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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Mon, 16 Sep 2024 19:11:47 GMT2024-09-16T19:11:47ZHypervelocity impacts into porous graphite: Experiments and simulations
http://hdl.handle.net/10985/15476
Hypervelocity impacts into porous graphite: Experiments and simulations
HÉBERT, David; SEISSON, Gabriel; RULLIER, Jean-Luc; BERTRON, Isabelle; HALLO, Ludovic; CHEVALIER, Jean Marc; THESSIEUX, C.; GUILLET, Francois; BOUSTIE, Michel; BERTHE, Laurent
We present experiments and numerical simulations of hypervelocity impacts of 0.5mm steel spheres into graphite, for velocities ranging between 1100 and 4500ms?1. Experiments have evidenced that, after a particular striking velocity, depth of penetration no longer increases but decreases. Moreover, the projectile is observed to be trapped below the crater surface. Using numerical simulations, we show how this experimental result can be related to both materials, yield strength. A Johnson-Cook model is developed for the steel projectile, based on the literature data. A simple model is proposed for the graphite yield strength, including a piecewise pressure dependence of the Drucker-Prager form, which coefficients have been chosen to reproduce the projectile penetration depth. Comparisons between experiments and simulations are presented and discussed. The damage properties of both materials are also considered, by using a threshold on the first principal stress as a tensile failure criterion. An additional compressive failure model is also used for graphite when the equivalent strain reaches a maximum value. We show that the experimental crater diameter is directly related to the graphite spall strength. Uncertainties on the target yield stress and failure strength are estimated.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/154762017-01-01T00:00:00ZHÉBERT, DavidSEISSON, GabrielRULLIER, Jean-LucBERTRON, IsabelleHALLO, LudovicCHEVALIER, Jean MarcTHESSIEUX, C.GUILLET, FrancoisBOUSTIE, MichelBERTHE, LaurentWe present experiments and numerical simulations of hypervelocity impacts of 0.5mm steel spheres into graphite, for velocities ranging between 1100 and 4500ms?1. Experiments have evidenced that, after a particular striking velocity, depth of penetration no longer increases but decreases. Moreover, the projectile is observed to be trapped below the crater surface. Using numerical simulations, we show how this experimental result can be related to both materials, yield strength. A Johnson-Cook model is developed for the steel projectile, based on the literature data. A simple model is proposed for the graphite yield strength, including a piecewise pressure dependence of the Drucker-Prager form, which coefficients have been chosen to reproduce the projectile penetration depth. Comparisons between experiments and simulations are presented and discussed. The damage properties of both materials are also considered, by using a threshold on the first principal stress as a tensile failure criterion. An additional compressive failure model is also used for graphite when the equivalent strain reaches a maximum value. We show that the experimental crater diameter is directly related to the graphite spall strength. Uncertainties on the target yield stress and failure strength are estimated.A comparison between Sobol’s indices and Shapley’s effect for global sensitivity analysis of systems with independent input variables
http://hdl.handle.net/10985/24587
A comparison between Sobol’s indices and Shapley’s effect for global sensitivity analysis of systems with independent input variables
VUILLOD, Bruno; MONTEMURRO, Marco; PANETTIERI, Enrico; HALLO, Ludovic
The model-based system engineering approach consists of assembling subsystems together to model a complete system. In this context, some functional blocks can have a considerable influence on the overall behaviour of the system. A preliminary identification of the influence of the subsystems on the output responses can help reducing the complexity of the overall system, with a negligible impact on the overall accuracy. Therefore, pertinent indicators must be introduced to achieve this goal. To this purpose, in this work, some well-established methods and algorithms for global sensitivity analysis (GSA) of linear and non-linear systems with independent input variables, i.e., approaches based on Sobol’s indices (different algorithms are considered), and Shapley’s effect, are compared on both benchmark functions and real-world engineering problems. Specifically, in this paper, real-world engineering problems dealing with linear and non-linear systems are modelled through commercial finite element software and/or dedicated programming languages for solving complex non-linear dynamics models, like Modelica. Regarding Modelica models, an efficient strategy based on functional mock-up units is presented to speed up the simulation of highly non-linear dynamic systems. All numerical models are interfaced with the algorithms used for GSA through ad-hoc routines coded in Python environment. For each problem, a systematic comparison between the results provided by the different algorithms making use of Sobol’s indices and Shapley’s indices is performed, in terms of reliability, accuracy and computational costs.
Thu, 01 Jun 2023 00:00:00 GMThttp://hdl.handle.net/10985/245872023-06-01T00:00:00ZVUILLOD, BrunoMONTEMURRO, MarcoPANETTIERI, EnricoHALLO, LudovicThe model-based system engineering approach consists of assembling subsystems together to model a complete system. In this context, some functional blocks can have a considerable influence on the overall behaviour of the system. A preliminary identification of the influence of the subsystems on the output responses can help reducing the complexity of the overall system, with a negligible impact on the overall accuracy. Therefore, pertinent indicators must be introduced to achieve this goal. To this purpose, in this work, some well-established methods and algorithms for global sensitivity analysis (GSA) of linear and non-linear systems with independent input variables, i.e., approaches based on Sobol’s indices (different algorithms are considered), and Shapley’s effect, are compared on both benchmark functions and real-world engineering problems. Specifically, in this paper, real-world engineering problems dealing with linear and non-linear systems are modelled through commercial finite element software and/or dedicated programming languages for solving complex non-linear dynamics models, like Modelica. Regarding Modelica models, an efficient strategy based on functional mock-up units is presented to speed up the simulation of highly non-linear dynamic systems. All numerical models are interfaced with the algorithms used for GSA through ad-hoc routines coded in Python environment. For each problem, a systematic comparison between the results provided by the different algorithms making use of Sobol’s indices and Shapley’s indices is performed, in terms of reliability, accuracy and computational costs.