1,721,230 research outputs found
Phonon- and electron-temperature waves in a Maxwell-Cattaneo heat-conduction theory
No full textA two-temperature model, which is fully compatible with the Maxwell-Cattaneo heat-conduction theory, is developed. It allows to account for different heat carriers’ temperatures, as well as for their mutual energy exchange. Its physical consistency is proved by means of the second law of thermodynamics. The propagation of phonon- and electron-temperature waves is also analyzed, and the results are plotted in the case of a (Formula presented.) sample at (Formula presented.)
Optimum design of damage resistant reinforced composite panels
No full textIn this work, an optimization procedure able to determine the optimum design of a stiffened aeronautical panel subjected to low velocity impacts is presented. As design variables, the number of plies and the stacking sequence of the panel have been considered. The optimization is based on a genetic algorithm, while the onset of the impact induced damage is predicted by means of an approach based on the critical impact force threshold. A multi-objective optimization has been carried out to determine, among the configurations able to withstand the low velocity impacts, the ones characterized by the maximum buckling load and the minimum weight
Overview and future advanced engineering applications for morphing surfaces by Shape Memory Alloy Materials
Full text linkThe development of structures able to autonomously change their characteristics in response to an external simulation is considered a promising research field. Indeed, these structures, called smart structures, can be adopted to improve the aerodynamic performance of air and land vehicles. In this work, an overview and future applications of Shape Memory Alloys (SMA)-based smart structures are presented. The use of SMA materials seems to be very promising in several engineering sectors. Advanced SMA-based devices, designed to improve the aerodynamic performance of vehicles by modifying the shape of the spoiler and the rear upper panel, are briefly introduced and discussed in this paper. Indeed, a simplified model simulating the SMA mechanical behavior has been considered to demonstrate the feasibility of the introduced smart structures for adaptive aerodynamic applications. Numerical simulations of the investigated structures are provided as a justification of the proposed designs
Nonlocal and nonlinear contributions to the thermal and elastic high-frequency wave propagations at nanoscale
No full textWe analyze the role played by nonlocal and nonlinear effects in the propagation of thermal and elastic high-frequency waves in nanosystems. The study is performed both in the case of a rigid body (i.e., for heat-pulse propagation) and in the case of a nonrigid body (i.e., for thermoelastic-pulse propagation). In the framework of extended irreversible thermodynamics, the compatibility of our theoretical models with second law is proved
Analytical tool for the preliminary design of an adhesively bonded T joint
No full textSeveral different methodology for the study of adhesively bonded joints can be found in literature. However, most of those methods are joint-specific. One of the most interesting joint case is the bonding between the skin and the stringer of an aeronautical panel. Unfortunately, this case is one of the less studied, due to the complexity of the load conditions. In this paper, the problem of the skin stringer debonding under a T-pull load condition is analyzed. The analysis is performed by means of the methodology developed by Bigwood and Crocombe, that differs from other bonding technique because it is not joint-specific. Indeed, this method allows to solve any type of joints for which it is possible to specify the end loading values on every adherends' sides. The results, in terms of peel and shear stress, are compared with the ones obtained via finite element methods, in order to validate the results for the specific load case considered
An Optimization Procedure for the Design of Damage Resistant Stiffened Panels
No full textIn the last few decades, the employment of composite materials in the industrial field is widely increasing, thanks to their high mechanical properties compared to metallic alloys of the same weight. In particular, the higher benefits can be found in the aeronautical field, where the research is mainly focused in the development of lightweight structures.
On the other hand, the damage behavior of composites is difficult to predict and control, leading to the development of structures heavier than needed, which reduce the intrinsic advantages, in terms of weight, of composite materials.
This work is focused on the development of an optimization procedure able to find the lighter configuration of a stiffened aeronautical panel resistant to impact damages located in the bay and on the stringer foot
Enhanced Model for the Analysis of Thermoelectric Effects at Nanoscale: Onsager’s Method and Liu’s Technique in Comparison
No full text: The aim of this paper is twofold. From the practical point of view, an enhanced model for the description of thermoelectric effects at nanoscale is proposed. From the theoretical point of view, instead, in the particular case of the proposed model, the equivalence between two classical techniques for the exploitation of the second law of thermodynamics is shown, i.e., Onsager's method and Liu's technique. An analysis of the heat-wave propagation is performed as well
Thermal solitons in nanotubes
No full textStarting from a recent proposal of a nonlinear Maxwell–Cattaneo equation for the heat transport with relaxational effects at nanoscale, in a special case of thermal-wave propagation we derive a nonlinear Schrödinger equation for the amplitudes of the heat-flux perturbation. The complete integrability of the obtained equation is investigated in order to prove the existence of infinite conservation laws, as well as the existence of infinite exact solutions. In this regards, we have considered the simplest nontrivial solutions, namely, the bright and dark (thermal) solitons, which may be interesting for energy transport and for information transmission in phononic circuits
Weakly nonlocal and nonlinear heat transport
No full textThe thermo-mechanical behavior of miniaturized systems, the characteristic lengths of which is of the order of few nanometers, is strongly influenced by memory, nonlocal, and nonlinear effects [1, 18, 27, 50]. In one-dimensional steady-state situations, in modeling the heat transport along nanowires or thin layers, some of these effects may be incorporated into a size-dependent effective thermal conductivity λeff [2, 43], and a Fourier law (FL)-type equation may still be used with λeff as the thermal conductivity, instead of the bulk value λ. However, in fast perturbations, or under strong heat gradients, or in axial geometries an effective thermal conductivity is not enough to overcome the different problems related to the FL, as for instance, the infinite speed of propagation of thermal disturbances, or some genuinely nonlinear effects in steady states [9, 17, 25, 28, 30, 38]. Therefore, in modeling heat conduction, it is necessary to go beyond FL by introducing more general heat-transport equations, and analyze more general geometries than those considered in Chaps. 3 and 4. In Chap. 2 the nonlinear heat-transport equation (2.16) has been introduced. Here we will analyze some consequences of it
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