Hilltop Inflation and Generation of Helical Magnetic Field

Primordial magnetic field generated in the inflationary era can act as a viable source for the present day intergalactic magnetic field of sufficient strength. We present a fundamental origin for such a primordial generation of the magnetic field, namely through anomaly cancellation of U(1) gauge field in quantum electrodynamics in the context of hilltop inflation. We have analysed at length the power spectrum of the magnetic field, thus generated, which turns out to be helical in nature. We have also found that magnetic power spectrum has significant scale-dependence giving rise to a non-trivial magnetic spectral index, a key feature of this model. Interestingly, there exists a large parameter space, where magnetic field of significant strength can be produced.

DESIGN AND STRENGTH ANALYSIS OF A CRANE HOOK WITH A 500 KG LIFTING CAPACITY

A bridge crane is a type of crane that is designed for lifting / lowering and transferring material in the horizontal direction and is used mainly in production halls, warehouses and transship points. A part of the lifting mechanism of the bridge crane is a crane hook on which the load is suspended. Sufficient strength is required from the crane hook in order to be able to withstand high loads relatively well. The most stressed part of the crane hook is the curved inner surface. This surface is considered critical in terms of strength. The goal of this paper is to select a suitable crane hook for a single girder bridge crane with a load capacity of 500 kg and a strength analysis of the selected crane hook. Strength analysis is performed by two methods, first is based on analytical calculation and second is based on finite element method (FEM) performed in Ansys software. The comparison of the obtained total stresses from both methods is the part of the analysis. From the results of the FEM analysis and analytical calculation it can be stated that the selected crane hook RSN 05 P - DIN 15401 with a load capacity of 500 kg is suitable for the above-mentioned bridge crane. It can also be concluded that the total stress determined by the analytical calculation is lower by 9.8 % compared to the stress obtained from the Ansys software.

Microstructure and Mechanical Properties of Inverse Nanocomposite Made from Polylactide and Hydroxyapatite Nanoparticles

Polymer nanocomposites have been extensively researched for a variety of applications, including medical osteoregenerative implants. However, no satisfactory solution has yet been found for regeneration of big, and so-called critical, bone losses. The requirement is to create a resorbable material which is characterised by optimum porosity, sufficient strength, and elastic modulus matching that of the bone, thus stimulating tissue regrowth. Inverse nanocomposites, where the ceramic content is larger than the polymer content, are a recent development. Due to their high ceramic content, they may offer the required properties for bone implants, currently not met by polymer nanocomposites with a small number of nanoparticles. This paper presents inverse nanocomposites composed of bioresorbable nano crystalline hydroxyapatite (HAP NPs) and polylactide (PLLA), produced by cryomilling and a warm isostatic pressing method. The following compositions were studied: 25%, 50%, and 75% of HAP NPs by volume. The mechanical properties and structure of these composites were examined. It was discovered that 50% volume content was optimal as far as compressive strength and porosity are concerned. The inverse nanocomposite with 50% nanoceramics volume displayed a compressive strength of 99 ± 4 MPa, a contact angle of 50°, and 25% porosity, which make this material a candidate for further studies as a bioresorbable bone implant.

DEVELOPMENT OF TECHNOLOGICAL PARAMETERS FOR THE FORMATION OF FASTS BY THE SLIDING CASTING METHOD

The materials of the article consider the effectiveness of additives for stabilization and dilution of clay-free slippers. For theproduction of radio-transparent ceramic materials of Celsius-Willemite composition, the most efficient and energy-saving methodof production is the method of slip casting. According to the charge composition, this technology is complicated by the lack of claycomponents, which shows the need to use impurities to improve the rheology of such a slip. The main characteristics of aqueousceramic slippers are density, humidity, fluidity, viscosity, density factor, rate of mass accumulation. The slip must meet thefollowing requirements: be free from foam and gas inclusions, have satisfactory fluidity under low viscosity; be aggregativelystable (characterized by the absence of aggregation, coagulation and sedimentation of solid phase particles); have a high filteringcapacity to ensure fast and defect-free weight gain; to be chemically inert, to provide sufficient strength and low shrinkage of semifinished products, as well as the possibility of their easy release from the mold.

Strength Evaluation and Failure Analysis of the Vortex Reducer under Overspeed Condition

Rotating parts of aeroengines need to have a high speed margin according to the civil aviation airworthiness regulations. Previous studies on burst speed are based on mechanical properties of standard specimens. In this paper, a new method for predicting burst speed by means of a tensile test of a simulative specimen is proposed, and the predicted results are compared with the traditional method. The results show that the stress gradient of the designed simulative specimen and the assessment location of vortex reducer are in good agreement, which indicates that they have similar stress characteristics. The burst speed predicted by the new method is greater than the traditional method. Both prediction methods can provide a reference for such a structure in the design stage. In addition, the overspeed test of a vortex reducer is carried out, and the results verify that it still has sufficient strength reserves at 120% relative speed.

Custom-Made Titanium Mesh Tray for Mandibular Reconstruction Using an Electron Beam Melting System

Mandibular reconstruction using a titanium mesh tray and autologous bone is a common procedure in oral and maxillofacial surgery. However, there can be material problems—such as broken titanium mesh trays—which may undermine long-term functionality. This study was designed to investigate the optimal conditions for a titanium mesh tray with an ideal mandibular shape and sufficient strength, using computer-aided design, computer-aided manufacturing technology, and electron beam additive manufacturing. Specimens were prepared using Ti-6Al-4V extra low interstitial titanium alloy powder and an electron beam melting (EBM) system. The mechanical strength of the plate-shaped specimens was examined for differences in the stretch direction with respect to the stacking direction and the presence or absence of surface treatment. While evaluating the mechanical strength of the tray-shaped specimens, the topology was optimized and specimens with a honeycomb structure were also verified. Excellent mechanical strength was observed under the condition that the specimen was stretched vertically in the stacking direction and the surface was treated. The results of the tray-shaped specimens indicated that the thickness was 1.2 mm, the weight reduction rate was 20%, and the addition of a honeycomb structure could withstand an assumed bite force of 2000 N. This study suggests that the EBM system could be a useful technique for preparing custom-made titanium mesh trays of sufficient strength for mandibular reconstruction by arranging various manufacturing conditions.

