Papers by Keyword: Rigidity

Abstract: The purpose of research is to determine the influence character of the way the composite rope is connected to the permanent structure elements on its stress-strain state and to develop a determination method for such a state. Research methodology involves constructing the models of interaction between rigid fibers in a rope of composite design, using the methods of mechanics of layered composite materials, with complex consideration of its design and mechanical properties, and the condition of connecting rope ends to the permanent structure. The model is solved analytically using Fourier series on a discrete axis of layer numbers of a finite length while defining the distribution patterns of internal forces and displacements in rope layers. The algorithm for determining a stress-strain state of a rope with rigid fibers while considering a rope connection scheme to the permanent structure is established. The scientific novelty of research is in determination of the character and influence mechanism of a connection scheme of a composite rope with rigid fibers to the permanent structure on its stress-strain state. Practical value of the research is in that the obtained results make it possible to consider the influence character of the rope connection scheme to the permanent structure on a rope stress state and this allows justified determination of its safe operation conditions.

Abstract: In this scientific study, the problem of automation of machine-building production is justified. A 3D model of the lathe is presented and its design is improved. Standard layout schemes based on the upgraded spindle assembly have been developed, which make it possible to increase the speed of this type of machine. The results obtained make it possible to achieve the desired cutting speed, which has significantly increased by 2-2,5 times. The constructed dependence of the deviation on the roundness of samples by the finite element method allows predicting the main indicators: feed rate, spindle speed, cutting depth, static imbalance, initial and final pressure. Also, the obtained analytical results allow us to establish the main regularities of forming the accuracy of this lathe.

Abstract: In this paper, the phenomenon in which the fluidity drops significantly once the concrete, which is a problem in the construction work, is called “stiffness”, and the hypothesis of the occurrence mechanism was hypothesized based on a microscopic image of cement paste. Then, author developed a chemical admixture (stiffness reducing agent) that suppresses the aggregation of cement particles and verified the effect through various tests. In the verification test, author tried to quantify the stiffness of concrete by a simple test called the vane shear test. Also, through various construction performance tests, author confirmed the possibility of stiffness affecting the construction work.

Abstract: This work indicates that the prediction of the geometric indicators of the quality of the machined surface in the design of technological operations for milling a profile surface of work-pieces with low rigidity is possible, on the basis of an analysis of the elastic displacements of the technological system elements, the flexural rigidity of the work-piece as a function of its initial dimensions, the locating chart and the physical and mechanical characteristics of the material being processed. The article describes the characteristics of the elements of the technological system for the profile milling of work-pieces of low rigidity; The analytical dependencies linking the elastic displacements of the work-piece during the processing of various wood species with elements of the milling mode and the design parameters of the mill are given. Extreme total elastic displacements of the technological system during the cutting process are determined. Mathematical models of the maximum geometric error of the machined surface, as a function of the work-piece's flexural rigidity and the spindle unit, are established. Based on the results of the analysis, recommendations for improving the accuracy of the product were developed.

Abstract: The construction of a mathematical model and the development of an algorithm of free vibrations investigation in the three-layered circular shell with a light-weight aggregate supported by annular rigidity ribs are considered in paper. The hypotheses of Kirchoff-Lyav are accepted for external bearing layers of shell and for aggregate there is accepted the linear law of tangential displacements change by thickness. The boundary conditions of a shell region closed between the ribs are established. Using the boundary transition, conditions along the lines of the ribs, taking into account and without deformations of displacement in the ribs, but without taking into account the torsional rigidity in the ribs are determined. The equation of motion of supported three-layered shell is obtained. The frequencies of free vibrations were investigated and values of parameter of the first frequency of free vibrations for a shell, supported by one and three rigidity ribs, were calculated. There are given values depending on the physical and mechanical properties of materials and geometric dimensions of the shell, the curvature parameter, and the rigidity parameter of an aggregate.

Abstract: Powder rolling is used for manufacturing long-length strip. For obtaining the product with high green density it is necessary to ensure shear strain in the deformation zone. Based on the principles of technologic adaptation the dual roll closed caliber with adaptively changed rigidity was constructed. It consists of upper bandage with shoulder, bottom bandage with groove in which the set of three rings (two aside and one central) is located. The pass is arranged by aside rings and outside surface of the central ring forming closed caliber while interacting with the shoulder of the upper bandage. The caliber output is equal to zero and the broadening at rolling is fully excluded. Such construction of the tool makes it possible to achieve high level of hydrostatic stress of tensor simultaneously with intensification of shear strains resulting in practically nonporous rolled strip. Taking into consideration peculiarities of calibre rolling the new criterion was proposed. This criterion enables to characterize roll system for each material, incompact materials in particular, considering retraction ability, to assess and identify the final square of the rolled material at different caliber configuration. Dependence of maximum value of powdered rolled strip thickness on dual roll closed caliber retraction surface value at different rolled strip width is presented.

Abstract: The mechanical behaviour of non-chiral multi-walled carbon nanotubes under tensile and bending loading conditions was investigated. For this purpose, a simplified finite element model of armchair and zigzag multi-walled carbon nanotubes, which does not take into account the van der Waals forces acting between layers, was tested in order to evaluate their tensile and bending rigidities, as well as the Young’s modulus. The current numerical simulation results are compared with data reported in the literature. The robustness of the simplified model for evaluation of the Young’s modulus of multi-walled carbon nanotubes is discussed.

Abstract: The objectives of this study are to observe the deformation of mitral leaflet in systole condition and compare the rigidity of heart valve leaflet during systole and diastole conditions. Two-dimensional model of the mitral valve leaflet with ventricle were created using fluid structure interaction model in computational simulations. The result shows rigidity of heart valve leaflet always opposite to degeneration and the simulated displacement models corresponded to normal deformation in physical heart valve in systole condition. Modeling simulation techniques are very useful in the study of degenerative heart valve and the findings would allow us to optimize feature and geometries to reduced deformation of heart valve failure.

Abstract: The study of the mechanical behaviour of single-walled carbon nanotube heterojunctions has been carried out, implementing nanoscale continuum approach. A three-dimensional finite element model is used in order to evaluate the elastic behaviour of cone heterojunctions. It is shown that the bending rigidity of heterojunctions is sensitive to bending conditions. The torsional rigidity does not depend on torsion conditions. Both rigidities of the heterojunction are compared with those of the thinner and thicker constituent nanotubes.

Abstract: In the paper a research methodology was developed and used to determine the rigidity in transversal direction of modular fixture structures. The paper presents experimental results regarding the total deformation of modular structure consisting of ”narrow” modules from modular kits. The research conducted showed the different evolution of deformation curves in the case of modular structure, with different shape and different sizes of modules, in the case of similar loads. The experimental results indicate displacements of the entire modular structure alongside the base plate and, also, tilting. The measured deviations of modules from fixture structure may cause "dimensional"/ position deviations (linear displacement of the measurement base) and deviations of shape and orientation-position (angular displacement of the measurement base) of the workpiece during severe machining conditions.