Influence Of Material Parameters Research Articles

From theory to application: Innovative ice-phobic polyurethane coatings by studying material parameters, mechanical insights, and additives

This investigation introduces new insights into the influence of material parameters on the anti-icing properties of polyurethane (PU) coatings, encompassing chemical characteristics, cross-link densities, mechanical analysis, and additive diversity. To comprehensively address these aspects, a meticulous exploration was conducted to delve into the effects of these parameters on wettability and icephobicity. To fabricate the PU coatings, three distinct acrylic polyols with various hydroxyl content along with two widely employed aliphatic isocyanates boasting diverse %NCO values were utilized. By employing stoichiometric and non-stoichiometric ratios, an array of coatings with different crosslink densities and mechanical properties was fabricated. The principal influence of crosslink density alterations in PU coatings on ice nucleation temperature and ice adhesion strength emerged distinctly, underpinned by the establishment of hydrogen bonds between water molecules and polar functional groups within the coating, coupled with the appearance of a quasi-liquid layer (QLL). The mechanical properties, wettability characteristics, and surface roughness of the coatings were examined and it was clearly demonstrated that Young's modulus and physicochemical properties play significant roles in the characteristics of ice adhesion strength. In particular, lower Young's modulus in the samples was associated with reduced ice adhesion, albeit with compromised durability. In the next step of this investigation, the matrix demonstrating optimal mechanical properties and icephobicity was subjected to surface energy adjustment. This was accomplished by introducing various concentrations of both fluorinated and non-fluorinated additives. This adjustment led to a significant reduction of ice adhesion strength, measuring less than 100 Kpa as an icephobic PU coating. Nevertheless, it was observed that the effectiveness of the fluorinated additives diminished after repetitive icing-deicing cycles, while the non-fluorinated additive maintained its influence on ice adhesion strength even after numerous cycles. The interplay between material attributes, mechanical properties, and additive influences has been meticulously unraveled, charting a course for further advancements in the pursuit of robust icephobic coating.

Efficient multiscale investigation of mechanical behavior in Nb3Sn superconducting accelerator magnet based on self-consistent clustering analysis

The High Luminosity Large Hadron Collider (HL-LHC) is one of the large-scale projects currently being developed at the European Organization for Nuclear Research (CERN). Many Nb3Sn superconducting magnets are employed in this project, which exhibit complicated multiscale characteristics. The mechanical behaviors of magnets, which are directly related to the safety and stability of the overall structure, are affected by the electromagnetic–mechanical-thermal loading in actual service conditions. However, detailed modeling of magnets requires significant computing resources. A reduced-order method named self-consistent clustering analysis (SCA) has been proposed recently to reduce the cost. We have combined the SCA and finite element method (FEM) as an efficient multiscale framework, which is utilized to analyze the mechanical behaviors of accelerator magnets. Firstly, the computation results by presented framework are compared with direct numerical simulation (DNS) and existed experimental data to validate the accuracy and efficiency. Then, the FEM-SCA2 framework is utilized to study the mechanical behaviors of MQXFS accelerator magnet model under assembly, cool-down and excitation steps. The influences of material parameters, friction coefficient and stiffness degradation are also discussed. This paper provides an efficient multiscale analysis framework for investigating mechanical behavior in Nb3Sn accelerator magnet, which could be employed to study other magnets.

Real-Time Nondestructive Viscosity Measurement of Soft Tissue Based on Viscoelastic Response Optical Coherence Elastography.

Viscoelasticity of the soft tissue is an important mechanical factor for disease diagnosis, biomaterials testing and fabrication. Here, we present a real-time and high-resolution viscoelastic response-optical coherence elastography (VisR-OCE) method based on acoustic radiation force (ARF) excitation and optical coherence tomography (OCT) imaging. The relationship between displacements induced by two sequential ARF loading-unloading and the relaxation time constant of the soft tissue-is established for the Kelvin-Voigt material. Through numerical simulation, the optimal experimental parameters are determined, and the influences of material parameters are evaluated. Virtual experimental results show that there is less than 4% fluctuation in the relaxation time constant values obtained when various Young's modulus and Poisson's ratios were given for simulation. The accuracy of the VisR-OCE method was validated by comparing with the tensile test. The relaxation time constant of phantoms measured by VisR-OCE differs from the tensile test result by about 3%. The proposed VisR-OCE method may provide an effective tool for quick and nondestructive viscosity testing of biological tissues.

