri inglobati un semplice modello già utilizzato per gli estensimetri installati in superficie. Il modello - che si basa sulle seguenti ipotesi: modulo di Young dell’estensimetro costante, distribuzione esponenziale delle tensione tangenziali all’interfaccia ER-struttura e larghezza della struttura uguale a quella dell’estensimetro – conduce ad una semplice formul…
Local reinforcement effect of embedded strain gauges
The reinforcement effect of strain gauges installed on low Young's modulus materials has received attention by many researchers with respect to both strain gauges installed on the surface [1,2] and embedded inside the material [3,4]. In the case of strain gauges installed on the surface, the evaluation of the local reinforcement effect gives [5] the following correction coefficient C, i.e. the ratio between the actual strain (without the strain gauge) and the strain ' measured by the strain gauge: * ' 1 sg s E C E (1) being * sg g , sg sg sg sg sg sg t L L E E L t t (2) where Esg is the Young’s modulus of the strain gauge, * Esg is a characteristic of the strain gauge which gives the strain…
On the Stiffness and the Reinforcement Effect of Electrical Resistance Strain Gauges
The reinforcement effect of a strain gauge installed on low modulus materials can be significant. The increasing use of low modulus materials requires therefore the evaluation of such effect. This paper concerns the relationship between the local reinforcement effect and the strain gauge stiffness. The conclusion is that the gauge stiffness alone does not allow the user a thorough evaluation of the reinforcement effect.