Advanced Materials Research Vol. 698

Abstract: This paper considers damage development mechanisms in composite laminates subjected to tensile loading. The continuum damage mechanics is the most widely used approach to capture the non linear behaviour of laminates due to cracking. In this study, a continuum damage model based on ply failure criteria, which is initially proposed by Ladevèze has been extended to cover all plies failures mechanisms using an accurate numerical model to predict the equivalent damage accumulation. However, this model requires a reliable representation of the elementary damage mechanisms which can be produced in the composite laminate. To validate this model, a numerical application has been carried on the cross-ply laminates of type [0_n/90_m]_s._. A shear lag model was adapted to calculate the average stress of the 0° and 90° plies. The solution presented is obtained by using finite element analysis which implements progressive failure analysis. The effect of the stacking sequences has been done by varying the thickness of the 90° plies.

Abstract: As a material removal process, metal milling process involves large geometry deformation, material thermo-visco-plastic flow coupled with damage and complex contact-friction problems. During simulation of metal milling, the finite elements distort severely at the local regions with high gradient of physical field such as stress, strain and temperature due to these problems. This paper presents numerical adaptive remeshing procedure dedicated to metal milling process. The procedure integrates Explicit solver of ABAQUS, OPTIFORM mesher and python script program transfer to execute step by step the incremental milling process. At each step, the meshes are refined and coarsened automatically based on geometrical and physical error estimations; the physical fields are transferred (point to point) from old to the new one using advanced algorithm. Johnson-cook material model is used to simulate the material plastic flow with ductile damage. Some numerical results are given to demonstrate the efficiency of the proposed procedure.

Abstract: This study presents experimental and numerical approaches to study the thermo-elasto-plastic behavior coupled to ductile damage of thin sheet. The study highlights the influence of temperature on the mechanical properties affecting the ability of forming aluminum sheet 1050A. The properties of the Swifts model hardening coupled to isotropic ductile damage variable and the Erichsen Index are obtained using inverse approach (Nelder-Mead method). The obtained results have established a correlation between the Index Erichsen formability of the material.

Abstract: Coupled constitutive equations, formulated in the framework of the thermodynamics of irreversible processes accounting for isotropic hardening as well as the isotropic ductile damage are used to simulate numerically, by the Finite Element Analysis, 3D metal hydroforming processes. The experimental study is dedicated to the identification of stress-strain flow and damage parameters by using the Nelder-Mead simplex algorithm optimization from the global measure of displacement and force. Applications are made to the simulation of thin sheet hydroforming using different at different temperature to show the efficiency of the proposed methodology and to localize plastic instability, thinning of sheet and damage initiation under complex forming conditions.

Abstract: In the context of high speed milling HSM, the feed rate does not always reach the programmed value during the machining process which implies an increase of machining time and non compliance with the programmed feed rate. This phenomenon leads to productivity issues and an underestimation of the cost of machining for the industry. The aim of this study is to identify the kinematic behaviour of the machine tool during any type of discontinuity between linear and circular contours in different combination by taking into account the specific machining tolerances. In order to achieve this, a model of the law of the axes motion and the actual trajectory at discontinuities is necessary. This method is based on the subdividing of the trajectory into elementary geometries according to the type of interpolation (circular or linear). The proposed method can estimate the cycle time with a maximum error of 5% between the actual and the prediction cycle time. Finally, an experimental study was carried out on a high speed machine. It is based on elementary tests in order to analyze the axes behavior during any type of discontinuity and to validate the developed models.

Abstract: The addition of a high percentage of silicon and a small percentage of magnesium to aluminum are the main enhancers largely used to improve the mechanical characteristics. Our goal, here, is to make a direct contribution to the mechanical properties in traction, the hardness, the resilience and the structural properties of the AlSi13 alloy used in sand molding and shell metal molding, mechanical as well as manual. The reference state is designated by crude casting, noted: F. To increase the characteristics and obtain substantially large yield stresses and higher stiffnesses, the material of numerical designation 44100 is subjected to the specific heat treatments, quenching and annealing. This study aims to determine the influence of the chemical composition, the structural hardening of sand casting and metal shell casting by gravity on the evolution of the tensile behavior, hardness, resilience and microstructure of the binary alloy 44100.

Abstract: The drilling of composite materials can produce, around the hole, defects and damages which decrease the mechanical resistance of the drilled workpiece. This study shows the influence of several tools (drill, mill and reamer) on the hole quality obtained, in the context of reference parts where surface integrity is a priority. An experimental study is suggested and the criteria used to assess the hole quality are defined. Results show the behavior of each type of cutting tool and their influence on the defects generated. Finally, this study helps creating a scale of recommended cutting conditions to reduce the tool wear and improve the hole quality.

Abstract: Generally, the sheet metal forming processes by plastic deformation are difficult to control owing to the multiple phenomena that can occur and disrupt the operation: the springback, the localization, the wrinkling, etc. The springback is a physico-mechanical phenomenon due to the return of the elastic energy stored during the loading phase, which leads to a change in the dimensions of the formed part. In fact, the improvement of the operation presents some complications because an important number of parameters that affect the springback and that can be accurately understood by the use of finite element analysis. In particular, the springback appears so prominent in the bending operations; this mode of deformation is the focus of this work which consists of two main parts: - Mechanical characterization of two alloys frequently used in aerospace manufacturing: aluminum 1050A and titanium T40 commercially available in the form of cold-rolled thin sheets. The conventional and rational curves are obtained by using a tensile test machine (Instron 50kN). - Finite element simulation of a V-bending operation of sheet metal with both materials. This study allows us to calibrate the numerical procedures that could be included in more complex operations.

Abstract: Since some years, the better understanding of the material cutting process has been shown with the benefit of the forces and moments measurement. In this article, simultaneous six mechanical components and chip orientation measurements were realized during turning tests. During these tests, the influence of the depth of cut or feed rate has been observed and correlation between the chip orientation and the moment vector orientation or the central axis characteristics has been shown. Nomenclature