An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9 wt%-Nd3 wt%-Zr0.5 wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Powder Bed Fusion–Laser Beam (PBF–LB) processing of magnesium (Mg) alloys is gaining increasing attention due to the possibility of producing complex biodegradable implants for improved healing of large bone defects. However, the understanding of the correlation between the PBF–LB process parameters and the microstructure formed in Mg alloys remains limited. Thus, the purpose of this study was to enhance the understanding of the effect of the PBF–LB process parameters on the microstructure of Mg alloys by investigating the applicability of computational thermodynamic modelling and verifying the results experimentally. Thus, PBF–LB process parameters were optimized for a Mg WE43 alloy (Mg-Y3.9 wt%-Nd3 wt%-Zr0.5 wt%) on a commercially available machine. Two sets of process parameters successfully produced sample densities > 99.4%. Thermodynamic computations based on the Calphad method were employed to predict the phases present in the processed material. Phases experimentally established for both processing parameters included α-Mg, Y2O3, Mg3Nd, Mg24Y5 and hcp-Zr. Phases α-Mg, Mg24Y5 and hcp-Zr were also predicted by the calculations. In conclusion, the extent of the applicability of thermodynamic modeling was shown, and the understanding of the correlation between the PBF–LB process parameters and the formed microstructure was enhanced, thus increasing the viability of the PBF–LB process for Mg alloys.

Modeling of thermal processes in the contact zones of fuel elements

In this work, using two specific examples, a general approach to the mathematical modeling of thermal processes in the contact zones of fuel elements in the development and optimization of various technological processes, systems and devices is considered. In the first example, a mathematical model of heat transfer in the contact zone (metal-hybrid thermal interface) between the heat-generating element and the heat-dissipating radiator is considered. In the second case, the thermal process in the processing of materials with a bonded diamond tool in the contact zone "diamond grain – binder – processed material" is considered and analyzed. The general approach to modeling thermal processes in the contact zones of various fuel elements makes it possible to optimize the parameters of technological processing modes and the correct operating conditions for products and systems

A COMPARATIVE ANALYSIS OF MACHINING PARAMETERS INFLUENCE ON ACCURACY AND ROUGHNESS IN WATERJET AND LASER CUTTING

The paper presents a comparative analysis of the technique of cutting materials such as water jet cutting and laser cutting. The tests were carried out while cutting plastic elements, such as: PMMA, HIPS and ABS. To compare the analysed cutting methods, it was necessary to limit the type of material to be cut to the selected plastics due to the limited thickness range of the samples cut with the use of the laser used for the tests. The workpiece was designed in AutoCAD. The geometry was designed in such a way that it was possible to compare the accuracy of cutting both straight sections, curves and holes using the cutting techniques tested. The roughness of the treated surfaces (edges of the samples) was also analysed. A roughness gauge was used to test the edges. The obtained research results were compiled and analysed to determine the optimal technology and parameters of cutting processes for individual types of selected materials and shapes. As it was shown, the wrong selection of the cutting technology in relation to the processed material or the wrong selection of machining parameters may lead to the destruction of the detail being made and incur significant costs.

Dynamic analysis of a ten-link tooth-lever differential transmission

This article discusses the dynamics of a ten-link tooth-lever differential transmission mechanism. The force analysis of the transmission mechanism is given in order to find the dependence for determining the reaction in kinematic pairs and the balancing moment of the pair of forces and to show some features of the tooth-lever transmission mechanism. The force calculation was carried out taking into account the accelerated movement of links since their acceleration in modern high-speed machines is very significant. To obtain a more accurate concept of the external forces and moments loading the transmission mechanism in the accelerated movement of the links, the dynamics of the transient process of roller technological machines was considered. Cases of feeding the processed material were considered both from the side of the intermediate gears and from the side opposite to the parasitic gears. Dependencies were obtained to determine the force characteristics of this mechanism. Cases of pressure unloading and overloading on the processed material from the side of the free shaft, depending on the location of the transmission mechanism are shown. The dependence of the reaction force of intermediate gears on their own axes of rotation on the angle between the levers is shown. With an increase in the angle between the levers, the reaction of the intermediate gears on the axis of rotation increases.

