Abstract: New nondestructive technique, namely an inverse technique based on vibration tests, to characterize nonlinear mechanical properties of adhesive layers in sandwich composites is developed. An adhesive layer is described as a viscoelastic isotropic material with storage and loss moduli which are both frequency dependent values in wide frequency range. An optimization based on the planning of experiments and response surface technique to minimize the error functional is applied to decrease considerably the computational expenses. The developed identification technique has been tested on aluminum panels and successfully applied to characterize viscoelastic material properties of 3M damping polymer ISD-112 used as a core material in sandwich panels.
Abstract: Earthquakes produce some of the most violent loading
situations that a structure can be subjected to and if a structure fails
under these loads then inevitably human life is put at risk. One of the
most common methods by which a structure fails under seismic
loading is at the connection of structural elements. The research
presented in this paper investigates the interlock systems as a novel
method for building structures. The main objective of this
experimental study wasto determine the dynamic characteristics and
the seismic behaviour of the proposed structures compared to
conventional structural systemsduring seismic motions. Results of
this study indicate that the interlock mechanism of the panels
influences the behaviour of lateral load-resisting systems of the
structures during earthquakes, contributing to better structural
flexibility and easier maintenance.
Abstract: This research is to design and implement a new kind
of agitators called differential agitator. The Differential Agitator is an
electro- mechanic set consists of two shafts. The first shaft is the
bearing axis while the second shaft is the axis of the quartet upper
bearing impellers group and the triple lower group which are called
as agitating group. The agitating group is located inside a cylindrical
container equipped especially to contain square directors for the
liquid entrance and square directors called fixing group for the liquid
exit. The fixing group is installed containing the agitating group
inside any tank whether from upper or lower position. The agitating
process occurs through the agitating group bearing causing a lower
pressure over the upper group leading to withdrawing the liquid from
the square directors of the liquid entering and consequently the liquid
moves to the denser place under the quartet upper group. Then, the
liquid moves to the so high pressure area under the agitating group
causing the liquid to exit from the square directors in the bottom of
the container. For improving efficiency, parametric study and shape
optimization has been carried out. A numerical analysis,
manufacturing and laboratory experiments were conducted to design
and implement the differential agitator. Knowing the material
prosperities and the loading conditions, the FEM using ANSYS11
was used to get the optimum design of the geometrical parameters of
the differential agitator elements while the experimental test was
performed to validate the advantages of the differential agitators to
give a high agitation performance of lime in the water as an example.
In addition, the experimental work has been done to express the
internal container shape in the agitation efficiency. The study ended
up with conclusions to maximize agitator performance and optimize
the geometrical parameters to be used for manufacturing the
differential agitator
Abstract: Silver nanoparticles were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and hydrazine hydrate as a reducing agent. The formation of the silver nanoparticles was monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of silver nanopart├¡cles by exhibing the typical surface plasmon absorption maxima at 418-420 nm from the UV–Vis spectrum. Comparison of theoretical (Mie light scattering theory) and experimental results showed that diameter of silver nanoparticles in colloidal solution is about 60 nm. We have used energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and, UV–Vis spectroscopy to characterize the nanoparticles obtained. The energy-dispersive spectroscopy (EDX) of the nanoparticles dispersion confirmed the presence of elemental silver signal no peaks of other impurity were detected. The average size and morphology of silver nanoparticles were determined by transmission electron microscopy (TEM). TEM photographs indicate that the nanopowders consist of well dispersed agglomerates of grains with a narrow size distribution (40 and 60 nm), whereas the radius of the individual particles are between 10 and 20 nm. The synthesized nanoparticles have been structurally characterized by X-ray diffraction and transmission high-energy electron diffraction (HEED). The peaks in the XRD pattern are in good agreement with the standard values of the face-centered-cubic form of metallic silver (ICCD-JCPDS card no. 4-0787) and no peaks of other impurity crystalline phases were detected. Additionally, the antibacterial activity of the nanopart├¡culas dispersion was measured by Kirby-Bauer method. The nanoparticles of silver showed high antimicrobial and bactericidal activity against gram positive bacteria such as Escherichia Coli, Pseudimonas aureginosa and staphylococcus aureus which is a highly methicillin resistant strain.
