Influence Of Elastic Deformation Research Articles

Numerical and experimental studies on a 2-module VLFS with hinged connector

The design of Very Large Floating Structures (VLFSs) often involves multiple modules with connectors. Consequently, Fluid Structure Interaction (FSI) has been attracted more and more attention in the design of VLFSs due to their considerable dimensions. This paper presented results of numerical and experimental studies on a 2-module VLFS with hinged connectors. A Flexible Module and Flexible Connector (FMFC) method was established in this paper, which allows for considering the influence of elastic deformation on each module and connectors. Model test was designed and conducted in wave basin, including wet modal tests in still water in, a white noise wave test and regular wave tests. The present method was verified by the model test, and good agreements were observed between the numerical and experimental results. Subsequently, the characteristic of wave loads in different wave directions was investigated by numerical calculation, and the design wave parameters were obtained by short-term analysis. Several useful conclusions were summarized, which can provide a reference for the analysis of dynamic responses, design, and construction of the VLFSs.

Axial Static Stiffness of Ball Screw Feed Drive System Incorporating Flexibility of Ball Screw and Rolling Bearing

Abstract Axial static stiffness is a main technical indicator for the ball screw feed drive system, and the elastic deformation outside the Hertz contact zone of the system affects its axial static stiffness. However, the influence of elastic deformation outside the Hertz contact zone on the axial stiffness has not been studied thoroughly. This study was to establish a flexible model of axial stiffness for the feeding system with considering the elastic deformation outside the Hertz contact zone. The axial stiffness of the feeding system was calculated using the proposed flexible model, and the model was verified by measuring the axial stiffness of the feeding system. The results show that the proposed flexible model can be more accurate compared with the conventional rigid model, and the method to analyze the elastic deformation outside the Hertz contact zone is practicable.

Elastic deformation of liquid spiral groove face seals operating at high speeds and low pressure

The uneven distribution of fluid pressure in the spiral groove area leads to the elastic deformation of the seal faces, which not only affects the sealing performance but also affects the running stability. In this paper, a numerical model of a high-speed spiral groove liquid face seal is proposed with the consideration of elastic deformation and cavitation medium compressibility. The novelty of this study is that the pressure of the cavitation region is modeled as an uneven distribution rather than as a constant. This uneven pressure distribution of sealing surfaces is generally regarded to have an influence on face deformation. Based on the assumption that the fluid exists at a complete gas state in the cavitation, the elastic deformation and pressure distribution of sealing surfaces are calculated. The influence of elastic deformation on sealing performance is further investigated. Results show that the elastic deformation of sealing surfaces and cavitation effect has a significant influence on the stability of sealing clearance, which may produce a negative effect on the sealing performance of liquid face seals. The face deformation causes a divergent gap between two seal faces. With the increase of rotational speed, the elastic deformation of sealing surfaces reduces at low seal pressure but increases at higher seal pressure, which may influence the cavitation behavior and pressure distribution of surfaces. Furthermore, the sealing performance of spiral groove liquid face seal becomes more complicated because of the coupling effect of cavitation effect and elastic deformation. The changing trend of sealing performance is different under various seal clearance and seal pressure. The obtained results may provide guidance for the future design of liquid face seals in engineering applications under high-speed conditions.

Influence of elastic deformations of a non-rigid box blanks, limited by the fixture design, on the accuracy of machined surfaces