Approach to setting the mode parameters in combined electro-erosive - electrochemical processing during piercing the deep holes of small diameter

The article considers the problem of forming the deep holes of small diameter by using the combined electro-erosive and electrochemical machining based on the electrochemical and electro-erosive processes. The approach to setting the mode parameters during piercing the deep holes with a diameter of less than 1 mm is suggested. The approach takes into consideration the influence of hydrodynamic losses in the inter-electrode gap on the limitation of the mode parameters of the electrochemical and electro-erosive components in the combined processing. It also takes into account the interrelation between the magnitude of the inter-electrode gap and the linear velocities of the removal of the processed material in each of the components during the combined processing. The validity of the approach to setting the mode parameters in the combined electro-erosive -electrochemical processing during piercing the deep holes with a diameter from 0.3 mm to 1 mm in the range of the inter-electrode gap from 0.025 mm to 1 mm is experimentally confirmed.

Evolution of Accretor Stars in Massive Binaries: Broader Implications from Modeling ζ Ophiuchi

Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day-period binary, consisting initially of a 25 M ⊙ star and a 17 M ⊙ star, which experiences stable mass transfer. We focus on the impact of mass accretion on the surface composition, internal rotation, and structure of the accretor. To anchor our models, we show that our accretor broadly reproduces the properties of ζ Ophiuchi, which has long been proposed to have accreted mass before being ejected as a runaway star when the companion exploded. We compare our accretor to models of single rotating stars and find that the later and stronger spin-up provided by mass accretion produces significant differences. Specifically, the core of the accretor retains higher spin at the end of the main sequence, and a convective layer develops that changes its density profile. Moreover, the surface of the accretor star is polluted by CNO-processed material donated by the companion. Our models show effects of mass accretion in binaries that are not captured in single rotating stellar models. This possibly impacts the further evolution (either in a binary or as single stars), the final collapse, and the resulting spin of the compact object.

The FDM Technique in Processes of Prototyping Spare Parts for Servicing and Repairing Agricultural Machines: A General Outline

The aim of this research was to determine the possibility of applying alternative techniques for the production of prototypes for spare parts in agriculture and to determine the possible directions of development of their applications in the engineering industry. Then, to determine which spare parts could be produced using the FDM technique, comparisons of the most important parameters of spare parts produced independently (using the FDM technique) and obtained from producers (produced using traditional methods in professional factories) were made. A number of factors were analysed, from technical parameters such as machine type, processed material and its consumption including required as support structures, to economic issues such as manufacturing or purchase delivery total time and cost. The FDM technique has proven itself in many ways in the production of spare parts for agricultural machinery.

Influence of laser-induced plasma parameters on the formation of laser-induced surface-periodic structures

The paper presents the results of processing a silicon surface with subpicosecond laser pulses under various exposure conditions. The variable conditions were: pressure in the working chamber, the speed of scanning the silicon surface with a laser beam and the laser pulse energy. Special attention was paid to the interaction of the laser-induced plasma plume with the surface of the processed material, with laser radiation and with the medium. The influence of the medium on the parameters of the laser-induced plasma is estimated. The result of this interaction is a change in the spatial characteristics of the laser-induced plasma channel, the period and type of the formed periodic surface structures, what is related to the change in the laser radiation passing through the medium at different pressures.

Investigation of the roof-breaking device parameters for unloading composting installations of the bunker type

The article discusses the increasing efficiency of composting animal waste by substantiating the unloading processes, taking into account the formation of vaults in composting bunker-type installations. The technology of accelerated composting and the characteristic features of unloading the processed material is presented. The design and layout of the working bodies of the arch-breaking unloading device are theoretically and experimentally substantiated. Based on the research results, the unloading device’s optimal design and operating parameters and the values of the consumed power have been determined.

Microstructure and properties evolution of Mg–2Y–0.6Nd–0.6Zr alloy rolled at room and liquid nitrogen temperature

The microstructure evolution, texture, mechanical behavior and twin deformation of the ECAPed Mg–2Y–0.6Nd–0.6Zr alloy at room and liquid nitrogen temperature were investigated by rolling samples. The ECAP processed material appeared the texture of 45° to the extrusion direction and its yield strength reached 93.6 MPa. The results showed that cryorolling encourages twinning in Mg–2Y–0.6Nd–0.6Zr alloy, enhancing the tensile strength and texture. Activation of {10–12} twinning during rolling was found to be more pronounced in the cryorolled samples than in the cold rolled samples owing to a lower temperature. As a result, the cryorolled samples had more twins than and cold rolled ones, the proportion of twin areas of room temperature rolling and ultra-low temperature rolling were: 2.45% and 4.23%.