Papers by Keyword: Shear Deformation

Abstract: Beams find extensive applications in Nanoelectromechanical systems (NEMS) and Microelectromechanical systems (MEMS). The mechanical characteristics of these microstructures are significantly influenced by both their inherent microstructure and the forces acting at the micro/nano scales. Classical continuum theories fall short in capturing these small-scale effects due to the absence of a length scale parameter in their constitutive relations. To address this limitation, the existing literature primarily relies on the stress gradient nonlocal approach, which, however, has been found flawed and its universal applicability questioned in various scenarios. Therefore, the authors have endeavored to emphasize the strain gradient nonlocal approach, which has been relatively less explored. In this study, carbon nanotubes are modeled using the isotropic Timoshenko beam theory. To introduce the small-scale size effect into the model, the second-order negative strain gradient theory (NSGT) is employed. The Euler-Lagrange differential equations of motion and their corresponding boundary conditions are derived through Hamilton's principle. Analytical solutions are developed for static bending under uniformly distributed transverse load and free vibration problems using Navier's approach. Mathematical results are presented to validate the proposed solutions. Both analyses reveal that the nonlocal effect implemented in this study stiffens the structures, resulting in reduced static deflection and increased natural frequencies. It is noteworthy that beams with dimensions comparable to microstructural length scales exhibit a significant nonlocal effect, which diminishes as the structure's size increases. Additionally, the response obtained using the Timoshenko beam model is softer in comparison to the Euler-Bernoulli model due to the consideration of shear deformation.

Abstract: The article is aimed at studying the distribution of deformation work in the layers of the explosion-welded composite Al-Cr-St3 with a diffusion barrier. It is established that the thickness of the chromium layer does not affect the value of the total deformation work. An increase in the thickness of the chromium interlayer leads to a decrease in the proportion of deformation work and strength.

Abstract: Two-dimensional lattices are widely used in many engineering applications. If 2D lattices have large numbers of unit cells, they can be accurately modeled as 2D homogeneous solids having effective material properties. When the slenderness ratios of struts in these 2D lattices are low, the effects of shear deformation on the values of the effective material properties can be significant. This study aims to investigate the effects of shear deformation on the effective material properties of 2D lattices with hexagonal unit cells, by using the homogenization method based on equivalent strain energy. Several topologies of hexagonal unit cells and several slenderness ratios of struts are considered. The effects of struts’ shear deformation on the effective material properties are examined by comparing the results of the present study, in which shear deformation is neglected, with those from the literature, in which shear deformation is included.

Abstract: In this paper, thermoelastic damping (TED) in a simply supported rectangular functionally graded material (FGM) micro plate with continuous variation of the material properties along the thickness direction is performed. The equations of motion and the heat conduction equation coupled with the thermal effects are derived based on the Mindlin plate theory and the one-way coupled heat conduction theory, respectively. The heat conduction equation with variable coefficients is solved by using the layer-wise homogenization approach. Analytical solution of TED is obtained by complex frequency method. Numerical results of TED are presented for the rectangular FGM micro plate made of ceramic-metal constituents with the power-law gradient profile. The effects of the shear deformation, the material gradient index, the plate thickness on the TED of the FGM micro plate are studied.

Abstract: Based on the first order shear deformation plate theory (FSDT) in the present studie, static and dynamic behavior of carbon nanotube-reinforced composite sandwich plates has been analysed. Two types of sandwich plates, namely, the sandwich with face sheet reinforced and homogeneous core and the sandwich with homogeneous face sheet and reinforced core are considered. The face sheet or core plates are reinforced by single-walled carbon nanotubes with two types of distributions of uniaxially aligned reinforcement material which uniformly (UD-CNT) and functionally graded (FG-CNT). The analytical equations are derived and the exact solutions for bending and vibration analyses of such type’s plates are obtained. The mathematical models provided and the present solutions are numerically validated by comparison with some available results in the literature. Influence of Various parameters of reinforced sandwich plates such as aspect ratios, volume fraction, types of reinforcement and plate thickness on the bending and vibration analyses of carbon nanotube-reinforced composite sandwich plates are studied and discussed. The findings suggest that the (FG-CNT) face sheet reinforced sandwich plate has a high resistance against deflections compared to other types of reinforcement. It is also revealed that the reduction in the dimensionless natural frequency is most pronounced in core reinforced sandwich plate.

