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Generation of Point to Point Trajectories for
Robotic Manipulators Under Electro-Mechanical Constraints, by T.
Chettibi, P. Lemoine
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Workspace and Singularities of a Constrained
Parallel Robot with 3 D.O.F. in Pure Translation, by A. Cherfia, A.
Zaatri
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Nonlinear Analysis of Conical Base Silentbloc, by
M. Ayadi, F. Dammak, L. Hammami, M. Haddar
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Dilation and Strain Effects on the Big End
Journals Bearings, by B. Mansouri, A. Bounif, T. Tamine
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Rayleigh-Ritz Function Approximations in
Computationally Intensive Genetic Design, by J. L. Marcelin
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Fatigue-Fractured Surfaces of Acrylic Bone Cements, by N.
Ihaddadene, P. Erani, L. Cristofolini, M. Baleani, M. Viceconti
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Effect of Different Cyclic Signals on
Three-Points-Bending Behavior of a Fibreglass and Epoxy Resin
Composite Materials, by K. Bey, L. Fatmi, S. Saad, A. El-Mahi
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The Influence of Hydrogen and Chromium on
Behavior Mechanic of the Welded Joints, by A. Aboura, A. Seddak, A.
Hebbar
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Measurement of Thermal Expansion by Moiré
Interferometry, by S. Meguellati, D. Bouzid
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Concentration Dependency of the Rheological
Behaviour of Oil-water Emulsions, by L. Benali
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International Review of
Mechanical Engineering - Papers
Generation of Point to Point Trajectories for Robotic Manipulators Under
Electro-Mechanical Constraints
by T. Chettibi, P. Lemoine
Abstract
- A simple direct method is applied to solve the problem of optimal trajectory
generation for serial manipulators under electro-mechanical constraints. The
goal is to increase the robot productivity by using its electric motors outside
of their continuous operating range. This is possible only if dynamics of
actuators is considered and inherent constraints are included. For this purpose,
a general electro-mechanical model for serial robots is first presented. Then,
the problem of trajectory generation is cast as a non-linear optimization
program using an approximation of joint position variables by means of algebraic
polynomial splines which interpolate a set of control points. Finally, the
optimization problem is solved using a sequential quadratic programming method
for the unknown transfer time and the unknown position of control points, while
minimizing a cost function and respecting elecro-mechanical constraints.
Numerical and experimental results are presented to illustrate the efficiency of
the proposed approach.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Robot, DC Motor, Dynamics, Trajectory, Optimization.
Workspace and Singularities of a Constrained Parallel Robot with 3 D.O.F. in
Pure Translation
by A. Cherfia, A. Zaatri
Abstract
- The geometrical model determination of a constrained parallel robot with three
degrees of freedom is carried out. The constraints consist of a passive central
segment of PPP type (P: prismatic ) which led the robot end-effector to a pure
translatory movements. A determination of the workspace based on the geometrical
model analysis is derived followed by a numerical calculation of all the
attainable points enabling a graphical visualisation of such workspace. In
addition, the analysis of the jacobian matrix has been also derived and
permitted to ensure that there are no singularities of type 1 and 2 in this
constrained structure. An experimental robot prototype has been buit up in order
to validate the theoretical analysis.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Constrained parallel robot, direct kinematics, inverse kinematics, passive
segment, singularity, workspace.
by M. Ayadi, F. Dammak, L. Hammami, M. Haddar
Abstract
- The objective of this study is to propose a numeric approach to analyze the
nonlinear dynamic behaviour of silentblocs. The dynamical analysis proposed is
based on the decomposition of analysis into nonlinear static one with large
displacements and linear dynamical analysis in the non linear deformed
configuration. In this work, modal approach for dynamical analysis of non linear
system with large displacements is adopted. The modal basis is determined in the
deformed prestressed configurations. Numerical results show the important effect
of prestressed on the vibratory behaviour.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Silentbloc, Rubber Component, prestressed, geometrically Nonlinearity, modal
analysis.
Dilation
and Strain Effects on the Big End Journals Bearings
by B. Mansouri, A. Bounif, T. Tamine
Abstract
- The heating and mechanics effects due to the temperatures and pressures in
bearings were largely studied these last years but separately; few studies are
devoted to the two phenomena acting together in dynamic mode, such as the
crankshaft and rod bearings; where the requirements are very severe. In order to
approach reality and confronting with other studies being interested in the
thermo-elastohydrodynamic phenomena (TEHD). The studied model takes into account
the deformations due to the pressures field for the bearing as well as the
dilation effect and the reduction of the lubricant viscosity, due to the heat
transfer effect, between oil and bearing. Simulation results of the connecting
rod bearings of in internal combustion engine are presented and show that the
thermal distortion has remarkable effects on the bearings performances;
therefore the thermo-elastohydrodynamic analysis is very recommended to predict
the performances of the journal bearings in internal combustion engines.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
compliance matrix, Elastic strain, Dilatation Thermo-elastohydrodynamic; T.E.H.D.
Rayleigh-Ritz Function Approximations in Computationally Intensive Genetic
Design
by J. L. Marcelin
Abstract
- This paper deals with the use of Rayleigh-Ritz function approximations in
computationally intensive genetic design, in the dynamic field. The research
strategy consists in substituting, for finite element calculations in the
optimization process (genetic algorithm), an approximate response from a
Rayleigh-Ritz method. For example, the possibility of finding the optimal
locations of passive dampers in structural engineering shells is investigated
with the use of a genetic algorithm (GA). Two examples of optimal damping of
shells are presented. It has been demonstrated that the GA used with the
Rayleigh-Ritz method is very attractive and powerful for such a problem, in
which the objective function has no derivatives, and when several optimal
solutions simultaneously exist.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Optimization, Rayleigh-Ritz, Structural Damping, Genetic Algorithm.
