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Sol–gel route was used to prepare Fe-doped CdTiO3 sample with 1 wt% and its optical and magnetic properties investigated. In particular, photoluminescence study revealed the existence of defects, such as oxygen vacancies, and of transitions from electronic states of Cd2+, Ti4+ and Fe2+ to those of O2−. Magnetic investigations showed the existence of two oxidation states of iron, 2+ and 3+, and of an antiferromagnetic order at temperatures inferior to 20 K with a slight canting of spin moments of the magnetic species leading to spontaneous magnetization which values decrease with the temperature. Above 20 K, a ferromagnetic behaviour is dominant and, at room temperature, a diamagnetic behaviour prevails. The latter has been interpreted as due to the presence of CdO impurities as revealed by XRD and photoluminescence results.

New trends in sheet metal forming are rapidly developing and several new forming processes have been proposed to accomplish the goals of flexibility and cost reduction. Among them, Incremental CNC sheet forming operations (ISF) are a relatively new sheet metal forming processes for small batch production and prototyping. In single point incremental forming (SPIF), the final shape of the component is obtained by the CNC relative movements of a simple and small punch which deform a clamped blank into the desired shape and which appear quite promising. No other dies are required than the ones used in any conventional sheet metal forming processes. As it is well known, the design of a mechanical component requires some decisions about the mechanical resistance and geometrical quality of the parts and the product has to be manufactured with a careful definition of the process set up. The use of computers in manufacturing has enabled the development of several new sheet metal forming processes, which are based upon older technologies. Although standard sheet metal forming processes are strongly controlled, new processes like single point incremental sheet forming can be improved. The SPIF concept allows to increase flexibility and to reduce set up costs. Such a process has a negative effect on the shape accuracy by initiating undesired rigid movement and sheet thinning. In the paper, the applicability of the numerical technique and the experimental test program to incremental forming of sheet metal is examined. Concerning the numerical simulation, a static implicit finite element code ABAQUS/Standard is used. These two techniques emphasize the necessity to control some process parameters to improve the final product quality. The reported approaches were mainly focused on the influence of four process parameters on the punch force trends generated in this forming process, the thickness and the equivalent plastic deformation distribution within the whole volume of the workpiece: the initial sheet thickness, the wall angle, the workpiece geometry and the nature of tool path contours controlled through CNC programming. The tool forces required to deform plastically the sheet around the contact area are discussed. The effect of the blank thickness and the tool path on the punch load and the deformation behaviour is also examined with respect to several tool paths. Furthermore, the force acting on the traveling tool is also evaluated. Similar to the sheet thickness, the effect of wall angle and part geometry on the load evolution, the distribution of calculated equivalent plastic strain and the variation of sheet thickness strain are also discussed. Experimental and numerical results obtained allow having a better knowledge of mechanical and geometrical responses from different parts manufactured by SPIF with the aim to improve their accuracy. It is also concluded that the numerical simulation might be exploited for optimization of the incremental forming process of sheet metal.

Anchorage parts for automobile safety belts and other safety parts must resist shock loadings without breaking. They are typically made from High Strength Low Alloy sheet metal and fabricated by blanking and bending operations. The study of their behaviour during fabrication and their resulting mechanical properties has been conducted experimentally and numerically. The experimental results were used to validate the numerical simulation. The resulting material damage is taken into account by a user subroutine in the Abaqus Standard Finite Element code. Damage is one of the objective functions intervening in the forming process of safety parts as well as in the prediction of unbending and shock loads. This study is based on the use of “the design of experiments technique” and the approximated representation by response surfaces. For unbending operations representative of dynamic shock loading conditions, the objective functions represent the maximum unbending load and maximum damage. The parameters that represent the die radius Rd and the sheet/die clearance C are optimised in order to obtain the most resistant safety part possible.

