Present Analysis Procedure Research Articles

Seismic analysis of a half-space containing a water-filled valley under 2D oblique incident waves by finite-infinite element method

This paper presents for the first time the seismic analysis of a half-space containing a water-filled valley under 2D oblique P- and SV-waves by the finite-infinite element (FE-IFE) method. The equivalent seismic forces for the Chi-Chi Earthquake on the near-field boundary are calculated based on the exact free-field response. The effect of water-filled valleys on the seismic response of the half-space is a problem not well treated previously, which is considered through the soil-liquid interface in this paper. The present analysis procedure including the soil-liquid coupling is verified against Luco et al. for a half-space with an empty semi-circular canyon. New findings of this paper include: (1) The horizontal acceleration is amplified on the “near” side (to incident waves) of the valley, which is higher for filled valleys under P-waves, but decayed by the filled valley under SV-waves. (2) The effect of overlying water body on vertical acceleration is less significant for SV- than for P-waves. (3) For SV-waves with overly critical angles, the horizontal acceleration is larger for the “far” than “near” side, and larger difference exists for deeper filled valleys, coupled by amplified vertical acceleration. Additional observations were made for the numerical analysis inside the text.

Parameter Interval Uncertainty Analysis of Internal Resonance of Rotating Porous Shaft-Disk-Blade Assemblies Reinforced by Graphene Nanoplatelets.

This paper conducts a parameter interval uncertainty analysis of the internal resonance of a rotating porous shaft–disk–blade assembly reinforced by graphene nanoplatelets (GPLs). The nanocomposite rotating assembly is considered to be composed of a porous metal matrix and graphene nanoplatelet (GPL) reinforcement material. Effective material properties are obtained by using the rule of mixture and the Halpin–Tsai micromechanical model. The modeling and internal resonance analysis of a rotating shaft–disk–blade assembly are carried out based on the finite element method. Moreover, based on the Chebyshev polynomial approximation method, the parameter interval uncertainty analysis of the rotating assembly is conducted. The effects of the uncertainties of the GPL length-to-width ratio, porosity coefficient and GPL length-to-thickness ratio are investigated in detail. The present analysis procedure can give an interval estimation of the vibration behavior of porous shaft–disk–blade rotors reinforced with graphene nanoplatelets (GPLs).

Frother distribution in an industrial coal flotation circuit

ABSTRACT In reuse of process water in flotation plants, the inability to measure residual frother concentrations in both flotation and plant water circuits in real time has created challenges for flotation process control. We previously developed a simple and fast method to measure frother concentration based on the guest–host interactions between frother molecules and specially formulated liquid comprising cyclodextrin and pyrene. In the present study, the formulation and analysis procedure were upgraded to further improve the measurement sensitivity. The potential of the present method was demonstrated through methyl isobutyl carbinol (MIBC) concentration measurement at six different locations across an industrial coal flotation circuit. The measured MIBC distribution was in good agreement with that obtained using the colorimetric method developed by Finch and coworkers at McGill University. The implications of the established MIBC distribution in the coal flotation circuit for frother dosing and water reuse were discussed.

Process Sensitivity and Significant Parameters Investigation in Metal Fused Filament Fabrication of Ti-6Al-4V

Metal fused filament fabrication (MF3) combines fused filament fabrication and sintering processes to fabricate complex metal components. To design for MF3, an understanding of part geometry, printing parameters and material properties' effects on processability, part quality and ensuing properties is required. However, such investigation is a complex problem having several linked geometry, process and material variables to be considered that influence the process outcome. Moreover, such investigations through the experimental trial-and-error approach are costly and time-consuming, and sometimes not even feasible due to so many input variables involved. This study investigated the sensitivity of key output parameters toward each of the input parameters in MF3. FEA-based thermomechanical process simulations were used to estimate the process outcome in response to variable inputs, and a systematic procedure for sensitivity analysis has been successfully developed for the printing phase of the MF3 process. Dimensionless sensitivity values for all output parameters were calculated in the response of each input parameter, which allows parameters with different units to be compared quantitatively with a single yardstick. Moreover, three different part geometries were studied to identify how the process sensitivity varies with part geometry. For each output parameter, the most influential input parameters were identified from the whole set of input parameters and their influence trends were evaluated for different part geometries. The present sensitivity analysis procedure is expected to be an invaluable tool not only for process parameters optimization but also for the development of material and part geometry for MF3, hence enabling design for MF3 (DfMF3).

