The Influence of Specimen Geometry and Loading Conditions on the Mechanical Properties of Porous Brittle Media

Dynamic tests of fine-grained fired dioxide-zirconia ceramics under compression under uniaxial stress conditions were carried out. The influence of the specimen length on the obtained strength and deformation properties of ceramics is investigated. The thickness of the specimen has a significant impact on the course of the obtained dynamic stress–strain diagrams: short specimens have a much more sloping area of active loading branch. The main contribution to the modulus of the load branch resulting from tests of brittle porous media is made by the geometry of the specimens and the porosity of the material. When choosing the length of specimens for dynamic tests, the optimal geometry of the tested specimens is preferable in accordance with the Davies–Hunter criterion, when the contributions of axial and radial inertia are mutually compensated, and the contribution of the effects of friction in the resulting diagram is minimal. When choosing the geometry of specimens of brittle porous media, the structure of the material should be taken into account so that the size of the specimen (both length and diameter) exceeds the size of the internal fractions of the material by at least five times.

An Investigation of Suitable Healing Agents for Vascular-Based Self-Healing in Cementitious Materials

Self-healing cementitious materials can extend the service life of structures, improve safety during repair activities and reduce costs with minimal human intervention. Recent advances in self-healing research have shown promise for capsule-based and intrinsic healing systems. However, limited information is available regarding vascular-based self-healing mechanisms. The aim of this work is to compare different commercially available healing agents regarding their suitability in a self-healing vascular network system by examining a regain in durability and mechanical properties. The healing agents investigated include sodium silicate, two polyurethanes, two water repellent agents and an epoxy resin. Sealing efficiencies above 100% were achieved for most of the healing agents, and both polyurethanes and the epoxy resin showed high regain in strength. The results obtained from this study provide a framework for selecting a healing agent given a specific application, as a healing agent’s rheology and curing properties can affect the optimal geometry and design of a vascular network.

Experimental efficiency evaluation of the of various geometry twisted bands for heat transfer intensification in the heat-exchange channels of a nuclear power unit equipment

The paper is devoted to experimental study of heat exchange and pressure drop of channel with various geometry twisted bands. The studies were carried out in the range of operating modes parameters of the nuclear power units’ heat exchange equipment. The three different designs of intensifiers are presented in the paper. The values of heat transfer coefficient and pressure drop are obtained. The dependences of the Nusselt number (Nu) on the Reynolds number (Re) were calculated. The comparative analysis of intensifiers is made. The efficiency factor was also calculated on experimental data. The most optimal geometry form of intensifier was selected.

Optimal Geometry of Holes in a Cable Tray for Offshore Plants

This study analyzes the crosstalk effects caused by the geometry of holes in a cable tray in offshore plants. Using the analysis results, we determine the optimal hole geometry that can effectively reduce the tray weight under minimum crosstalk. It was previously shown that metal cable trays can reduce crosstalk among cables. However, the impact of hole geometry was not considered. This study demonstrates the impact of hole geometry on the crosstalk. In addition, an algorithm is proposed to determine the optimal geometry of holes in the cable tray. The simulation results validate the proposed algorithm and can be useful for the designers of cable trays with holes.

Cleanroom and Template Free Fabrication of Single Polygonal Shaped Microneedle

For painless skin penetration, microneedles require optimal geometry due to human skin’s inherent elastic properties. The fabrication of desired shape microneedle is very critical. To our knowledge, the polygonal geometry microneedle has not been investigated before. To address this issue, in this communication, we propose a novel cleanroom free fabrication of single metal microneedle with square cross section. The microneedle was fabricated using sputtering technique without any mask or template. The morphological analysis with respect to various sputtering parameters via. Argon (Ar) pipe position, rotating speed, working pressure was discussed in detail. The microneedle geometry, its assisted pain was visualized using finite element analysis (FEM). The theoretical evaluations were subsequently compared with experimentally fabricated microneedle. This is the first step towards more rational design of polygonal microneedle geometry.

CFD Analysis and Taguchi-Based Optimization of the Thermohydraulic Performance of a Solar Air Heater Duct Baffled on a Back Plate

In this paper, a solar air collector duct equipped with baffles on a back plate was numerically investigated. The Reynolds number (Re) was varied from 5000 to 20,000, the angle baffle (a) from 30° to 120°, the baffle spacing ratio (Pr) from 2 to 8, and the baffle blockage ratio (Br) from 0.375 to 0.75 to examine their effects on the Nusselt number (Nu), the friction factor (f), and the thermohydraulic performance parameter (η). The 2D numerical simulation used the standard k-ε turbulence model with enhanced wall treatment. The Taguchi method was used to design the experiment, generating an orthogonal array consisting of four factors each at four levels. The optimization results from the Taguchi method and CFD analysis showed that the optimal geometry of a = 90°, Pr = 6, and Br = 0.375 achieved the maximum η. The influence of Br on all investigated parameters was considerable because as Br increased, a larger primary vortex region was formed downstream of the baffle. At Re = 5000 and the optimal geometry parameters, a maximum η of 1.01 was reached. A baffle angle between 60° and 90° achieved a high Nusselt number due to the impingement heat transfer.

Improvement of efficiency of metal recycling in metallurgical production

The article deals with the most effective primary utilization and subsequent processing of the main waste of machine-building enterprises-metal chips. To solve the above problems, the recycling of metal waste the most effective method is a comprehensive approach to the conditions of machine-building enterprises working in the conditions of the automated production consists of solutions to several problems, the main of which are submitted to the necessary properties of the chips produced and optimization of the technological equipment used for initial processing and subsequent briquetting of the chip. The solution of the problem of obtaining chips of the specified characteristics after the analysis of existing methods of its solution is proposed to be performed by applying the method of preliminary local physical impact on the surface of the workpiece. The proposed method makes it possible to obtain chips of such parameters that will meet the technical conditions of the type of automatic line for its processing and disposal, which is available in a particular production. The problem of optimization of the technological line of primary processing of chips is proposed to be solved on the basis of preliminary engineering analysis of chip crushing devices, which allows you to choose the optimal geometry of the cutter inserts depending on the type and material of the chips being crushed. The proposed set of measures should help machine-building enterprises to increase the profitability of production.

Optimal Rotor Design of Synchronous Reluctance Machines Considering the Effect of Current Angle

The torque density and efficiency of synchronous reluctance machines (SynRMs) are greatly affected by the geometry of the rotor. Hence, an optimal design of the SynRM rotor geometry is highly recommended to achieve optimal performance (i.e., torque density, efficiency, and power factor). This paper studies the impact of considering the current angle as a variable during the optimization process on the resulting optimal geometry of the SynRM rotor. Various cases are analyzed and compared for different ranges of current angles during the optimization process. The analysis is carried out using finite element magnetic simulation. The obtained optimal geometry is prototyped for validation purposes. It is observed that when considering the effect of the current angle during the optimization process, the output power of the optimal geometry is about 3.32% higher than that of a fixed current angle case. In addition, during the optimization process, the case which considers the current angle as a variable has reached the optimal rotor geometry faster than that of a fixed current angle case. Moreover, it is observed that for a fixed current angle case, the torque ripple is affected by the selected value of the current angle. The torque ripple is greatly decreased by about 34.20% with a current angle of 45° compared to a current angle of 56.50°, which was introduced in previous literature.