Author: Claire DUNE

06-03-21 Maxime Chalvin and Alexis Claude Seminar

Alexis CLAUDE and Maxime CHALVIN will present their research work during the 

SEMINAR on June 3, 2021 

starting at 1:30 pm 
This seminar will be held in M141 and on zoom. 
Participate to the Zoom meeting
https://us04web.zoom.us/j/71569589921?pwd=OGV2WVBtUld6Vm1nRmdYa2dTcUV1Zz09

Meeting ID: 715 6958 9921
Secret code : bHJ4F3

 

Thermal analysis of manufacturing strategies for cylindrical parts with thick walls
by WAAM additive manufacturing
Alexis CLAUDE

Abstract: The seminar will focus on the development of additive manufacturing strategies for thick-walled cylinders obtained by WAAM (arc welding). The material used for the study is an aluminum alloy 5183 deposited with a robotic CMT source.

In order to do so, it was necessary to set up an in-situ temperature measurement system (pyrometer) as well as an adapted interlayer temperature management strategy. This process is indeed crucial in order to guarantee the manufacturability and the expected geometry.

In order to reach an optimal manufacturing method for thick-walled cylinders, several filling strategies are studied: the strategy of juxtaposition of beads, the strategy of periodic advance pattern (sine type) and finally the strategy of periodic pattern with contours. The work consisted firstly in defining the parametrization of the pattern in simplified configuration; then in applying it to the final geometry sought.

For the moment, the work carried out mainly concerns the juxtaposition strategy. Following difficulties encountered when juxtaposing strands with a constant inter-strand distance, an alternative strategy has been developed and implemented.

 

Layer-by-layer temperature management for WAAM additive manufacturing

Maxime CHALVIN(a)(b)*, Alexis CLAUDE(b)(c), Sébastien CAMPOCASSO(b), Vincent HUGEL(b)
(a) SEGULA Technologies, 19 rue d’Arras, 92000 Nanterre
(b) University of Toulon, COSMER, Toulon, France
(c) University of Toulon, MAQ3D Platform, Toulon, France
* Correspondent : maxime.chalvin@univ-tln.fr

Abstract: WAAM additive manufacturing, based on a wire-arc welding process, allows the production of large metal blanks at interesting economic conditions for small series. However, the quality of the parts depends strongly on the temperature management during the manufacturing process. Indeed, the deposition method implies a significant heat transfer to the part and it may be necessary to stop the deposition to allow its cooling. In order to determine the influence of heat on the geometrical quality of thin-walled parts of revolution, a method of in-situ temperature measurement using a pyrometer and a strategy of inter-layer temperature management is proposed. The inter-layer temperature measurement and management methods are applied to the fabrication of thin-walled cylinders of different nominal diameters. The geometrical control of the latter allows to evaluate the impact of the diameter on the geometrical quality at iso-conditions of manufacture. The material studied is an aluminum alloy 5183 deposited with a robotic CMT source. The proposed method of measuring and managing the inter-layer temperature allows to guarantee the deposition of each layer under similar thermal conditions, in order to control the manufacturing operating conditions.

Key words: Additive manufacturing, WAAM, Temperature, Thin walls.

 

04-22-2021 Thierry Champion Seminar

 

Thierry CHAMPION will present a part of his research work during the 

SEMINAR on April 22, 2021 

from 1:30 pm 
which will take place in room M005.

Video link for those who cannot attend: https://zoom.us/j/96942693591?pwd=a2dEUktkNFI2K2NYQ1E0a0w2VDN1dz09

Title: Convergence of penalization methods in convex optimization

Abstract: My objective in this talk is to introduce the classical penalty methods in convex optimization (which includes linear programming) and the study of their convergence, both primal and dual. I will discuss both the theoretical point of view (without going into too specialized mathematical considerations) and the practical implementation.

