Effect of artificial aging treatment on microstructure, mechanical properties and fracture behavior of 2017A alloy

The effect of artificial aging treatment on 2017A aluminum alloy microstructure, mechanical properties, and fracture behavior was investigated. The samples were taken from the as-received alloy and aged at 170 °C for 5, 10, 15, 20, and 30 hours. An optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), microhardness and tensile strength tests were used to characterize mechanical and microstructural properties. The microstructural analysis revealed that as the aging treatment duration is increased, the size and density of precipitates grow larger and more numerous. According to X-ray diffraction measurements, the microstructural evolution caused by aging treatments is primarily due to an increase in precipitation of the hardening phase -Al2Cu. According to the tensile test results, the yield stress increases with increasing aging duration. The fracture surface analysis of failed specimens subjected to tensile loading revealed that the aging treatment conditions had a significant impact on the morphology and mode of fracture: the mixed-mode (ductile-brittle) failure was established for intermediate aging durations (aging at 170 °C for 15 and 20 h), and the intergranular fracture was found to be more pronounced when the aging duration is prolonged due to the coalescence of fine precipitates at the grain boundary

Modelling of thermal ageing effect on elastic-viscoplastic behaviour of semi-cristallin polymers by D.N.L.R approach

AbstractThis work is devoted to the numerical and experimental study of thermal ageing effect on microstructure and mechanical properties of HDPE. Uniaxiale tension tests were conducted at 25 0C in order to characterize the large deformation response of HDPE. The influence of thermal ageing on the alteration of the large deformation response of HDPE was examined. A Distribution of Non Linear Relaxation (D.N.L.R) Approach was used to describe the mechanical response of virgin HDPE. The thermal ageing effect was incorporated into the constitutive model to capture the stress-strain behaviour up to failure of aged HDPE. The model is shown to be in good agreement with experimental results

Study of the slant fracture in solid and hollow cylinders: Experimental analysis and numerical prediction

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the 2017A-T4 aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporate shear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure

Study of the slant fracture in solid and hollow cylinders: Experimental analysis and numerical prediction

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the2017A-T4aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporateshear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure

The calculation of drag on nano-cylinders

A novel formulation, based on the molecular dynamics approach, has been proposed to calculate localised drag forces over nano-cylinders. The computational evidence suggests that the existing methods underestimate drag coefficients at nano-scales at least by 20-40%. These coefficients are also up to seven times higher than the ones calculated by continuum based analytical solutions. The deviation increases at Reynolds number values less than one. The proposed formulation describes a new method for calculating localised values for both the kinetic and configurational parts of the Irwin-Kirkwood stress tensor at given fixed positions within the computational domain

Computational model of collaborative negotiation based on the interpersonal relation of dominance

L'essor des travaux en informatique affective voit la naissance de diverses questions de recherches pour étudier les interactions agents /humains. Parmi elles, se pose la question de l'impact des relations interpersonnelles sur les stratégies de communications. Les interactions entre un agent conversation et un utilisateur humain prennent généralement place dans des environnements collaboratifs où les interlocuteurs partagent des buts communs. La relation interpersonnelle que les individus créent durant leurs interactions affecte leurs stratégies de communications. Par ailleurs, des individus qui collaborent pour atteindre un but commun sont généralement amenés à négocier. Ce type de négociation permet aux négociateurs d'échanger des informations afin de mieux collaborer. L'objectif cette thèse est d'étudier l'impact de la relation interpersonnelle de dominance sur les stratégies de négociation collaborative entre un agent et un humain. Ce travail se base sur des études en psychologie sociale qui ont défini les comportements liés à la manifestation de la dominance dans une négociation. Nous proposons un modèle de négociation collaborative dont le modèle décisionnel est régi par la relation de dominance. En effet, en fonction de sa position dans le spectre de dominance, l'agent est capable d'exprimer une stratégie de négociation spécifique. En parallèle, l'agent simule une relation interpersonnelle de dominance avec son interlocuteur. Pour ce faire, nous avons doté l'agent d'un modèle de théorie de l'esprit qui permet à l'agent de raisonner sur les comportements de son interlocuteur afin de prédire sa position dans le spectre de dominance. Ensuite, il adapte sa stratégie de négociation vers une stratégie complémentaire à celle détectée chez son interlocuteur. Nos résultats ont montré que les comportements de dominance exprimés par notre agent sont correctement perçus. Par ailleurs, le modèle de la théorie de l'esprit est capable de faire de bonnes prédictions avec seulement une représentation partielle de l'état mental de l'interlocuteur. Enfin, la simulation de la relation interpersonnelle de dominance a un impact positif sur la négociation: les négociateurs atteignent de bon taux de gains communs. De plus, la relation de dominance augmente le sentiment d'appréciation entre les négociateurs et la négociation est perçue comme confortable.The rise of work in affective computing sees the emergence of various research questions to study agent / human interactions. Among them raises the question of the impact of interpersonal relations on the strategies of communication. Human/agent interactions usually take place in collaborative environments in which the agent and the user share common goals. The interpersonal relations which individuals create during their interactions affects their communications strategies. Moreover, individuals who collaborate to achieve a common goal are usually brought to negotiate. This type of negotiation allows the negotiators to efficiently exchange information and their respective expertise in order to better collaborate. The objective of this thesis is to study the impact of the interpersonal relationship of dominance on collaborative negotiation strategies between an agent and a human. This work is based on studies from social psychology to define the behaviours related to the manifestation of dominance in a negotiation. We propose a collaborative negotiation model whose decision model is governed by the interpersonal relation of dominance. Depending on its position in the dominance spectrum, the agent is able to express a specific negotiation strategy. In parallel, the agent simulates an interpersonal relationship of dominance with his interlocutor. To this aim, we provided the agent with a model of theory of mind that allows him to reason about the behaviour of his interlocutor in order to predict his position in the dominance spectrum. Afterwards, the agent adapts his negotiation strategy to complement the negotiation strategy detected in the interlocutor. Our results showed that the dominance behaviours expressed by our agent are correctly perceived by human participants. Furthermore, our model of theory of mind is able de make accurate predictions of the interlocutor behaviours of dominance with only a partial representation of the other's mental state. Finally, the simulation of the interpersonal relation of dominance has a positive impact on the negotiation: the negotiators reach a good rate of common gains and the negotiation is perceived comfortable which increases the liking between the negotiators

