Investigation of Process Parameters in High-Speed Die-less Water Jet Spin-Forming of Copper Sheets

A new forming method called high speed water jet spin-forming was developed. This new forming method is a combination of water jet incremental forming and sheet metal spinning without any mandrel. The forming speed has been significantly increased by spinning of the sheet using a lathe machine. The effects of the forming parameters such as water jet pressure, rotation speed and relative water jet diameter on formability and surface quality of deformed copper parts were investigated. The experimental results indicate that the water jet pressure and the sheet rotation speed have a significant effect on the final depth, wall angle, and surface smoothness. It was also concluded that the final depth exponentially increases as the sheet rotational speed reduced. In addition, when the water jet pressure is low, sheet rational speed does not play a significant role in the final depth of the specimen. Furthermore, it has been determined from the results that high water jet pressure plays an important role in improving the surface quality and wrinkling at different rotational speeds, and as the pressure is increased, the wrinkling decreases and thus the surface quality is improved.

Non-destructive pole-figure measurements on workshop-made silver reference model of archaic objects

Based on the knowledge of crystallographic texture, the parameters of the metal-forming heat treatment of metallic objects can be reconstructed well when conventional technologies (e.g. rolling, deep drawing, etc.) are applied. The characterisation of texture has been possible only by using destructive techniques, apart from neutron diffraction. Recently, a non-destructive texture measurement method has been developed for centreless diffractometers, providing a new dimension to the examination of archaic objects. In the present study, two types of Stresstech G3R centreless diffractometer were used with this new method, which proved it to be applicable to both the tabletop and robotic arm-assisted versions of the diffractometer. Although the texture of archaic objects can be revealed using this method, the production of these objects cannot be directly deduced from the results, since their manufacturing steps are not identical to the metal-forming operations applied today. In this study, workshop-made silver reference samples were produced with the help of three silversmiths. Wrinkling, metal spinning and intermediate annealing were applied to the rolled silver sheet with the aim of making real-sized silver cups. The workshop-made reference cups were then subjected to non-destructive texture examinations. The results reveal the textures developed during the conventional manufacturing steps of silver cups. The obtained information greatly assists future research in understanding the pole figures of archaic objects and the reconstruction of their manufacturing technology.

Numerical study of radiative non-Darcy nanofluid flow over a stretching sheet with a convective Nield conditions and energy activation

Numerous industrial processes such as continuous metal casting and polymer extrusion in metal spinning, include flow and heat transfer over a stretching surface. The theoretical investigation of magnetohydro-dynamic thermally radiative non-Darcy Nanofluid flows through a stretching surface is presented considering also the influences of thermal conductivity and Arrhenius activation energy. Buongiorno’s two-phase Nanofluid model is deployed in order to generate Thermophoresis and Brownian motion effects [1]. By similarity transformation technique, the transport equations and the respective boundary conditions are normalized and the relevant variable and concerned similarity solutions are presented to summarize the transpiration parameter. An appropriate Matlab software (Bvp4c) is used to obtain the numerical solutions. The graphical influence of various thermo physical parameters are inspected for momentum, energy and nanoparticle volume fraction distributions. Tables containing the Nusselt number, skin friction and Sherwood number are also presented and well argued. The present results are compared with the previous studies and are found to be well correlated and are in good agreement. The existing modelling approach in the presence of nanoparticles enhances the performance of thermal energy thermo-plastic devices.

On the influence of the shaped charge liner manufacture technology on the high-speed element characteristics

The paper introduces the results of numerical simulation of the functioning of shaped charges, whose liners are made of different materials. As a result of their functioning, these charges form high-speed elements. Typically, liners for such charges are produced by the cold stamping technology. An alternative method for producing the liners is metal spinning. Moreover, a spin formed liner is expected to have higher physical and mechanical properties compared to a stamped liner made of the same material and having the same geometrical parameters. To reveal the patterns of molding high-speed elements from stamped and spin formed liners, the action of shaped charges comprised of steel or copper segmental liners of small bending, was simulated numerically using the apparatus of continuum mechanics. The influence of the liner manufacture method was taken into account by varying the values of the physical and mechanical characteristics of the liner material. The design parameters of the simulated charge, with the exception of the liner bending, during the calculation study remained unchanged and corresponded to the parameters of the currently used samples. Following the numerical experiments results, the study shows that the elements molded from spin formed liners are less likely to become fractured while being formed and are also more integral (continuous) in comparison to the elements molded from stamped shaped charge liners.