Tires are the most influential component of the vehicle as they constitute the only contact between the vehicle and the road and have to generate and transmit forces necessary for the driver to control the vehicle. Hydroplaning is a phenomenon which occurs when a layer of water builds up between the tires of a vehicle and the road surface which leads to loss of traction that prevents the vehicle from responding to control inputs such as steering, braking or acceleration. It has become an extremely important factor in the automotive and tire industry to study the factors affecting vehicle hydroplaning. Nearly 10-20% of road fatalities are caused by lack of traction on wet surfaces. The tire tread pattern, load, inflation pressure, slip and camber angles influence hydroplaning to a great extent. Finite Element Analysis, although computationally expensive, provides an excellent way to study such Fluid Structure Interactions (FSI) between the tire-water-road surfaces. Abaqus FSI CEL approach has been used to study tire traction with various vehicle configurations. The tire force data obtained from the Finite Element simulations is used to develop a full vehicle hydroplaning model by integrating the relevant outputs with the commercially available vehicle dynamics simulation software, CarSim. / Master of Science

In this thesis, the dynamics of two plates overlapping and connected by three bolts are studied. The data collected in the test are used in modal analysis. The vibrational test and the modal analysis were made using an LMS system. Hammer excitation is used for the tests. The main purpose of this thesis is to study how the suspensions affect the extracted eigenfrequencies and modal dampings. In this thesis, more than 10 suspensions were examined. Another objective in this thesis work is to build an FE-model. This model is made using the software Abaqus. To improve the reliability of the FE-model, a set of reliable experimental data is used to calibrate the model. The calibrated FE-model, using the measurement data, has a dynamic behavior close to the measurement data.

Le « Frittage Flash » ou « Spark Plasma Sintering (SPS) » est utilisé pour consolider des poudres en des temps relativement courts (quelques minutes). Ce procédé utilise un haut courant continu pulsé (quelques kA), traversant les parties conductrices du système et générant une montée rapide en température induite principalement par effet Joule. L’application d’un chargement mécanique, via des pistons, et d’une rapide montée en température permet d’obtenir une pièce dense sans grossissement excessif des grains. L’objectif de ce travail a été de proposer une simulation numérique thermo-électro-mécanique du procédé « Frittage Flash » sur ABAQUS, afin de suivre in situ les évolutions de température, de porosité et des contraintes difficilement accessibles expérimentalement. Dans ce travail, un modèle de comportement des corps poreux est proposé. Cette approche est basée sur les modèles micromécaniques de la littérature et modifiés de manière heuristique pour reproduire la densification réelle du matériau pour des porosités comprises entre 0 et 50%. Les simulations thermo-électro-mécanique incluant ce modèle, intègrent la dépendance en porosité et température des paramètres matériaux. Quatre cycles d’élaboration de poudre de nickel ont été réalisés avec différentes histoires de température. Les évolutions de la température et de la porosité calculées ont été confrontées avec des résultats expérimentaux. Des analyses post mortem sur des échantillons densifiés confortent la distribution de la température obtenue par le calcul. Ce travail ouvre de nombreuses perspectives, notamment, la possibilité d’optimiser le procédé / Nowadays, Spark Plasma Sintering (SPS) is used to consolidate powders in a relative short time (few minutes). This process uses a pulsed high DC electrical current (few kA) which flows through the conductive part of the device and generates large heating rate mainly due to Joule effect. The application of an uniaxial pressure via punches combined with a rapid heating allow the production of near net shape specimen. The thermal electrical mechanical numerical simulation of SPS process is a powerful tool to capture in situ evolutions of temperature, porosity and stresses which are difficult to obtain in experiments. In this work, a new constitutive model is presented for the description of the behavior of porous medium. This model is based on original viscoplastic micromechanical models of the literature and modified in a heuristic manner to better reproduce the real densification of sintered material for porosity in the range [0;0,5]. The model has been implemented in ABAQUS software. A thermal electrical mechanical simulation of SPS is performed where the dependence of material parameters on temperature and porosity is taken into account. Four processing cycles of nickel have been conducted with different temperature histories. Calculated porosity and temperature evolutions are compared to experimental results. Post-mortem analyses of the material (grain size, yield stress) confirm the temperature distribution obtained by numerical simulations in the sample made of nickel. This simulation is seen to be able to capture experimental trends. The work will permit in a near future the optimization of the sintering conditions to reach prescribed properties