WOOD-GLASS-FIBER COMPOSITE MATERIALS BASED ON POLYESTER RESINS FOR TIMBER RAILWAY SLEEPER STRUCTURES

Wood-glass-fiber composite materials (WGFCM) are used in transport construction (sleepers, switch bars, etc.). Polymer solutions based on furfuralacetone monomer (FAM) served as a matrix for the manufacture of WGFCM. The article suggests using Holex HAS- 2061 polyester resin as a matrix, which, in turn, has chemical resistance, dielectric properties, increased impact strength, having sufficient strength characteristics, and significant extensibility. For the application of the above material in the structural elements of sleepers of logging railways, it is necessary to know its operation under repeated loading. Endurance experiments were conducted at different coefficients of the load application cycle asymmetry pb=0,1; 0,3; 0,6. As a result of the experiments, the values of the endurance limit of the material under study were obtained, which allow us to conclude that it can be used in the construction of timber railway sleepers.

MANUFACTURING METHOD OF THE MORPHING WING STRUCTURE FOR UAV BY CFRP WITH APPLYING THE ELECTROFORMED RESIN MOLDING METHOD

Aircraft flight control usually requires driving flaps and ailerons. However, the air drags increase significantly due to the corners of flaps and aileron. Especially, the gap between mother wing and flap / aileron causes a drag increase. Therefore, studies are being conducted on morphing wings that smoothly and greatly deform the wing surface. For aircraft wing, it is needless to say that strength is important to sustain lift and drag for the aircraft during the flight. For morphing wings, in addition, actuators must be mounted inside the wing to enable the morphing deformation. Moreover, for the aircraft wing, weight is quite important. Therefore, carbon fiber reinforced plastic (CFRP) is currently most suitable for aircraft wing structural materials. However, it is difficult to mold CFRP so that it has sufficient strength and can be morphed. In this study, by using CFRP, the morphing wing structure was prototyped with targeting a small unmanned aerial vehicle (UAV) weighing 3 kg. The CFRP lattice structure that enables morphing deformation was designed and manufactured by applying the electrodeposition resin molding (ERM) method which was developed by the authors. In the ERM method, firstly, the carbon fiber was fixed with a jig according to the designed morphing wing structure, and immersed in the electrodeposition solution. Secondly, the epoxy polymer particle in the solution were electrophoresed and impregnated between carbon fibers. After thermal curing, the morphing wing structure was fabricated. Further, the loading-unloading torsion and bending tests of the morphing wing structure were carried out. Smooth morphing deformation and sufficient strength were confirmed.

Fibrin Glue and Conduit Form a Composite Structure in Digital Nerve Repair

Repair of severed nerves without auto- or allograft has included suture, suture with glue alone, suture with conduit and suture with glue augmentation to conduit, where use of conduit is considered for separation of the nerve ends from 5mm to 3cm. Repairs must not only serve acutely to provide apposition of nerve ends but must enable the healing of the nerve. Using biological conduit can place suture at the ends of the conduit while fibrin glue alone eliminates suture but with limited strength. The combination of conduit and glue offers the growth guidance of conduit with sufficient strength from the glue to maintain the nerve within the conduit. The role of glue in the repair integrity remains an open question, however. We sought to determine the factors in the strength of a glue-conduit-nerve construct and include consideration of standard suture repair. Fresh-frozen cadaveric digital nerves were repaired with suture alone, with glue alone or with suture and glue together and loaded to failure. Previously tested specimens with conduit, suture and glue were considered for comparison. The suture alone (2.02N) and suture with glue (2.24N) were not statistically different from each other but were statistically stronger than glue alone (0.15N). Compared to the earlier results of the strength of conduit with glue (0.65N), these results show that the glue and conduit act together. The increased area over which the glue adheres to the nerve and conduit creates a composite structure stronger than either alone.

PECULIARITIES OF UNIVERSAL BODY DESIGN FOR INNOVATION REFRIGERATOR CARS

There are considered analysis results of stress-strain state in the load-bearing structure of three versions of refrigerator cars with different arrangement solutions of refrigerating-heating plants (RHP) and a thermos car at its cooling with liquid nitrogen. By means of the “APM WinMachine” application there are presented model parameters of a basic universal body. The analysis of calculation results has shown sufficient strength and potentialities for updating an available car metal structure for the application as a universal body of a refrigerator car. Work purpose: the estimation of a stress-strain state in the load-bearing structure of a basic body for insulated cars of different types of refrigerator- and thermos cars. Investigation methods: for the analysis of the stress-strain state in a load-bearing structure in three versions of the bodies of refrigerator- and thermos cars under loads with “Normal” modes there was used the “APM WinMachine” software complex realizing a finite element method. Results and novelty: for the first time there are offered arrangement solutions for the location of refrigeration-heating plants earlier not used for refrigeration rolling-stock (RRS). A stress-strain state of the body of the thermos car at the impact of overpressure upon it of gaseous nitrogen evaporated in cargo compartment is estimated. Conclusions: the analysis of calculation results for all three versions of the RHP arrangement and a solid body of a thermos car has shown sufficient strength and possibility regarding simple updating an available body metal structure which may be used as a universal car set.