EVALUATION OF DEFORMABILITY OF MATERIAL OF PREPARATIONS DURING ROLLING

The article presents the results of development and research of the technological process of cold forming rolling of aluminum billets. The main obstacle to the implementation of such processes is the danger of destruction of materials, which necessitated the study of the stress-strain state, plasticity and assessment of the deformability of the workpiece material. To experimentally determine the ductility of metals, a rolling method was developed, according to which the deformation of the free side surface of the cylindrical sample occurs under uniaxial tension. Increasing the degree of deformation and bringing the material to fracture is provided due to the increase in the radii of the rolls during rolling and deformation of the sample on the wedge. Analysis of the stress-strain state of the free side surface of the cylindrical workpiece was performed by the finite element method, which used a specialized engineering software package DEFORM 3D. As a result, a significant inhomogeneity of the stress-strain state in the deformation zone is established. The most severe stress state is observed on the free side surfaces of the workpiece, which causes the danger of its destruction in this area. The dependence between the relative compression of the workpiece during rolling and the intensity of deformation on its side surface is obtained, which allows to determine the limiting thickness of the workpiece before destruction. As a result of the assessment of the deformability of aluminum alloys during cold rolling, using the curves of limit deformations and the scalar criterion of deformation, the limits to the destruction of the intensity of deformation and the limit value of the relative compression of the workpiece. The use of constructed models makes it possible to determine the value of the used plasticity resource at intermediate stages of rolling.

Theoretical Investigations for the Defect Structure and the Spin Hamiltonian Parameters of Divalent Cobalt in LiMgPO4

The spin Hamiltonian parameters (SHPs, g factors and hyperfine structure constants) defect structure for LiMgPO4 doped with 0.1% Co2+ at 4.2 K are theoretically investigated from the perturbation formulas of the SHPs for a rhombically distorted octahedral 3d7 cluster. The impurity Co2+ on host Mg2+ site is found to suffer the larger axial relative compression ratio ρ (≈ 0.76%) and the planar angular variation Δφ (≈ 6.64°) related to the host oxygen octahedron due to size mismatch. The calculated SHPs based on the above defect structure show good agreement with the measured results. Present study can be helpful to the preparation and characterization for the local structures for transition-metal impurities in lithium-magnesium phosphate, which may is helpful to search for the phosphor materials with better dosimetric characteristics.

Mixed evidence for the compression of morbidity hypothesis for smoking elimination—a systematic literature review

Background There is debate around the composition of life years gained from smoking elimination. The aim of this study was to conduct a systematic review of the literature to synthesize existing evidence on the effect of smoking status on health expectancy and to examine whether smoking elimination leads to compression of morbidity. Methods Five databases were systematically searched for peer-reviewed articles. Studies that presented quantitative estimates of health expectancy for smokers and non-/never-smokers were eligible for inclusion. Studies were searched, selected and reviewed by two reviewers who extracted the relevant data and assessed the risk of bias of the included articles independently. Results The search identified 2491 unique records, whereof 20 articles were eligible for inclusion (including 26 cohorts). The indicators used to measure health included disability/activity limitations (n=9), health-related quality of life (EQ-5D) (n=2), weighted disabilities (n=1), self-rated health (n=9), chronic diseases (n=6), cardiovascular diseases (n=4) and cognitive impairment (n=1). Available evidence showed consistently that non-/never-smokers experience more healthy life years throughout their lives than smokers. Findings were inconsistent on the effect of smoking on the absolute number of unhealthy life years. Findings concerning the time proportionally spent unhealthy were less heterogeneous: nearly all included articles reported that non-/never-smokers experience relatively less unhealthy life years (e.g. relative compression of morbidity). Conclusions Support for the relative compression of morbidity due to smoking elimination was evident. Further research is needed into the absolute compression of morbidity hypothesis since current evidence is mixed, and methodology of studies needs to be harmonized.