Tese de mestrado. Engenharia Mecânica. 2005. Faculdade de Engenharia. Universidade do Porto

This work aims at providing a numerical tool for the efficient design of the multidirectional carbon fiber reinforced composite material by means of finite element simulations. Abaqus/ CAE v 6.9-1 software has been used to establish a 3D model for simulation of the tensile test on the composite specimen. The aim of this analysis of multidirectional carbon fiber reinforced composite is to predict the strain and stress distribution in different plies through thickness. Tensile test experiment was carried out and the result was analyzed by ARAMIS to calculate the young’s modulus, stress, loads and strain of the composite specimen. The numerical model was compared against the result obtained from tensile test experiment to arrive at meaningful results for validation. This is done in order to understand the mechanical strength and strain at failure of the composite material. In this work three types of CFRP composite specimens are used, all have same 15 no. of ply but stacked in different orientation. It is found out that mechanical strength, failure load and strain differ slightly depending on this different ply orientation. A series of different modeling technique has also been done to verify the best modeling technique. The micromechanics of composite material is complex and the experimental predictions are time consuming and expensive. Though using FEM frequently solves the problem.

This thesis concerns one of the upcoming and well discussed subjects withincalculations these days, namely how to perform an analysis of the interactionbetween fluid and structure, called FSI (Fluid Structure Interaction). In the report,evaluations of two different methods of simulating FSI are done. These are knownas Practical FSI (P-FSI) and Direct Coupled FSI (DC-FSI). The methods aredeveloped by Acusim in cooperation with Simulia and the softwares used areAbaqus and AcuSolve.The first part of the thesis is dedicated to explain the general theory and thegoverning equations for FSI. After the general explanation a more delimitatedexplanation regarding P-FSI and DC-FSI are given. After this we show how tosetup and perform the couplings regarding which parameters that need to bedefined and how to perform the analyses using Abaqus and AcuSolve.The last section of the thesis covers the evaluation process. We started withevaluating the methods against a benchmark problem where we compared thecalculation time and accuracy regarding displacements and frequencies. The nextthing we evaluated was how different numbers of modes used in the P-FSIcoupling affects the result. The last thing we evaluated was the robustness of themethods using different mass densities of the structure and different time-stepsizes.The result of the evaluation regarding the criteria: accuracy, calculation time androbustness showed that the P-FSI method is the most efficient method comparedto DC-FSI regarding FSI problems when the structural response is linear.

The aim of this study was to use the finite element method to model crack, corrosion, and Crack-in-Corrosion defects in a pipeline. The pipe material under investigation for this study was API 5L X60, 508 mm diameter with a wall thickness of 5.7 mm. The pipe material was evaluated using Tensile, Charpy, and J testing in order to model the defects and to establish the numerical failure criteria. Corrosion defects were modeled as flat-bottomed grooves. The collapse pressure was predicted when the deepest point in the bottom of the defect reached a critical stress. Based on this criterion, the FE corrosion failure pressure predictions were conservative compared to the experimental failure pressures, conducted by Hosseini [9], with an average error of 10.13%. For crack modeling, the failure criteria were established considering the plastic collapse limit and the fracture limit. Both the Von Mises stress in the crack ligament and the J-integral values around the crack were monitored to predict the failure pressure of the model. The crack modeling was done based on two approaches, the uniform depth profile and the semi-elliptical profile. The crack with uniform depth profile was done because the uniform shape is the logical equivalent shape for a colony of cracks. The crack with the semi-elliptical profile was done to have a less conservative results and because the experiments were done with semi-elliptical cracks. The FE crack modeling results were conservative compared to the experimental collapse pressure with an average error of 19.64% for the uniform depth profile and 5.35% for the semi-elliptical profile. In crack-in-corrosion (CIC) defect modeling, the crack was modeled with uniform depth because it was very difficult to model the semi-elliptical crack profile when the crack defect is coincident with a corrosion defect. The results were conservative compared to the experimental results with an average error of 22.18%. In general, the FE modeling provides the least conservative failure pressure prediction over the existing analytical solutions for pipe with longitudinal corrosion, crack, and CIC defects.

