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Comparison between down scaled flat rolling experiments of thin round wire and numerical simulation of those experiments have shown that the production process of manufacturing micro strip out of thin round wire is influenced by size effects. Decreasing the wire diameter into the microscopic domain is accompanied by decreasing yield stresses of the wire and turned out to be the dominating size effect for low rolling reductions. For high rolling reductions an increase of friction becomes of major influence. The plane strain compression test is applied as an experimental simulation of the rolling process. It is also used for further investigation of the determined size effects. An experimental set-up has been built, that allows scaled experiments on small and miniaturised specimens maintaining geometric similarity. Micro structural effects, such as the Hall-Petch effect and effects on the evolution of the surface roughness have been determined with this plane strain compression set-up.

The miniaturization of sheet deep drawing is one possible solution for the production of metallic microparts. However, when reducing the product size to dimensions around 1 mm and using foils down to 40 μm, a reduction of process reproducibility is observed, also in industrial manufacturing. Consequently differences between “macro‐deep drawing” and “micro‐deep drawing” were studied by Finite Element Analysis and experimental investigations.Implicit axisymmetric 2D simulation was used to study the influence of transverse anisotropy, friction and deviations of process‐determining geometric factors, e.g. the drawing gap, on the micro deep drawing process for producing cups of 8 to 1 mm from CuZn37 foils with thicknesses from 300 to 80 μm. Deviations of tool geometry within the product tolerances of the tool can have a decisive influence on the deep drawing result. For example, the punch force changes by up to 12.8% if the drawing gap deviates from the nominal value by a few hundredths of a millimeter within ...

Incremental CNC sheet forming (ISF) is a relatively new sheet metal forming process for small batch production and prototyping. In ISF, a blank is shaped by the CNC movements of a simple tool in combination with a simplified die. The standard forming strategies in ISF entail two major drawbacks: (i) the inherent forming kinematics set limits on the maximum wall angle that can be formed with ISF. (ii) since elastic parts of the imposed deformation can currently not be accounted for in CNC code generation, the standard strategies can lead to undesired deviations between the target and the sample geometry.Several enhancements have recently been put forward to overcome the above limitations, among them a multistage forming strategy to manufacture steep flanges, and a correction algorithm to improve the geometric accuracy. Both strategies have been successful in improving the forming of simple parts. However, the high experimental effort to empirically optimize the tool paths motivates the use of process model...

The majority of all metals will undergo a rolling process during the production chain from metal generation to the final product. These rolling processes may be used to define the product geometry, the material properties or functional surface properties. The paper reviews selected processes for tailor rolled products as well as modeling techniques helping to design or optimize these processes. Their common goal is to improve material efficiency in flat rolling and in application of rolled products.

International audience; The ceramic coatings deposited by Physical Vapour Deposition (PVD) are known for their high hardness. They offer a wide variety of friction coefficients. They have been used for a number of years for the coating of cutting tools; they have shown high efficiency in this field. Considering this, some of these coatings might prove efficient in the field of metal rolling. Yet to the best of the authors' knowledge, they have never been used industrially for rolling mill rolls. TiBN is one of the PVD coatings with the highest hardness. It is also known for its anti-adhesive property. In this study, the interest of TiBN in cold rolling is analyzed. In this application, the potential productivity is determined by the maximum pair (reduction, speed) above which seizure and transfer degrade tribological properties. The fatigue resistance is also studied and therefore, the potential influence of the coating on the roll life under conditions similar to those of rolling. Two well adapted tribological tests have been used for these two purposes: a plate-on-ring test, and a twin-disk Amsler test. The results of this study show a high potential of TiBN as coating for rolling mill rolls: good anti-adhesive property, very high resistance to wear and fatigue. It shows better performance than hard chromium, which is now widely used in this application

International audience; Numerical models of many forming processes of metals rely on description of rheological characterization of the metallic alloys, which can turn very difficult at high temperature. In this work, a direct resistance heating machine (Taboo) has been developed to perform cyclic loadings at very low strain rates (10-3 and 10-4 s-1) between 900°C and the solidus temperature. We fir st describe the experimental setup; then we present several measurement techniques. A specificity of resistance heating machines is to deal with non negligible temperature gradients around the center of the sample which induce heterogeneous strains. To measure displacements, a specific set-up has been constructed using speckle correlation. It has several advantages like full field and non destructive displacement measurement. Thanks to this method we obtain full field measurements. Electric current and resistivity measurements are also performed all along the heating/cooling and deformation stages. They can be correlated to phase transformation. Finally, we describe a numerical model for simulating and analysing the tests with a combined electrical, thermal and mechanical model. The main goal is to help designing optimal sample geometry using to identify mechanical parameters by inverse analysis.

Warm bulging test is a particular kind of sheet hydroforming. The presence of a warm fluid requires a proper tooling design in order to achieve the benefits related to these particular forming conditions, minimizing blank ruptures and wrinkles presence. The fluid is injected in a properly designed chamber and it produces a sheet bulging deformation. Also the tooling and the sheet are warmed in order to maintain a constant process temperature. In this working conditions, it is necessary to accurately design the tooling layout taking into account: interaction forces, fluid volume, vision system in order to record the deformation conditions and safety systems in order to prevent damage to the workers caused by the warm fluid possible leakage (approximately 200° ÷ 300° C). CAE techniques have a relevant role in order to define proper process parameters such as: sheet thickness, bulging height, fluid pressure. An explicit solver has been used to calculate the forces distribution, developed during the warm sheet bulging, and the needed fluid volume. The obtained values have been used as input data in the structural tooling validation. The authors have designed a warm bulging test layout. The sheet deformation, etched with a grid, is detected through CCD cameras. Diffuse lights, a thermometer and a laser beam adopted to detect the dome height complete the tooling control system.

Most of the aeronautic skin parts are made through stretch forming of aluminium or titanium sheet metals over rigid fixed dies. In the aerospace industry, the stretch forming of aluminium or titanium sheets is widely used to produce aircraft skin, such as blended wing body sections, fuselage sections and nacelle skins. As the demand for more efficient and economical commercial transport increases, the requirements for reduced weight and improved performance become greater. In this work explicit FEM simulations have been used to analyze the forming process of an aeronautical engine fairing in order to numerically compare: tangential stretch forming, extensively used in the aerospace industry and single action drawing processes effects on the studied component. Titanium alloys have their advantages and disadvantages, and two important tasks are the understanding of the behaviour of the alloys and the matching among particular alloys and processes in order to maximize structural and operational efficiency. Equally important it is the ability to develop a fabrication practice that does not severely degrade material properties and that can be implemented at reasonable cost.