Ultimate bearing capacity of strip footings above rectangular voids in Hoek-Brown rock masses

The bearing capacity of a rigid strip footing placed on a rock mass with a rectangular void is determined using the upper bound finite element limit analysis in conjunction with the adaptive mesh refinement technique. The rock mass is assumed to obey the generalized Hoek-Brown (GHB) yield criterion. The optimization model is solved by using the second order cone and power cone programming, which enables the GHB yield criterion to be used in its native form, without the need for smoothing. Based on the method, the reduction factor is calculated and presented in a series of dimensionless charts for design purpose. The influence of material parameters (such as the geological strength index GSI, material constant mi and intact rock strength σci) and geometric parameters (including the height and width of the void, as well as the horizontal and vertical distance between the void and the strip footing) on the reduction factor is considered. Typical failure patterns are discussed in detail to offer a deeper explanation of how the voids affect the bearing capacity of strip footing.

Propagation of shear waves in viscoelastic layered structure

• Shear wave through orthotropic material on functionally graded viscoelastic substrate. • Analytical dispersion relation. • Influence of material parameters on dispersion. The presented analytical study deals with the propagation of shear waves (S waves) in the layered structure containing an orthotropic material layer bonded with an heterogeneous viscoelastic half-space. Separate governing differential equations are applied while obtaining the analytical solution of transverse displacement in the respective media. The dispersion relation (complex form separated into real and imaginary parts) is finally derived in the closed form for the considered system employing suitable boundary conditions and the derived displacements. The obtained results are also shown to match with the classical Love waves equation (for isotropic media case). The phase- and damping velocity terms are plotted against the wavenumber (all quantities in dimensionless form) for the different values of material parameters. The effect of heterogeneity parameter, viscoelastic parameter, and the layer thickness on the wave propagation is graphically presented that can be used while exploring the nature of S wave propagation through similar composite structures.

Thermally induced structural response of a solar sail spacecraft in Earth orbit

The solar sail spacecraft for earth missions experience shadow region in Earth orbit, the resulting temperature field changes will induce the structural response on the sail films and the booms of the solar sail, thus disturb the attitude control of the spacecraft. Therefore, it is valuable to study the thermally induced structural response of solar sails caused by abrupt temperature filed. In this paper, the solar sail with square films and booms is studied. A sequential-coupled analysis method is proposed. Based on this method, the thermal analysis model of the solar sail is established, then the temperature variation law of the solar sail during orbiting the earth is obtained through simulation. Based on the structural analysis model of the solar sail, the structural response caused by temperature change is calculated, and the influence of material parameters on such response is analyzed. The results show that, the sudden change of temperature field will not only cause the shrinkage and expansion of the film, but also lead to obvious vibration on the boom. This vibration can be reduced by using thermal control coating or increasing the boom thickness. The results of this paper have important referential value for the design of thermal control system of solar sails.

Crack initiation characteristics of brittle materials with I‐II mixed mode crack under uniaxial compression

AbstractConsidering T‐stress components under compression, the crack initiation characteristics of HT200 and PMMA under uniaxial compression have been investigated by theoretical analysis and experimental study for central cracked plate (CCP) and compact tension shear (CTS) specimens with I‐II mixed mode crack. Crack initiation angles of CCP and CTS specimens under compressive load were theoretical predicted according to modified maximum tangential stress (MMTS) criterion and modified maximum shear stress (MMSS) criterion. The influence of material parameters and specimen geometrical configurations on crack initiation characteristics was illustrated through experiments. It demonstrates that the modified fracture criterion considering T‐stress components is more consistent with experiments. Crack initiation angle is related to material properties. Limit load PL is controlled by KII under compression for CCP specimen, and PL of PMMA is less than that of HT200. The closure effect on CTS specimens is less significant than that on CCP specimens.

