Influence Of Material Parameters Research Articles

Numerical Study on the Variability of Plastic CTOD.

This paper presents a numerical study on the influence of material parameters and loading variability in the plastic crack tip opening displacement (CTOD) results. For this purpose, AA7050-T6 was selected as reference material and a middle-cracked tension specimen geometry was considered. The studied input parameters were the Young’s modulus, Poisson’s ratio, isotropic and kinematic hardening parameters and the maximum and minimum applied loads. The variability of the input parameters follows a Gaussian distribution. First, screening design-of-experiments were performed to identify the most influential parameters. Two types of screening designs were considered: one-factor-at-a-time and fractional factorial designs. Three analysis criteria were adopted, based on: main effect, index of influence and analysis of variance. Afterwards, metamodels were constructed to establish relationships between the most influential parameters and the plastic crack tip opening displacement (CTOD) range, based on two types of designs: Face-Centered Central Composite Design and Box-Behnken design. Finally, the metamodels were validated, enabling the expeditious evaluation of the variability in the plastic CTOD range; in addition, the variability in the fatigue crack growth rate was also evaluated.

Asymmetric Gaussian confinement potential and decoherence effect on polaron in quantum disk with electromagnetic field

Selecting the asymmetric Gaussian potential to describe the electron that is confined in a quantum dot, the ground and first excited state energy and wave function of the system are derived by using the Pekar-type variational method, and the two-level structure required for a qubit is constructed. The influence of the electron–phonon (EP) coupling constant on the probability density of the electron in the superposition state and the period of the oscillation of a qubit with electromagnetic field are investigated. By studying the effect of the dispersion coefficient, the EP coupling constant and the electromagnetic field on the spontaneous emission rate of the LO phonon, the influence of material parameters and the electromagnetic field on the decoherence of the qubit in quantum dots is revealed, and the theoretical scheme of suppressing the decoherence of qubit in quantum dots by phonon effect is enriched and perfected.

Time-dependent behavior of laminated functionally graded beams bonded by viscoelastic interlayer based on the elasticity theory

A two-dimensional (2-D) elasticity solution is developed to investigate the time-dependent response of laminated functionally graded beam with viscoelastic interlayer. The elastic modulus in each functionally graded layer varies through the thickness following an exponential function, and the mechanical property of each layer is described by the exact 2-D elasticity equations. Viscoelastic property in the interlayer is simulated by the Maxwell–Wiechert model, in which the memory effect of it is neglected. By virtue of the recursive matrix method, the solution of stress and deformation can be obtained efficiently. The comparison studies indicate that the relative error of the Euler–Bernoulli solution is slight for slender beam with small gradient factor, but it significantly increases as the beam thickness or the gradient factor grows. The finite element solution is close to the present one with large number of sub-layers in FE modeling and small gradient factor of FG layer, while the error of FE solution increases as the number of sub-layers decrease or the gradient factor increases. Besides, the influences of material parameters upon the time-dependent behavior and the optimization for the stress and deformation in the beam are discussed in detail.

Correction to: On the Influence of Material Parameters in a Complex Material Model for Powder Compaction

The material parameter L should in the text, Table 1, and Figures 8 and 9 have the notation L/X. In Figure 1 and the equations, the parameter L is defined correctly.