An analysis is given of the forced alignment of inaccurate base surfaces of the workpiece with the exact base surfaces of the fixture by applying a distributed load to it with the help of rigid fixture elements that have the correct geometric shape. As a rigid element, a prismatic insert with cutouts on the upper and lower surfaces is used, which is installed inside the box-shaped housing made of sheet 1.5 GOST 19904-90 made of 30XGSA steel. It is shown that this eliminates the uncertainty of basing, which creates the prerequisites for increasing the accuracy of machining and increases the rigidity of the fixed workpiece, which helps to reduce vibrations and improve the quality of the machined surface. It has been established that there is an optimal width of the insert cutout on the base-clamping surface, at which the elastic deformations of the base surface of the workpiece are within acceptable limits. The rational value of the liner cutout width should be either less than 55 mm or more than 70 mm. Such fastening causes additional errors in the position of the side surfaces of the housing, which are the measuring bases for milled surfaces and drilled holes. In the work, their numerical evaluation was carried out, which showed that the elastic displacements of the surfaces, which are the measuring bases, are within acceptable limits. It has been established that if the workpiece was sent to a fixed mounting base using an adjustable bracket and fixed without applying clamping forces, then in this case a more uniform and smaller (about 0.01-0.08 mm) elastic deformation of the side walls of the workpiece occurs, than when fixing with a force (about 0.02-0.20 mm.).

Characteristics of statistical properties of deformation defects of structural metallic materials within elastic deformations

At this paper was established result of the correlations characteristics of structural parameters of low-carbon steels during periodic loading under elastic deformations. According to the results of the research, the kinetic characteristics of the influence of the load parameter on the distribution of deformation defects of the surface layer of structural materials under elastic deformations are obtained. The regularities of the influence of elastic deformations on the distribution of discrete surface properties are revealed. Linear dependences of the parameter of distribution of discrete relief properties of the deformed surface on loading are revealed. The regularities of the influence of elastic deformations on the distribution of discrete surface properties are revealed. It is established that regardless of the type of load, the surface density of deformation defects of scattered fracture accumulates in the mother to a certain state of damage, which is characterized by the current state of density of elements of deformation defects.

The influence of elastic deformations in high-strength structural materials on the hydrogen transport

In this work, the diffusion equation for the gas-solid system is revised to describe the non-uniform distribution of hydrogen in steels. The first attempt to build a theoretical and general model and to describe the diffusion process as driven by a chemical potential gradient is made. A linear elastic solid body and ideal gas, diffusing into it, are considered. At this stage, we neglect any traps and non-linear effects. The coupled diffusion-elastic boundary problem is solved for the case of the cylinder under the tensile loads. The obtained results correspond to the experimental ones. Based on them, the assumptions about the correctness of the model and its further improvement are suggested.

An adaptive trajectory planning algorithm for robotic belt grinding of blade leading and trailing edges based on material removal profile model

• An adaptive trajectory planning algorithm for robotic belt grinding of blade edges is proposed. • The proposed algorithm is verified through simulation and experiment. • The average profile errors at blade leading and trailing edges are 0.0319 mm and 0.0342 mm. • The average Ra values reach 0.277 μm and 0.264 μm on blade convex and concave. • Variable process parameter strategy with force control is suitable for blade grinding. Robotic belt grinding of the leading and trailing edges of complex blades is considered to be a challenging task, since the microscopic material removal mechanism is complicated due to the flexible contact state accompanied with greatly varying curvature that finally affects the machined profile accuracy. The resulting poor accuracy of blade edges, to a great extent, is attributed to the trajectory planning method which less considers the dynamics. In this paper, an iso-scallop height algorithm based on the material removal profile (MRP) model is developed to plan the tool paths by taking into consideration the elastic deformation at contact wheel-workpiece interface. An improved constant chord-height error method considering the influence of elastic deformation is then proposed to adaptively plan the grinding points according to the curvature change characteristics of the free-form surface. Based on these two steps, a MRP model based adaptive trajectory planning algorithm is constructed to enhance the profile accuracy facing the robotic belt grinding operation. Simulation and experimental results demonstrate the effectiveness of the proposed trajectory planning algorithm for the robotic belt grinding of blades from the perspectives of surface roughness, profile accuracy and processing efficiency. Particularly this technology serves to solve the problem of over-cutting at the blade leading and trailing edges.

