Michel Gerard

• PhD
• Engineer at École Nationale Supérieure de Mécanique et des Microtechniques

Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal...

It is now well recognized that the material data obtained from a tensile test is less appropriate than those from a Tube Bulging Test (TBT) for a finite element simulation of tube hydroforming. However, the manufacturers still use classical data (often tensile test data) for designing metal operations due to the lack of standard for the TBT and a m...

During tube hydroforming process, the friction conditions between the tube and the die have an importance on the thickness distribution in the final conponement: But it is difficult to characterize the friction coefficient conditions. Then it’s necessary to have a good evaluation of the friction coefficient for running predictive numerical simulati...

During tube hydroforming process, the friction conditions between the tube and the die have an importance on the thickness distribution in the final conponement: But it is difficult to characterize the friction coefficient conditions. Then it's necessary to have a good evaluation of the friction coefficient for running predictive numerical simulati...

The friction conditions are responsible of the thickness distribution in a part realized by tube hydroforming. Then it is essential to have a good evaluation of the friction coefficient for running predictive finite element simulations. The tube expansion in a square die is one of tests proposed for the friction evaluation. In the literature, sever...

The effect of the friction coefficient in the strain path of hydroformed tube is discussed in this paper. A finite element simulation with the LS-DYNA/Explicit software has been performed and experiments have been carried out. The localized thinning can be related to necking and then, the use of the Forming Limit Curve (FLC) and the analysis of the...

A focus on the effect of friction condition on tube hydroforming during corner filling in a square section die is proposed. Three approaches have been developed: an analytical model from the literature has been programmed, finite element simulations have been conducted and experiments have been carried out. Effect of friction coefficient on the thi...

Last years analytical or finite element models of milling become more efficient and focus on more physical aspects, nevertheless the milling process is still experimentally unknown on a wide range of use. This paper propose to analyse with accuracy milling operations by investigating the cutting forces values, shape of cutting forces curves obtaine...

The aim of this study is to optimize micro-mills and their conditions of use to manufacture plastic injection molds in hardened tool steels by micro-milling. The presented results deal with the test of four types of tungsten carbide square end micro-mills in elementary operations with different feed rates and cutting speeds in order to analyze the...

The present work focuses on developing cost-efficient, fast and precise tooling for prototyping and smallseries manufacture of polymer chips using injection moulding. Exchangeable mould inserts were manufactured on thick silicon wafers patterned using SU-8 negative epoxy-based resist. First masters with feature size from a few tens to hundreds of m...

The paper is focused on a sensitivity analysis developed to study the relevance of experimental hardening curves obtained from tube bulging test to quantify the influence and the contribution of experimental uncertainties on the response variability. The experiments are based on “online” measurements of the internal pressure and the bulge height. A...

There is need for less expensive and rapid tooling for prototyping components and systems in thermoplastics using microreplication technique such as injection moulding. This paper presents the adaptation of a conventional injection moulding process using a microstructured silicon mould insert. Microstructures with aspect ratio of 4 were produced by...

The sintering behaviours of injection moulded components in 316L stainless steel powder are investigated by means of the bending and dilatometric tests in the furnace. Various thermal cycles are realised for different tests. The experimental results are used to determine the parameters of uniaxial viscosity and sintering stress in the viscoplastic...

The paper is related to the analysis of shape distortions and springback effects arising in single point incremental sheet forming in order to study the use of a FE model based on shell elements to perform simulation of the process. A comparison between numerical and experimental results is made to assess the suitability of the model. The measureme...

In recent years, micro powder injection molding process continually grows and demonstrates excellent economic prospects. Micro-PIM researches have been developed in our lab with a professional equipment in which mono-injection and co-injection experiments with 316L stainless steel powder of 3.4μm (d50) have been realized. In this paper, numerical s...

An inverse method of identification for the determination of material parameters that are used for the FEM simulation of milling processes is proposed. First of all, a special device has been instrumented and calibrated to perform force and torque measures, directly during milling experiments in using a piezoelectric dynamometer and a high frequenc...