The ballistic impact of Twaron CT709® plain weave fabrics is studied using an explicit finite element method. Many existing approximations pertaining to woven fabrics cannot adequately represent strain rate-dependent behavior exhibited by the Twaron fabrics. One-dimensional models based on linear viscoelasticity can account for rate dependency but are limited by the simplifying assumptions on the fabric architecture and stress state. In the current study, a three-dimensional fabric model is developed by treating each individual yarn as a continuum. The yarn behavior is phenomenologically described using a three-dimensional linear viscoelastic constitutive relation. A user subroutine VUMAT for ABAQUS/Explicit® is developed to incorporate the constitutive behavior. By using the newly developed viscoelasticity model, a parametric study is carried out to analyze the effects of various parameters on the impact behavior of the Twaron fabrics, which include projectile shape and mass, gripping conditions, inter-yarn friction, and the number of fabric layers. The study leads to the determination of the optimal number of fabric layers and the optimized level of inter-yarn friction that are needed to achieve the maximum energy absorption at specified impact speeds. The present study successfully utilizes the combination of 3D weave architecture and the strain rate dependent material behavior. Majority of the existing work is based either on geometry simplification or assumption of elastic material behavior. Another significant advantage with the present approach is that the mechanical constitutive relation, coded in FORTRAN®, is universal in application. The desired material behavior can be obtained by just varying the material constants in the code. This allows for the extension of this work to any fabric material which exhibits a strain-rate dependent behavior in addition to Twaron®. The results pertaining to optimal number of fabric layers and inter-yarn friction levels can aid in the manufacturing of fabric with regard to the desired level of lubrication/additives to improve the fabric performance under impact.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Cherkaoui, Mohammed; Committee Member: Neu, Richard; Committee Member: van der Sluis, Olaf. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The aim of this study was to use the finite element method to model crack, corrosion, and Crack-in-Corrosion defects in a pipeline. The pipe material under investigation for this study was API 5L X60, 508 mm diameter with a wall thickness of 5.7 mm. The pipe material was evaluated using Tensile, Charpy, and J testing in order to model the defects and to establish the numerical failure criteria. Corrosion defects were modeled as flat-bottomed grooves. The collapse pressure was predicted when the deepest point in the bottom of the defect reached a critical stress. Based on this criterion, the FE corrosion failure pressure predictions were conservative compared to the experimental failure pressures, conducted by Hosseini [9], with an average error of 10.13%. For crack modeling, the failure criteria were established considering the plastic collapse limit and the fracture limit. Both the Von Mises stress in the crack ligament and the J-integral values around the crack were monitored to predict the failure pressure of the model. The crack modeling was done based on two approaches, the uniform depth profile and the semi-elliptical profile. The crack with uniform depth profile was done because the uniform shape is the logical equivalent shape for a colony of cracks. The crack with the semi-elliptical profile was done to have a less conservative results and because the experiments were done with semi-elliptical cracks. The FE crack modeling results were conservative compared to the experimental collapse pressure with an average error of 19.64% for the uniform depth profile and 5.35% for the semi-elliptical profile. In crack-in-corrosion (CIC) defect modeling, the crack was modeled with uniform depth because it was very difficult to model the semi-elliptical crack profile when the crack defect is coincident with a corrosion defect. The results were conservative compared to the experimental results with an average error of 22.18%. In general, the FE modeling provides the least conservative failure pressure prediction over the existing analytical solutions for pipe with longitudinal corrosion, crack, and CIC defects.