Stress Analysis and Performance Evaluation of Flange Spool Subjected to Pressure

In the present scenario, the prevention of failure of a component is having a vital role in piping industry. Failure of a single component can cease the entire functionality of the system. So the prevention of failure is significant to satisfy the customer needs not only aesthetic but also functionality, reliability and utility of the system. With the advancement of new technologies, finding out the failures and giving a pertinent solution is possible. Value engineered component is an added advantage to the industry in all aspects. A flange spool is a basic type of dismantling joint that connect long pipes with flanges at the ends so that they can be bolted to another pipe with matching flange. The flange joint involves interaction between bolts, flange and gasket and it is the most essential part of Pressure vessel, Condenser, Heat exchanger and Storage tank. This flange joint aims at preventing fluid leakage and maintaining the structural integrity of the joint. The objective of this paper is to design and analyze a flange spool which is used to carry and transport processed fluid and gas. This work deals with the replacement of molybdenum steel material flange spool with a silicon-manganese flange spool. The modeling was done using CATIA software as per API standards. The flange spool is modeled and simulated using ANSYS 15 Software. The design optimization also showed significant potential improvement in the performance of flange spool. In the present work finite element analysis procedure is used in ANSYS simulation to predict the levels of stress and deformation of flange spool under subjected loads.

Correlations between microstructures and properties of Cu-Ni-Si-Cr alloy

A commercial Cu-Ni-Si-Cr alloy used as a model material was annealed and then peak-aged. The detailed microstructure and property analyses were performed to determine the correlations between the microstructure characteristics and properties. Theoretical calculations, which gave results in good agreement with experimental results, demonstrated that solid-solution scattering and Orowan bypass of precipitate strengthening were the key mechanisms for electrical and mechanical properties, respectively. Furthermore, the effects of composition on the aging behaviors and then electrical and mechanical properties for Cu-Ni-Si series alloys were systematically investigated, showing that both the precipitation extent and mechanical properties improved simultaneously with nominal or effective concentration of the precipitates. Quick estimation on the basis of the present analysis procedure indicates that our work is applicable with high accuracy in real cases.

Temperature stress analysis for bi-modulus beam placed on Winkler foundation

The materials with different moduli in tension and compression are called bi-modulus materials. Graphene is such a kind of materials with the highest strength and the thinnest thickness. In this paper, the mechanical response of the bi-modulus beam subjected to the temperature effect and placed on the Winkler foundation is studied. The differential equations about the neutral axis position and undetermined parameters of the normal strain of the bi-modulus foundation beam are established. Then, the analytical expressions of the normal stress, bending moment, and displacement of the foundation beam are derived. Simultaneously, a calculation procedure based on the finite element method (FEM) is developed to obtain the temperature stress of the bi-modulus structures. It is shown that the obtained bi-modulus solutions can recover the classical modulus solution, and the results obtained by the analytical expressions, the present FEM procedure, and the traditional FEM software are consistent, which verifies the accuracy and reliability of the present analytical model and procedure. Finally, the difference between the bi-modulus results and the classical same modulus results is discussed, and several reasonable suggestions for calculating and optimizing the certain bi-modulus member in practical engineering are presented.

Finite element implementation of Puck's failure criterion for failure analysis of laminated plate subjected to biaxial loadings

The present work proposes a finite element implementation of Puck's failure criterion for ultimate failure analysis of laminated composite plate via well-established higher order shear deformation theory (HSDT). A seven degree of freedom and C0 continuity finite element model using nine noded isoparametric elements is developed for precise computation of ply-by-ply stresses of laminated composite plate subjected to various bi-axial loading. The physically based Puck's failure criterion based on Mohr–Coulomb hypothesis and a degradation model proposed by Puck is used in the present failure analysis procedure for computing first-ply failure (FPF) and last-ply failure (LPF) stress. The finite element implementation is carried out through a finite element code developed in MATLAB, where material non-linearity due to material behaviour under in plane loading and post FPF damage, was taken into account. The results obtained by present approach are compared with classical Tsai–Wu, Tsai–Hill, Lee's failure criteria and experimental results available in various literatures. The FPF and LPF stress envelopes for a critical lamina are obtained for various lamination schemes, thickness ratio, modulus ratio and different biaxial loading conditions for symmetric angle-ply and cross-ply laminates.