Elastic Deformations and Wigner–Weyl Formalism in Graphene

We discuss the tight-binding models of solid state physics with the Z 2 sublattice symmetry in the presence of elastic deformations in an important particular case—the tight binding model of graphene. In order to describe the dynamics of electronic quasiparticles, the Wigner–Weyl formalism is explored. It allows the calculation of the two-point Green’s function in the presence of two slowly varying external electromagnetic fields and the inhomogeneous modification of the hopping parameters that result from elastic deformations. The developed formalism allows us to consider the influence of elastic deformations and the variations of magnetic field on the quantum Hall effect.

Influence of Elastic Deformations on the Adhesion of the ZRN Coating on the Clinching Tool

Influence of Elastic Deformations on the Adhesion of the ZRN Coating on the Clinching Tool

Thermo-Elastohydrodynamic Study on Textured Journal Bearing with High-Speed and High-Specific-Pressure

The performance of supporting journal bearing of the star gear transmission system in the geared turbo fan engine (GTF) is analyzed. A thermal-elastohydrodynamic analysis model was developed for textured journal bearing used in high-speed and high-specific-pressure conditions. The Navier-Stokes equation, energy equation, and viscosity-temperature equation were calculated by the computational fluid dynamics method. The influence of elastic deformation on bearing thermal hydrodynamic performance was studied in detail. The results indicate that the elastic deformation has an influence on the distribution of oil temperature and oil pressure. Besides, a comparative thermo-elastohydrodynamic analysis was conducted between the textured bearing and the un-textured bearing, and the discrepancies of maximum oil pressure, load carrying capacity and the maximum oil temperature are few. However, the textured bearing has a lower elastic deformation than the un-textured bearing.

Real-Time Simulation and Optimization of Elastic Aircraft Vehicle Based on Multi-GPU Workstation

Modern aircraft such as missile and rocket, due to the large slenderness ratio of slender body vehicles, the influence of elastic deformation and vibration on navigation, guidance, and engine modules in simulation can not be ignored. For the problems of slow calculation speed and incapability of real-time simulation for time-domain simulation, by analyzing the time proportion of each calculation step under different computing scale, the dynamic parallel construction of octree is used to represent the aerodynamic parameter table under the environment of single and multi GPU. Meanwhile, an innovative parallel algorithm of element stiffness matrix based on finite element model is designed in GPU architecture. Accordingly, the optimized performance is enhanced through the adaptive hardware resources and rational use of shared memory. Furthermore, A multi-threaded asynchronous framework based on task queue and thread pool is proposed to realize the parallel task calculation with different granularities. The numerical result shows that the acceleration ratio of about 20 times in the single GPU condition can be obtained, and the acceleration ratio of at least 30 times can be obtained by the parallel computing of dual GPUs, enabling the real-time simulation of the flexible aircraft with 1200 elements within 20ms.

Comparison of finite and boundary element methods in problems of oscillations of a composite shell of revolution with a liquid

The phenomenon of sloshing can be described as the movement of the free surface of a liquid contained in a reservoir under the action of a suddenly applied load. H. Olsen cited the classification of free-surface fluctuations in liquids by identifying three main forms of sloshing: a) longitudinal sloshing, b) vertical sloshing c) rotating sloshing. Sloshing is a phenomenon that is found in a wide range of industrial applications: in containers for storing liquefied gas, fuel tanks of missiles and airplanes, in tanks of cargo tankers. The vibrations of the real tanks are caused by sloshing of the fluid and vibration of the elastic walls. In completely (or almost completely) filled tanks, the free surface cannot experience strong oscillations. This corresponds to the launch of the launch vehicle. However, in further stages of flight, when the level of liquid aggregate falls, the sloshing effect becomes dominant. It was repeatedly noted that powerful sloshing can lead to a violation of the flight trajectory, as happened, for example, during the launch of the Falcon 1 launch vehicle in 2006, 2007 and 2008. The next important problem in the study of the oscillations of the fuel tanks is the study of the associated hydro-elastic oscillations of the fluid interacting with the elastic walls of the tank. New analytical method and computer technology have been developed for analyzing free and forced vibrations of composite fuel tanks of missiles at different stages of flight: during overloads and in microgravity conditions, including sloshing fuel. The proposed method allows us for more accurate analysis of fuel tank oscillations, taking into account the mutual influence of elastic deformations of tank walls and tank filling levels changing during missions and the shape of the free surface of the liquid, the presence of elastic and rigid damping internal partitions, and the change in acceleration of gravity. A mathematical model has been developed for the analysis of fuel sloshing at large amplitudes. The free oscillations of the launch vehicle tanks are considered.

