Calculation Of Material Properties Research Articles

Using a novel microstructure generator to calculate macroscopic properties of multi-phase non-oxide ceramics in comparison to experiments

A novel method to generate microstructures and calculate thermal and elastic properties in non-oxide ceramics, namely in Aluminum Nitride (ALN), Silicon Nitride (Si3N4), and Silicon Carbide (SiSiC) is presented. Structural features like dihedral angle (ALN), anisotropic material properties of grains (Si3N4), and multiscale structure (SiSiC) are considered. To ensure that the simulated structures are close to the real materials, several samples of all ceramics were prepared by the artifact-free method of cross section polishing and imaged by scanning electron microscopy (SEM). By image analysis chord lengths, phase fractions, connectivity between grains or elongation of grains were obtained. The same parameters were extracted from 2-dimensional sections of 3-dimensional representative volume elements produced by a structure generator. Structure generation followed closely the structure formation in the real process. It was repeated until close agreement between experimental and theoretical structures was obtained. Then, thermal and mechanical properties were calculated by finite element simulations. The calculated material properties showed good agreement to the obtained experimental data.

Determination of Flow Curve and Plastic Anisotropy of Medium-thick Metal Plate: Experiments and Inverse Analysis

Sheet bulk metal forming is widely used for medium-thick metal plate due to its convenience in the manufacture of accurately finished 3D functional components. To obtain precise anisotropy and flow curve of metal plate is a prerequisite for correct simulation of sheet bulk metal forming processes. Inverse analysis of compression test was introduced here to evaluate the sensitivity of different flow curve models and geometric influence of compression test specimen. Besides, a methodology was proposed to compute plastic anisotropic coefficients of Hill quadratic yield criterion, which is based on the ratios of flow curves obtained by inverse analysis of compression tests using specimens cut in six directions on the medium-thick metal plate. The obtained flow curves and anisotropic coefficients were compared with those calculated from tensile tests. Flow curves based on inverse analysis of compression tests cover the curves of the tensile tests well, while the anisotropic coefficients are different, especially for the coefficient related to the RT45 direction. To estimate the effectiveness of the proposed method, the calculated material properties and those based on the traditional tensile tests were applied in a rim-hole process simulation. The simulation results based on the material properties from inverse analysis of compression tests accorded with the tested properties better.

Tensile mechanical properties of human forearm tendons

Previous studies of the mechanical properties of tendons in the upper limb have used embalmed specimens or sub-optimal methods of measurement. The aim of this study was to determine the biomechanical properties of all tendons from five fresh frozen cadaveric forearms using updated methodology. The cross-sectional area of tendons was accurately measured using a laser reflectance system. Tensile testing was done in a precision servo-hydraulic device with cryo-clamp fixation. We determined that the cross-sectional area of some tendons is variable and directly influences the calculated material properties; visual estimation of this is unreliable. Data trends illustrate that digital extensor tendons possess the greatest tensile strength and a higher Young's modulus than other tendon types.

Numerical study of the hydrodynamic drag force in atomic force microscopy measurements undertaken in fluids

When atomic force microscopy (AFM) is employed for in vivo study of immersed biological samples, the fluid medium presents additional complexities, not least of which is the hydrodynamic drag force due to viscous friction of the cantilever with the liquid. This force should be considered when interpreting experimental results and any calculated material properties. In this paper, a numerical model is presented to study the influence of the drag force on experimental data obtained from AFM measurements using computational fluid dynamics (CFD) simulation. The model provides quantification of the drag force in AFM measurements of soft specimens in fluids.The numerical predictions were compared with experimental data obtained using AFM with a V-shaped cantilever fitted with a pyramidal tip. Tip velocities ranging from 1.05 to 105μm/s were employed in water, polyethylene glycol and glycerol with the platform approaching from a distance of 6000nm. The model was also compared with an existing analytical model. Good agreement was observed between numerical results, experiments and analytical predictions. Accurate predictions were obtained without the need for extrapolation of experimental data. In addition, the model can be employed over the range of tip geometries and velocities typically utilized in AFM measurements.

