Search results for "Elastic"
showing 10 items of 2162 documents
A review of the general theory of thermoelastic stress analysis
2003
Thermoelastic stress analysis (TSA) is now a well-known experimental technique providing information on the surface stress field in structures. Many studies have assessed the potential of the technique for a number of applications and some useful and detailed reviews of these investigations are available, focusing mainly on the experimental aspects related to the measurement of the thermoelastic signal. In this work, instead, a complete and detailed insight into the origins of the various forms of the equations describing the thermoelastic effect is given with reference to the concepts of the thermodynamic theory of a continuum. A discussion on the theory leading to the thermoelastic effec…
Fractional Viscoelasticity Under Combined Stress and Temperature Variations
2020
Nowadays polymeric materials or composites with polymeric matrices are widely used in a very wide range of applications such as aerospace, automotive, biomedical and also civil engineering. From a mechanical point of view, polymers are characterized by high viscoelastic properties and high sensitiveness of mechanical parameters from temperature. Analytical predictions in real-life conditions of mechanical behaviour of such a kind of materials is not trivial for the intrinsic hereditariness that imply the knowledge of all the history of the material at hand in order to predict the response to applied external loads. If temperature variations are also present in the materials, a reliable eval…
A unifying variational framework for stress gradient and strain gradient elasticity theories
2015
Abstract Stress gradient elasticity and strain gradient elasticity do constitute distinct continuum theories exhibiting mutual complementary features. This is probed by a few variational principles herein presented and discussed, which include: i) For stress gradient elasticity, a (novel) principle of minimum complementary energy and an (improved-form) principle of stationarity of the Hellinger–Reissner type; ii) For strain gradient elasticity, a (known) principle of minimum total potential energy and a (novel) principle of stationarity of the Hu–Washizu type. Additionally, the higher order boundary conditions for stress gradient elasticity, previously derived by the author (Polizzotto, Int…
Limited Resistance Rigid Perfectly Plastic Hinges for Steel Frames
2017
The paper concerns the proposal of a new special device for steel frames that can be utilized as external constraint as well as internal one connecting the structure beam elements. The device is designed as a rigid perfectly plastic hinge characterized by suitably chosen stiffness and resistance. Its constituting material is steel. The elastic stiffness and the limit resistance, treated as independent of each other, are fixed with the aim of satisfying special features required to the structure. The proposed device is thought as a sandwich section with wing thickness appropriately variable. Its dimensions are designed so that it can exhibit the fixed independent stiffness and limit resistan…
An efficient framework for the elasto-plastic reliability assessment of uncertain wind excited systems
2016
Abstract In this paper a method to efficiently evaluate the reliability of elastic-perfectly plastic structures is proposed. The method is based on combining dynamic shakedown theory with Subset Simulation. In particular, focus is on describing the shakedown behavior of uncertain elasto-plastic systems driven by stochastic wind loads. The ability of the structure to shakedown is assumed as a limit state separating plastic collapse from a safe, if not elastic, state of the structure. The limit state is therefore evaluated in terms of a probabilistic load multiplier estimated through solving a series of linear programming problems posed in terms of the responses of the underlying linear elast…
Solid-State Analog of an Optical Interferometer
2004
To some extend one may treat a metal ring with two probes as a solid-state analog of an optical interferometer. One node can be considered as a beam splitter (bi-prism, for example), and the electric current at the other node as an equivalent to a light intensity of an interference pattern formed at a screen. In optics, to obtain a stationary pattern one should use a monochromatic source of radiation, as afterwards in a conventional passive media (i.e. air) the phase of the radiation is preserved. On the contrary, in solids the phase of a conducting electron wavefunction is randomly altered due to inelastic collisions (mainly phonons at high temperatures). Hence, to satisfy the condition of…
Antiferromagnetism and the node structure of the superconducting order parameter of UPd Al
2000
The node structure of the superconducting order parameter of the heavy-fermion system is analyzed within the weak-coupling theory. A pairing interaction induced by the exchange of antiferromagnetic spin excitations is assumed as suggested by recent inelastic neutron scattering experiments and tunneling spectroscopy. The multi-sheeted Fermi surface is taken into account. Based on a model susceptibility for the simple antiferromagnetic structure of , line nodes result at the rim of the magnetic Brillouin zone.
Superconductivity mediated by spin fluctuations in the heavy-fermion compound UPd2 Al3
1999
It is well known that any weak attractive electron–electron interaction in metals can in principle cause the formation of Cooper pairs, which then condense into a superconducting ground state1. In conventional superconductors, this attractive interaction is mediated by lattice vibrations (phonons). But for the heavy-fermion and high-temperature superconductors, alternative pairing interactions are considered to be possible2. For example, the low-temperature properties of heavy-fermion systems are dominated by antiferromagnetic spin fluctuations, which have been considered theoretically3 as a possible cause for Cooper-pair formation. This picture recently received some experimental support: …
Isotopic Effects and Surface Absorption in $^{35-37}$Cl+$^{24}$Mg Interactions
1992
Abstract The few-nucleon transfer is found to play an important role in the isotopic effects observed in absorption. This conclusion is obtained by measuring elastic scattering and quasielastic reactions and by analysing elastic data with both phenomenological and microscopic models. The sensitivity domain is found to be different for imaginary and real potentials. The implication for the validity of the dispersion relation for phenomenological potentials at the real sensitivity radius, when transfers are important, is discussed.
Investigation on the influence of the surface resin rich layer on the thermoelastic signal from different composite laminate lay-ups
2006
This work presents a set of experimental results based on the measured thermoelastic signal from GRP composite coupons adopting different lay-ups. A comparison is made with the thermoelastic signal predicted by two different analytical models: one based on the classical law of the thermoelastic effect for orthotropic materials, and the other based on a novel theory accounting for the presence of a resin layer on the external surface of the composite structure. The composite coupons were designed such to determine a significant difference in the predictions made by the two theoretical models. Experimental results have shown a far better match with the predictions based on the novel theory ac…