Multiscale thermopiezoelectric analysis of laminated plates with integrated piezoelectric fiber composites

Abstract This study presents a comprehensive multiscale analysis of laminated plates with integrated piezoelectric fiber composite actuators. A detailed framework based on the asymptotic expansion homogenization method is developed to couple the microscale and macroscale field variables. The microscale fluctuations in temperature, mechanical displacement and electric potential are related to the macroscale temperature change, mechanical strain and electric fields through 43 distinct characteristic functions. The local thermal, mechanical and charge equilibrium equations yield a system of partial differential equations for the characteristic functions that are solved using standard finite element techniques. The homogenized thermoelectroelastic properties of a representative material element are computed using the characteristic functions and the constituent material properties. The Eshelby–Stroh formalism is used to analytically solve the three-dimensional macroscopic equilibrium equations for thick and thin laminated piezoelectric plates with arbitrary boundary conditions at the edges. Interscale transfer operators emerging from the asymptotic expansion homogenization method relate the macroscale fields to the microscale heat flux, stress and electric displacement in the individual fibers and matrix. The present multiscale analysis procedure is demonstrated by considering two model problems. In the first problem, a simply-supported sandwich plate consisting of a piezoceramic fiber composite shear actuator embedded between two graphite/epoxy layers is studied. The second problem concerns a simply-supported graphite/epoxy substrate with piezoceramic fiber composite extension actuators attached to its top and bottom surfaces. In both model problems, the responses of the laminated plates under thermal and electrical loading conditions are examined. Results are presented for the homogenized material properties, macroscale deformation, macroscale average stresses and microscale stress distributions.

Effective longitudinal shear moduli of periodic fibre-reinforced composites with functionally-graded fibre coatings

This paper presents a homogenization method for unidirectional periodic composite materials reinforced by circular fibres with functionally graded coating layers. The asymptotic homogenization method is adopted, and the relevant cell problem is addressed. Periodicity is enforced by resorting to the theory of Weierstrass elliptic functions. The equilibrium equation in the coating domain is solved in closed form by applying the theory of hypergeometric functions, for different choices of grading profiles. The effectiveness of the present analytical procedure is proved by convergence analysis and comparison with finite element solutions. The influence of microgeometry and grading parameters on the shear stress concentration at the coating/matrix interface is addressed, aimed at the composite optimization in regards to fatigue and debonding phenomena.

Compressive strengths and dynamic response of corrugated metal sandwich plates with unfilled and foam-filled sinusoidal plate cores

The compressive strengths and dynamic response of corrugated sandwich plates with unfilled and foam-filled sinusoidal plate cores are investigated. The “effective” compressive strengths of the unfilled and foam-filled sinusoidal plate cores are derived and numerically analyzed. Finite element method is employed to analyze the dynamic response of fully clamped metal sandwich plates with unfilled and foam-filled sinusoidal plate cores subjected to impulsive loading. Moreover, a simplified plastic-string model is developed to analytically predict the large deflection and time responses of the clamped sandwich plates under impulsive loading. One can see a good agreement between the analytical and numerical predictions. It can be seen that the present analytical procedure is efficient and simple to evaluate the dynamic response of corrugated sandwich plates.

Response spectrum analysis for regular base isolated buildings subjected to near fault ground motions

This paper presents a response spectrum analysis procedure suitable for base isolated regular buildings subjected to near fault ground motions. This procedure is based on the fact that the isolation system may be treated separately since the superstructure behaves as a rigid body on well selected isolation systems. The base isolated building is decomposed into several single-degree of freedom systems, the first one having the total weight of the building is isolated while the remainder when superposed they replicate approximately the behavior of the superstructure. The response of the isolation system is governed by a response spectrum generated for a single isolated mass. The concept of the procedure and its application for the analysis of base isolated structures is illustrated with an example. The present analysis procedure is shown to be accurate enough for the preliminary design and overcomes the limits of applicability of the conventional linear response spectrum analysis.