Vacuum metrology based on refractive index of gas

With the development of vacuum technology, subject to the influence of directional flow and uneven temperature, the thermodynamic equilibrium state is destroyed. In this case, the pressure reference is not suitable for characterizing the vacuum state. To ensure the long-term stability and reproducibility of the measurement system, vacuum metrology will be characterized by gas density. The precisive measurement of gas refractive index based on a Fabry-Perot cavity can be used to derive the gas density. This kind of an optical measurement of vacuum links macroscopic dielectric constants of gases with microscopic polarization parameters of atoms and molecules. It replaces the physical standard based on the mercury pressure gauge with the quantum standard. In this paper, we discuss the reverse process from refractive index to gas pressure, and use the laser-locked Fabry-Perot cavity method to measure the refractive index of argon gas. The contribution of related parameters to the uncertainty of determined gas pressure is analyzed. The influences of material parameters and experimental parameters such as gas molar susceptibility, molar susceptibility, dielectric second Virial coefficient and temperature on gas pressure accuracy are analyzed. The result shows that the uncertainty in our measurement of argon within 1 atm is <inline-formula><tex-math id="M2">\begin{document}$u = \sqrt {{{(6\;{\rm{mPa}})}^2} + {{(73 \times {{10}^{ - 6}}p)}^2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.png"/></alternatives></inline-formula>. Currently, the uncertainty mainly comes from the measurement deviation of gas temperature inside the cavity. After repeating the measurement a few times, the results show that the statistical uncertainty of refractive index is within 100 ppm, which is limited by the accuracy of the pressure gauge used here. In addition, we compare the dipole calculated by the <i>ab initio</i> method with that by the DOSD method. The results show that the dynamic polarizability obtained by the <i>ab initio</i> method is consistent with our experimental results. In conclusion, these experimental results show that the measurement of gas pressure based on the gas refractive index has high repeatability and accuracy. If the temperature control and corresponding measurement accuracy of the gas are further improved, this method can also be used to obtain high-precision microscopic parameters such as the polarizabilities of atoms and molecules. In the future work, we will focus on improving the temperature control and the design of the cavity to reduce cavity leakage and deflation. It is possible that the measurement accuracy of the gas pressure will be increased to 10 ppm level, which is the same level as the current standard pressure gauge and will become a new standard for pressure measurement in the future.

Transport properties at a sigmoidal graded heterojunction

A sigmoidal grading profile is proposed for the efficient study of the influence of material parameters and effective mass mismatch on the properties of graded heterojunctions. For the interest of accessing bound and scattering states, we have shown the exact solvability of the model on the entire real line. Focussing on transport across a compositionally graded heterojunction, we have discussed the effect of interface width and effective mass mismatch on the transmission probability.

Brownian Motion and Thermophoretic Diffusion Effects on Micropolar Type Nanofluid Flow with Soret and Dufour Impacts over an Inclined Sheet: Keller-Box Simulations

The principal objective of the current study is to analyze the Brownian motion and thermophoretic impacts on micropolar nanofluid flow over a nonlinear inclined stretching sheet taking into account the Soret and Dufour effects. The compatible similarity transformations are applied to obtain the nonlinear ordinary differential equations from the partial differential equations. The numerical solution of the present study obtained via the Keller-Box technique. The physical quantities of interest are skin friction, Sherwood number, and heat exchange, along with several influences of material parameters on the momentum, temperature, and concentration are elucidated and clarified with diagrams. A decent settlement can be established in the current results with previously published work in the deficiency of incorporating effects. It is found that the growth of the inclination and nonlinear stretching factor decreases the velocity profile. Moreover, the growth of the Soret effect reduces the heat flux rate and wall shear stress.

Nonlinear vibration of imperfect FG-CNTRC cylindrical panels under external pressure in the thermal environment

An analytical approach for the nonlinear vibration analysis of imperfect functionally graded carbon nanotube-reinforced composite (FG-CNTRC) cylindrical panels is presented. The FG-CNTRC cylindrical panel is subjected to external pressure in the thermal environment. The nonlinear temperature distribution in the thickness direction is assumed. The classical thin shell theory with the von-Kármán strain-displacement kinematic nonlinearity is employed in the constitutive laws of the shell. The governing equation is solved by utilizing Galerkin’s method in conjunction with the stress function concept. Finally, to find the nonlinear dynamic responses, the fourth order Runge-Kutta method is used. The effect of the four various types of the CNTs distributions, such as UD, FG-Λ, FG-X, and FG-O is considered on the cylindrical panel. The influence of material parameters, initial imperfection, and temperature on the nonlinear vibration response of functionally graded CNTRC cylindrical panel is presented.

