Papers by Keyword: Torsion

Abstract: The experimental investigations were carried out to study the behavior of reinforced concrete beams strengthened by CFRP sheets under different loading conditions (pure bending, combined bending and torsion and pure torsion). The experimental work included testing twenty RC beams of the rectangular cross-section of dimensions of 160×240 mm and of 2600 mm length with an area of the ordinary reinforcement being kept constant for all beams. Two parameters were taken into consideration (Twisting to bending moment ratio (T/M) and CFRP strengthening pattern). The tested beams are divided into five groups. Each group consists of four beams; the first beam is without CFRP strengthening, the other three are strengthened with CFRP sheets of different arrangements (U-stirrups, U-stirrups and longitudinal CFRP sheets in the bottom and Full U- stirrups wrapping). Each beam is loaded to a different loading conditions (pure bending, T/M = 0.5, T/M = 1.0, T/M = 2.0 and pure torsion). The CFRP sheets were attached externally to the beam. Test results were analyzed based on the influence of CFRP on the ultimate load, vertical mid-span deflection and failure modes. In the experimental work, it was found that all strengthening patterns of CFRP sheets exhibited a significant increase in ultimate strength. This increase reached up to 78.9% for tested beams, when the beam strengthened in the form of full U- stirrups wrapping pattern for T/M = 0.5. In this study, it is observed that the use of external CFRP sheets attached to the tension sides of beams (U-stirrups and longitudinal CFRP in the bottom) could enhance the ultimate load capacity by 32.7% over the capacity of the unstrengthen control beam for T/M = 1.0.

Abstract: In this paper, based on the technical theory developed by the article contributors and the theory designed for twisting of a composite laminated rod of any cross section, a computer program for numerical stress-strain analysis of laminated composite blades in the centrifugal forces field is presented. The naturally twisted laminated composite blade is considered to be under the combined action of the tensile stresses, bending and twisting moments or under the influence of centrifugal forces. In the program, the technological problem of blade unfolding into petals is solved. These petals lie in planes which are parallel to the rod axis and appear due to the varying cross-section along the length of the blade. The investigated blade is represented with eight sections. The results of research on stress-strain behaviour of boron aluminium laminated compressor blades which operate in the fields of centrifugal forces are analysed.

Abstract: The paper discusses the principles of precast concrete hollow-core slabs taking into account their spatial work. It is shown that consideration of spatial work makes it possible to determine the forces in individual floor slabs significantly more precise. The fact that strain redistribution between precast floor slabs depends on slabs’ bending and torsional stiffness is shown. The research has been mostly devoted to determination of the bending stiffness with regard to formation of cracks and the change in torsional stiffness, especially considering the presence of normal cracks, which is still unstudied. This paper presents the technique for determining the torsional stiffness of hollow-core slabs with normal cracks. In order to determine the components included in the resolving system of equations, it is proposed to use an approximation method based on the processing of numerical data using spatial finite elements.

Abstract: An axisymmetric contact problem concerning the torsion of a circular shaft of an orthotropic-nonhomogeneous half-space is considered. By means of the technique of integral transformations of Laplace and Hankel, with the subsequent application of the orthogonal polynomial method, an approximate solution in the transformant space is constructed. Also was performed reverse transformation. Calculated formulas for the angle of rotation of the shaft and the tangential stress acting on the contact area are obtained. Numerical calculations for certain types of heterogeneity have been performed. Comparison of the obtained results with the previously known results is made.

Abstract: Drawing is the basic operation of wire manufacturing. At drawing a wire contacts with a die resulting in decrease of its diameter. During this interaction wire microstructure changes, especially on the contact area between a die and a wire. Specificity of microstructure changing on outer surface of carbon steel wire at drawing and its combination with torsion is presented in the paper. Using optical microscopy, it was found out that in the outer surface of carbon steel wire a narrow layer of highly deformed grains is formed. It is shown that thickness of this layer depends on the deformational processing intensity and is very specific depending on carbon content of the wire.

Abstract: At present time tendencies in the development of engineering and technologies in the manufacturing the metal ware need the effective complex impact on material microstructure by methods of different nature. Special attention should be paid to the combined processes of deformational treatment which are constructed on such basic operations as drawing, rolling, pressing, etc. Despite a plenty of studies and high efficiency of combined methods the problem of understanding the scientific grounds for choice the processing parameters which ensure the guaranteed level and high stability of metals and alloys properties has not been solved jet. Medium carbon steel is used for a wide range of metal ware products. Medium carbon steel wire with 0.5 %C was chosen for the experiments. It was subjected to different kinds of deformational processing such as tensile deformation, alternating bending, twisting and their combination. Complex of experimental research was carried out in order to study the influence of different kinds of plastic deformation on the medium carbon steel wire microstructure. By scanning electron-microscope analysis the peculiarities of pearlite behavior after deformational processing with different total deformation degree were studied. The comparative analysis of cementite changing after different kinds of deformation was conducted.

Abstract: According to the common design methods of calculation of the stress state induced by torsion of massive prismatic concrete structural elements, the structural system is reduced to a simple cage consisting of ties and struts. This model has, however, a number of principal shortcomings, the major of them is the fact that all of simultaneously acting effects like axial forces, bending moments and shear forces are not taken into account – the compressive axial forces increase very significantly the torque capacity of structural members, while due to action of tensile forces, bending moments and shear forces the torque capacity is reduced. These phenomena, applying non-linear approaches, are analysed and assessed.

Abstract: Intensive development of Russian aviation and aerospace industries put an emphasis to the problem of quality of using materials and workpieces and to the value of technical and economical indexes in the context of planned production level [1, 2]. Waste-free technologies are preferred. Cutting by torsion or cutting by shear are preferable technologies if thin-walled tube cutting is the main blanking operation. Build-up of workpiece deformation zone plays an important role in the cutting process. Deformation zone determines stability of details during further processing and exploitation. An extended research was conducted about tube separation process using torsion with an active counterpressure. Some parameters was defined in the result of research, in particular: distribution of deformation zone along length and thickness of workpiece, angular deflection and compression force and workpiece heating temperature impact on build-up of whisker disposition in the cut zone. It allows identifying optimum compression force range and temperature conditions. Compliance with recommended practices allows conducting thin-walled tube separation simultaneously with build-up on the workpieces whisker structure that is fortunate for further pressure treatment and exploitation.

Abstract: Calculation of the cross-sectional properties of the concrete box-girder with two-cells using Vlasov`s theory and Generalized Beam Theory. Calculation of the internal forces of the St. Venant torsion, the warping torsion, the antisymmetrical and the symmetrical distortion on the basis analogy with beam on the elastic foundation loaded by transverse actions and tension force at the end of the beam. Creating of influence lines of torsion, antisymmetrical distortion and symmetrical distortion internal forces of large concrete cable-stayed bridge with continuous box-girders with two spans. The application for real reinforced concrete Harp bridge over pond Jordán near Tábor in Czech Republic is investigated. Evaluation of internal lines for action according to Eurocode EN 1991-2.

Abstract: . In this paper a parametric static and torsion analysis on a catamaran ship structure made out of composites materials is performed. The best solution for material selection is based on specific criteria for certain analysis. For dynamic analysis, the main criteria is to obtain the structure natural frequencies in a range, far from the resonance frequencies produced by the ship propulsion installation, wave loads etc. For static analysis the comparative criteria is to obtain the lowest weight of structure for the same strength. Also, buckling item is other criteria for comparative analysis. The comparative analysis is performed between rule based scantling structure and a FEM based structure for a composite material twin hull deck, in order to reduce the total hull weight. Material used for ship deck structure of the analyzed ship is e-glass polyester.