Dorin Luca

Rotary swaging (RS) is applied for the manufacturing of bars, stepped shafts, tubes with complex internal profiles, bimetallic composites, and similar products. This process falls under the category of severe plastic deformation (SPD) methods, which produce ultrafine-grained materials that provide superior properties in service. Our study investigated the effect of cold RS on the structure, grain size, and microhardness of AISI 304 stainless steel and CK45 carbon steel. Tubular specimens were processed by RS with the purpose of obtaining conical parts with a closed end, achieving a maximum reduction of nearly 44%. Samples were taken by longitudinal sectioning along the diameter from three zones with different degrees of deformation and subjected to structural analysis using scanning electron microscopy (SEM). The investigations were complemented by microhardness measurements in the axial direction for samples of both steels. The resulting structures revealed material texturing and a continuous decrease in grain size with increasing swaging ratio. The average grain size was reduced by approximately 46% in AISI 304 steel and by around 50% in CK45 steel. The microhardness of the materials increased by about 179% for AISI 304 steel and by approximately 95% for CK45 steel. The obtained results are discussed, highlighting the effect of cold RS processing on the two steels studied.

Development of forming methods for surface-coated metals is a current concern due to their economic and environmental advantages. For a successful forming operation, it is necessary that both components, the substrate and the coating, are able to withstand stress without damage until the final shape and dimensions are reached. This goal can be achieved through good knowledge of the elastic and plastic properties of the substrate and the coating, the compatibility between them, the appropriate surface treatment, and the rigorous control of technological forming parameters. Our study was carried out with flat specimens of pre-painted Al 99.0 sheet that were electromagnetically formed by bulging. Forming behavior was investigated as depending on the initial thickness of the substrate, on the aluminum sheet pretreatment, as well as on the plastic deformation path of the metal–paint structure. To verify the damage to the paint layer, tests with increasing strains were performed, and the interface between the metal and the coating layer was investigated by scanning electron microscopy. The obtained results indicate that electromagnetic forming of pre-painted sheets can be a feasible method for specific applications if the forming degree of the substrate is tightly correlated with the type of desired coating and with the pretreatment method used for the metal surface.

By decreasing manufacturing costs for different civic purposes, glass recycling is an economically significant technology that also helps conserve natural resources and mitigates environmental problems. Throughout the recycling process, this study used recycled domestic glass in compliance with European guidelines for recycling of household garbage. The purpose of this research is to examine the chemical and mechanical properties of recycled and crushed glass with particle sizes varying from 0.1 mm to 2 mm as a function of various treatment temperatures. This might pave the way for novel building materials, artwork, and interior design components, among other potential uses. “Silica glass”, the most common and ancient kind of glass, which includes SiO_k, Na_kO, CaO, and small amounts of other elements, was utilized in the investigation. Several materials can be successfully modified or altered using step heat treatment. The mechanical and chemical properties of recycled and shattered glass were assessed using microhardness, compressive, and chemical testing. These samples were then compared to mosaics from Murano, Italy, and Dynasty Smalti, China. The recycled and heat-treated glass produced microhardness values of 550.6 HV and 555.0 HV, respectively, when tested with forces of 0.981 N and 2.942 N. These values were higher than those of Murano (Italy) and were comparable to those of Dynasty Smalti mosaic (China). Furthermore, compression testing demonstrated that tempered and heat-tempered glass, which might include up to 5 g of TiO₂, could endure compressive strains of up to 16 MPa. This is in sharp contrast to Dynasty Smalti, which could only withstand tensions of 6–8 MPa, and Murano, which could only withstand stresses of 3–4 MPa. Tests conducted chemically over a seven-day period using KOH at 30 g/L and 100 g/L, along with HCl at 3% and 18%, showed that the samples did not alter in any way; their surface, color, and weight were untouched. Crushing and heating recycled glass makes it a viable alternative to using new glass in civil engineering projects. This helps make material reuse more efficient, which in turn helps the environment. Sturdy and resilient in a variety of contexts, the material shares mechanical and chemical properties with standard mosaics.

Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous materials. In this paper, the electromagnetic forming behavior of aluminum alloy, copper and steel sheets was investigated through experiments. The disk-shaped specimens were electromagnetically free bulged with increasing deformation energies and parts with different deformation depths were obtained. The deformation was done with and without clamping the movement of the specimens’ edges. The specimens were printed with a mesh of diametrical lines and concentric circles with a predetermined pitch. The mesh served to determine the displacements in the mesh nodes after the deformation of the specimens, with which the axial, radial and circumferential strains were then calculated. The experimental data obtained was subjected to statistical correlation and regression analyses, and the mathematical models for the three main strains in each material were established. The strains of AlMn0.5Mg0.5 and Cu-OF parts are maximum in the center and have a similar variation, while the FeP04 parts have the maximum strains in an intermediate zone between the center and the edge.

The dimensional effect of electric charge storage with a density of up to 270 μF/g by the hydrated ZrO₂-nanoparticles system was determined. It was found that the place of localization of different charge carriers is the generalized heterophase boundary-nanoparticles surface. The supposed mechanism of the effect was investigated using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors, which consists of the formation of localized electronic states in the nanoparticle material due to donor–acceptor interaction with the adsorption ionic atmosphere. The effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics because it allows overcoming the basic physical restrictions on the size, temperature, and operation frequency of the device, caused by leakage currents.

Proposed and accomplished finite element simulations in this paper started from the idea that materials which are plastically deformed and those from which electromagnetic deformation devices are built can influence the development of transitory magnetic phenomenon during the working process. Workpieces from paramagnetic, diamagnetic and ferromagnetic materials and devices that contain metallic and non-metallic materials were taken into study. FLUX2D modelling and simulating software was used to achieve numerical values and graphical images for the main process parameters: magnetic induction and magnetic pressure (of deformation). A finite element model, previously validated through experiment, was used to perform the simulations in order to assure a high degree of accuracy for the presented results.

Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that the tool carrying the deformation force does not touch the workpiece. This paper presents research regarding the electromagnetic forming of Al 99.0 (EN AW-1200) sheet with coils, having different configurations. The purpose of the research was to find the flat spiral coil configuration that ensures maximum deformation of the workpiece. Flat spiral coils with different gaps between the coil and the workpiece, and coils with different number of windings were tested. The influence of these parameters was monitored on the maximum strain of the free bulged parts. The analysis of the results obtained for different configurations of the flat spiral coils allowed the selection of the significant parameters that influenced the electromagnetic forming process of the Al 99.0 flat workpiece, which aimed to elaborate the mathematical model and to optimize the investigated process.

Everyday, biomaterials are becoming more widespread in the medical field and also in the metallurgical, aerospace, and even automotive industries. Mg-based biodegradable biomaterials are increasingly being studied and improved for their use in the medical field, even if Mg has a low corrosion resistance and not only can be alloyed to increase its strength and biocompatibility. The most commonly used and known elements with which Mg can be: Ca, Zn, Zr, Gd, Y, Si, Mn, etc. The purpose of this paper is to investigate the properties of Mg-2Ca-5Y alloy in order if it is suitable to use for use in medical applications. Surface morphology was characterized by electronic scanning microscopy (SEM) with EDAX, optical microscopy and X-ray diffraction (XRD). Following the XRD analysis, it was observed that certain specific compounds were formed: Mg₂Ca, MgY, Mg₂₄Y₅ having the main structural hexagonal phase. Micro-indentation and scratch tests were also performed on the casted alloy. As a final conclusion it is shown that the Mg-2Ca-5Y is recommended for medical applications.

Extrusion is the plastic deformation process that allows for the highest degree of complexity profiles to be obtained. This paper presents the simulation of a cold forward extrusion process using the finite element method. The results obtained show the stresses, strains and temperatures during the plastic deformation of the material, as well as the stresses and strains in the punch and die. The analysis of the results obtained for different geometric dimensions of the working tools allowed the optimization of the studied extrusion process. In order to validate the finite element model, experiments were carried out with the data acquisition from the real process, which allowed the appreciation that numerical and experimental data are found in a good agreement.