Influence of material parameters on the performance of niobium-based superconducting radiofrequency cavities

A detailed thermal analysis of a niobium (Nb)-based superconducting radiofrequency (SRF) cavity in a liquid helium bath is presented, by taking into account the temperature and magnetic field dependence of surface resistance and thermal conductivity in the superconducting state of the starting Nb material (for SRF cavity fabrication) with different impurity levels. The drop in SRF cavity quality factor ( $$Q_{0}$$ ) in the high acceleration gradient regime (before the ultimate breakdown of the SRF cavity) is studied in detail. It is argued that the high-field $$Q_0$$ -drop in SRF cavity is considerably influenced by the intrinsic material parameters such as electrical conductivity and thermal diffusivity. The detailed analysis reveals that the current specification on the purity of Nb material for SRF cavity fabrication is somewhat overspecified, as also inferred by the experimental work reported by some of the laboratories in the recent past. In line with these encouraging experimental results, in this paper, based on a rigorous calculation, we show that the Nb material with relatively low purity can very well serve the purpose for the accelerators dedicated for spallation neutron source (SNS) or accelerator-driven subcritical system (ADSS) applications, where the required accelerating gradient is typically up to $$20~\hbox {MV m}^{-1}$$ . This information will have important implication towards the cost reduction of superconducting technology-based particle accelerators for various applications. We think this theoretical work will be complementary to the experimental efforts performed in various laboratories at different corners of the globe.

Bending analysis of functionally graded beam with porosities resting on elastic foundation based on neutral surface position

In this paper, the Timoshenko beam theory is developed for bending analysis of functionally graded beams having porosities. Material properties are assumed to vary through the height of the beam according to a power law. Due to unsymmetrical material variation along the height of functionally graded beam, the neutral surface concept is proposed to remove the stretching and bending coupling effect to obtain an analytical solution. The equilibrium equations are derived using the principle of minimum total potential energy and the physical neutral surface concept. Navier-type analytical solution is obtained for functionally graded beam subjected to transverse load for simply supported boundary conditions. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions. The influences of material parameters (porosity distributions, porosity coefficient, and power-law index), span-to-depth ratio and foundation parameter are investigated through numerical results.
 Keywords: functionally graded beam; bending analysis; porosity; elastic foundation; bending; neutral surface.
 Received 10 December 2018, Revised 28 December 2018, Accepted 24 January 2019

Influence of material parameters on the interfacial crack growth in thermal barrier coating system

Surface crack failure and interfacial crack failure are typical failure modes in thermal barrier coating (TBC) system. The most common failure form is the peeling of top coat (TC) caused by interfacial crack. In this study, the influence of material parameter on the energy release rate of interfacial crack in TBC system was studied by extended finite element method. The influence of the elastic modulus of TC and the elastic modulus of bond coat (BC) was considered, and the effect of the crack position and length was also taken into account. The results show that the value of the energy release rate at TC/thermally grown oxide (TGO) and TGO/BC interfaces increases with the increase of the elastic modulus of TC, and the increase rate increases with the increase of crack length. With the increase of crack length, the value of the energy release rate and the increase rate increase. With the increase of the elastic modulus of BC, the influence of the shorter cracks at TC/TGO interface decreases, while for the longer cracks, the value of the energy release rate decreases with the increase of the elastic modulus of BC, and the decrease rate of the energy release rate decreases with the elastic modulus of BC increasing. For TGO/BC interface crack, the value of the energy release rate gradually decreases with the increase of the elastic modulus of BC, and the longer the crack length is, the more obvious the influence is. Both the elastic moduli of TC and BC have more influence on TC/TGO interfacial cracks than on TGO/BC interfacial cracks.

Experimental Study on Influence of Material Parameters on Bond Behavior of Glued-in Rod Connection

Abstract Glued-in rod connection for timber structure has shown great potential for engineering applications because of its high strength, stiffness, and aesthetic appeal. During the past few decades, extensive research has been carried out to investigate the effects of geometrical parameters on bonding behavior of glued-in rod connection. On the other hand, comprehensive studies on the effects of material parameters are rare. This article presents an experiment program to study the effects of a number of material parameters—adhesive type, rod surface type, glued-in direction—of glued-in rod connection. Twenty-four glued-in rod specimens were tested using a universal testing machine, and the full bond-slip behaviors of specimens were collected. Test result shows that bond strength of glued-in rod connection with epoxy resin is 20 % to 30 % higher than that with polyurethane, and the effect of rod types on bond strength is negligible. Although parallel-to-grain glued-in rod connection has higher bond strength than that of perpendicular-to-grain connection, sudden brittle failure is observed for parallel-to-grain glued-in rod connection. Furthermore, a new bonding strength model is proposed to account for the effects of material parameters.

