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The initiation and growth of wrinkles are influenced by many factors such as stress ratios, the mechanical properties of the sheet material, the geometry of the workpiece, contact condition, etc. It is difficult to analyze wrinkling initiation and growth while considering all the factors because the effects of the factors are very complex and studies of wrinkling behavior may show a wide scattering of data even for small deviations in factors. The finite element analyses of wrinkling initiation and growth in sheet metal forming process provide detailed information about the wrinkling behavior of sheet metal. The direct analysis of wrinkling initiation and growth, however, brings about a little difficulty in complex industrial problems because it requires large memory size and long computation time. From the industrial viewpoint of tooling design, therefore, readily available information on the possibility and location of wrinkling is sometimes more preferable to detailed and time‐consuming analysis results. In the present study, in order to give such readily available information on wrinkling initiation, the wrinkling factor, which shows the locations and relative possibility of wrinkling initiation, is proposed as a convenient tool of relative wrinkling estimation based on the energy criterion. The reliability of the wrinkling factor is verified through the buckling analyses of sheet strips. The location and relative possibility of wrinkling initiation are predicted by calculating the wrinkling factor in various sheet metal forming processes such as cylindrical cup deep drawing, spherical cup deep drawing, and elliptical cup deep drawing. Finally, the wrinkling factor proposed in the present study is also implemented in the prediction of wrinkling in the door inner stamping process. For verification of the calculated wrinkling factor, detailed zone analyses with fine meshes are carried out for the regions where wrinkling is predicted.

The automotive industry is very interested in sheet metal forming simulation using numerical techniques such as the finite element method. A cooperative research program between the Stamping Division of FIAT Auto and the Mechanics Department of the Politecnico di Torino was established with the aim of exploring the present possibilities of these techniques. This paper deals with the simulation of the deep forming of an axisymmetrical component, the axisymmetry being characterized by a double curvature profile, and is considered to be the first feasibility study. A sheet was modelled by fournode axisymmetric elements; the punch, the die and the blankholder were modelled by gap elements. The metal sheet was free to move along the punch and the die edges, with a continuous variation of the boundary conditions. The highly non‐linear problem requires an adequate description through the carefully considered use of the appropriate options of the MARC package (release K2). Moreover, some subroutines were written ad hoc to complete the discretization. Results are presented as strain and stress histories during the stamping process and as total forming force exerted by the punch to deform the sheet. In addition the spring‐back phase was considered in order to calculate the back deformation and the residual stress. Lastly, a comparison of the behaviour obtained with two different kinds of steel are reported.

The lubrication process may become interrelated with corrosion phenomena. Lubricants may be the products of a corrosion process, e.g., during boundary lubrication. They may also serve as a medium which protects the metal during the lubrication process from the corrosive attack of a humid and acidic atmosphere. For better understanding of the relation between lubrication and corrosion phenomena, the theory of corrosion is presented.

In the previous two articles the emphasis was on wet and electrochemical techniques, with particular reference to the potentiostat. The physical examination of corrosion products is of equal importance, especially, for example, in the study of oxidation by dry gases at elevated temperatures where electrochemical studies are not normally feasible. In this article the application of physical techniques to corrosion studies will be discussed.

The purpose of the present paper is to develop a new technology for producing magnesium alloy twin-rib aircraft brackets by the forging method.

An overall description of magnesium alloys is given, with particular emphasis placed on magnesium wrought alloys that are used in the aircraft industry. Methods for producing ribbed brackets are discussed and the location of these parts in aircraft structure is described. The forging process for producing AZ31 magnesium alloy twin-rib brackets was modelled numerically, and selected results of the simulations performed are presented. The simulation results were then verified under laboratory conditions using a three-slide forging press equipped with three movable working tools. It was assumed that the use of this machine would allow for obtaining twin-rib aircraft brackets with improved both functional and strength properties compared to the production methods used so far.

The results demonstrate that the method developed by the present authors permits the production of twin-rib brackets. Positive theoretical results and preliminary experimental results prove that it is justified that the research on magnesium alloys used in the aircraft industry be continued.

The production of twin-rib aircraft brackets from magnesium alloys by the technology developed by the present authors would lead to enhanced product quality with simultaneous reduction in production costs (reduced labour costs and material consumption as well as increased process efficiency). At present, magnesium alloy aircraft parts, mainly obtained from semi-finished products imported to Poland, are produced by casting and machining methods. They exhibit, however, much worse properties than elements produced by metal forming methods. In addition to that, the application of machining in the production of these part leads to higher production costs.

The originality of this study stems from the presentation of an innovative metal forming technology for producing twin-rib brackets. This method is unique on a global scale, and its basic assumptions have been granted patent protection. Also, the originality of the study stems from the fact that brackets are made from magnesium alloys, as these light metals are considered the future of structural materials used in the aircraft industry. Given the above, the research on developing the technology for producing parts made from these alloys using a three-slide press is justified.

Every metal has a range of environmental conditions against which it is resistant or sufficiently resistant as to make the metal economically feasible. Unfortunately it is almost a rule of thumb that the more expensive the metal the smaller the range. In most cases the resistance of the metal is a function of the metal thickness, but the function is such that relatively thin metals can produce very long lives.

The purpose of this paper is to study the corrosion inhibition performance of an eco-friendly drug clozapine on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions.

The corrosion inhibition nature of inhibitor molecule was evaluated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization studies. An attempt was made to correlate the molecular properties of neutral and protonated forms of inhibitor molecule using quantum chemical calculations. The effect of temperature on the corrosion inhibition efficiency was also studied using electrochemical impedance spectroscopy. The potential of zero charge was determined to explain the mechanism of corrosion inhibition.

The studies on corrosion inhibition performance of clozapine showed that it has good corrosion inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The adsorption of clozapine molecules onto the copper surface obeyed the Langmuir adsorption isotherm. The value of free energy of adsorption calculated is very close to −40 kJmol⁻¹, indicating that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in the value of energy of activation with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface. The potential of zero charge and quantum chemical studies confirmed that the protonated molecules also get involved in the corrosion inhibition process through physisorption.

The present work indicates that clozapine can act as a good corrosion inhibitor for the corrosion of copper in acid media.

Describes dieless forming, an innovative sheet metal forming technology developed in Japan which enables a metal part to be formed directly from a CAD file in just a few minutes and with the utmost precision. The patented “dieless forming” technology involves a cold forming process that takes place on a three‐axis vertical CNC machine. On the vertical axis of the CNC machine is mounted a pencil‐like tool with a rounded end which progressively forms the sheet metal.

The purpose of this paper is to analyze theoretically the influence of normal stress on the formability of aluminum alloy sheets in non-linear strain paths.

Four loading modes of non-linear strain paths are investigated in detail to consider the effect of normal stress on formability of aluminum alloy sheets.

Results show that the influence of normal stress in the first stage can be ignored. However, the normal stress in the second stage enhances the formability of aluminum alloy sheets obviously. Besides, the normal stress in the second stage is found to have larger effect on forming limit stress than that in the first stage.

Maybe more experiment data should be obtained to support the theoretical findings.

This current study provides a better understanding of normal stress effect on the formability of aluminum alloy sheets in non-linear strain paths. Since the reacting stage of normal stress play important roles in normal stress effect on the formability of aluminum alloy sheets, the insight obtained in this paper will help to judge the instability of aluminum alloy sheets in complex forming processes with normal stress reacting on the sheet or tube.