Search results for "LIMIT"
showing 10 items of 2826 documents
Size effects on the plastic collapse limit load of thin foils in bending and thin wires in torsion
2011
Abstract Following a previous paper by the author [Strain gradient plasticity, strengthening effects and plastic limit analysis, Int. J. Solids Struct. 47 (2010) 100–112], a nonconventional plastic limit analysis for a particular class of micron scale structures as, typically, thin foils in bending and thin wires in torsion, is here addressed. An idealized rigid-perfectly plastic material is considered, which is featured by a strengthening potential degree-one homogeneous function of the effective plastic strain and its spatial gradient. The nonlocal (gradient) nature of the material resides in the inherent strengthening law, whereby the yield strength is related to the effective plastic st…
A theoretical and experimental study to point out the notion of loading mode in damage mechanicsApplication to the identification and validation of a…
2002
A model of fatigue-induced intralaminar cracking in strongly anisotropic laminates is presented. The features of the microscopic phenomenon are explicitly taken into account at the macroscopic level by the use of two variables, which define a new concept in Damage Mechanics that results not only in a coherent model of crack density evolution, but also in a coherent treatment of damage deactivation. Damage evolution indeed is strongly dependent on the local loading mode in each ply where cracking occurs. Experiments on complex lay-ups provided sufficient data for complete calibration of the model. These tests also allowed to validate the theoretical choice of the damage variable. Finally, nu…
Transform-limited spectral compression by self-phase modulation of amplitude-shaped pulses with negative chirp
2011
International audience; Spectral compression by self-phase modulation of amplitude- and phase-shaped pulses is demonstrated as superior compared to pulses that have only been phase shaped. We synthesize linearly negatively chirped parabolic pulses, which we send through a nonlinear photonic crystal fiber, in which self-phase modulation compresses the spectrum of the pulses to within 20% of the Fourier transform limit.
Synthesis of optical pulses by use of similaritons.
2009
We propose and demonstrate experimentally a novel method for synthesizing chirp-free pulses of any desired temporal shape by means of chirp compensation and spectral filtering of optical Raman similaritons. The synthesized pulse shape is independent of the waveform, wavelength and energy of the initial pulses that are used for the similariton generation. Pulses are fully characterized by means of different techniques including cross-correlation and spectrum measurements, and the PICASO technique.
Relative phase locking of pulses in a passively mode-locked fiber laser
2003
In a passively mode-locked fiber ring laser, we report the experimental observation of relative phase locking of pulses in a wide variety of cases. Relative phase locking is observed in bunches of N pulses separated by more than 20 pulse widths as well as in close pulse pairs. In the latter case, the phase relationship between the two pulses is measured to be ±π/2, which is related to theoretical predictions formerly obtained from a Ginzburg-Landau distributed model. We have developed a simplified numerical model adapted to our laser, which keeps its essential features while significantly reducing the number of free parameters. The agreement with the experiment is excellent. © 2003 Optical …
Study of the Formability of Light Metallic Materials
2015
There is a continuing interest in using laminated materials for the production of lightweight parts, the resulting parts having the same functionality and even an increased stiffness and length of operation compared to conventional materials. The present paper aims to study the forming behavior of the laminated materials that requires the unfolding of tests to determine the tensile mechanical properties and the intrinsic properties, determining the forming limit curves by means of the Nakajima test and the analysis of the behavior at unconventional incremental forming.
Reduction of temperature coefficients in multicrystalline silicon solar cells after light-induced degradation
2015
This study focuses on the variations of the temperature coefficients after light-induced degradation (LID) of compensated multicrystalline silicon solar cells from three different ingots. The ingots have been chosen to see the effect of the compensation level, the resistivity and the impact of adding gallium to keep the resistivity as constant as possible along the ingot. The temperature coefficients of the efficiency experience a major decrease after LID on all ingots. We found that this decrease varies along the ingot height and does not correspond to the VOC drop. Moreover, no direct correlation with the interstitial oxygen concentration profiles could be seen.
Selenium adsorption on Mo(110): A first-principles investigation
2013
Selenium adsorption on molybdenum surfaces is a relevant process in the production of thin-film solar cells, in particular as far as the formation of the layered compound MoSe${}_{2}$ is concerned. In this paper we investigate the energetics of Se adsorption on the (110) surface of molybdenum using first-principles calculations in the two limiting cases of low and high coverage, and we establish a comparison with the more extensively investigated case of sulfur adsorption at submonolayer coverage. The studied system provides the opportunity for testing the most crucial approximations, namely, the choice of the exchange-correlation functional and the pseudopotential generation. We find that …
Modeling the Fatigue Damage Evolution in Welded Joints
2017
The present paper presents a two-phase model for the fatigue damage evolution in welded steel joints. The argument for choosing a two-phase model is that crack initiation and subsequent crack propagation involve different damage mechanisms and should be treated separately. The crack initiation phase is defined as the number of cycles to reach a crack depth of 0.1 mm. This phase is modelled based on the Dang Van multiaxial stress approach. Both a multiaxial stress situation introduced by the acting loads and the presence of the multiaxial welding residual stresses are accounted for. The local notch effect at the weld toe becomes very important and the irregular weld toe geometry is character…
Limits of stability in supported graphene nanoribbons subject to bending
2016
Graphene nanoribbons are prone to in-plane bending even when supported on flat substrates. However, the amount of bending that ribbons can stably withstand remains poorly known. Here, by using molecular dynamics simulations, we study the stability limits of 0.5-1.9 nm wide armchair and zigzag graphene nanoribbons subject to bending. We observe that the limits for maximum stable curvatures are below ~10 deg/nm, in case the bending is externally forced and the limit is caused by buckling instability. Furthermore, it turns out that the limits for maximum stable curvatures are also below ~10 deg/nm, in case the bending is not forced and the limit arises only from the corrugated potential energy…