 

14-01-2021 : A. SLADEN et Y. HELLO, CNRS GEOAZUR

Title : Fiber optic cables for the study of the oceans and the Earth system

Distributed Acoustic Measurement (DAS) on optical fiber is a recent instrumental approach that allows to transform any optical fiber into a dense network (m) of seismo-acoustic sensors (0.1-1000Hz) over large distances (50km+). It is therefore a solution that can address the problems of cost, complexity and reliability of the best current systems for seafloor instrumentation. After an introduction to the technology and the presentation of the first results, we will discuss the current limitations and the envisaged and possible strategies to overcome them.

 

https://zoom.us/j/91807316648?pwd=MHVLeUFZMnQzc1ZDSTVJRDd1UmNGQT09

 

Juliette DRUPT

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PhD student Funding: E-mail: juliette-drupt at etud.univ-tln.fr LinkedIn: https://www.linkedin.com/in/juliette-drupt-3a7051159/ Bio I recently graduated from the Ecole de Mines de Saint-Etienne that ended with a one-year specialization in robotics at the Read more →

June the 24th – PhD Defense Nicolas Gartner

Abstract

Identification of hydrodynamic parameters by simulation with Smoothed Particle Hydrodynamics

This thesis focuses on techniques that allows the simulation of dynamic interactions between an underwater vehicle and the surrounding water. The main objective is to propose a satisfactory solution to be able to test control algorithms and hull shapes for underwater vehicles upstream of the design process. In those cases, it would be interesting to be able to simulate solid and fluid dynamics at the same time. The idea developed in this thesis is to use the Smoothed Particles Hydrodynamics (SPH) technique, which is very recent, and which models the fluid as a set of particles without mesh. In order to validate the simulation results a first study has been performed with a hydrodynamic pendulum. This study allowed the development of an innovative method for estimating the hydrodynamic parameters (friction forces and added mass) which is more robust than previous existing methods when it is necessary to use numerical derivatives of the measured signal. Then, the use of two types of SPH solver : Weakly Compressible SPH and Incompressible SPH, is validated following the validation approach proposed in this thesis. Firstly, the behaviour of the fluid alone is studied, secondly, a hydrostatic case, and finally a dynamic case. The use of two methods for modelling the fluid-solid interaction : the pressure mirroring method and the extrapolation method is studied. The ability to reach a limit velocity due to friction forces is demonstrated. The results of the hydrodynamic parameters estimation from simulation tests are finally discussed. The simulated added mass of the solid approaches reality, but the friction forces currently seem not to correspond to reality. Possible improvements to overcome this problem are proposed.

Keywords : Hydrodynamic parameters, SPH, Numerical method, Interaction, Fluid-solid, Fluid-structure, Incompressible flow, Underwater robotics.

PhD Defense of Maxime Chalvin, July the 9th

Additive manufacturing of tubes by multi-axis robotized wire deposition :
Trajectory generation and optimization

Additive manufacturing through Directed Energy Deposition (DED) enables small batches
of parts to be rapidly manufactured. However, manufacturing trajectories usually used
for the manufacture of overhanging parts require the use of supports, material which
is not useful for the finished part and time consuming. If multi-axis trajectories can be
used to avoid them, they present generally a heterogeneous local inter-layer distance, thus
requiring a variation of the deposition parameters to adapt the layer height ; variation that
can be harmful to the mechanical characteristics of the final part. This thesis first proposes
a constant local inter-layer trajectory generation method for DED additive manufacturing
of tubular parts defined by parametric curves and which can have profile radius variations.
The proposed trajectories have been validated by robotized manufacturing trials of polymer
parts. Since the rotation about a coaxial deposition tool axis has no impact on the deposit,
the use of 6-axis robots offers a redundancy. Using this redundancy, a layer by layer
optimization of the trajectory in the robot space is then proposed. In a constrained robot
configuration, the trajectory optimization allows the manufacturing of parts that cannot
be manufactured in the usual way, and improves the geometrical quality of the parts with
a better repeatability.