Creep Failure of Roof Stratum Above Mined-Out Area

By taking into account the rheological behavior of the rock mass, the creep failure of a roof stratum seated on pillars in mined-out area is analyzed through a newly developed visco-elastic model. The time-dependent deflection of the roof stratum is obtained by numerical inversion of Laplace transform. The study shows that when creep properties of both the pillars and roof stratum are considered, the expected deflection in the roof stratum increases with time. Consequently, the roof would fail when the critical tensile stress is reached as the result of the increased deflection. To demonstrate the present analytical procedure, the failure time of roof stratum of the Xingtai Gypsum Mine in China was estimated, and the results obtained agreed with the observation. The case study indicates that the analytic approach provides a new way to assess the potential impact of the time-dependence of the roof stratum deformation and is useful in predicting its stability above a mined-out area.

FIRST-PRINCIPLE ANALYSIS FOR ELECTROMAGNETIC EIGEN MODES IN AN OPTICAL METAMATERIAL SLAB

Electromagnetic (EM) eigen modes in a flshnet metamate- rial (MM) slab have been comprehensively analyzed in an experimental conflguration, based only on precise solutions of Maxwell equations. The EM eigen modes were directly detected from light-absorption peaks. Each mode was explicitly characterized by the dispersion di- agram and EM fleld distributions. It was consequently found that the modes were classifled into either inner modes inside the slab or a mode at the interface with the surrounding media. The symmetric properties of the inner modes were clarifled using group theory. The in- terface mode was found to come from surface plasmon polariton at ∞at metal/insulator interface. The present analysis procedure is generally applicable to MM slabs and enables to clarify the properties without models or assumptions, which have been usually used in MM studies.

Development of analytical procedure for the determination of methyltin, butyltin, phenyltin and octyltin compounds in landfill leachates by gas chromatography–inductively coupled plasma mass spectrometry

Landfilling is the most common disposal of municipal waste. During the decomposition of different waste materials, several toxic compounds are leached. Although organotin compounds (OTC) represent an important group of pollutants in landfill leachates, there are only few analytical procedures reported for their analysis. These procedures are complex or recommend the use of enriched stable isotopes that are available only for butyltins. In the present work analytical procedure for simultaneous routine speciation analysis of methyl-, butyl-, phenyl- and octyl-tins in landfill leachates by GC–ICP-MS was developed. For this purpose the applicability of methanol as co-extraction reagent and Tris–citrate buffer for adjustment of pH for derivatization of OTC in landfill leachates was carefully investigated. The use of NaBEt 4 and NaBPr 4 as derivatization reagents for liquid–liquid extraction into hexane was critically evaluated. 15 m GC column was used for rapid separation of OTC. The developed analytical procedure was sensitive (LODs for OTC investigated in general better than 2 ng Sn L −1) with good repeatability of measurement (RSDs mostly better than 3%) and was successfully applied in the analysis of OTC in landfill leachates using standard addition calibration method. Due to its simplicity and reliability it is appropriate to be used in routine laboratories for monitoring of OTC in landfill leachates.

High-throughput determination of urinary hexosamines for diagnosis of mucopolysaccharidoses by capillary electrophoresis and high-performance liquid chromatography