Studies for aeroelastic characteristics and nonlinear response of FG-CNT reinforced composite panel considering the transient heat conduction

A solution of computing the aero-thermal-elastic problem of FG-CNT reinforced composite panel is proposed, in which the aerodynamic heating and transient heat conduction are accounted for. The Von-Karman theory and the third-order piston theory are employed to establish the motion equation of FG-CNT panel, where the thermo-mechanical properties of polymer matrix and carbon nanotubes are set to be location- and temperature-dependent. The Ecker’s reference temperature method and heat flux equation are adopted to calculate the heat flux. Two dimensional transient heat conduction including in-plane and through-thickness directions are computed using a finite difference approach. In the calculation process, the influence of elastic deformation on the aero-heating and aero-heating on panel stiffness is included. The aeroelastic stability analysis is presented for the influential parameters such as CNT volume fraction, distribution and aspect ratio of the panel. Moreover, the effects of the oblique shock wave parameters on the critical flutter pressure and dynamic response are discussed. Numerical results show that the coupled solution leads to the inhomogeneous aero-heating, which results in nonuniform temperature distributions and material property degradations. Consequently, the stability boundary and dynamic response are varied with respect to the case without considering the coupling effect.

On the Influence of Elastic Deformation for Residual Stress Determination by Sharp Indentation Testing

The determination of residual stresses in engineering materials using sharp indentation testing is studied analytically and numerically. The numerical part of the investigation is based on the finite element method. In particular, the effect from elastic deformations on global indentation properties is discussed in detail. This effect is essential when residual stresses are to be determined based on the change of the contact area due to such stresses. However, standard relations for this purpose are founded on the fact that the material hardness is invariant as regards residual (applied) stresses. Presently, this assumption is scrutinized and it is shown that it is only valid at dominating plastic deformation around the contact region. The hardness dependence of residual stresses can, however, be correlated in the same way as in the case of stress-free materials, indicating that the wealth of characterization formulas pertinent to indentation hardness is available also for the purpose of residual field determination. Only cone indentation of elastic-perfectly plastic materials is considered, but the generality of the results is discussed in some detail.

Effect of Mechanical Stress on the Properties of Steel Surfaces: Scanning Kelvin Probe and Local Electrochemical Impedance Study

The influence of mechanical stress on the electrochemical properties of ferritic steel SAE 1008 and austenitic stainless steel 301LN was studied using Scanning Kelvin Probe and Localized Electrochemical Impedance Spectroscopy (LEIS) techniques. The probe-working electrode Volta potential difference was mapped in situ under load. It was found that the influence of elastic deformation on the potential was small. Plastic deformation decreased the potential of steel by 150–300 mV, whereas the relaxation of the load from the plastic domain increased the Volta potential. However, some locations, which can contain residual stress, remained at low potential. The pre-strained surfaces were characterized by X-ray Photo Electronic Spectroscopy and by Atomic Force Microscopy. Distribution of the capacitance across strained and strain-free surfaces was studied by LEIS in boric/borate electrolyte. The plastic stress increases the capacitance and decreases the ability of the steels to passivate the surface indicating that emerging of pile-ups of dislocations create defective oxide films.