Prediction of flatness defects and of the stable configuration of thin multilayer assemblies due to chemical shrinkage

The manufacturing process of multimaterial and multilayer assemblies involving pre-impregnated laminates consist of heating the composite structure at high temperature, typically of the order of 200 °C, at which polymerization occurs. During the curing, a permanent deformation, called chemical shrinkage strain, is generated and may strongly influence the future flatness of the assembly. Moreover, the cooling generates additional thermal deformations, which also participate into the manifestation of flatness defects at room temperature. To predict warpage or flatness defects, the chemical shrinkage strain needs to be precisely determined.This work proposes an analytical approach dedicated to flatness prediction of multilayer composites taking into account shrinkage strain generated during processing. Our contribution also aims at predicting and analyzing stable and unstable solutions of flatness defects. The proposed analytical model, developed for any multilayer composite, is obtained from an extension of the classical laminate theory (CLT). Geometrical nonlinearities are also accounted for. The analytical approach relies on trial fields for strain and displacements, and on total potential energy minimization. The theory is applied to a bilayer laminate consisting of a cured layer made of epoxy/glass fiber composite and of a pre-impregnated one of the same material. Results obtained from the analytical modeling are validated by numerical simulations. Influence of material parameters is also analyzed for this configuration. Finally, from experimental measurements of curvatures on bilayer composite samples, an inverse method and a minimization procedure, the proposed analytical development provides an estimate of the effective shrinkage strain, which is responsible for the flatness defect. Illustration of this strategy is exemplified by considering a bilayer composite manufactured for this work.

Influence of Materials Parameters of the Coil Sheet on the Formation of Defects during the Manufacture of Deep-Drawn Cups

During the process of deep drawing of cylindrical thin-walled products from aluminum sheets, the occurrence of product defects in the form of breaking the material continuity is observed. This has a very large impact on the efficiency of production lines and the number of generated scraps. The number of defects depends on many factors, including the material and the process properties. Because the problem appears after changing one material to another, while the process parameters do not change, it was assumed that the material has the main influence on the number of defects. To reduce the number of defects, a tool is needed to predict threats to the process. Decision tree models were used for this purpose. Using the tree interaction algorithms, the influence of the chemical composition and strength parameters of the 3xxx series aluminum alloy on the number of generated defects was investigated. Increased Silicon (Si) and Iron (Fe) values generated a higher number of defects. Increased yield strength (YS) and decreased elongation (E) also generated a higher number of defects. Based on the results, a defect prediction tool was created, where after entering the parameters of the material, it is possible to predict production hazards.

A high-fidelity human cervical muscle finite element model for motion and injury studies

Abstract Active muscle response is a key factor in the motion and injury of the human head and neck. Due to the limitations of experimentation and the shortcomings of previous finite element models, the influence of material parameters of cervical muscle on motions of the head and neck during a car crash have not been comprehensively investigated. In the present work, a model of the cervical muscle in a 50th-percentile adult male was constructed. The muscles were modelled using solid finite elements, with a nonlinear-elastic and viscoelastic material and a Hill material modelling the passive and active parts of each muscle, respectively. The head dynamic responses of the model were validated using results obtained from volunteer sled tests. The influence of the material parameters of a muscle on head and neck motions were determined. Our key finding was that the greater the stiffness and the contraction strength of the neck muscles, the smaller the rotation angle of the head and the neck, and, hence, the lower the risk of head and neck injury to occupants in a car crash.

