Levaillant Christophe

CLIN

In France, the main issues for high-tech greenhouses are to reduce the use of fossil energy for heating, because this type of energy is responsible for greenhouse gas emissions, and to control by cooling the temperature which increases during spring and summer periods due to climate change. A first feasibility study showed that a solar collector fi...

In the current context of predicted shortage of fossil fuels, increasing carbon tax and of awareness of environmental preoccupations (e.g. greenhouse gas emissions), using renewable energy to heat greenhouse vegetable crops has become a priority. In France, most heated greenhouses use natural gas-fired combined heat and power systems for heating (5...

A new concept of greenhouse building and solar heating system for sustainable urban agriculture

solar thermal solutions for heating dehumidifying and cooling of tomato greenhouse

The effects of temperature as well as the initial hardness in the range 42 to 50HRC on the fatigue behaviour and life of a 5%Cr tool steel are investigated. Total strain controlled isothermal fatigue experiments between 200 °C and 600 °C are carried out under 1Hz frequency. The significant softening induced by tempering and/or cyclic loading is rel...

Carbide-forming elements (W, Mo, Nb, V), as well as elements that influence only the tempering kinetics (Co, Ni), were added to a 5% Cr tempered martensitic steel in order to modify its precipitation. The main goal was to shift the secondary hardening peak towards higher tempering temperatures. Small angle neutron scattering and X-ray diffraction e...

In a hot strip mill, the contact established between the hot strip and the work rolls in the first times of running has to be oxide on oxide to allow the strip to be pulled in the roll bite. The oxide scale formed on the roll is submitted to thermo-mechanical stresses and grows up. From a critical thickness, the scale spalls and causes some superfi...

The tribology behaviour of the die radius, in the deep-drawing process, results from surface interactions between the metal sheet and the tool under contact pressure. Friction, degradation of the sheet, surface quality and tool wear are a result of this interaction.This article aims to study degradations of the radius portion of a die in the deep-d...

In comparison with the conventional AISI H11 tool steel, which contains approximately 1 wt.% silicon, the modified steel AISI H11 (∼0.35 wt.% silicon) exhibits improved tensile and fatigue properties at 550 °C – the estimated tool surface temperature during the high-pressure injection of aluminium alloys. The effect of silicon on the stability of s...

The high-temperature oxidation of a silicon nitride-titanium nitride (Si3N4–TiN) composite has been investigated via scanning electron microscopy and energy-dispersive and wavelength-dispersive spectrometry. At 1150°C, the oxidation of both the silicon nitride and titanium nitride phases takes place. Several oxidation processes act simultaneously a...

Relevant microstructural characteristics ensuring a good mechanical strengthening up to 600 °C of a tempered martensitic steel containing 5% Cr (AISI H11) were investigated using transmission electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction and extraction of carbides. Softening induced by tempering and cyclic loading is rela...

In this work, the deformation behaviour of high manganese austenitic Hadfield steel sheet samples was studied under uniaxial tensile test conditions. The tests were performed at various strain rates and temperatures to examine the effect of strain rate and microhardness on the strain hardening and formability of sheet samples for production of bull...

Injection-moulded thick plates were produced using a short glass fibre-reinforced thermoplastic. We studied the effect of processing parameters on voids rate inside the parts. Voids rate was measured using an optical microscope. Mass and density measurements were compared with each other in order to define the most relevant method for voids detecti...

The sheet metal forming process involves severe contact conditions. The draw die radius is the most affected zone that leads to wear damage. This phenomenon is the result of intense local tribological conditions. Wear mech- anisms are depending on tool material and coating properties. But the local- izations of wear for all kind of draw die radii a...

In hot forming processes, the interface tool/product is important for the quality of the finished product. In hot rolling, the scale formed on the roll material plays an essential role. As soon as the contact oxide–oxide is established between the roll and the slab, friction allows the process to start. However, the oxide scale will continue to gro...