Abstract: Modern press forging manufacture of large steel forgings is moving along the way of increasing service properties and reducing energy-power parameters. This is evidenced by a significant number of works devoted to the study of forging technology with the use of special tools allowing to implement severe plastic deformation. As a result, it is possible to improve significantly the metal structure at the same values of the forge reduction. The paper presents the results of the development and investigation of a new method of forging large steel billets with the intensification of shear deformation and with the use of standard anvils. The analysis of the stress-strain state in comparison with traditional forging scheme on an example of forging billets made of high speed steel R6М5 (State Standard GOST 19265-73) is presented. It is shown that the accumulated degree of shear deformation, as well as the uniformity of its distribution, is higher for the new method with the same reduction values. Approbation of the new method of forging on a hydraulic press was carried out for the blanks made of aluminium alloy D16 (State Standard GOST 21488-97).

Abstract: Casing shear deformation, which is caused by fault slipping, is the main morphology of casing deformation occurred during multistage fracturing. In order to determine the relationship between fault slipping and casing shear deformation, the micro seismic data collected from engineering field which can reflect the reality of the formations was analyzed. A new numerical model was developed, and the influential factors on casing shear deformation were studied, including the fault slip distance of lower and upper interface, fault dip angle, the thickness of cement sheath and casing. The results of research shows that: (1) Fault is easily activated by fracturing, which was the main reason of casing shear deformation; (2) The greater the fault dip angel, the slip distance, the greater the casing shear deformation; (3) Increasing the wall thickness of casing or cement sheath is beneficial to decrease the degree of the shear deformation; (4) Two ways can be used to avoid and control the casing shear deformation, one is keeping the designed horizontal segment of well trajectory keep away from fracture-developed area, or be parallel to natural fracture, the other is using stage cementing technology. Research results can provide important reference for design and control of casing integrity during multistage fracturing in shale gas wells.

Abstract: This paper discusses the structure and regularities of formation of compounds during explosive welding plate steel-aluminum composite. The influence of thickness of the welded element on the structure and the shear deformation of the metal in the heat-affected zone under different conditions of explosive loading was investigated.

Abstract: The aim of the present work is to study the linear free symmetric vibration of three-layer sandwich beam using the energy method. The zigzag model is used to describe the displacement field. The theoretical model is based on the top and bottom layers behave as Euler-Bernoulli beams while the core layer as a Timoshenko beam. Based on Hamilton’s principle, the governing equation of motion sandwich beam is obtained in order to calculate the linear frequency parameters. Two types of boundary conditions simple supported-simple-supported (SS-SS) and clamped-clamped (C-C) under the influence of materials properties and geometrical parameters are studied. The validation of results is done by comparing with another studies, which available in the literature and found good agreement between the studies.

Abstract: Unalloyed titanium was rolled with 20% reduction in each pass at 293 K using a cross rolling mill, where the upper and lower rolling axes were skewed each other at an angle of 0, 5 or 10 degree with parallel position. Multi-pass flat-rolling was carried out without any lubricants up to the true strain of 1, where two kinds of rolling directions such as tandem (uni-direction for all passes) and reverse (opposite direction in every passes) were adopted. The strain of specimens was increased proportionally as higher passes regardless of the rolling conditions. The transverse direction (TD) split deformation texture in titanium was generally developed under the cross angle of 0 degree. In the present strips of tandem, a main orientation was identified as (-12-18)[10-10]. In the case of tandem with the cross angle of 5 degree, a fiber texture was developed along (-12-18). That is the reason why a rotation in the rolling direction (RD) was overlapped. In the case of reverse with the cross angle of 5 degree, the main orientation was separated into [10-10] and [2-311] that were corresponded to TD and RD splits, respectively.