Influence of material parameters on 2D-martensitic transformation based on the phase-field finite-element method

Obtaining an accurate microscopic representation of the martensitic transformation process is key to realizing the best performance of materials and is of great significance in the field of material design. Due to the martensite phase transformation is rapidly, the current experimental is hard to capture all the information in the Martensite phase transformation process. Combining the phase-field method with the finite-element method, a model of martensitic transformation from a metastable state to a steady state is established. The law of a single martensite nucleus during martensitic transformation is accurately described. By changing the key materials that affect martensite transformation and the phase-field parameters, the effects of the parameters on the single martensitic nucleation process are obtained. This study provides an important theoretical basis for effectively revealing the essence of martensite transformation and can determine effective ways to influence martensite transformation, obtain the optimal parameters and improve the mechanical properties of such materials.

Temperature distribution in a composite rod, taking into account nonlocal spatial effects

One of the important directions in the field of creating new structural and functional materials is the study of materials with a complex structure and unique strength or temperature properties. Due to the heterogeneity of their structure, such materials are called “structurally sensitive”. The heterogeneity of the structure of such materials is justified by the technological features of their creation. Structurally sensitive materials can be obtained by compacting nanopowders, deposition on a substrate, etc. The paper considers a mathematical model of heat propagation in a composite rod. At one of the ends of the rod, a protective coating of structurally sensitive material is used. Using the finite element method, numerical solutions are found for a problem with conditions of ideal thermal contact of rod parts. The results of the numerical calculation for various materials are given. The influence of material parameters on the heat distribution in the rod is analysed.

The numerical study of the influence of material parameters on the regime of adhesive wear of surface asperities

In the paper, we developed a discrete element model of adhesive interaction of materials with taking into account the “cold welding” effect. Based on this model, we carried out a detailed analysis of the factors controlling regimes of adhesive wear for elastic-plastic materials with non-ideal plasticity. We proposed an empirical criterion of transition from “breakaway” to “grinding” regime of wear. The extended form of the given criterion takes into account the dependence of material strength on hydrostatic pressure.

Contact resonance spectroscopy for on-the-machine manufactory monitoring

A piezo resistive, phase locked loop (PLL) controlled micro tactile measurement system for on-the-machine contact resonance spectroscopy (CRS) mapping of square centimetre-sized areas is developed and characterized. The CRS uses the influence of material parameters like the Young’s modulus on the contact stiffness between probing tip and sample surface and thus, the resonance frequency of the in-contact cantilever. Recently, we showed a robust, large-dimension, piezo resistive silicon cantilever (5 mm × 200 μm × 50 μm) with a silicon tip at its free end for tactile probing of high-aspect-ratio geometries and high-speed topography scans (i.e., up to 15 mm/s). For CRS-based layer and material analysis, this cantilever can be excited into resonance by a piezo chip actuator as described in this work. A compact, LabVIEW-controlled, fully automated scanning system using a homemade, μ-controller-implemented software PLL for resonance frequency tracking and out-reading was realized. To verify the measurement principle, analytical modelling was done. Different layer thicknesses of photo resist (PR) on silicon (11 ± 2 nm to 1653 ± 76 nm), point-by-point line scans of material transitions with various Young’s moduli (Si-PR-Si), bulk materials and nano-/micro-structures were investigated to validate the system. For optimization of the sensor sensitivity and efficiency, amplitude and phase were analysed under different conditions (contact force, excitation amplitudes). On-the-machine CRS with tools and work pieces can be a valuable method for quality assurance and reproducibility of future industrial manufacturing and just-in-time production.