Metallic and ceramic tools for superplastic forming (SPF) were examined. The performances of heat resistant cast steels, ceramic refractories and vitreous silica based ceramics were investigated. The resistance of the tool materials to specific mechanical and thermal constraint of the SPF process was studied.

39èmes journées du cercle d'études des métaux, 17-18 mai 2000, Saint-Etienne, FRANCE

A fracture prediction criterion for brittle materials has been introduced in the POLLUX finite-element code in order to predict the risk-of-rupture of ceramic tools during a forging operation. POLLUX is a software dedicated to the simulation of forging operations, initially developed by INSA (Lyon). The chosen probabilistic fracture model is based...

Dies and molds are subjected to severe mechanical and thermal loads during injection or forging operations, As fatigue is one of the most important cause of tool steels damage, we studied isothermal (between 200°C and 600°C) fatigue behaviour and damage of two grades (SMV3 and ADC3) of a tempered martensitic 5 % Cr steel. More than 100 fatigue test...

Extrait de : Matériaux, usures et corrosion - 38èmes Journées du cercle d'études des métaux, Liège, BELGIQUE, 26-27 mai 1999

A fracture prediction criterion for brittle materials has been introduced in the POLLUX finite-element code, in order to predict the risk of rupture of ceramic tools during a forging operation. The POLLUX code, developed by INSA (Lyon) especially to simulate forging operations, is presented. The fracture model is based on the weakest link theory an...

37èmes journées du cercle d'études des métaux, 27-28 mai 1998, Albi, FRANCE

37èmes journées du cercle d'études des métaux, 27-28 mai 1998, Albi, FRANCE

The transmission electron microscopy in-situ straining technique is employed to measure the breaking angles of strengthening precipitates in aluminium alloy 6056-T6 as they are sheared by dislocations. The experimental determination of the character of bowed dislocation segments when dislocations are pinned on precipitates allows us to calculate th...

Carbon Fibre Reinforced Plastic (C.F.R.P.) materials are widely used in the aeronautical industry to increase performances of aircrafts. Some structural parts, like wings and ailerons, need to be protected against the environment, especially lightning impacts. Plasma sprayed electrical conductive coating made by atmospheric plasma spray. A parametr...

High resolution electron microscopy and in situ straining experiments are performed on aluminum alloy 6056 T6 to charaterize the morphology of precipitates and the processes of precipitate overcoming by the dislocations. Two types of precipitates (needles and laths) are identified. They are found to be sheared by the dislocations and the maximum fo...

Titanium-aluminium alloy matrix composites reinforced by long SiC fibers are considered as potential replacements for the conventional alloys used in aerospace applications for higher temperature service. A direct elaboration route of such composites is the hot uniaxial pressing of an assembly of metal foils stacked between uniaxial fiber mats. The...

Due to enhanced mechanical and corrosion resistance properties, aluminum alloy 6056 T6 might substitute for commonly used 2024 alloy in the manufacturing of aircraft fuselage skins. To understand the mechanical properties of this precipitation hardening alloy, tensile tests, HRTEM analysis and TEM in situ straining technique are used. The variation...

A thermomechanical three-dimensional (3-D) finite element analysis of solidification is presented. The heat transfer model is based on a multidomain analysis accounting for noncoincident meshes for the cast part and the different mold components. In each subdomain, a preconditioned conjugate gradient solver is used. The mechanical analysis assumes...

Static Recrystallization (SR), is here used as a way to get an ASTM [1] grain size of 3 or so. Making a prediction of the effect of both deformation and temperature on the kinetics of the SR phenomena is the first step toward a global microstructure prediction at the end of the manufacturing sequence. It is the main goal of the study here after des...

The literature survey about the thermomechanical behavior of the mushy state first demonstrates the lack of data about the theological parameters for viscoplastic component. Then it shows discrepancies between experimental and modelling studies about the elastic component. In order to fill the gap underlined in the first point, we develop a new met...

This paper reports the results of an investigation of the mechanical and formability properties of Hadfield steel at room temperature. The formability characterization was obtained by performing the usual tensile test, notched-tensile test, hydraulic bulge test and stretch-forming test. The Forming-limit diagram (FLD) for this steel was characteriz...