Recent developments in molecular simulation approaches to study spherical virus capsids

Viruses are particularly challenging systems to study via molecular simulation methods. Virus capsids typically consist of over 100 subunit proteins and reach dimensions of over 100 nm; solvated viruses capsid systems can be over 1 million atoms in size. In this review, I will present recent developments which have attempted to overcome the significant computational expense to perform simulations which can inform experimental studies, make useful predictions about biological phenomena and calculate material properties relevant to nanotechnology design efforts.

The effects of manufacturing parameters on geometrical and mechanical properties of copper foams produced by space holder technique

We describe a powder metallurgical space holder method to produce open-cell metallic foams. By changing the values of the main manufacturing parameters such as volume percentage and the particle size of the space holder agent, we produce different copper foam samples which cover a wide range of solid fraction, pore size and cell wall thickness. All the specimens were synthesized based on a series of designed experiments. We demonstrate how the foams’ density, cell size and specific surface area can be accurately controlled using two easily adjustable manufacturing parameters. The three-dimensional structure of these foams was investigated using X-ray micro tomography. The image quality is sufficient to measure local structure and connectivity of the foamed material, and the field of view large enough to calculate material properties. By combining the finite element method with the tomographic images, we calculate the mechanical response of the foams. We show that the foams’ bulk and shear moduli are strongly correlated to their cell size, cell wall thickness and specific surface area. These parameters can be easily controlled during manufacturing.

Prediction of material properties of biaxial and triaxial braided textile composites

Biaxial and triaxial braided composites are modeled using finite element methods to predict effective material properties: for biaxial braids, diamond pattern (1/1), regular pattern (2/2), and Hercules pattern (3/3) are modeled, while for triaxial braids, a regular pattern (2/2) is modeled. A micromechanical approach is adopted to calculate material properties of the tows, which are critical compositions of braided composites. By applying periodical boundary conditions (PBC), four representative unit cells (RUC) in correspondence to the four types of braids are analyzed and compared. Subsequently, effective material properties are obtained with the braiding angle varying from 15° to 75° with an increment of 5°, from which the variation of the engineering constants with the braiding angle is studied. The prediction results are compared with the experimental values for two material systems, and good agreement is achieved.

Thermodynamic Calculations and Kinetic Simulations of some Advanced Materials

The Thermo-Calc and DICTRA software/database/programming-interface packages, through many successful applications in the fields of Computational Thermodynamics and Kinetics, have tremendously contributed to quantitative conceptual design and processing of various advanced materials. Materials scientists and engineers can efficiently apply such unique and comprehensive tools in calculating material properties, predicting material structures and simulating material processes, which are of wide-ranging industrial and academic importance.

205204 溶接後熱処理の応力緩和シミュレーションに必要なクリープ特性の評価(一般01 材料科学・材料力学3)

Creep properties for stress mitigation simulation in post weld heat treatment (PWHT) were specified. Material properties of both the deposited metal and the base metal of nickel based alloy and austenitic stainless steel were examined. First, creep tests were conducted at 625℃, which is a holding temperature in PWHT. Test specimens were subjected to certain stresses, and creep strain rates were measured. The power law model was used to simulate the creep strain rates. Material properties for the power law model were calculated from the creep strain rate data. Then, relaxation tests were conducted at 625℃. Test specimens were subjected to certain strains, and stress mitigation was measured. The experimentally measured stress mitigation data were simulated using the power law model with the calculated material properties. The simulation data showed good agreement with the experimental data. Accordingly, the material properties calculated in this study can be considered valid.

Development of a Software to Optimize Parameters of Interatomic Potentials for Solid Systems

Generally, it is difficult to develop practical interatomic potentials which can be used in classical molecular dynamics calculations, since a method for development had not been established. In order to solve such problems, we had proposed a framework to develop interatomic potentials. However, the framework had not been widely used due to the difficulty of coding a process to optimize potential-parameters, which was involved in the framework. In this work, a practical software to optimize potential-parameters for solid systems, was developed based on real-coded genetic algorithm (GA). Fitness (=optimization-function) in GA for potential-parameter optimization could be calculated in practical time, and a concept of the corresponded module in GA-code was proposed. The developed software has an extensible structure: a user can define a new crystal-structure, or a new potential function to use in potential-parameter optimization by defining a corresponded class for that in separated header files. Convenient interfacial class to calculate equilibrium material properties of crystals and that to calculate material properties of user-inputted atomic-structures were prepared to define optimization-function. Several sample input files and header files were available for easy starting. As a result of distribution, several effective interatomic potentials were developed by using the software. As a sample of the development of interatomic potential, Tersoff-type potential for SiO2 systems were shown.