The paper is focused on the determination of mechanical characteristics for metallic materials shaped like tubes as used in tube hydroforming process. First, a procedure is described to carry out experimental tube bulging tests. It permits to identify a law linking the internal pressure to the bulge height. Second, based on this law and an original...

This paper is focused on the determination of mechanical characteristics for metallic materials shaped like tubes [1,2,3] as used in hydroforming process. Like for other processes (forging, deep-drawing), specific laboratory tests can be required for material characterization. For tube hydroforming, it has been found that tube bulging test is more...

Micro injection molding is one of the key technologies to produce small and complicated components in various materials, including plastic, metal, ceramics etc. In order to improve product quality and to reduce manufacturing cost, the specified experiments have been realized to analyze the process parameters. A specially designed mould with fiv...

High Speed Machining has become one of the most used processes in macro and micro mechanical manufacturing. The understanding of the physical phenomena and the identification of material behaviour in machining are the main issues for the industrial process optimization. Some analytical models and FEM models are available in the literature. To impro...

An identification procedure for the determination of material parameters that are used for the FEM simulation of milling processes is proposed. This procedure is based on the coupling of a numerical identification procedure and FEM simulations of milling operations. The experimental data result directly from measurements performed during milling ex...

An identification procedure for the determination of material parameters that are used for the FEM simulation of High Speed Machining processes is proposed. This procedure is based on the coupling of a numerical identification procedure and FEM simulations of milling operations. The experimental data result directly from measurements performed duri...

The paper is concerned with the development of the injection molding process for micro-parts with an application to injection moulding of micro-gears with the volume less than 0.2 mm3. First the paper describes the equipment that is used consisting in a micro-injection equipment that that is used consisting in a micro-injection that permits simulta...

At the beginning, a special device has been instrumented and calibrated to perform force measures, directly during milling experiments in using a piezoelectric dynamome-ter and a high frequency charge amplifier. Then FEM simulations of milling are performed using explicit ALE based FEM code. The material behaviour is described from a Johnson-Cook c...

At the beginning, a special device has been instrumented and calibrated to perform force measures, directly during milling experiments in using a piezoelectric dynamometer and a high frequency charge amplifier. Then FEM simulations of milling are performed using explicit ALE based FEM code. The material behaviour is described from a Johnson-Cook co...

Nous avons développé un outil de simulation numérique directe, basé sur une approche par domaine fictif, et adapté pour les suspensions de particules solides dans une matrice fluide. L'outil, basé sur une méthode d'éléments finis mixtes, permet de simuler l'écoulement d'une suspension de particules solides à grande concentration solide (jusqu'à 60%...

In order to study the properties of 316L in heat affected zone (HAZ) of weld, the tensile tests of the thermal simulation process were performed at 20°C, 600°C, 1000°C and 1100°C. The stress-strain curves of 316L at different strain rates were obtained. The results show that both Young's module E and yield strength σ0.2 decrease obviously with the...

Summary Timber-concrete composite structures represent an emerging technology in France. At present, the objectives are to try and get the best performance by using characteristics of both timber and concrete. But timber has specific mechanical properties and the connection between two various materials is not so simple as we could imagine; further...

L'Usinage à Grande Vitesse (UGV) est de plus en plus utilisé dans l'industrie mécanique ou micromécanique. La compréhension des phénomènes présents lors du procédé est un enjeu majeur pour l'optimisation des procédés industriels. Un certain nombre de modèles analytiques et de modèles par éléments finis sont disponibles dans la littérature. Pour aug...

Les structures minces soumises à un chargement sismique sont sensibles au flambage malgré le fait qu'elles soient dimensionnées correctement pour les chargements statiques vis-à-vis des règles actuelles. Cette étude est menée dans le but de répondre aux questions concernant l'effet d'un chargement dynamique de cisaillement sur des coques minces. Po...