3,338 research outputs found
Lamp modulator provides signal magnitude indication
Lamp modulator provides visible indication of presence and magnitude of an audio signal carrying voice or data. It can be made to reflect signal variations of up to 32 decibels. Lamp life is increased by use of a bypass resistor to prevent filament failure
A micromechanics-enhanced finite element formulation for modelling heterogeneous materials
In the analysis of composite materials with heterogeneous microstructures,
full resolution of the heterogeneities using classical numerical approaches can
be computationally prohibitive. This paper presents a micromechanics-enhanced
finite element formulation that accurately captures the mechanical behaviour of
heterogeneous materials in a computationally efficient manner. The strategy
exploits analytical solutions derived by Eshelby for ellipsoidal inclusions in
order to determine the mechanical perturbation fields as a result of the
underlying heterogeneities. Approximation functions for these perturbation
fields are then incorporated into a finite element formulation to augment those
of the macroscopic fields. A significant feature of this approach is that the
finite element mesh does not explicitly resolve the heterogeneities and that no
additional degrees of freedom are introduced. In this paper, hybrid-Trefftz
stress finite elements are utilised and performance of the proposed formulation
is demonstrated with numerical examples. The method is restricted here to
elastic particulate composites with ellipsoidal inclusions but it has been
designed to be extensible to a wider class of materials comprising arbitrary
shaped inclusions.Comment: 28 pages, 12 figures, 2 table
eXtended Variational Quasicontinuum Methodology for Lattice Networks with Damage and Crack Propagation
Lattice networks with dissipative interactions are often employed to analyze
materials with discrete micro- or meso-structures, or for a description of
heterogeneous materials which can be modelled discretely. They are, however,
computationally prohibitive for engineering-scale applications. The
(variational) QuasiContinuum (QC) method is a concurrent multiscale approach
that reduces their computational cost by fully resolving the (dissipative)
lattice network in small regions of interest while coarsening elsewhere. When
applied to damageable lattices, moving crack tips can be captured by adaptive
mesh refinement schemes, whereas fully-resolved trails in crack wakes can be
removed by mesh coarsening. In order to address crack propagation efficiently
and accurately, we develop in this contribution the necessary generalizations
of the variational QC methodology. First, a suitable definition of crack paths
in discrete systems is introduced, which allows for their geometrical
representation in terms of the signed distance function. Second, special
function enrichments based on the partition of unity concept are adopted, in
order to capture kinematics in the wakes of crack tips. Third, a summation rule
that reflects the adopted enrichment functions with sufficient degree of
accuracy is developed. Finally, as our standpoint is variational, we discuss
implications of the mesh refinement and coarsening from an energy-consistency
point of view. All theoretical considerations are demonstrated using two
numerical examples for which the resulting reaction forces, energy evolutions,
and crack paths are compared to those of the direct numerical simulations.Comment: 36 pages, 23 figures, 1 table, 2 algorithms; small changes after
review, paper title change
Restitution and Dissent in the Late Medieval Renewal Movements: the Waldensians, the Hussites and the Bohemian Brethren
Two-stroke-cycle engines with unsymmetrical control diagram : supercharged engines
As no investigation of supercharging in 2-stroke-cycle engines has been published up to the present, this article is an attempt in that direction, with a view to establishing the mathematical principles and the constructive rules for the design of such engines
- …