Tidal evolution of close binary asteroid systems

We provide a generalized discussion of tidal evolution to arbitrary order in the expansion of the gravitational potential between two spherical bodies of any mass ratio. To accurately reproduce the tidal evolution of a system at separations less than 5 times the radius of the larger primary component, the tidal potential due to the presence of a smaller secondary component is expanded in terms of Legendre polynomials to arbitrary order rather than truncated at leading order as is typically done in studies of well-separated system like the Earth and Moon. The equations of tidal evolution including tidal torques, the changes in spin rates of the components, and the change in semimajor axis (orbital separation) are then derived for binary asteroid systems with circular and equatorial mutual orbits. Accounting for higher-order terms in the tidal potential serves to speed up the tidal evolution of the system leading to underestimates in the time rates of change of the spin rates, semimajor axis, and mean motion in the mutual orbit if such corrections are ignored. Special attention is given to the effect of close orbits on the calculation of material properties of the components, in terms of the rigidity and tidal dissipation function, based on the tidal evolution of the system. It is found that accurate determinations of the physical parameters of the system, e.g., densities, sizes, and current separation, are typically more important than accounting for higher-order terms in the potential when calculating material properties. In the scope of the long-term tidal evolution of the semimajor axis and the component spin rates, correcting for close orbits is a small effect, but for an instantaneous rate of change in spin rate, semimajor axis, or mean motion, the close-orbit correction can be on the order of tens of percent. This work has possible implications for the determination of the Roche limit and for spin-state alteration during close flybys.

복합재료판 구조물의 고유진동수 위상최적화에 관한 연구

The aim of this research is to construct eigenfrequency optimization codes for plates with Arbitrary Rank Microstructures. From among noise factors, resonance sound is main reason for floor's solid noise. But, Resonance-elusion design codes are not fixed so far. Besides, The prediction of composite material's capability and an resonance elusion by controlling natural frequency of plate depend on designer's experiences. In this paper, First, using computer program with arbitrary rank microstructure, variation on composite material properties is studied, and then natural frequency control is performed by plate topology optimization method. The results of this study are as followed. 1) Programs that calculate material properties along it's microstructure composition and control natural frequency on composite material plate are coded by Homogenization and Topology Optimization method. and it is examined by example problem. 2) Equivalent material properties, calculated by program, are examined for natural frequency. In this paper, Suggested programs are coded using <TEX>$Matlab^{TM}$</TEX>, Feapmax and Feap Library with Homogenization and Topology Optimization method. and Adequacy of them is reviewed by performing the maximization or minimization of natural frequency for plates with isotropic or anisotropic materials. Since the programs has been designed for widely use. If the mechanism between composite material and other structural member is identified, extension application may be possible in field of structure maintenance, reinforcement etc. through application of composite material.

Polymerisation stress modelling in acrylic bone cement

Fatigue failure of the cement mantle has been proposed as one of the failure processes contributing to aseptic loosening of cemented joint replacements. It has also been suggested that fatigue failure is dramatically accelerated by residual stress generated during the cement polymerisation process. Previous computational models of the polymerisation process have investigated only the latter part of polymerisation by assuming both instantaneous hardening of the material (a stress locking point) and that all residual stress results from thermal shrinkage after this stress locking point. In this study, finite element models which use the local degree of polymerisation to calculate material properties and shrinkage have been used to predict residual stresses in two models of total hip replacement cement mantles. Results indicate that the final value of cement mantle stress may not be the highest stresses that the cement is subjected to during the polymerisation process. Two models are presented, a 2-dimensional model, which was adapted from a similar model in the literature ( Lennon and Prendergast, 2002) and a 3-dimensional concentric-cylinders model. In both cases a chemical kinetics model was used to predict the progress of the polymerisation reaction and a second linear model used to predict cement mechanical properties and density, and so stress generation and volume change, over time. There was good agreement of the results of the 2D model with its counterpart in the literature. For the 3D model, the final residual stress magnitudes and patterns showed good agreement with similar physical and computational models in the literature.