Experimental study of heating of a polyurethane shock absorber under cyclic loading

Based on the results of the experiments, an empirical dependence was obtained to determine the heating temperature of polyurethane shock absorbers of different hardness under cyclic loading, depending on the relative compression deformation, loading frequency and vibration amplitude. Keywords: polyurethane, shock absorber, heating temperature, empirical dependence. [email protected]

THERMOPHYSICAL AND PHYSICO-MECHANICAL CHARACTERISTICS OF EPOXYURETHANE COMPOSITES

Epoxy urethane composites (EU) have been developed based on polyisocyanate (PIC), epoxy resin (ED-20), and sodium silicate (SS). The results of the study of the influence of the ratio of the components of the EU on their thermophysical and physicomechanical characteristics are presented. The method ofdifferential scanning calorimetry revealed thatthese systems do not have clear temperature transitions, which indicates a fairly homogeneous and rigid structure. Studies of thermal properties by the method of dynamic thermogravimetry have shown that as the amount of sodium silicate increases, the temperature of the onset of decomposition of the EU is shifted by 20 ° C towards lower temperatures. At the same time, there is a slowdown in the decomposition of epoxy urethanes (weight loss is 12-14%), due to the presence of heterocyclic isocyanurate fragments, which is inherent in its own high thermal stability. The mechanical properties of the EU, such as compressive strength, modulus of elasticity, relative compression deformation, flexural strength, and water absorption, are determined depending on the ratio of components. High mechanical properties are shown regardless of the inorganic component amount. The modulus of elasticity, strength, and relative deformation in compression is in the range of 1916.4 - 4187.6 MPa, 117.4 - 133.1 MPa, and 24.7-30.4%, respectively. The highest flexural strengths are characterized by the EC composition of the PIC / SS / ED-20 = 80/20/20, and the lowest - the EC composition of the PIC / SS / ED-20 = 70/30/20. The results of the studies show that, by changing the ratio of organic and inorganic constituents in the EC, it is possible to regulate the thermal stability and physicomechanical properties of epoxy urethane composites depending on their purpose.

Visual Analysis of Research Paper Collections Using Normalized Relative Compression

The analysis of research paper collections is an interesting topic that can give insights on whether a research area is stalled in the same problems, or there is a great amount of novelty every year. Previous research has addressed similar tasks by the analysis of keywords or reference lists, with different degrees of human intervention. In this paper, we demonstrate how, with the use of Normalized Relative Compression, together with a set of automated data-processing tasks, we can successfully visually compare research articles and document collections. We also achieve very similar results with Normalized Conditional Compression that can be applied with a regular compressor. With our approach, we can group papers of different disciplines, analyze how a conference evolves throughout the different editions, or how the profile of a researcher changes through the time. We provide a set of tests that validate our technique, and show that it behaves better for these tasks than other techniques previously proposed.

Establishment of a Laminated Crushed Products Function and Numerical Analysis

A model of the relative compression ratio for single-particle crushed products, based on the distinct element method (DEM) and numerical analysis, was established to describe precisely the crushed products of granular particles during laminated crushing. The relative compression ratio model was used to describe the functional relationship between the total compression ratio and the single-particle compression ratio, which can be described by lognormal distribution. The single-particle crushed products model was used to describe the functional relationship between the single-particle compression ratio and the distribution of single-particle crushed products. The distribution of single-particle crushed products was described by a three-parameter beta distribution. On the basis of the above model, the function of laminated crushed products of granular particles was established. According to the simulation results of EDEM under confining pressure, a functional relationship between total compression ratio, particle size, and height of the granular particles for laminated crushed products of granular particles was built. It was proved that the function of the theoretical particle size distribution coefficient of laminated crushed products of granular particles was not too different from the actual value determined by simulation. The function is universal and can be used to provide a theoretical basis and a design reference for the design of cone crushers, high-pressure roller mills, and other crushing equipment.