Influence of Material Parameters on the Stability of Artificial Skyrmion in Hard/Soft Magnetic Bilayers

Herein, the influence of material parameters on the core diameter of the artificial skyrmions in hard magnetic/soft magnetic bilayer thin film is investigated. It is found that the perpendicular magnetic anisotropy (PMA) constant and the interlayer exchange constant play a key role in the realization of artificial skyrmions. Through simulation, the PMA constant of the hard magnetic materials should be between 1.0 × 105 and 4.5 × 105 J m−3. Therefore, some rare earth materials with high magnetic anisotropy or other materials with low magnetic anisotropy do not meet the requirement. The initial skyrmion spin texture is Bloch‐type artificial skyrmion in the hard/soft magnetic bilayer system. In the presence of 1.0–1.5 × 105 J m−3 PMA constant and 0 J m−1 interlayer exchange constant, the Néel‐type artificial skyrmions are formed in the hard/soft magnetic bilayer system. The size of the hard magnetic layer material has little effect on the stability of skyrmions, so the stability of skyrmions should mainly be adjusted with the PMA of the hard magnetic materials or by changing the material types.

Frictional contact problem of a rigid charged indenter on two dimensional hexagonal piezoelectric quasicrystals coating

ABSTRACT This paper reports the frictional contact problem of a rigid charged indenter on two-dimensional (2D) hexagonal piezoelectric quasicrystals (PEQCs) coating. Using the rigorous operator theory and Almansi theorem, two sets of three-dimensional (3D) general solutions for 2D-hexagonal PEQCs are obtained. The frequency response functions (FRFs) for displacements and stresses of phonon and phason, electric potentials and electric displacements, which are the multifield responses of material under generalised unit point load in the Fourier domain, are obtained by applying double Fourier integral transforms to the general solutions and boundary conditions. The contact responses, such as pressures and stresses, are solved by the discrete convolution-fast Fourier transform technique (DC-FFT). Numerical results are given to reveal the influences of material parameters and loading conditions on the contact behaviour. The obtained 3D contact solutions are not only helpful further analysis and understanding of the coupling characteristics of phonon, phason and electric field, but also provide a reference basis for experimental analysis and material development.

Modelling Material Parameters of Selected Composite Structures of Tires

The paper presents selected results of experimental and computational modelling of composite material samples of tires with cord ply (casing) and breaker textile reinforcement. The computational modelling included applications of finite element methods. The output is to determine and verify the influence of material parameters of textile reinforcement. The results were confirmed by the experiment and computational modelling verification. For elastomeric matrices hyperelastic behavioural patterns of this material were considered.

Analysis of 120m Circular Enclosed Coal Yard Based on Finite Element Mechanics

Large diameter circular closed coal yard has large coal pile, high coal pile height, and the cancellation of expansion joints, which has many adverse effects on the structure. The study of finite element analysis method, in view of the large stack on the effect of pile and pile of coal load and temperature effect on structure to do the analysis, the influence of material parameters was verified the correctness of the structure internal force under the condition of various loads is obtained as a result, the temperature effect may produce several times the pile of coal load internal force, provides reference for engineering design.

Static and dynamic hygrothermal postbuckling analysis of sandwich cylindrical panels with an FG-CNTRC core surrounded by nonlinear viscoelastic foundations

In this article, analytical and semi-analytical methods are used to analyze the nonlinear static and dynamic hygrothermal postbuckling response of sandwich cylindrical panels with functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core. The sandwich cylindrical panels with an FG-CNTRC core are resting on generalized nonlinear viscoelastic foundations which are consisted of a Winkler and Pasternak foundation parameters augmented by a Kelvin-Voigt viscoelastic model and a nonlinear cubic stiffness. The sandwich cylindrical panels with four types of FG-CNTRC core are considered such that the CNTs distribution types consist of the FG-O, FG-Λ, FG-X, and UD. Regarding to the classical shell theory and geometrical nonlinearity in von Kármán-Donnell sense, the governing equation is obtained and discretized utilizing the Galerkin method. The nonlinear dynamic hygrothermal (NDHT) postbuckling is analyzed by means of the fourth-order Runge-Kutta method. The influences of material parameters, various geometrical characteristics, and nonlinear viscoelastic foundation parameters are studied on the nonlinear static hygrothermal (NSHT) postbuckling and NDHT postbuckling analysis of sandwich cylindrical panels with an FG-CNTRC core. The results show that the different types of CNTs distribution and nonlinear viscoelastic foundation parameters have a strong effect on the hygrothermal postbuckling behaviors of sandwich cylindrical panels with an FG-CNTRC core.