In this study, the original Hadfield steel (1.2%C and 12%Mn) is investigated under uniaxial tensile test conditions in order to evaluate the mechanical behaviour at different strain rates and temperatures. The constitutive equation of Hadfield steel is determined as a function of strain, strain rate and temperature. In an attempt to explain the mec...

An exact comparison between materials properties can be made only if the test samples are made under the same conditions as those used for the actual component. For zinc alloys, many properties are knowm to be sensitive to wall thickness. A series of samples of zinc alloys and glass-reinforced PA66 nylon were produced by pressure die casting and in...

This paper aim at presenting the various defects involved in sheet metal forming and recalling the experimental procedure that are used to obtain these defects in laboratory type tests. The material and process conditions that have a significant influence on defects are reviewed. Finally, the prediction of defect by numerical simulation and especia...

The assessment of the Forming Limit Diagram (FLD) of the sheet metals used in automotive stamping requires several testing geometries including stamping tests for example like ERICHSEN or NAKAZIMA tests. These tests involve many parameters for material behaviour and friction conditions. This paper aims at determining the FLD through testing procedu...

The rheology of titanium Ti - 6 % Al - 4 % V alloy was studied by torsion test between 800 and 1200 °C at deformation speeds included between 10-5 and 10 s-1. At room temperature, the studied structures present a starting morphology that is either equiaxial or stretched or spaghetti. The torsion tests were analyzed according to the Sellars and Tega...

The microstructural evolutions during superplastic flow can be either favorable or detrimental to the retention of the latter. The paper reviews these dynamic implications. A qualitative description of the phenomena is given which leads to the distinction between the initial superplastic behavior conditioned by the initial microstructural state (fi...

The superplastic behaviour of nickel based superalloy NK17CDAT( Astroloy) has been studied using torsion testing. The evolutions of stress and average grain size are found to follow the same classical behaviour as other nickel based alloys under similar conditions. The superplastic flow is characterised by a strain rate sensitivity exponent of 0·5...

Two approaches can be developed to account for the effect of microstructure during the superplastic flow of Ti-6%Al-4%V. The classical {S}={D} assumption gives a good fit of the material behaviour but the {S}={D,s} hypothesis appears more suitable for the understanding of the actual microstructural mechanisms that are involved. The integrative form...

The dependence between the equivalent stress, isothermal forging conditions and microstructure for the nickel base superalloy NK17CDAT has been studied by means of torsion experiments. Two sets of constitutive relationships are proposed based on two different ideas of what should conveniently represent the microstructure. The first one assumes that...

During subsequent loading in the so called superplastic range, the materials are likely to exhibit some micros tructura 1 evolutions whose implications can be either detrimental or favorable to the superplastic behaviour. The present paper tries to classify these implications and attempts to give simple predictive tools to take into account the mic...

During forming at high temperatures and low strain rates, dynamic microstructural changes can be detrimental to the superplastic (SP) properties of metallic alloys. This paper first reviews these possible variations and implications. A classification is set up. Then, starting from the viewpoint that the microstructure is best represented by the gra...

Nous proposons une simulation monodimensionnelle par éléments finis de l' essai de traction dynamique. Nous mettons en évidence les conséquences d'une réduction locale de la sectioninitiale de l'éprouvette et des effets d'inertie, en particulier sur l'histoire de la déformation et de la vitesse de déformation. L'influence des paramètres rhéologique...

Using 3D finite element method (F.E.M.), hot rolling of heavy ingots is modeled using viscoplatic description of the material through a NORTON-HUFF law. In order to predict surface defects the material damage is estimated by the OYANE criterion.

Warm working of a . 42% carbon steel was investigated by tension and torsion tests over the temperature range 600-800 degree C. Deformation mechanisms involve essentially dynamic recovery of the ferrite. The H. P. Stuewe model used to describe dynamic recovery of the ferrite is discussed. In the ( alpha plus gamma ) domain, the influence of phase p...