Fatigue-Fractured
Surfaces of Acrylic Bone Cements
by N. Ihaddadene, P. Erani, L. Cristofolini, M. Baleani, M. Viceconti
Abstract
- Acrylic bone cements have been widely used in orthopaedic surgery for the
fixation of artificial joints. In total hip prosthesis, the fracture of PMMA,
through crack initiation, propagation and fracture whether at an interface or
within the bulk material is of serious concern since it leads to the implant
failure. In the present study, cyclic fatigue fractured surfaces of five bone
cements, were investigated using cleaved beads indicator (percentage of cleaved
pre cured beads per fractured area). Fatigue fractured surfaces of the cements
tested were obtained using a methodology based on ASTM-E647-05. All cements
tested showed three different morphologies which are in relation to the crack
growth rate and cement type. Cleaved beads indicator is able to discriminate
between the three zones and thus, is a quantitative inspection of the fractured
surfaces (factorial ANOVA, p<0.0005).
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Cleaved beads, Crack propagation, Fatigue fracture, Fracture surface morphology,
PMMA bone cement.
Effect of Different Cyclic Signals on Three-Points-Bending Behavior of a
Fibreglass and Epoxy Resin Composite Materials
by K. Bey, L. Fatmi, S. Saad, A. El-Mahi
Abstract
- The study of mechanical behavior during three point-bending fatigues has been
systematically associated with a sinusoidal cyclic signal. The purpose of this
work is to study and to analyze the behavior of composite materials, composed
from glass fiber and epoxy resin under the effect of two other cyclic waves
having respectively a square and a triangular signal. In the present work a new
experiment is carried out to evaluate the cyclic signals (sinusoidal, square and
rectangular waves) influence on the fatigue behavior. This material has been
tested under bending in order to determine the maximum displacement which helps
to fix the maximum loading level during tests. The tested samples damage and
rupture caused by the application of the three cyclic waveforms has been
observed by optical microscope, results are compared and discussed.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Composite materials, damage, delaminating, Fatigue, laminate, 3-point bending.
The Influence of Hydrogen and Chromium on Behavior Mechanic of the Welded Joints
by A. Aboura, A. Seddak, A. Hebbar
Abstract
- In this present work the effect of hydrogen on the mechanical behavior of the
welded joint of two types of steels A42E26 and Z2CN18-10 was studied. The
specimens of the tension test were manufactured in accordance with standard ASTM
by machining from plane sheet. Hydrogen was superficially introduced at 50°C by
the electrolytic method by using a solution acid 1NH2SO4
with 0.25 g/l As2O3, a platinum anode and a density of
current of 100 mA/cm2 for various durations. The mechanical tests
were carried out at ambient temperature and in air. With an aim of bringing a
reflex ion on the influence of hydrogen and chromium on the mechanical behavior
of the welded joints of two types of steels the A42E26 and Z2CN18-10, the
experiments were carried out, by simultaneously varying parameters considered to
be influential, to lead to the modeling of the maximum loading and Ultimate
elongation.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Stainless steel, Welded Joint, Hydrogen embrittelment, Design of experiment.
Measurement
of Thermal Expansion by Moiré Interferometry
by S. Meguellati, D. Bouzid
Abstract
- In this paper we present a simple optical method, used the moiré phenomenon,
which is a straightforward method for contactless non-destructive metrological
measurements, used to measure the thermal expansion and shrinkage of materials.
This method comes in complement with the other existing methods. Indeed, at the
time of measurement of expansion or the expansion coefficients, as well as, the
other thermal parameters, there is the risk, that the result of measurement is
sullied by errors, which are due to the measurement system. The method proposed
in this paper, is based on an optical system, which uses the moiré techniques as
method of control, which can currently detect nano-movement, who can reach 40 10-9
m. This value can be improved, because the optical system allows it. In this
arrangement the link between the specimen to be analyzed and the system of
measurement is made by optical way, which decreases the influence of the system
on the result. The method proposed, allows a continuous assessment in real time,
and gives results with good accuracy, owing to the fact that the optical system
is not affected by the heat of furnace, which also offers the possibilities of
controlling a material at the highest temperature with precision measurements.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
diffraction pattern, moiré method, contactless metrology, thermal expansion.
Concentration Dependency of the Rheological Behaviour of Oil-water Emulsions
by L. Benali
Abstract
- The evolution of viscosity with the oil concentration was measured in a
rotating cylinder viscosimeter. The measurements were performed for an oil
emulsion used for lubrication of drilling and cutting tools and for crude oil
emulsions. At low concentrations the rheological behaviour of the lubricant
emulsion is weakly Binghamian. At higher concentrations a power law model was
used to fit the data. For both emulsions a peak of viscosity was observed for an
concentration ranging between 70 and 80 vol% . The results have also show that a
Richardson like exponential model of the viscosity evolution with concentration
is only valid for high shear rates and concentrations close to the critical
concentration corresponding to the peak of viscosity.
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Concentration, Crude oil emulsion, Cutting oil emulsion, Peak of viscosité,
Rheological behavior.
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