Performance Characteristics of a New Generation Pressure Microsensor for Physiologic Applications

A next generation fiber-optic microsensor based on the extrinsic Fabry-Perot interferometric (EFPI) technique has been developed for pressure measurements. The basic physics governing the operation of these sensors makes them relatively tolerant or immune to the effects of high-temperature, high-EMI, and highly-corrosive environments. This pressure microsensor represents a significant improvement in size and performance over previous generation sensors. To achieve the desired overall size and sensitivity, numerical modeling of diaphragm deflection was incorporated in the design, with the desired dimensions and calculated material properties. With an outer diameter of approximately 250 microm, a dynamic operating range of over 250 mmHg, and a sampling frequency of 960 Hz, this sensor is ideal for the minimally invasive measurement of physiologic pressures and incorporation in catheter-based instrumentation. Nine individual sensors were calibrated and characterized by comparing the output to a U.S. National Institute of Standards and Technology (NIST) Traceable reference pressure over the range of 0-250 mmHg. The microsensor performance demonstrated accuracy of better than 2% full-scale output, and repeatability, and hysteresis of better than 1% full-scale output. Additionally, fatigue effects on five additional sensors were 0.25% full-scale output after over 10,000 pressure cycles.

Theoretical study of optical characteristics of multilayer coatings ZnO/CdS/CdTe using first-principles calculations

A new method for predicting optical characteristics of multilayer coatings based on calculated material properties is presented. This method combines the use of the full potential linear-augmented plane wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) and the optical matrix approach for modeling the multilayer assembly. The simulation process is applied to thin films of the II–VI semiconductors compounds. The optical constants of each thin film are determined by using the first principle calculations. Each layer is represented by the square Abeles matrix, including all necessary data in the calculation of the optical characteristics (as transmittance, reflectance and absorbance). The simulation of multilayer optical response includes the effect of thickness, light polarization and incident angle. The obtained results are helpful in the design of the multilayer systems with required properties.

Incorporating self‐consistently calculated mineral physics into thermochemical mantle convection simulations in a 3‐D spherical shell and its influence on seismic anomalies in Earth's mantle

Phase assemblages of mantle rocks calculated from the ratios of five oxides (CaO‐FeO‐MgO‐Al2O3‐SiO2) by free energy minimization were used to calculate the material properties density, thermal expansivity, specific heat capacity, and seismic velocity as a function of temperature, pressure, and composition, which were incorporated into a numerical thermochemical mantle convection model in a 3‐D spherical shell. The advantage of using such an approach is that thermodynamic parameters are included implicitly and self‐consistently, obviating the need for ad hoc parameterizations of phase transitions which can be complex in regions such as the transition zone particularly if compositional variations are taken into account. Convective planforms for isochemical and thermochemical cases are, however, not much different from those computed using our previous, simple parameterized reference state, which means that our previous results are robust in this respect. The spectrum and amplitude of seismic velocity anomalies obtained using the self‐consistently calculated material properties are more “realistic” than those obtained when seismic velocity is linearly dependent on temperature and composition because elastic properties are dependent on phase relationship of mantle minerals, in other words, pressure and temperature. In all cases, the spectra are dominated by long wavelengths (spherical harmonic degree 1 to 2), similar or even longer wavelength than seismic tomographic models of Earth, which is probably due to self‐consistent plate tectonics and depth‐dependent viscosity. In conclusion, this combined approach of mantle convection and self‐consistently calculated mineral physics is a powerful and useful technique for predicting thermal‐chemical‐phase structures in Earth's mantle. However, because of uncertainties in various parameters, there are still some shortcomings in the treatment of the postperovskite phase transition. Additionally, transport properties such as thermal conductivity and viscosity are not calculated by this treatment and are thus subject to the usual uncertainties.

