Elastic Deformation Process Research Articles

Особенности процессов упругой деформации в ауксетичных монокристаллических сплавах ВЖМ8 при ударном нагружении

Особенности процессов упругой деформации в ауксетичных монокристаллических сплавах ВЖМ8 при ударном нагружении

New insights into the microstructures and mechanical responses of large-scale colliding aluminum nanospheres

Aluminum nanospheres are served as a promising solid propellant, but the dynamic responses of their impact-induced agglomerations are not fully understood. For this reason, ReaxFF-molecular dynamics simulations were performed to investigate in detail the microstructures and mechanical behaviors of large-scale colliding aluminum nanospheres with diameter 10 nm at three impact velocity scenarios over the range of 200–2000 m/s. In terms of the microstructural evolutions of all considered systems, two aluminum nanospheres were adhered to each other but their directional deformations varied with the impact velocity. According to the stress-strain curves analyses, aluminum nanospheres underwent an important mechanical process of elastic deformation transiting to plastic deformation along with the increase in the impact velocity. Interestingly, we found that the impact-dependent elastic-plastic deformation gave rise to the structural transition of fcc to hcp by using the common neighbor analysis method. It most favors the hcp phase embryo nucleation while the impact velocity was 1200 m/s, and the fraction of hcp atoms reaches up to 40% under such condition. Moreover, the atomic mechanism of local fcc-hcp transition was revealed in this study, providing a quantitatively understanding of the phase transition process for controllable dynamical mechanical characteristics of large-scale colliding aluminum nanospheres.

Multiscale Comparison Study of Void Closure Law and Mechanism in the Bimetal Roll-Bonding Process

The void closure mechanism during the roll-bonding process was investigated using a multiscale approach, which includes contact deformation at the macro-scale and atomic bonding at the micro-scale. The closure process of the voids was observed using roll-bonding tests of 304 stainless steel/Q235 carbon steel. A finite element model was built to simulate the macroscopic deformation process of 304/Q235 material, and a molecular dynamics model established to simulate the deformation process of the microscopic rough peaks. The closure law and mechanism of interface voids at the macro- and micro-scales were studied. The results show that the closure rate of interface voids decreases with the decrease in the average contact stress during the contact deformation process. In the atomic bonding process, the void closure rate is slow in the elastic deformation process. The ordered atoms near the interface become disordered as plastic deformation occurs, which increases the void closure rate and hinders dislocation propagation through the interface, resulting in significant strengthening effects via plastic deformation. Ultimately, a perfect lattice is reconstructed with void healing. In addition, the interface morphology after roll-bonding at the macro scale was determined by the morphology of the 304 steel with larger yield strength ratio, while the interface morphology at the micro-scale was mainly determined by the morphology of the Q235 steel with a higher yield strength.

Experimental and numerical study of the axial stiffness of bolted joints in steel lattice transmission tower legs

Steel lattice transmission towers are constructed through the bolted assembly of various sizes of angle steel members and joint slip is inevitable; ignorance of this slip, which is the prevailing practice in transmission tower design engineering, can lead to an overestimation of the axial stiffness of bolted joints. This study investigates the impact of joint slip effects under tensile loading through a series of 30 tensile tests of 10 typical bolted joint configurations (3 specimens for each tested configuration) used in classic 500 kV lattice steel transmission line towers in China. Finite element analyses were also conducted as a complement and validation of concepts. Particular focus was placed on the load-deformation/slip curves of the tensile tests. The experimental results show that the joint slip was realized through a complicated process consisting of elastic deformation caused by the frictional load transfer and the asynchronous joint slip. Meanwhile, when subjected to an incremental axial tension, the axial stiffness of the bolted joints was highly nonlinear with regard to the elastic deformation. A simplified multi-linear strain-stress model was created using the experimental data to represent this nonlinearity in finite element analysis. The results from finite element analysis of the 30 tensile tests using this multi-linear strain-stress model show that the model can well predict the failure load level and positions of rupture of the angle members. The actual average axial stiffness of the tested bolted joints during the elastic deformation process of load transfer by bolt bearing is approximately 30% of the theoretical value. Finally, a general nodal element is proposed to describe the joint slippage effects and introduce this important factor in the structural analysis of lattice transmission towers in view of safer and more reliable design.

