Simplified numerical approach for incremental sheet metal forming process

The current work presents a finite element approach for numerical simulation of the incremental sheet metal forming (ISF) process, called here ‘‘ISF-SAM’’ (for ISF-Simplified Analysis Modelling). The main goal of the study is to develop a simplified FE model sufficiently accurate to simulate the ISF process and quite efficient in terms of CPU time. Some assumptions have been adopted regarding the constitutive strains/stresses equations and the tool/sheet contact conditions. A simplified contact procedure was proposed to predict nodes in contact with the tool and to estimate their imposed displacements. A Discrete Kirchhoff Triangle shell element called DKT12, taking into account membrane and bending effects, has been used to mesh the sheet. An elasto-plastic constitutive model with isotropic hardening behaviour and a static scheme have been adopted to solve the nonlinear equilibrium equations. Satisfactory results have been obtained on two applications and a good correlation has been shown compared to experimental and numerical results, and at the same time a reduction of CPU time more than 60% has been observed. The bending phenomenon studied through the second application and the obtained results show the reliability of the DKT12 element

Modal Competition for Freight in Land Transportation on Jakarta-Surabaya corridor

As a part of a set of research studies about the railways transport in Indonesia, we propose this results advancement. Nowadays, the freight railways system in Indonesia suffers a complex and an apparently not easy to solve situation. The freight service is in constant degradation and it lost demand progressively, more the new highways development plans threat to increase the attractively of road transport in detriment of railways. The identifications of the structural problems will let us to propose aimed and precisely solutions to broke the current vicious circle of the freight railways system. Our analysis is supported by questionnaires applied to 93 forwarders/shippers in 186 opinions that usually contract freight transport services on the link. Each forwarder answered the same questions about his/her preferences for rail and for road freight services. We analyzed this data by the Logit model to identify the “factors of service” or variables which influence the decision of forwarders/shippers in the most important way. The results show clearly the relative importance of some railways “factors and service” in function with the others for the same mode, as well as their relative influence for the modal decision compared with the road freight transports. This paper aims to identify the structural problems of the freight railways service of “KERETA API” in the Java Island, especially between the cities of Jakarta and Surabaya which are the most important city in Indonesia. Key words: Indonesia railway development, modal competition, freight transportation, modal choic

Développement d'une Approche Simplifiée de la simulation numérique du formage incrémental

La simulation numérique du formage incrémental permet de prédire la formabilité et la qualité de la géométrie pour une trajectoire donnée. Avec les modèles classiques, le temps CPU de la simulation est très long. Le principe de l'Approche Simplifiée est d'éviter la description de l'outil et du contact en le remplaçant par une imposition locale et évolutive de déplacement à certains n uds. L'AS permet d'avoir une bonne estimation de la géométrie et de l'épaisseur de la pièce avec un temps de calcul réduit. Un travail sur l'adaptation d'un élément fini de type coques DKTRF est effectué

The DKMQ-SS Solid-Shell Element: Formulation Aspects and Applications

In this paper we present the formulation of a solid-shell element with 24 dof (the three cartesian components of displacement at the eight nodes of a solid hexahedron element), taking into account previous contributions to avoid shear, trapezoidal and thickness locking. But we also enhance the 3D displacement field by incomplete quadratic terms to improve the bending and transverse shear energies as was done for the performing DKMQ plate bending element proposed by Katili. After the formulation aspects, we present the results for some classical benchmark problems and for the linear analysis of a particular shallow foundation system called 'spider net system footing' used in Indonesia

Intercity Mode Choice Modelling: Considering the Intracity Transport Systems with Application to the Jakarta-Bandung Corridor

The choice among modes of intercity transport depends on conditions of not only intercity transport modes but also intracity transport in both the departure city and the arrival city. Intracity transport conditions might be advantageous for one intercity mode and disadvantageous for others. Intercity and intracity transport conditions are complex and need to be approached systemically. This study proposes an approach based on the passengers’ preferences. The logit model was adapted to evaluate the transport modes’ choices in competition. This model is called the “Adapted Mixed Multinomial Logit Model” (AMML). It was applied on the Jakarta-Bandung corridor in both directions. It contributes to a complete approach for intercity transport mode choice by considering the influence of the intracity transport conditions in both the departure and arrival cities. The results proved that the choice of intercity transport mode depends not only on its own quality of service but also, importantly, on that of the intracity transport systems

