The main objective of this research work is to develop a simulation procedure for modeling the soil-tool interaction for a blade of arbitrary shape. The primary motivation for this study is developing agricultural robots with limited power and pulling force to help farmers in crop production. In this thesis, a finite element (FE) investigation of soil-blade interaction is presented. The soil is considered as an elastic-plastic material with the non-associated Drucker-Prager constitutive law. A separation procedure to model the cutting of soil and a method of calculating the forces acting on the blade are proposed and discussed in detail. The procedure uses a separation criterion that becomes active at consecutive nodes on the predefined separation surfaces. In order to mimic soil-blade sliding and soil-soil cutting phenomena contact elements with different properties are applied. To verify correctness of the FE model developed and the procedures used, the FE results are first compared with analytical results available for straight rectangular blades from classical soil mechanics theories; and then the FE results are compared with the experimental ones. Also the effects of blade width, depth and rake angle on blade’s draft force were studied by simulating soil-blade interaction with different blade’s dimensions. After the analytical and experimental validation of the results for straight rectangular blade, the rectangular curved shape blade was modeled in order to investigate the effects of changing the blade’s radius of curvature on the blade’s draft force. The soil interaction with straight triangular blade in different rake angles was simulated next. Since the analytical solutions are limited to rectangular blades, calculated draft forces for triangular blade were verified only experimentally. The triangular and rectangular blades with the same width and depth of interaction were also investigated. The results showed that triangular blade draft force is around half of the amount of force acting on the rectangular blade with the same rake angle. Also the effect of triangular blade’s sharpness and changing the blade’s radius of curvature on draft force was discussed. By changing the blade’s sharpness, the draft forces of triangular blade were calculated in two conditions of constant blade’s width and constant blade’s contact length. The approach presented in this thesis can be used to investigate the soil-tool interactions for real and more complex blade geometries and soil conditions, and ultimately for improving design of blades to be used in tillage operations.

Le but principal de cette thèse est de présenter deux contributions dans le domaine desassemblages frettés en prenant en considération les défauts de forme et d’état de surface. Lapremière contribution concerne l’étude de l’influence du défaut de forme sur les caractéristiquesdes assemblages frettés en utilisant une approche basée sur la modélisation par éléments finis.Nous avons constaté que ce défaut a une influence notable sur la résistance de l’assemblage. Destravaux déjà réalisés dans le laboratoire de mécanique de l’université de Bourgogne ont étéconfirmés. Dans la deuxième contribution, nous avons proposé d’intégrer les défauts d’état desurface (rugosité) en créant un élément fini homogénéisé d’interface. Cette technique nous afacilité le maillage de l’interface formés par de macro-éléments traduisant le comportement desaspérités. Ce comportement particulier, dépend de plusieurs paramètres mécaniques etgéométriques qui ont été pris en compte pour définir et identifier numériquement une loid’élasticité isotrope transverse. Cette nouvelle loi a permis de simuler correctement lesassemblages frettés en prenant en compte le défaut d’état de surface. Les résultats obtenus ont étéconfrontés aux expérimentations. En fin, une méthodologie de conception des spécifications dufrettage en considérant le processus d’élaboration des surfaces a été proposée. / The main purpose of this thesis is to present two contributions in the field of shrink fitassembly taking into account the defects of form and roughness surfaces. The first contributionconcerns the study of the influence of the defect forme on the characteristics of shrinked assemblyusing an approach based on finite element modeling. We found that this defect has a significantinfluence on the resistance of the assembly. The work already done in the laboratory of mechanicsat the University of Bourgogne have been confirmed. In the second contribution, we proposed tointegrate the surface defects (roughness) by creating a homogenized finite element interface. Thistechnique has facilitated the mesh of the interface formed by the macro-elements reflecting thebehavior of the asperities. This particular behavior, depends on several mechanical andgeometrical parameters that have been taken into account in defining and identifying a digitallytransverse isotropic elastic law. The new law was used to simulate properly shrinked assembliestaking into account the defect of roughness surface. The results were compared withexperiments. In the end, a design methodology specification by considering the shrinking processof surfaces has been proposed