Temperature Field Analysis of Light Steel Structure Beam-column Composite Joint

The ABAQUS analysis software is used to establish a finite element theoretical analysis model of the thin-walled steel beam-column composite node under the ISO-834 fire temperature rise curve. Through the parameter-analysis of the temperature-time curve of the thin-walled steel beam-column node, the influence of material parameters on the fire resistance of the structure is obtained.

Analysis of the effect of gradation and maximum nominal particle size on coarse aggregate movement

The formation of ruts is closely related to the movement of the aggregate. In order to analyze the movement law of the aggregate during compaction, this paper based on the discrete element model, the coordination number, void ratio, average contact force, and axial stress are used as indicators to investigate the effects of gradation and maximum nominal particle size on the law of aggregate movement. The influence of material parameters on aggregate movement was explored from the microscopic level so as to provide suggestions for design grading and improving rutting resistance of asphalt pavements.

Analysis of influence of aggregate stiffness on coarse aggregate movement of asphalt mixture

The movement law of aggregate is more complicated in the static pressure process of asphalt mixture. In order to analyze the evolution law of the aggregate, the objective of this paper is to develop 3D (3-dimensional) mixture compaction models. The coordination number, void ratio, average contact force, and axial stress are used as indicators to investigate the effects of aggregate stiffness on the law of aggregate movement. The influence of material parameters on aggregate movement was explored from the microscopic level so as to provide suggestions for the design of graded.

An Elasto-plastic Contact Solving Method for Two Spheres

The traditional Hertz contact theory has been widely used in solving contact problems. However, it is only applicable to the elastic contact, and cannot truly reflect the contact stress distribution and contact radius in the elasto-plastic contact. In this work, based on the Hertz contact theory, a fast solving method is proposed to calculate the contact stress distribution and contact radius in the elasto-plastic contact between two spheres. It is assumed that the elastic contact only occurs at the outer edge of contact patch and its contact stress distribution satisfies the Hertz contact theory, and the contact stress distribution at the inner edge of contact patch can be superimposed by a constant contact stress and several small ellipsoidal contact stress distributions. Moreover, based on the equivalent relation between the resultant force of contact stress and the normal external load, the contact radius in the elasto-plastic contact can be solved. Finally, an elasto-plastic contact example of two spheres is given based on the power-law hardening material model, and the influences of material parameters, contact radii and normal external loads on the accuracy of the proposed method are discussed by comparing the differences between the numerical results by finite element method and the predicted ones by the proposed method. It is shown that the proposed method can accurately calculate the maximum contact stress and contact radius in the elasto-plastic contact, and the relative errors of both maximum contact stress and contact radius are within $$\pm \,5{\%}$$. To sum up, the proposed fast solving method can be applied to perform the elasto-plastic contact analysis in engineering practice.

A Discrete Element Model for Masonry Vaults Strengthened with Externally Bonded Reinforcement

ABSTRACT The paper investigates the effectiveness of two-dimensional Discrete Element Method as a tool for structural analysis of arches provided with buttresses and backfill and strengthened with externally bonded reinforcement. Masonry vault and buttresses are modelled as an assembly of 2D rigid blocks interacting through non-linear contact joints, the backfill is discretized into deformable elastic-plastic triangular elements, while the reinforcement is modelled by means of truss elements bonded to the substrate through non-linear springs. A parametric analysis on the influence of material parameters and the effect of the discretization of the backfill is carried out, and the outcome of different reinforcement systems, consisting of Steel Reinforced Grout applied either at the intrados or at the extrados, are analysed. The comparison with experimental full-scale tests proved the ability of the numerical approach to capture hinges position, load bearing capability, as well as the increase in deflection and load capacity provided by the reinforcement.