Topology of Wrinklons in Graphene Nanoribbons in the Vicinity of Constrained Edge

Most of the two-dimensional materials possessing low bending stiffness tend to lose the flat shape to form topological defects in the form of wrinkles and folds under the action of external factors. One of the striking examples of such material is graphene, where the presence of wrinkles leads to changes in physical, mechanical, and chemical properties of the material. Thus, changing the geometry of wrinkles, one can purposefully control properties of graphene. In this paper, we studied the characteristics of wrinkles appearing in graphene under the influence of elastic deformation, as well as the evolution of the configuration of wrinkles in the vicinity of the constrained edge of the graphene nanoribbon at different initial conditions. It is found that near the constrained edges of the deformed graphene nanoribbons, it is profitable to form wrinklons, that is, transition regions, where two or more wrinkles merge into one. The stability of two types of wrinklons formed by merging of the two or three wrinkles in one is shown. It is shown that in the process of the structure relaxation of the uniformly deformed graphene depending on the initial configuration of wrinkles, hierarchy of wrinkles containing wrinklons of one or another type is formed near the constrained edges. The results allow to explain the experimentally observed topology of the graphene sheet in the vicinity of the constrained edge.

The influence of elastic deformations on the hysteresis properties of a two-layer ferromagnet composed of components with magnetostrictions of opposite signs

The influence of an elastic deformation that is produced by an uniaxial extension (compression) on the behavior of several magnetic characteristics of Armco iron and nickel, whose magnetostrictions have opposite signs, and a two-layer material composed of them was studied. The magnetic characteristics were measured both under the conditions of a closed magnetic circuit and using attachable transducers along and across the direction of an applied load. The results are explained from the standpoint of the formation of magnetic anisotropy, which is induced by the action of normal stresses. The results of measurements of the hysteresis and magnetostriction properties of the investigated materials are compared. The magnetic parameters of the investigated materials that monotonically change with an increase in the applied stresses are determined.

Analysis of a circular journal bearing lubricated with micropolar fluids including EHD effects

Purpose – The performance of finite circular journal bearing lubricated with micropolar fluids taking into account the elastic deformation of the bearing liner is presented. The paper aims to discuss these issues. Design/methodology/approach – The modified Reynolds equation is obtained using the micropolar lubrication theory. The solution of the modified Reynolds equation is determined using finite difference technique. The static characteristics in terms of load-carrying capacity, attitude angle, side leakage and friction coefficient for micropolar and Newtonian fluids are determined for various values of eccentricity ratio and different values of elastic coefficient. Findings – Compared with Newtonian fluids, the micropolar fluids produce an increase in the load-carrying capacity and a reduction in the attitude angle, the friction factor and side leakage for both the rigid and deformable bearings. Originality/value – It is concluded that the influence of elastic deformation on the bearing characteristics lubricated with micropolar fluids is significantly apparent compared with bearing lubricated with Newtonian fluids.

弹性形变对手征液晶螺旋光轴及电光响应时间的影响

弹性形变对手征液晶螺旋光轴及电光响应时间的影响

Characterization of strain rate sensitivity in pharmaceutical materials using indentation creep analysis

Understanding how a material's response to stress changes as the stress is applied at different rates is important in predicting performance of pharmaceutical powders during tablet compression. Widely used methods for determining strain rate sensitivity (SRS) are empirically based and can often provide inconsistent or misleading results. Indentation creep data, collected during hardness tests on compacts formed from several common tableting excipients, were used to predict each material's relative sensitivity to changes in strain rate. Linear relationships between Ln(indentation hardness) and Ln(strain rate) were observed for all materials tested. The slope values taken from these relationships were compared to traditional strain rate sensitivity estimates based on in-die Heckel analysis. Overall, the results from the two methods were quite similar, but several advantages were evident in the creep data. The most notable advantage was the ability to characterize strain rate sensitivity derived from plastic behavior with little influence of elastic deformation. For example, two grades of corn starch had very similar creep behavior, but their yield pressures were affected very differently when the compaction rate was increased. This inconsistency was related to the difference in the viscoelastic recovery exhibited by these two materials. This new method promises to allow a better understanding of strain rate effects observed during tablet manufacturing.