Advanced Materials Research Vol. 423

Abstract: Numerous modeling techniques exist, as well as many modeling formats. Point modeling, edge loop modeling, box modeling and paint modeling are a few of the polygon modeling techniques. Polygon proxy modeling is a variation of subdivision modeling. NURBS surfaces are used extensively in industrial design, manufacturing, and the automotive industry. Texturing and lighting transforms the dull-gray denizens of the modeling world into lifelike objects. Although texturing is nothing without good lighting, good lighting is nothing without good texturing. This article presents the process of modeling, texturing, lighting and rendering a scene in 3D. It also shows how create realistic fur, and implement studio lighting to create nice and soft shadows and highlights.

Abstract: The ACCENT Project (FP7-AAT-2007-RTD-1) will allow the European Aero Engine manufacturers to improve their competitiveness by applying adaptive control techniques to the manufacturing of their components. For the critical rotating parts of aircraft engines, the surface integrity generated after machining is a key factor on the life cycle. In this context, one particular attention has to be carried out on tool condition. The aim of this paper is to define a monitoring approach able to detect the tool condition and machining disturbances. The main failure modes characterizing this particular Nickel base drilling and the apparition of embedded chips over the machined surface were identified. By experimental techniques, cartography of failure modes was performed. The results show that flank wear and notch are the main failure modes limiting the tool life. For some cutting conditions, the tool failure occurs after the first hole due to the important cutting forces. Some interesting combinations are made between the spindle current/accelerometers/ thrust force and flank wear, tool breakage and notch. Before these correlations, a detailed signal analysis was performed, considering different disturbing phenomena, such as chips evacuation problem. Finally, a “synopsis” for process monitoring is proposed, considering the analyzed phenomena.

Abstract: These last years, hemp fibres are using as reinforcement for compounds based on polymer in different industrial manufacturing for their interesting mechanical and ecological properties. The hemp fibres present a non constant cross section and complex geometry that can have a high effect on their mechanical properties. The mechanical properties of hemp fibres (Young moduli, longitudinal stress and failure strain) are rather difficult and request a specific characterization method. In this study, a micro-traction test coupled with a numerical imaging treatment and a finite elements method are used. The mechanical tensile test allows to determinate the evolution of the traction load in function of the displacement until the fibre crack. The numerical imaging allows to measure finely the hemp cross section along the fibre and aims to reconstruct a 3D hemp fibre object model from an image sequence captured by a mobile camera. And lastly, the finite elements method allows to take the real fibre geometry into consideration for the mechanical characterization using inverse optimization simplex method.

Abstract: The main objective of the study is to understand the mechanisms of the preform reinforcement (2D, stitched and 2.5D) in laminated composite materials. The study is focusing on the mode I interlaminar fracture toughness for glass/vinylester based composites. Starting from DCB tests we quantify the critical energy release rate for the various cases of reinforcement, conclusive that 2.5D reinforcement can increase resistance x7 in comparison with the standard composite. Moreover, the existence of z-fibres made the fracture more complex and caused several characteristic phenomena, so that the required fracture energy for crack propagation was strongly increased. It is shown that a finite element model is successful in reproducing qualitatively the cracking initiation and propagation through the un-reinforced and 3D reinforced sample provided that the action of the through-thickness reinforcement is modelled by discrete nodal forces so as to replicate the physical phenomena.

Abstract: The aim of this paper is to analyse the behaviour of various shear deformation laminated plate theories previously proposed by Reissner [1] , Reddy [2] and Touratier [3]. The accuracy of those theories is compared on two problems laminates for which an analytical solution has been given by Timoshenko for isotropic and Lekhniski for anisotropic plate. Retaining the best model among those compared, interlaminar continuity conditions have been taken into account in this best response for laminates and show how important these interlaminar conditions are to improve accuracy by comparison with the finite element solution. Models which have been introduced are two-dimensional ones and imply the three standard generalized displacements associated with shear-bending. Studies limited to symmetric and orthotropic plates. Finally, an analysis of edge effects has been conducted for a circular symmetric orthotropic clamped plate. Edge effects have been observed with refined shear deformation theories but not with the first-order shear deformation theory due to Reissner.

Abstract: The studies on the development and profitability of forming processes of thin structures, plastic deformation, continue to grow. Their goals are the prediction and assessment of default risks incurred by parts manufacturing phase. The quality of numerical predictions depends on the accuracy and reliability of the models selected. This justifies the development of different techniques for the identification of skills forming sheets and tubes. This study fits within this frame work, a method of identifying the coefficients characterizing the elastoplastic damage behavior of sheet metal based on the analysis of variance (ANOVA) was developed. Performance evaluation of the ANOVA analysis has been conducted through a confrontation of results with those identified by the inverse method.

Abstract: In this study, we present an experimental/numerical methodology which aims to improve 3D thin sheet hydroforming considering coupled constitutive equations formulated in the framework of irreversible processes accounting for isotropic hardening as well as isotropic ductile damage. The experimental study is dedicated to the identification of stress-strain flow from the global measure of pole displacement, thickness evolution and internal pressure expansion. Indeed, Hill48 yield surface anisotropy parameters and coefficients of the Swift law coupled to ductile damage allowing to locate plastic instability zones of hydroformed sheets are identified with three dies cavities shapes. Or during the hydroforming processes severe mesh distortion of element occur after a few incremental steps. Hence an automatic mesh generation with remeshing capabilities is essential to carry out the FEA. The proposed technique based on geometrical criteria includes adaptive refinement and coarsening procedure is integrated in a computational environment.

Abstract: A dynamical modeling of spindle with Active Magnetic Bearing (AMB) is presented. All the required parameters are included in the model for stability analysis. The original map of stability is generated by Time Domain Simulation. The major importance of forced vibrations is highlighted for a spindle with AMB. Milling test are used to quickly evaluate the stability. Finally, the simulation results are then validated by cutting tests on a 5 axis machining center with AMB.

Abstract: Electronic power modules devices are paramount components in the aeronautical, automotive and military applications. The solder layers are the most critical parts of the module and are usually subjected in their whole life to complex loading conditions. To improve the design task, realistic thermoelastoviscoplastic and lifetime prediction models which can describe efficiently the deformation-damage of the electrical device must be chosen carefully. Some of the most common behavior models are based on the separation between creep and plasticity deformations such as power law, Garofalo, Darveaux… So, to take into account the creep-plasticity interaction, the thermal cycling as well as the hardening-softening effects, unified viscoplastic models are increasingly being used to describe more efficiently the physical state of the material. We propose in this framework a survey of some unified viscoplastic models used in the electronic applications for the viscoplastic modeling of the solder as well as creep-fatigue life prediction rules. The models are used for the characterization of a SnAgCu solder and are briefly compared within tensile, creep data and stabilized responses.