Papers by Keyword: Torsion

Abstract: Recent years there have been observed a wide application of a metalware in industrial and civil engineering. Special place in the building industry is belonged to light steel thin-walled constructions having a lot of technological advantages. In the article the first development cycle of a numerical method creating is considered – creating of the stiffness matrixes of thin-walled finite elements of various types using the semisheared theory (by V.I.Slivker) – depending on a way of approximation of functions of deformations (torsion and warping): 1. Linear approximation of torsional functions with a 2-central finite element having 4 transitions; 2. Quadratic approximation of torsional functions and linear approximation of warping function with a 3-central finite element having 5 transitions; 3. Cubical approximation of functions of torsional and warping functions with a 3-central finite element having 6 transitions. Thus deformation functions (torsional angle and warping) are approximated as mutually independent functions.

Abstract: In this paper, the folded-beam torsion MEMS mirror that meets a set of specified constraints was developed. An optimization algorithm that we newly adopted in the RCS(restricted competition selection) GA(genetic algorithm) could overcome some difficulties in single-search algorithms. Moreover, by the proposed method, the designer’s experience, and view and judgment could be reflected effectively.

Abstract: Tensile, Torsion, and Hardness behavior of welded and un-welded Aluminium Alloy 6061 T6 were investigated. Tests were conducted to evaluate the impact of tungsten Gas Arc welding (TIG) on some of the mechanical properties of the alloy. Different zones with different mechanical properties were created as a result of the welding process. Welding was found to have enormous impact on the tensile, torsion, and hardness properties of the alloy. Welded tensile specimens were failed at the welded area whereas not welded ones were failed at the centre. Welded torsion specimens were failed at the HAZ but not welded ones failed at the centre. The hardness of HAZ was decreased as a result of the heat generated during the welding process. Hardness values were increased as we moved away from the welded region.

Abstract: RC beams as a structural member contain a variety of non-uniform loads. These non-uniform loads caused combined effects of flexure and torsion. There are numerous studies available, that suggests different strengthening schemes using FRP laminates, as a solution for flexure and torsion deficient beams. Most of the experimental studies suggested individual strengthening schemes for flexure or torsional deficiency RC beams. However, the combined effects were not studied due to difference in experimental setup, testing procedure and specimen detailing. Therefore, the outcome of previous studies was needed to combine together to facilitate the strengthening process as a guideline case of such deficiency. Therefore, a combined review is presented by suggesting different configuration for flexure and torsion deficient RC beams. Most of the studies suggested that the application of FRP laminates at the soffit of beam is suitable for flexural strengthening. The application of U-shape or full wrap are suitable for strengthen torsion deficient beams. Similarly, 45° wraps are more effective than 90°wraps for improving ductility of torsion deficient beams.

Abstract: Eccentric loads are very common in structures due to building configuration. Unequal slab length, circular ramp, large cantilevers are very common in modern architecture. The RC beams in previous studies were tested under the three and four point uniform loads. Therefore, a simple testing setup was arranged to understand the behaviour of RC beam under eccentric load applied at mid span. In this study the single point load applied eccentrically on RC beam. The beams were tested at different eccentricity and compared with control beam tested under the uniform load or zero eccentricity. Results have shown a drastically reduced crack load up to 54% compared to control beam as the eccentricity increased. However, small changed in ultimate load carrying capacity was observed up to 60mm eccentricity. Eccentric load caused biaxial bending due to high concentration of load on one side of beam, which change failure mode of RC beam from ductile to brittle.

Abstract: Mechanics of materials are based on the relative deformation to discuss the calculation of the circular shaft torsion deformation, But the relative torsion angle can not reflect the real deformation of a specific cross-section. According to the plane hypothesis, to discuss the absolute deformation of several common shaft withstand the simple torque, defined the neutral cross-section of torsion deformation and given the method to calculate absolute torsion angle, for the rational design of engineering components have a certain reference value.

Abstract: A special situation arises when multiaxial fatigue loadings are present, given not only the time-dependency of extreme principal stress values, but also the fact that principal plane positions change during one load cycle (non-proportional loading). Thus, the analysis of principal stress and principal direction variation becomes a very important step, necessary to be carried out before starting any multiaxial fatigue testing. Based on the above, the authors present a generalized method for computing principal stresses and determining principal plane positions, applicable for cyclic tension-torsion loadings with zero mean stresses but with different phase shifts and amplitude ratios. Based on original experimental data and data collected from the literature, the authors point out in the final part of the paper that the maximum principal shear stress can be considered as the main parameter for plotting Wöhler curves.