Features of the processes of elastic deformation in cubic crystals

Features of the processes of elastic deformation in cubic crystals

Features of the processes of elastic deformation in cubic crystals

Features of the processes of elastic deformation in cubic crystals

Експлуатаційні дослідження показників кутового зсуву клейової полімерної пластини корінцевої частини книжкового блоку

The purpose of the work is to study the deformation of the adhesive layer of the root portion of the book block, stitched threads, the influence of the bending angles of the polymeric adhesive plate during the exploitation of book products, which contribute to the creation of zones of variable concentration of destructive stresses of the internal structure of the plate, as well as the influence of the time of the load on these areas, that proportionally influence on the reduction of the elastic properties of the plate and the development of residual plastic deformation phenomena. The amount of deformation of individual sections of a radial adhesive polymer plate, during operational loads when using book blocks stitched together, depends not only on the elastic material properties of the adhesive composition, its isotropy, the thickness of the applied layer, but also on the angles of the plate kinks that contribute to creating variable zones concentration of destructive stresses of the internal structure. Stresses occur at the edges of the joints of the glue plate with the paper of the folds of the backs of the notebooks on the one hand, and the edging paper, on the other hand, in the form of sections of compression and tension in places of discrete kinks. The duration of the loads in these areas, in proportion to the decrease in the elastic properties of the plate and the increase in the phenomena of residual deformation. Taking into account the negative influence of discrete angular bends of rooted glue polymeric plates in any part of it and the heterogeneity of the duration of loads during the exploitation of book products lead to deformation formed during bending of the plate and promotes the accelerated transformation of processes of elastic deformation into residual processes of plastic deformation. The use of high strength and high elastic adhesive compositions, which do not have a negative effect on the stiffness and bending stability of the glued system, can minimize the disadvantages of the angular displacement, which in turn will provide a prolonged operating period and a favorable competitive appearance of book products.

Finite element modeling of a multi-physics poro-elastic problem in multiscale media

We present an iterative algorithm for mathematical modeling of an elastic deformation process in a fluid-saturated fractured-porous medium. A three-dimensional multi-physics problem describes the coupled isothermal processes of the solid elastic deformation and slightly compressible fluid flow under external pressure. Mathematical models of these processes are connected via interface conditions for the pressure and density fields on the surface of a fractured-porous medium. For solving the multi-physics problem, a special multiscale procedure was developed. We use a heterogeneous multiscale finite element discretization on coarse polyhedral grids for the solid elastic deformation problem. Multiscale shape functions are constructed using special interface conditions for a hydrodynamic pressure on the surface of pores. We apply a discontinuous Galerkin method and a stabilized finite element discretization on fine tetrahedral grids for solving the hydrodynamics problem in fluid-saturated pores. In this case, we can realize an effective parallel procedure for solving the multi-physics problem. In each pore, hydrodynamics problems can be solved in parallel and independently. Verifications of the computational schemes are presented. We consider three-dimensional media with a different volume concentration of cracks and pores. Computational modeling results are presented. A time of solving the multi-physics problem using fine and coarse grids is shown.

Molecular Characterization of Elastic Deformation in Elastin Mimetic Peptide [LGGVG

Owing to the dramatic elasticity of elastin mimetic peptides, attention is accumulating to the molecular properties of the elastic polymers. This work reports on the molecular characterization of elastic deformation in an elastin mimetic peptide [LGGVG]3 via molecular dynamics simulation. The elastic deformation process is captured by pulling, holding and releasing the peptide. The molecular properties of the released peptide from being pulled are observed almost identical to that of the relaxed peptide, and this indicates the excellent elasticity of the elastic biopolymer. From the results, it is suggested that the scheme implemented in this work could be used in studies of other elastic polymers.DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18432

Variant of the Nonlinear Wave Equations Describing Cylindrical Axisymmetrical Waves

New nonlinear wave equations are derived using the Murnaghan five-constant elastic potential. A feature of these equations is the following two assumptions: the elastic deformation process is physically nonlinear (geometric nonlinearity is neglected) and the deformation is geometrically axisymmetric and described by cylindrical coordinates. Therefore, the system of wave equations contains only two coupled equations. Such a statement allows us to use these new equations to analyze surface waves propagating along a circular cylindrical cavity in an elastic medium. Another feature of the nonlinear equations is that every equation includes the classical linear part. The nonlinear terms of the equations are quadratically nonlinear and contain twenty-three types of nonlinearities in the first equation and twenty-two types in the second equation.