Geometrically nonlinear analysis of shell structures using flat DKT shell elements

This report describes nonlinear analysis o t arbitrary thin shell structures subjected to static loads. The nonlinear analysis includes pre and post-buckling behavior for any degree ot nonlinearity due to large displacements and large rotations but small strains. The formulation includes some recent developments of piate and shell theories, automatic solution strategies for the nonlinear equations; all adapted for implementation in mini and micro-computers with virtual memory.supported by the Dav'd w. Taylor Naval Ship Research and Development Center througu work request N00167-85-WR5-0372http://archive.org/details/geometricallynon00batoN00167-85-WR5-0372N

Comparison between incremental deformation theory and flow rule to simulate sheet-metal forming processes

Numerical simulation of the deep drawing process for the manufacture of aeronautical or automotive components should predict with good accuracy the behaviour during the forming operation, taking into account, the material and the process parameters. Existing simulation strategies give good results, however calculation time are long due to the high degree of non-linearities of these problems. The objective of this work is therefore to decrease the calculation time, resulting from the non-linear material behaviour. A new algorithm based on incremental deformation theory (related to Hencky Theory) is presented, in order to compute the plasticity rule in a finite element code (ABAQUS). This algorithm is used to simulate two sheet-metal forming processes: typical stretch forming operation and incremental single point sheet forming. For each case the new algorithm is compared with a classical flow rule plasticity law. In order to have a valid comparison in terms of CPU time, the two material behaviour laws have been implemented in ABAQUS EXPLICIT using the material user function (VUMAT). Good agreement in terms of the stress state and thickness distribution is obtained with the new approach. A significant decrease in CPU time is observed when the major source of non-linearity comes from the material behaviour

Contribution à l'élaboration d'un logiciel métier par éléments finis pour l'analyse thermomécanique globale d'échangeurs de chaleur à plaques et ondes

Ce travail consiste à développer un logiciel métier basé sur la modélisation thermomécanique linéaire de l'échangeur tout en intégrant les techniques d'homogénéisation. Une méthodologie de modélisation de l'échangeur constitué par un empilement de différentes ondes et tôles brasées, est donc adoptée. Cette méthodologie suppose que le comportement global de chaque couche d'ondes et tôles, est encadré par deux comportements limites déterminés par des approches mécanique périodique (HMP) et cinématique périodique (HCP). Ces deux approches sont mises en œuvre pour l application numérique tout en étudiant le chargement interne global dû à la température et à la pression. Un outil d'homogénéisation (HomPass) est ensuite développé afin de déterminer automatiquement les comportements équivalents à chaque onde et tôle brasées. Cela contribue au développement de l'outil métier final (SiTEME) dédié à l'étude thermomécanique globale de l'échangeur.This work consists of developing a software tool based on the linear thermomechanical modeling of the heat exchanger using homogenization techniques. A methodology for modeling the heat exchanger constituted by stacking of different brazed fins and sheets is adopted. This methodology assumes that the global behavior of every layer of fins and sheets is found between two behavior limits determined by periodic mechanical approach (HMP) and periodic kinematical approach (HCP). These techniques are implemented for numerical application while studying global loading due to the temperature and pressure internal loads. A homogenization tool (HomPass) is then developed in order to calculate automatically equivalent behaviors to each layer of brazed fins and sheets. That contributes to the development of the final software tool (SiTEME) dedicated to the global thermomechanical study of the heat exchanger.NANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Formulation et évaluation d'une nouvelle famille d'éléments finis incompatibles de membrane, plaques et coques de type Kirchhoff discret

COMPIEGNE-BU (601592101) / SudocSudocFranceF

Contribution à l'optimisation des paramètres du procédé d'emboutissage des tôles minces par l'approche inverse

COMPIEGNE-BU (601592101) / SudocSudocFranceF