Some Interesting Traveling Waves in a Transversely Isotropic Incompressible Hyperelastic Semi-infinite Rod

In this paper, the bounded traveling wave solutions are examined for a system of partial differential equations with certain boundary conditions. Interestingly, this system can be used to describe the axially symmetric motion of a semi-infinite incompressible hyperelastic cylindrical rod. With the aid of traveling wave transformations, the partial differential equations can be reduced to a traveling wave equation. The implicit analytical expressions determining the traveling waves are derived. Significantly, the influences of material parameters on the qualitative properties are discussed in detail by using the phase portraits of the traveling wave system. Smooth solutions such as the periodic traveling wave solutions and the solitary wave solutions with the peak form are shown. In particular, some interesting singular traveling wave solutions including the solitary cusp wave solutions and the periodic cusp wave solutions with the peak form are obtained. Numerical examples for all these waves are given.

Impact response of low-density foam impinging onto viscoelastic bar: A theoretical analysis

The Taylor-Hopkinson test is widely used in predicting the dynamic strength of materials. For low-density foam materials, the output bar in the Taylor-Hopkinson test is often made from much weaker materials like polymethylmethacrylate (PMMA) to reduce the wave impedance mismatch between the foam sample and the output bar. These low impedance materials exhibit viscoelastic properties and may affect the dynamic stress prediction of foam samples. In this paper, the shock wave theory for the foam sample in conjunction with the viscoelastic wave propagation in the output bar is employed to illustrate the influence of the viscoelastic output bar on the dynamic response of foam samples in the Taylor-Hopkinson impact. The theoretical model presented in this paper can be degenerated into previous elastic target bar model and rigid target bar model. Finite element simulations are further performed to verify the proposed theory. The influence of material parameters on the final deformation of the foam sample, impact duration and residual velocity of the foam sample are investigated. The results in this paper not only help in understanding the effect of the viscoelastic bar on the dynamic response of foam samples, but also set up guidelines to perform the Taylor-Hopkinson test more precisely.

Influence of inertia and material properties on discrete simulation of dynamic fracture of concrete

It is well known that the material resistance to fracture increases with increasing strain rate. For relatively slow strain rates, the response is strongly dependent on the material fracture properties such as material strength or fracture energy, whereas with further increase of loading rate, the loading force is getting influenced predominantly by the material inertia. The response of the material changes with strain rate in the sense of loading force as well as character of the crack pattern. The contribution is focused on simulations of fracture experiments at various strain rates. Dynamical concrete fracture is simulated using meso-scale discrete model, i.e. a system of interconnected discrete particles. Material properties in the model are randomly distributed within the volume domain. Similar to quasi-static loading rates, the material randomness influences the dynamic fracture as well. Deterministic and probabilistic simulations are compared and the influence of material parameters and their strain rate dependence are discussed.

Numerical study on secondary flows of viscoelastic fluids in straight ducts: Origin analysis and parametric effects

Abstract Numerical simulations were conducted on viscoelastic fluid flows in straight ducts with different cross sections, for which the origin of secondary flows and influences of material parameters and flow passage geometrical configuration were numerically investigated. The Giesekus constitutive model was chosen to describe the viscoelastic fluid with the second normal stress difference N 2 , and solved by embedding UDF (User-defined Function) into the CFD (computational fluid dynamics) code FLUENT. The origin of such kind of secondary flow was theoretically studied from the perspective of the budget of vorticity energy for the first time. Sufficient and necessary condition for the existence of secondary flow was then developed in terms of N 2 , the gradient of N 2 and cross-sectional geometry ϑ (i.e., generation term E Ω ). Moreover, helicity density was considered as an excellent indicator of secondary flow pattern. Effects of material properties (including anisotropic parameter α , solvent viscosity ratio β and relaxation time λ ) and flow passage geometrical configuration (aspect ratio of cross sections r , the number of polygon sides n ) on secondary flow strength and pattern were investigated with E Ω . Finally, a universal variable σ s was proposed to describe non-circularity of cross section, based on which the results for ducts with different cross sections can be normalized together.