Nonlinear Local Deformations of Red Blood Cell Membranes: Effects of Toxins and Pharmaceuticals (Part 2)

Modifiers of membranes cause local defects on the cell surface. Measurement of the rigidity at the sites of local defects can provide further information about the structure of defects and mechanical properties of altered membranes. The purpose of the study: a step-by-step study of the process of a nonlinear deformation of red blood cells membranes under the effect of modifiers of different physico-chemical nature. Materials and methods. The membrane deformation of a viscoelastic composite erythrocyte construction inside a cell was studied by the atomic force spectroscopy. Nonlinear deformations formed under the effect of hemin, Zn2+ ions, and verapamil were studied. Results. The process of elastic deformation of the membrane with the indentation of a probe at the sites of local defects caused by modifiers was demonstrated. The probe was inserted during the same step of the piezo scanner z displacement; the probe indentation occured at the different discrete values of h, which are the functions of the membrane structure. At the sites of domains, under the effect of the hemin, tension areas and plasticity areas appeared. A mathematical model of probe indentation at the site of membrane defects is presented. Conclusion. The molecular mechanisms of various types of nonlinear deformations occurring under the effect of toxins are discussed. The results of the study may be of interest both for fundamental researchers of the blood cell properties and for practical reanimatology and rehabilitology.

Dynamic Compressive Behaviour of Closed-Cell Foam Materials Using Load-Measuring Apparatus with Opposite Load-Cells

It is necessary to evaluate the mechanical properties of foam materials at wide range of strain rates, since these materials have the strain rate dependence of strength. In this study, we evaluated the dynamic compressive behaviour of the closed-cell foam materials using the load-measuring apparatus with opposite load-cells, which is applying the drop-weight testing machine. In order to measure large deformation at dynamic strain rate range, universal rate range load-cell, which can reduce the influence of the reflected stress wave, was used. In addition, load equilibrium can evaluate using opposite load-cells which consist of movable (drop-weight) and stationary load-cells. In this study, the commercially available ALPORAS closed-cell aluminum foam was used. From the results of quasi-static tests, three deformation processes of elastic response, plateau deformation and densification were confirmed in stress-strain relation. Within the set of experiments, the closed-cell aluminum foam was locally deformed from cells with low strength and the stress variation occurred during plateau deformation, regardless of the strain rate. In addition, it was clarified that the stress equilibrium was not achieved at the dynamic strain rate. This is thought to be a phenomenon caused by local deformation of cell structure.

Crack nucleation in solid materials under external load - simulations with the Discrete Element Method

Numerical analysis of cracking processes require an appropriate numerical technique. Classical engineering approach to the problem has its roots in the continuum mechanics and is based mainly on the Finite Element Method. This technique allows simulations of both elastic and large deformation processes, so it is very popular in the engineering applications. However, a final effect of cracking - fragmentation of an object at hand can hardly be described by this approach in a numerically efficient way since it requires a solution of a problem of nontrivial evolving in time boundary conditions. We focused our attention on the Discrete Element Method (DEM), which by definition implies “molecular” construction of the matter. The basic idea behind DEM is to represent an investigated body as an assemblage of discrete particles interacting with each other. Breaking interaction bonds between particles induced by external forces imeditelly implies creation/evolution of boundary conditions. In this study we used the DEM approach to simulate cracking process in the three dimensional solid material under external tension. The used numerical model, although higly simplified, can be used to describe behaviour of such materials like thin films, biological tissues, metal coatings, to name a few.

Applying an Ultrasonic Lamb Wave Based Rechnique to Testing the Condition of V96ts3T12 Aluminum Alloy

Possibilities offered by an ultrasonic inspection technique that is based on using Lamb waves for monitoring the state of metal materials under static and cyclic loading have been studied. Dogbone V96ts3T12-aluminum-alloy specimens of the following two types have been used for research: initial material and a sample with a weld at the working zone center. The digital-image correlation method has been used as an additional source of information. Based on the tests, dependences of various informative parameters of acoustic vibrations on the applied load (for static tests) and running time (for cyclic tests) have been obtained. These dependences have been further supplemented with the results of calculation of deformation fields. The data gathered indicate sensitivity of the proposed ultrasonic inspection technique to various (elastic and plastic) deformation processes and allow one to monitor the growth of cracks under cyclic tests. Further development of the method assumes its examination from the viewpoint of embedded testing systems (the Structural Health Monitoring concept).

Application of 1 D Finite Element Method in Combination with Laminar Solution Method for Pipe Network Analysis

The features of application of the 1D dimensional finite element method (FEM) in combination with the laminar solutions method (LSM) for the calculation of underground ventilating networks are considered. In this case the processes of heat and mass transfer change the properties of a fluid (binary vapour-air mix). Under the action of gravitational forces it leads to such phenomena as natural draft, local circulation, etc. The FEM relations considering the action of gravity, the mass conservation law, the dependence of vapour-air mix properties on the thermodynamic parameters are derived so that it allows one to model the mentioned phenomena. The analogy of the elastic and plastic rod deformation processes to the processes of laminar and turbulent flow in a pipe is described. Owing to this analogy, the guaranteed convergence of the elastic solutions method for the materials of plastic type means the guaranteed convergence of the LSM for any regime of a turbulent flow in a rough pipe. By means of numerical experiments the convergence rate of the FEM - LSM is investigated. This convergence rate appeared much higher than the convergence rate of the Cross – Andriyashev method. Data of other authors on the convergence rate comparison for the finite element method, the Newton method and the method of gradient are provided. These data allow one to conclude that the FEM in combination with the LSM is one of the most effective methods of calculation of hydraulic and ventilating networks. The FEM - LSM has been used for creation of the research application programme package “MineClimate” allowing to calculate the microclimate parameters in the underground ventilating networks.