Relevance of Incorporating Cavity Shape Change in Modelling the Ductile Failure of Metals

The purpose of this paper is to assess the relevance of considering the cavities shape change in the context of physically based modelling of the ductile rupture in metals. Two thermomechanical models have been used in this study: the GTN model, developed by Gurson, Tvergaard, and Needleman for spherical cavities keeping their shape unchanged during loading, and the GLD model, proposed by Gologanu, Leblond, and Devaux for ellipsoidal cavities that can change their shape. The GTN and GLD models have been extended to take into account material thermal heating due to plastic dissipation. These two constitutive laws have been implemented into the commercial finite element code Abaqus/Explicit in order to simulate the necking of a round bar and the failure of a sheet deep drawing. The results showed the importance of incorporating the shape effects of the cavities for a correct description of the material failure

Modèle de négociation collaborative basé sur la relation interpersonnelle de dominance

The rise of work in affective computing sees the emergence of various research questions to study agent / human interactions. Among them raises the question of the impact of interpersonal relations on the strategies of communication. Human/agent interactions usually take place in collaborative environments in which the agent and the user share common goals. The interpersonal relations which individuals create during their interactions affects their communications strategies. Moreover, individuals who collaborate to achieve a common goal are usually brought to negotiate. This type of negotiation allows the negotiators to efficiently exchange information and their respective expertise in order to better collaborate. The objective of this thesis is to study the impact of the interpersonal relationship of dominance on collaborative negotiation strategies between an agent and a human. This work is based on studies from social psychology to define the behaviours related to the manifestation of dominance in a negotiation. We propose a collaborative negotiation model whose decision model is governed by the interpersonal relation of dominance. Depending on its position in the dominance spectrum, the agent is able to express a specific negotiation strategy. In parallel, the agent simulates an interpersonal relationship of dominance with his interlocutor. To this aim, we provided the agent with a model of theory of mind that allows him to reason about the behaviour of his interlocutor in order to predict his position in the dominance spectrum. Afterwards, the agent adapts his negotiation strategy to complement the negotiation strategy detected in the interlocutor. Our results showed that the dominance behaviours expressed by our agent are correctly perceived by human participants. Furthermore, our model of theory of mind is able de make accurate predictions of the interlocutor behaviours of dominance with only a partial representation of the other's mental state. Finally, the simulation of the interpersonal relation of dominance has a positive impact on the negotiation: the negotiators reach a good rate of common gains and the negotiation is perceived comfortable which increases the liking between the negotiators.L'essor des travaux en informatique affective voit la naissance de diverses questions de recherches pour étudier les interactions agents /humains. Parmi elles, se pose la question de l'impact des relations interpersonnelles sur les stratégies de communications. Les interactions entre un agent conversation et un utilisateur humain prennent généralement place dans des environnements collaboratifs où les interlocuteurs partagent des buts communs. La relation interpersonnelle que les individus créent durant leurs interactions affecte leurs stratégies de communications. Par ailleurs, des individus qui collaborent pour atteindre un but commun sont généralement amenés à négocier. Ce type de négociation permet aux négociateurs d'échanger des informations afin de mieux collaborer. L'objectif cette thèse est d'étudier l'impact de la relation interpersonnelle de dominance sur les stratégies de négociation collaborative entre un agent et un humain. Ce travail se base sur des études en psychologie sociale qui ont défini les comportements liés à la manifestation de la dominance dans une négociation. Nous proposons un modèle de négociation collaborative dont le modèle décisionnel est régi par la relation de dominance. En effet, en fonction de sa position dans le spectre de dominance, l'agent est capable d'exprimer une stratégie de négociation spécifique. En parallèle, l'agent simule une relation interpersonnelle de dominance avec son interlocuteur. Pour ce faire, nous avons doté l'agent d'un modèle de théorie de l'esprit qui permet à l'agent de raisonner sur les comportements de son interlocuteur afin de prédire sa position dans le spectre de dominance. Ensuite, il adapte sa stratégie de négociation vers une stratégie complémentaire à celle détectée chez son interlocuteur. Nos résultats ont montré que les comportements de dominance exprimés par notre agent sont correctement perçus. Par ailleurs, le modèle de la théorie de l'esprit est capable de faire de bonnes prédictions avec seulement une représentation partielle de l'état mental de l'interlocuteur. Enfin, la simulation de la relation interpersonnelle de dominance a un impact positif sur la négociation: les négociateurs atteignent de bon taux de gains communs. De plus, la relation de dominance augmente le sentiment d'appréciation entre les négociateurs et la négociation est perçue comme confortable