Abstract: The (sub)-optimal soolution of linear filtering problem
with correlated noises is considered. The special recursive form of
the class of filters and criteria for selecting the best estimator are
the essential elements of the design method. The properties of the
proposed filter are studied. In particular, for Markovian observation
noise, the approximate filter becomes an optimal Gevers-Kailath filter
subject to a special choice of the parameter in the class of given linear
recursive filters.
Abstract: Full - Scale Accelerated Loading System, one part of
“the Eleventh - Five - Year National Grand Technology Infrastructure
Program" is a facility to evaluate the performance and service life of
different kinds of pavements subjected to traffic loading under full -
controlled environment. While simulating the environments of frigid
zone and permafrost zone, the accurate control of air temperature, road
temperature and roadbed temperature are the key points and also
aporias for the designment. In this paper, numerical simulations are
used to determine the design parameters of the frozen soil simulation
system. At first, a brief introduction of the Full - Scale Accelerate
Loading System was given. Then, the temperature control method of
frozen soil simulation system was proposed. Finally, by using finite
element simulations, the optimal design of frozen soil simulation
system was obtained. This proposed design, which was obtained by
finite element simulations, provided significant referents to the
ultimate design of the environment simulation system.
Abstract: Nonlinear finite element method and Serendipity eight
nodes element are used for determining of ground surface settlement
due to tunneling. Linear element with elastic behavior is used for
modeling of lining. Modified Generalized plasticity model with nonassociated
flow rule is applied for analysis of a tunnel in Sao Paulo –
Brazil. The tunnel had analyzed by Lades- model with 16 parameters.
In this work modified Generalized Plasticity is used with 10
parameters, also Mohr-Coulomb model is used to analysis the tunnel.
The results show good agreement with observed results of field data
by modified Generalized Plasticity model than other models. The
obtained result by Mohr-Coulomb model shows less settlement than
other model due to excavation.
Abstract: Development of intelligent assembly cell conception includes new solution kind of how to create structures of automated and flexible assembly system. The current trend of the final product quality increasing is affected by time analysis of the entire manufacturing process. The primary requirement of manufacturing is to produce as many products as soon as possible, at the lowest possible cost, but of course with the highest quality. Such requirements may be satisfied only if all the elements entering and affecting the production cycle are in a fully functional condition. These elements consist of sensory equipment and intelligent control elements that are essential for building intelligent manufacturing systems. Intelligent behavior of the system as the control system will repose on monitoring of important parameters of the system in the real time. Intelligent manufacturing system itself should be a system that can flexibly respond to changes in entering and exiting the process in interaction with the surroundings.
Abstract: The paper presents the case study of hazard
identification and sensitivity of potential resource of emergency
water supply as part of the application of methodology classifying
the resources of drinking water for emergency supply of population.
The case study has been carried out on a selected resource of
emergency water supply in one region of the Czech Republic. The
hazard identification and sensitivity of potential resource of
emergency water supply is based on a unique procedure and
developed general registers of selected types of hazards and
sensitivities. The registers have been developed with the help of the
“Fault Tree Analysis” method in combination with the “What if
method”. The identified hazards for the assessed resource include
hailstorms and torrential rains, drought, soil erosion, accidents of
farm machinery, and agricultural production. The developed registers
of hazards and vulnerabilities and a semi-quantitative assessment of
hazards for individual parts of hydrological structure and
technological elements of presented drilled wells are the basis for a
semi-quantitative risk assessment of potential resource of emergency
supply of population and the subsequent classification of such
resource within the system of crisis planning.
Abstract: In this study the elastic-plastic stress distribution in
weld-bonded joint, fabricated from austenitic stainless steel (AISI
304) sheet of 1.00 mm thickness and Epoxy adhesive Araldite 2011,
subjected to axial loading is investigated. This is needed to improve
design procedures and welding codes, and saving efforts in the
cumbersome experiments and analysis. Therefore, a complete 3-D
finite element modelling and analysis of spot welded, bonded and
weld-bonded joints under axial loading conditions is carried out. A
comprehensive systematic experimental program is conducted to
determine many properties and quantities, of the base metals and the
adhesive, needed for FE modelling, such like the elastic – plastic
properties, modulus of elasticity, fracture limit, the nugget and heat
affected zones (HAZ) properties, etc. Consequently, the finite
element models developed, for each case, are used to evaluate
stresses distributions across the entire joint, in both the elastic and
plastic regions. The stress distribution curves are obtained,
particularly in the elastic regions and found to be consistent and in
excellent agreement with the published data. Furthermore, the
stresses distributions are obtained in the weld-bonded joint and
display the best results with almost uniform smooth distribution
compared to spot and bonded cases. The stress concentration peaks at
the edges of the weld-bonded region, are almost eliminated resulting
in achieving the strongest joint of all processes.