Abstract: Carbon nanotubes (CNTs) have been proposed as one of the most promising materials for nanoelectro-mechanical system due to high elastic modulus, high failure strength and excellent resilience [1,. Recent development of many-body interaction [3, made possible realistic molecular dynamics (MD) simulations of carbon-made systems. We carried out such studies for carbon nanotubes under generic modes of mechanical load: axial compression, bending, and torsion. A singular behavior of the nanotube energy at certain levels of strain corresponds to abrupt change in morphology. In this letter, we report the torsional instability analysis of single wall carbon nanotube filled with hydrogen via molecular dynamics simulations. The simulations are carried out at a temperature 77K which previous study obtained the hydrogen storage inside CNT at this condition [A. C. Dillo. Here we use atomistic simulations to study a flexible surface narrow carbon nanotube with tube diameters 10.8 Å. According to conventional physisorption principles, the gas-adsorption performance of a porous solid is maximized when the pores are no larger than a few molecular diameters [8]. Under these conditions, the potential fields produced at the wall overlap to produce a stronger interaction force than that observed in adsorption on a simple plane. However, the mechanisms responsible for the adsorption and transportation of hydrogen in nanoporous solids or nanopores are not easily observed using experimental methods. As a result, the use of computational methods such as molecular dynamics (MD) or Monte Carlo (MC) simulations have emerged as the method of choice for examining the nanofluidic properties of liquids and gases within nanoporous materials [9,1. Several groups have performed numerical simulations to study the adsorption of water in CNTs [11-1, while others have investigated the diffusion of pure hydrocarbon gases and their mixtures through various SWNTs with diameters ranging from 2 ~ 8 nm [17-19] or the self-and transport diffusion coefficients of inert gases, hydrogen, and methane in infinitely-long SWNTs [20-21]. In general, the results showed that the transport rates in nanotubes are orders of magnitude higher than those measured experimentally in zeolites or other microporous crystalline solids. In addition, it has been shown that the dynamic flow of helium and argon atoms through SWNTs is highly dependent on the temperature of the nanotube wall surface [22]. Specifically, it was shown that the flow rate of the helium and argon atoms, as quantified in terms of their self-diffusion coefficients, increased with an increasing temperature due to the greater thermal activation effect. Previous MD simulations of the nanofluidic properties of liquids and gases generally assumed the nanoporous material to have a rigid structure. However, if the nanoporous material is not in fact rigid, the simulation results may deviate from the true values by several orders of magnitude. Several researchers have investigated the conditions under which the assumption of a rigid lattice is, or is not, reasonable [23, 24]. In general, the results showed that while the use of a rigid lattice was permissible in modeling the nanofluidic properties of a gas or liquid in an unconfined condition, a flexible lattice assumption was required when simulating the properties of a fluid within a constrained channel. Moreover, in real-world conditions, the thermal fluctuations of the CNT wall atoms impact the diffusive behavior of the adsorbed molecules, and must therefore be taken into account. This study performs a series of MD simulations to investigate the transport properties of hydrogen molecules confined within a narrow CNT with a diameter of 10.8 Å (~ 1 nm) at temperatures ranging from 100 ~ 800 K and particle loadings of 0.01~1 No/Å. To ensure the validity of the simulation results, the MD model assumes the tube to have a flexible wall. Hydrogen molecules are treated as spherical particles. In performing the simulations, the hydrogen molecules are assumed to have a perfectly spherical shape. In addition, the interactions between the molecule and the CNT wall atoms and the interactions between the carbon atoms within the CNT wall are modeled using the Lennard-Jones potential [25,2. The simulations focus on the hydrogen adsorption within the SWNT not adsorption in the interstices or the external surface of nanotube bundles.

Abstract: In the case of shaft-hub joints with cylindrical pins found in both macro and micro-devices, a longitudinal gutter with an almost half-circular cross section is practiced along the length of the shaft segment. The center of the circular arc is placed on the circular edge of the cross section. The present paper aims to model strain and stress states within such a shaft, when the material elastic properties are known along with shaft segment length and applied torque. Using the MathCad environment, 3D and constant stress level plots were obtained for the distribution of tangential stresses over the cross section. After application of torque, the transverse cross sections shift and become anti-symmetric as illustrated by the obtained 3D and constant strain plots.

Abstract: Based on Yuzhen palace integral lifting engineering of Wudang Mountain, the writer uses the finite element analysis to simulate bearing capacity of section steel column in the bidirectional eccentricity. The finite element data is slightly larger than the test, but the date keep in same value in the main. During the process of the integral lifting, the bearing capacity of steel column will sharply decrease with the bidirectional eccentricity increasing and produce torsion; it has a lethal effect on the whole upper structure. And the writer analyzes the problem that how to avoid the eccentric problems from two aspects of the design and construction, and the writer proposes some relevant suggestions and opinions. It can provide reference that how to design and construction in a similar project.