Effects of returns on composition, microstructure and mechanical properties of GH4169 superalloy

To recycle the returned alloy effectively, effects of returns proportion on alloy composition, microstructure and compression properties of superalloy GH4169 were studied by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and thermal-mechanical simulator. The results show that returns addition has no significant effect on the main alloy elements content and the principle precipitates, but increases the volume fraction of Al2O3 inclusions, resulting in the increase of oxygen level of GH4169 alloy. Returns addition does not change the elastic and plastic deformation process at room temperature or at 1,150 °C, but high returns proportion GH4169 alloy shows improved compression strength and yield strength. The alloy with 100% returns shows a maximum compression strength 1,153.45 MPa at room temperature, while the alloy with 80% returns has a maximum value 69.3 MPa at 1,150 °C. Returns addition increases fluctuation range and reduces the stability of yield strength and compression strength of GH4169 alloy at room temperature. It is noted that the volume fraction and the size of Al2O3, and the fraction of Laves phase reach their maximum values in the GH4169 alloy with 60% returns, which exhibits maximum yield strength of 516.65 MPa at room temperature and 62.17 MPa at 1,150 °C.

Stress Applied Patterns to the Influence of Stress Impedance Effect in Silicon/FeCuNbSiB Amorphous Powder Compound Film

We made use of compression-testing machine and LCR digital electric bridge to apply pressure stress and record the value of impedance which controlled by a computer throughout the whole testing process. Four stress loading methods were designed for testing, and a systematic research had been done with a scanning frequency at 1KHz for silicon/FeCuNbSiB amorphous powder compound films. It has been found that rubber matrix film is a kind of elastomer, which has some elastic deformation phenomenon such as elastic hysteresis and ratcheting. The radical reason of stress impedance (SI) effect is the internal relations between elastic deformation and impedance change. Deformation of elastic film will directly influenced the impedance, and the function of stress applied on the film will directly cause elastic deformation, thereby indirectly cause the change of impedance. Result shows, stress impedance effect is relevant to the recover process of elastic deformation. In the course of stress loading, the longer deformation recovered, the more indistinctively changed of impedance.

Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses

AbstractThe newly designed Ti-based bulk metallic glass (BMG) in which case of fracture behavior was observed 1990MPa to compressive strength with a wide plastic deformation around 7% after process of elastic deformation. This phenomenon can be compared with those of Ti-based alloys and other Ti-based BMGs and indicates high potential to be applied in use. It was evaluated the Ti-based BMG for thermal stability that the reduced glass parameters, ΔTx,Trgand γ, are 79K, 0.50 and 0.38, respectively. In addition, it reveals high activation energies for crystallization in which are estimated toEx1= 291.77 ±9.71 kJ/mol,Ex2= 588.77 ±28.88 kJ/mol andEx3= 330.26 ±3.61 kJ/mol on kissinger plotting in this study.

In-plane flexural behaviour and failure prediction of carbon fibre-reinforced aluminium laminates

This paper investigated the in-plane bending behaviour of carbon fibre-reinforced aluminium laminates (CARALL). The flexural progressive damage and failure mechanisms were analysed numerically and experimentally. Four types of CARALL specimens with a 3/2 configuration were prepared via hot-pressing using different aluminium alloy materials (2024-T3, 7075-T6 aluminium alloy) and fibre orientations ([0°/90°/0°]3, [45°/0°/−45°]3). The three-point bending tests were conducted under static loading. It was found that the primary damage modes were aluminium layer yielding in the mid-span and delamination between the aluminium and carbon fibre-reinforced polymer (CFRP) layers. A user-defined FORTRAN subroutine VUMAT based on ABAQUS was used to simulate the failure of the CFRP, a cohesive zone model was used to predict the inter-laminar failure, and a von Mises plastic model was used to define the isotropic hardening behaviour of the aluminium layers. The predicted results agreed well with the experimental ones. Two convenient calculation methods based on the elasticity mechanics and material mechanics were derived. And the non-linear behaviour of aluminium was considered in the elasticity mechanics method. The theoretical results matched closely with the experimental findings during the linear elastic deformation process.

Mechanics of magnetic fluid column in strong magnetic fields

Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.