Abstract: This work is focused on the numerical prediction of the fracture resistance of a flat stiffened panel made of the aluminium alloy 2024 T3 under a monotonic traction condition. The performed numerical simulations have been based on the micromechanical Gurson-Tvergaard (GT) model for ductile damage. The applicability of the GT model to this kind of structural problems has been studied and assessed by comparing numerical results, obtained by using the WARP 3D finite element code, with experimental data available in literature. In the sequel a home-made procedure is presented, which aims to increase the residual strength of a cracked stiffened aluminum panel and which is based on the stochastic design improvement (SDI) technique; a whole application example is then given to illustrate the said technique.
Abstract: At present, the tendency to implement the conditionbased
maintenance (CBM), which allows the optimization of the
expenses for equipment monitoring, is more and more evident; also,
the transformer substations with remote monitoring are increasingly
used. This paper reviews all the advantages of the on-line monitoring
and presents an equipment for on-line monitoring of bushings, which
is the own contribution of specialists who are the authors of this
paper. The paper presents a study of the temperature field, using the
finite element method. For carrying out this study, the 3D modelling
of the above mentioned bushing was performed. The analysis study is
done taking into account the extreme thermal stresses, focusing at the
level of the first cooling wing section of the ceramic insulator. This
fact enables to justify the tanδ variation in time, depending on the
transformer loading and the environmental conditions. With a view
to reducing the variation of dielectric losses in bushing insulation, the
use of ferrofuids instead of mineral oils is proposed.
Abstract: The quality of a machined surface is becoming more and more important to justify the increasing demands of sophisticated component performance, longevity, and reliability. Usually, any machining operation leaves its own characteristic evidence on the machined surface in the form of finely spaced micro irregularities (surface roughness) left by the associated indeterministic characteristics of the different elements of the system: tool-machineworkpart- cutting parameters. However, one of the most influential sources in machining affecting surface roughness is the instantaneous state of tool edge. The main objective of the current work is to relate the in-process immeasurable cutting edge deformation and surface roughness to a more reliable easy-to-measure force signals using a robust non-linear time-dependent modeling regression techniques. Time-dependent modeling is beneficial when modern machining systems, such as adaptive control techniques are considered, where the state of the machined surface and the health of the cutting edge are monitored, assessed and controlled online using realtime information provided by the variability encountered in the measured force signals. Correlation between wear propagation and roughness variation is developed throughout the different edge lifetimes. The surface roughness is further evaluated in the light of the variation in both the static and the dynamic force signals. Consistent correlation is found between surface roughness variation and tool wear progress within its initial and constant regions. At the first few seconds of cutting, expected and well known trend of the effect of the cutting parameters is observed. Surface roughness is positively influenced by the level of the feed rate and negatively by the cutting speed. As cutting continues, roughness is affected, to different extents, by the rather localized wear modes either on the tool nose or on its flank areas. Moreover, it seems that roughness varies as wear attitude transfers from one mode to another and, in general, it is shown that it is improved as wear increases but with possible corresponding workpart dimensional inaccuracy. The dynamic force signals are found reasonably sensitive to simulate either the progressive or the random modes of tool edge deformation. While the frictional force components, feeding and radial, are found informative regarding progressive wear modes, the vertical (power) components is found more representative carrier to system instability resulting from the edge-s random deformation.
Abstract: A study of electromagnetic flow meter is presented in the paper. Comparison has been made between the analytical and the numerical results by the use of FEM numerical analysis (Quick Field 5.6) for determining polarization voltage through the circle cross section of the polarization transducer. Exciting and geometrical parameters increasing its effectiveness has been examined. The aim is to obtain maximal output signal. The investigations include different variants of the magnetic flux density distribution around the tube: homogeneous field of magnitude Bm, linear distribution with maximal value Bm and trapezium distribution conserving the same exciting magnetic energy as the homogeneous field.
