Search results for " Bending"
showing 10 items of 63 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…
Assessment of multiaxial fatigue behaviour of welded joints under combined bending and torsion by application of a fictitious notch radius
2004
Abstract A major problem in the assessment of the multiaxial fatigue behaviour in welded joints is the determination of local notch stresses, since the real local radii in most cases are not known. This can be circumvented by introducing a fictitious notch radius, according to Neuber and Radaj. The calculations of local equivalent stress amplitudes for welded joints (tube–tube and flange–tube) under pure bending, pure torsion and combined in- and out-of-phase bending with torsion can then be carried out by stress-based and strain energy density-based criteria. Among the investigated methods, the most reliable results are obtained with the effective equivalent stress hypothesis, an integral …
B7.3 - Field Effect SnO2 Nano-Thin Film Layer CMOS-Compatible
2009
The integration of metal oxide gas sensing layers into CMOS electronic still a challenge especially due to the high operating temperatures that do not comply with silicon transistor limits , even more critical, and metal oxide annealing temperatures. External electric fields will allow control over the energy levels of the sensing layer and thus over adsorption sensitivity, consequently the interaction between gas and sensitive layer is modulated. As the absorbed gas on the surface produces a band bending, it changes conduction paths allowing gas detection through resistance measurements. With this configuration, field switch offers fast desorption and thus handling of low temperature respo…
Three-Point Flexural Behaviour of GFRP Sandwich Composites: A Failure Map
2010
In this work, the failure mechanisms of GFRP/PVC foam core sandwich structures subjected to three-point bending are analysed. By varying the skin thickness (t ) and the span length between supports (l), experimental tests were carried out in order to find the relationship between the geometrical configuration of the sandwiches and the failure mechanism. By plotting failure mechanism on a graph of l against t , a failure map was created identifying the three typical failure mode regions of these sandwiches. The graph clearly shows the failure mode corresponding to each combination of l and t . To help optimise the use of these sandwich beams as structural elements, a theoretical failure mode…
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…
Dimensional reduction for energies with linear growth involving the bending moment
2008
A $\Gamma$-convergence analysis is used to perform a 3D-2D dimension reduction of variational problems with linear growth. The adopted scaling gives rise to a nonlinear membrane model which, because of the presence of higher order external loadings inducing a bending moment, may depend on the average in the transverse direction of a Cosserat vector field, as well as on the deformation of the mid-plane. The assumption of linear growth on the energy leads to an asymptotic analysis in the spaces of measures and of functions with bounded variation.
Common defects of parts manufactured through single point incremental forming
2021
Single point incremental forming is one of the most intensely researched die-less manufacturing process. This process implies the usage of a CNC equipment or a serial robot which deforms a sheet metal with the help of a relatively simple tool that follows an imposed toolpath. As every cold metal forming process, besides the many given advantages it has also some drawbacks. One big drawback in comparison with other cold metal forming processes is the low accuracy of the deformed parts. The aim of this research is to investigate the sheet metal bending mechanism through finite element method analysis. The results shows that the shape of the retaining rings has a big influence over the final g…
Noble metal nanoparticles in organic matrix
2020
Abstract The purpose of this work is the synthesis and study of the properties of nanocomposite structures created by noble metal (silver) nanoparticles (NP's), an exciting class of materials with unique properties differ from both bulk and atomic behavior, which are self-organize in a thin organic film of copper phthalocyanine (CuPc). The structure and morphology of this material, depending on the amount of deposited silver, was studied in ultrahigh vacuum using transmission electron microscopy (TEM) and photoelectron spectroscopy (PES). Metallic atoms deposited on the surface of an organic substrate diffuse into the substrate, forming NPs with a narrow size distribution, which correlates …
A correction method for the analysis of continuous linear one-dimensional systems under moving loads
2008
A new correction procedure for dynamic analysis of linear, proportionally damped, continuous systems under traveling concentrated loads is proposed; both cases of non-parametric (moving forces) and parametric (moving mass) loads are considered. Improvement in the evaluation of the dynamic response is obtained by separating the contribution of the low-frequency (LF) modes from that of the high-frequency (HF) modes. The former is calculated, as usual, by classical modal analysis, while the latter is taken into account using a new series expansion of the corresponding particular solution. The advantage of the suggested method is immediately shown in the calculation of the stress distribution s…
<title>Spin-polarized electron kinetics under high-intensity picosecond excitation</title>
2003
ABSTRACT Spin-polarized electron kinetics is studied by time-resolved polarized photoemission with picosecond resolution. The re-sponse time of strained layer photocathodes is found to be in a range of a few picosecond offering an ultrafast response andhigh spin-polarization of emitted electrons. The studies of the sub-picosecond spin dynamics are facilitated in high-intensityexcitation regime when the length of the emission pulse is enlarged due to the dispersion of acceleration time and Coulombrepulsion ofthe electrons in their flight in the vacuum.Keywords: optical orientation, spin kinetics, strained semiconductor layer, time-resolved emission. 1. INTRODUCTION GaAs, layers are known to …