Enhanced spin-density wave in LaFeSbO from first principles

We predict atomic, electronic, and magnetic structures of a hypothetical compound LaFeSbO by first-principles density-functional calculations. It is shown that LaFeSbO prefers an orthorhombic stripe-type antiferromagnetic phase [i.e., spin-density wave (SDW) phase] to the tetragonal nonmagnetic (NM) phase, with a larger Fe spin moment and greater SDW-NM energy difference than those of LaFeAsO. In the NM-phase LaFeSbO, the electronic bandwidth near the Fermi energy is reduced compared with LaFeAsO, indicating smaller orbital overlap between $\text{Fe}\text{ }d$ states and subsequently enhanced intra-atomic exchange coupling. The density of states at the Fermi energy is greatly increased and the calculated Fermi surface in the NM phase shows increased nesting between hole and electron sheets compared with LaFeAsO. Based on monotonous changes found in our calculated material properties of LaFePnO ($\text{Pn}=\text{P}$, As, and Sb) along with reported superconducting properties of doped LaFePO and LaFeAsO, doped LaFeSbO is possibly a candidate of superconductor with a higher superconducting transition temperature.

Multi-scale modelling of 3D multi-layered braided composite tubes

The mechanical behavior of 3Dmulti-layeredbraidedcomposite tubes was analyzed using a multi-scale modelling approach. Considering the braiding parameters and the fiber volume fraction of the composite tubes, firstly a unit-cell of the composites was determined based on the motion of yarn carriers and modeled using TEXGEN software. The unit-cell was imported into finite element software to calculate its meso-scale material properties. In this calculation the yarns in the unit-cell were assumed to be solid constituents without considering each filament in them, i.e., a meso-scale approach was adopted for the yarn modelling. Then, the calculated material properties were used to analyze macroscopic deformation behavior of the composite tubes using finite element analysis. The validity of the current meso- and macro-scale analysis will be discussed for designing composite tubes such as mountain bike (MTB) frames, e.g., in finding optimums of the fiber volume fraction, the braiding angle, and the number of layers.

High-accuracy V-bending system by real time identifying material property

A bending system was proposed in order to realize high precision V-bending. This system can calculate the appropriate bending condition during work progress and its calculation algorithm is satisfactorily time-efficient for a practical use. The essential point of this system is that the work-piece is released once just before the punch reaches the final target position. Using this method the system can collect the data, calculate material properties and predict the final target position. This position is determined by considering the spring-back after release. However, the spring-back is not constant due to the differences of material properties between each work-piece. In the proposed system, the material properties: flow stress, Young's modulus and hardening ratio were calculated based on information of load, tilt angle of plate and spring-back at the pre-release phase for determination of appropriate bending conditions. The proposed bending system can realize high-precision bending and has successfully been adopted in actual operation.

Inversion of time‐dependent nuclear well‐logging data using neural networks

ABSTRACTThe purpose of this work was to investigate a new and fast inversion methodology for the prediction of subsurface formation properties such as porosity, salinity and oil saturation, using time‐dependent nuclear well logging data. Although the ultimate aim is to apply the technique to real‐field data, an initial investigation as described in this paper, was first required; this has been carried out using simulation results from the time‐dependent radiation transport problem within a borehole. Simulated neutron and γ‐ray fluxes at two sodium iodide (NaI) detectors, one near and one far from a pulsed neutron source emitting at ∼14 MeV, were used for the investigation. A total of 67 energy groups from the BUGLE96 cross section library together with 567 property combinations were employed for the original flux response generation, achieved by solving numerically the time‐dependent Boltzmann radiation transport equation in its even parity form. Material property combinations (scenarios) and their correspondent teaching outputs (flux response at detectors) are used to train the Artificial Neural Networks (ANNs) and test data is used to assess the accuracy of the ANNs. The trained networks are then used to produce a surrogate model of the expensive, in terms of computational time and resources, forward model with which a simple inversion method is applied to calculate material properties from the time evolution of flux responses at the two detectors.The inversion technique uses a fast surrogate model comprising 8026 artificial neural networks, which consist of an input layer with three input units (neurons) for porosity, salinity and oil saturation; and two hidden layers and one output neuron representing the scalar photon or neutron flux prediction at the detector. This is the first time this technique has been applied to invert pulsed neutron logging tool information and the results produced are very promising. The next step in the procedure is to apply the methodology to real data.