Abstract: For maintenance of a spine stability during the
postoperative period a transpedicular fixing of its elements is often
used. Usually the transpedicular systems are formed of rods which as
a result form a design of the frame type, fastening by screws to
vertebras. Such design should be rigid and perceive loadings
operating from the spine without essential deformations. From the
perfection point of view of known designs their stress
whole, and each of elements, in particular is of interest. In this study
the modeling of the transpedicular screw is performed and
estimation of its deformations taking into account interaction with a
vertebra body having variable structure is made.
Abstract: Data mining is an extraordinarily demanding field referring to extraction of implicit knowledge and relationships, which are not explicitly stored in databases. A wide variety of methods of data mining have been introduced (classification, characterization, generalization...). Each one of these methods includes more than algorithm. A system of data mining implies different user categories,, which mean that the user-s behavior must be a component of the system. The problem at this level is to know which algorithm of which method to employ for an exploratory end, which one for a decisional end, and how can they collaborate and communicate. Agent paradigm presents a new way of conception and realizing of data mining system. The purpose is to combine different algorithms of data mining to prepare elements for decision-makers, benefiting from the possibilities offered by the multi-agent systems. In this paper the agent framework for data mining is introduced, and its overall architecture and functionality are presented. The validation is made on spatial data. Principal results will be presented.
Abstract: Stress analysis of functionally graded composite plates
composed of ceramic, functionally graded material and metal layers is
investigated using 3-D finite element method. In FGM layer, material
properties are assumed to be varied continuously in the thickness
direction according to a simple power law distribution in terms of the
volume fraction of a ceramic and metal. The 3-D finite element model
is adopted by using an 18-node solid element to analyze more
accurately the variation of material properties in the thickness
direction. Numerical results are compared for three types of materials.
In the analysis, the tensile and the compressive stresses are
summarized for various FGM thickness ratios, volume fraction
distributions, geometric parameters and mechanical loads.
Abstract: This paper deals with analysis of flexural stiffness,
indentation and their energies in three point loading of sandwich
beams with composite faces from Eglass/epoxy and cores from
Polyurethane or PVC. Energy is consumed in three stages of
indentation in laminated beam, indentation of sandwich beam and
bending of sandwich beam. Theory of elasticity is chosen to present
equations for indentation of laminated beam, then these equations
have been corrected to offer better results. An analytical model has
been used assuming an elastic-perfectly plastic compressive behavior
of the foam core. Classical theory of beam is used to describe three
point bending. Finite element (FE) analysis of static indentation
sandwich beams is performed using the FE code ABAQUS. The
foam core is modeled using the crushable foam material model and
response of the foam core is experimentally characterized in uniaxial
compression.
Three point bending and indentation have been done
experimentally in two cases of low velocity and higher velocity
(quasi-impact) of loading. Results can describe response of beam in
terms of core and faces thicknesses, core material, indentor diameter,
energy absorbed, and length of plastic area in the testing. The
experimental results are in good agreement with the analytical and
FE analyses. These results can be used as an introduction for impact
loading and energy absorbing of sandwich structures.
Abstract: The objective of global optimization is to find the
globally best solution of a model. Nonlinear models are ubiquitous
in many applications and their solution often requires a global
search approach; i.e. for a function f from a set A ⊂ Rn to
the real numbers, an element x0 ∈ A is sought-after, such that
∀ x ∈ A : f(x0) ≤ f(x). Depending on the field of application,
the question whether a found solution x0 is not only a local minimum
but a global one is very important.
This article presents a probabilistic approach to determine the
probability of a solution being a global minimum. The approach is
independent of the used global search method and only requires a
limited, convex parameter domain A as well as a Lipschitz continuous
function f whose Lipschitz constant is not needed to be known.
Abstract: This paper presents an approach which is based on the
use of supervised feed forward neural network, namely multilayer
perceptron (MLP) neural network and finite element method (FEM)
to solve the inverse problem of parameters identification. The
approach is used to identify unknown parameters of ferromagnetic
materials. The methodology used in this study consists in the
simulation of a large number of parameters in a material under test,
using the finite element method (FEM). Both variations in relative
magnetic permeability and electrical conductivity of the material
under test are considered. Then, the obtained results are used to
generate a set of vectors for the training of MLP neural network.
Finally, the obtained neural network is used to evaluate a group of
new materials, simulated by the FEM, but not belonging to the
original dataset. Noisy data, added to the probe measurements is used
to enhance the robustness of the method. The reached results
demonstrate the efficiency of the proposed approach, and encourage
future works on this subject.