Pierre Margerit

Ecole Nationale Supérieure d'Arts et Métiers | ENSAM · Laboratoire Procédés et Ingénierie en Mécanique et Matériaux (PIMM)

Directed energy deposition (DED) is a class of additive manufacturing (AM) processes using a moving focused heat source to melt feed-stock material simultaneously deposited by a moving nozzle. Both single and multi-track scanning strategies can be performed to build multilayer thin-walled structures and massive parts alike. Process parameters have...

In recent years, significant progress has been made in modeling various additive manufacturing processes such as Fused Deposition Modeling (FDM) for polymers, Directed Energy Deposition (DED) for metals (including and Wire Arc Additive Manufacturing (WAAM) and Wire Laser Additive Manufacturing (WLAM)), or 3D Printed Concrete (3DPC). However, there...

Directed energy deposition (DED) is a class of additive manufacturing (AM) processes using a moving focused heat source to melt feed-stock material simultaneously deposited by a moving nozzle. Both single and multi-track scanning strategies can be performed to build multilayer thin-walled structures and massive parts alike. Process parameters have...

This article investigates the application of a multi-robotic platform to the fabrication of complex “free-form” timber structures. A concept of “smart factory”, with a 13-DOF robotic cell combining robotic mobility with fixed workstations, is proposed. A computational workflow was implemented to allow for fast iterations during the early design sta...

This paper introduces the problem formulation of kernel-based subspace estimates for line spectral estimation. Subspace methods suffer from cubic time complexity: specifically, the original ESPRIT algorithm relies on obtaining the signal's singular vectors by SVD/EVD. We show that the original ESPRIT algorithm does not need the signal's singular ve...

We introduce two FFT-based ESPRIT algorithms for line spectral estimation which have lower time complexities than the original ESPRIT algorithm's O(N^3). The preferred method, named FFT-ESPRIT, can be characterized as being a kernel-based subspace estimator that achieves super-resolution at O(N log N) for frequency estimates. First, we demonstrate...

We introduce two FFT-based ESPRIT algorithms for line spectral estimation which have lower time complexities than the original ESPRIT algorithm's O(N^3). The preferred method, named FFT-ESPRIT, can be characterized as being a kernel-based subspace estimator that achieves super-resolution at O(N log N) for frequency estimates. First, we demonstrate...

The detection of anomalies is at the basis of any 3D printing control. In this paper, we propose a methodology for detection of anomalies based on computer vision. This methodology is composed of three modules: (1) image acquisition, (2) interlayer line and layer segmentation and (3) characterization of the local geometry and texture of the layers...

Various technologies of in-line reinforcement for extrusion-based 3D printing have been proposed in the recent years. With such techniques, knowledge of the dynamic rheological properties of the extruded material is a key point for several issues, such as its ability to properly impregnate reinforcement, and possibly to pull the reinforcement thank...

The issue of reinforcement for 3D concrete printing has received considerable attention, as constructions have to comply with reliability principles and building standards. Here a specific process called Flow-Based Pultrusion for additive manufacturing (FBP), inspired by pultruded composite manufacturing and built on existing extrusion-based 3D pri...

Manufacturing strains and subsequent residual stresses are key elements in the behavior of thin-walled structures, as they induce buckling, warping, and failure. This work proposes a combined experimental and numerical analysis of these features by investigating the additive manufacturing of a thin-walled structure using directed energy deposition....

Manufacturing strains and subsequent residual stresses are key elements in the behavior of thin-walled structures, as they induce buckling, warping, and failure. This work proposes a combined experimental and numerical analysis of these features by investigating the additive manufacturing of a thin-walled structure using directed energy deposition....

The response of architectured structures is characterized by multi-scale kinematics, which complex relation and effect on the engineering load response is still not completely understood and therefore needs further investigations. More precisely, the lack of experimental methods enabling to provide multi-scale data remains a key issue. The paper pr...

An original experimental setup, dedicated to the measurement of the dynamic response of structures, is presented. Called the Robotized Laser Doppler Vibrometer (RLDV), it consists in the assembly of a fixed point Laser Doppler Vibrometer (LDV) on a 6-axis industrial robot arm. This allows to measure the 3D velocity on the surface of objects with a...

The multi-scale nature of architectured materials raises the need for advanced experimental methods suitable for the identification of their effective properties, especially when their size is finite and they undergo extreme deformations. The present work demonstrates that state-of-the art image processing methods combined with numerical and analyt...

Mechanical properties of as-printed 316L stainless steel thin-walled structures obtained by directed energy deposition are investigated. In-situ tensile and fracture tests are performed on small samples obtained from a additively manufactured square section tube and extracted with three different orientations with respect to the part build directio...

Elastic sheets with architectured cut-outs can be engineered to exhibit unusual mechanical characteristics, such as auxeticity and extreme extensibility. In this work, a combination of experimental and numerical tools is used to shed new light on the deformation patterns of soft auxetic sheets undergoing large tensile and shear strains. A multi-sca...

This paper is concerned with the prediction of the propagation of flexural waves in anisotropic laminated plates with relatively high slenderness ratios by means of refined plate models. The study is conducted using the Bending-Gradient theory which is considered as an extension of the Reissner–Mindlin theory to multilayered plates. Two projections...

The High Resolution Wavevector Analysis (HRWA) is presented and its application illustrated. Extending the High Resolution Wavenumber Analysis method [1] to 2D signals, it allows the wide-band and local characterization of the linear elastic behavior of anisotropic plates. The method belongs to the family of experimental wavenumber-based characteri...

The aim of this paper is to discuss the dialectic form-finding of a complex timber structure based on an innovative structural system: shell-nexorade hybrids. Nexorades, also known as reciprocal frames are elegant structures that suffer from a relatively poor structural behavior due to in-plane shear and bending of the members. Introducing plates a...

Le présent travail, réalisé dans le cadre du projet ANR MAESSTRO, concerne le remplacement des tables d’harmonie de piano traditionnellement constituées d’épicéa par des structures composites stratifiées. Cette démarche suppose une connaissance fine des matériaux à remplacer et des matériaux de remplacement. La contribution de la thèse consiste don...

The High-Resolution Wavenumber Analysis (HRWA) is presented. It identifies complex wavenumbers and amplitudes of waves composing the harmonic response of a beam. Based on the frequency dependence of these wavenumbers, experimental dispersion equations of various beam mechanisms (e.g bending, torsion) can be retrieved. The HRWA method is compared to...