In this paper, an experimental micro-hardness procedure is proposed to evaluate the evolution of HSLA steel behaviour during each sequence of sheet forming process. As micro-hardness technique offers a reliable inspection, it was retained here to follow the mechanical characteristic changes, which may happen during manufacturing progress. This contribution consists in characterisation of sheet material at different steps: virgin sheet, unreeled sheet, straightened sheet and bent sheet. Measurement performed on virgin HSLA steel showed that material is highly heterogeneous within the sheet thickness. The micro-hardness profiles examined after the bobbing-off step showed a high sensitivity of sheet behaviour to straightening operation that is widely adopted in steel working in order to make sheet sufficiently flat for forming. A level of hardening ratio between virgin material and straightened material has been clearly observed. Moreover, micro-hardness is investigated on bent parts at the fold zone for displaying the mechanical properties modifications under a large gradient deformation. In this way, hardening phenomenon and damage phenomenon, which are generally activated simultaneously for elastoplastic steel, are quantified accurately. Results compared into them gave a good idea about the interaction of process–material during manufacturing.

Bending has significant importance in sheet metal product industry such as automotive security parts. The present work presents a general framework of numerical simulation of wiping die bending processes. A Computer Aided Design (CAD) for bending process using finite element method is presented which consists of metal forming operation characterised by complete material deformation. In this paper, we describe robust methods of predicting load bending evolution and stress distribution of specimens in 3D modelling subjected to bending deformation. The values are determined in a local frame according to elements deformation. A numerical approach of the problem requires a comprehensive finite element modelling due to the diversity of physical phenomena involved, such as friction effects, material and geometrical non-linearities, large plastic deformation and material failure. Lemaitre's material damage within the sheet was taken into account in the simulation during forming process. The interface contact law is defined by Coulomb's friction model and the elastoplastic constitutive laws are integrated by means of an incremental formulation which has been implemented in the finite element code ABAQUS. The influence of punch/die clearance and die shoulder radius are analysed. An algorithmic loop programmed in Script language of ABAQUS was retained to investigate the mechanical responses of the part for each case of parameters combination. The punch load and the distribution of stresses could be predicted in view of optimising the value of the main parameters of the process. An optimisation technique based on the use of Design Of Experiments (DOE) and Response Surface Methodology (RSM) is proposed in the work in order to minimise the tensile and compressive stresses found in the most damaged zone during the bending operation. Numerical results have shown the robustness of the proposed model and are discussed in more detail and enlightened by corresponding plots.

Bending has significant importance in the sheet metal product industry. Moreover, the springback of sheet metal should be taken into consideration in order to produce bent sheet metal parts within acceptable tolerance limits and to solve geometrical variation for the control of the manufacturing process. Nowadays, the importance of this problem increases because of the use of sheet-metal parts with high mechanical characteristics (high strength low alloy steel). This work describes robust methods of predicting springback of parts in 3D modelling subjected to bending and unbending deformations. Also the effects of tool geometry in the final shape after springback are discussed. The first part of this paper presents the laboratory experiments in wiping die bending, in which the influence of process variables, such as die shoulder radius, punch-die clearance, punch nose radius and materials properties are discussed. The second part summarises the finite element analysis by using ABAQUS software and compares these results with some experimental data. The final results of the FEM simulation are in good agreement with the experimental ones. An optimisation methodology based on the use of experimental design method and response surface technique is proposed in the third part of this paper. This makes it possible to obtain the optimum values of clearance between the punch and the die and the optimum die radius, which can reduce the springback without cracking and damage of product.

Bending has significant importance in the sheet metal product industry. Moreover, the springback of sheet metal should be taken into consideration in order to produce bent sheet metal parts within acceptable tolerance limits and to solve geometrical variation for the control of manufacturing process. Nowadays, the importance of this problem increases because of the use of sheet-metal parts with high mechanical characteristics (High Strength Low Alloy steel). This work describes robust methods of predicting springback of parts in 3D modelling subjected to bending and unbending deformations. Also the effects of tool geometry in the final shape after springback are discussed. The first part of this paper presents the laboratory experiments in wiping die bending, in which the influence of process variables, such as die shoulder radius, punch-die clearance, punch nose radius and materials properties were discussed. The second part summarises the finite element analysis by using ABAQUS software and compares these results with some experimental data. It appeared that the final results of the FEM simulation are in good agreement with the experimental ones. An optimisation methodology based on the use of experimental design method and response surface technique is proposed in the third part of this paper. That makes it possible to obtain the optimum values of clearance between the punch and the die and the optimum die radius which can reduce the springback without cracking and damage of product.

e20721 Background: To report the epidemiologic, clinical, extension, treatment and results of CEP in a Tunisian population from a department of medical oncology. Methods: We collected retrospective...