Mucopolysaccharidoses (MPS) diagnosis is often delayed and irreversible organ damage can occur, making possible therapies less effective. This highlights the importance of early and accurate diagnosis. A high-throughput procedure for the simultaneous determination of glucosamine and galactosamine produced from urinary galactosaminoglycans and glucosaminoglycans by capillary electrophoresis (CE) and HPLC has been performed and validated in subjects affected by various MPS including their mild and severe forms, Hurler and Hurler-Scheie, Hunter, Sanfilippo, Morquio, and Maroteaux-Lamy. Contrary to other analytical approaches, the present single analytical procedure, which is able to measure total abnormal amounts of urinary GAGs, high molecular mass, and related fragments, as well as specific hexosamines belonging to a group of GAGs, would be useful for possible application in their early diagnosis. After a rapid urine pretreatment, free hexosamines are generated by acidic hydrolysis, derivatized with 2-aminobenzoic acid and separated by CE/UV in ∼10 min and reverse-phase (RP)-HPLC in fluorescence in ∼21 min. The total content of hexosamines was found to be indicative of abnormal urinary excretion of GAGs in patients compared to the controls, and the galactosamine/glucosamine ratio was observed to be related to specific MPS syndromes in regard to both their mild and severe forms. As a consequence, important correlations between analytical response and clinical diagnosis and the severity of the disorders were observed. Furthermore, we can assume that the severity of the syndrome may be ascribed to the quantity of total GAGs, as high-molecular-mass polymers and fragments, accumulated in cells and directly excreted in the urine. Finally, due to the high-throughput nature of this approach and to the equipment commonly available in laboratories, this method is suitable for newborn screening in preventive public health programs for early detection of MPS disorders, diagnosis, and their treatment.

A multiscale method for analysis of heterogeneous thin slabs with irreducible three dimensional microstructures

A multiscale method is presented for analysis of thin slab structures in which the microstructures can not be reduced to two-dimensional plane stress models and thus three dimensional treatment of microstructures is necessary. This method is based on the classical asymptotic expansion multiscale approach but with consideration of the special geometric characteristics of the slab structures. This is achieved via a special form of multiscale asymptotic expansion of displacement field. The expanded three dimensional displacement field only exhibits in-plane periodicity and the thickness dimension is in the global scale. Consequently by employing the multiscale asymptotic expansion approach the global macroscopic structural problem and the local microscopic unit cell problem are rationally set up. It is noted that the unit cell is subjected to the in-plane periodic boundary conditions as well as the traction free conditions on the out of plane surfaces of the unit cell. The variational formulation and finite element implementation of the unit cell problem are discussed in details. Thereafter the in-plane material response is systematically characterized via homogenization analysis of the proposed special unit cell problem for different microstructures and the reasoning of the present method is justified. Moreover the present multiscale analysis procedure is illustrated through a plane stress beam example.

P⿢V⿢T relation of MgO derived by simultaneous elastic wave velocity and in situ X-ray measurements: A new pressure scale for the mantle transition region

Simultaneous elastic wave velocity and in situ synchrotron X-ray measurements on polycrystalline MgO were carried out with a V/V0 between ⿱/40.9 and 1.0, which corresponds to the pressures up to 23.6GPa in our P⿢V⿢T relation of MgO, and temperatures up to 1650K using a multi-anvil apparatus. The experimentally observed adiabatic bulk modulus and unit-cell volume led to the first pressure-scale-independent P⿢V⿢T relation of MgO. We obtained a pressure derivative of the isothermal bulk modulus (K⿲T0=4.35(10)) and a volume dependent Grñ/4neisen parameter (q0=1.5(5)), which reproduces the existing pressure-scale-independent data set (temperature dependence of elastic properties at ambient pressure and shock compression). Thus the present experimental and analytical procedure based on simultaneous elastic wave velocity and in situ X-ray diffraction measurements can give strong constraints on P⿢V⿢T equations of states (EoS) of minerals without any pressure scale. The present P⿢V⿢T EoS of MgO determined at pressure and temperature conditions comparable to the mantle transition region should be an important pressure scale to accurately determine the phase transition boundaries in this region. Application of the present pressure scale to the post-spinel transition boundary yields a transition pressure of 23.0GPa at 1873K, which is only marginally lower than that of the 660km discontinuity.

Effective longitudinal shear moduli of periodic fibre-reinforced composites with radially-graded fibres

This paper presents a closed-form expression for the homogenized longitudinal shear moduli of a linear elastic composite material reinforced by long, parallel, radially-graded circular fibres with a periodic arrangement. An imperfect linear elastic fibre-matrix interface is allowed. The asymptotic homogenization method is adopted, and the relevant cell problem is addressed. Periodicity is enforced by resorting to the theory of Weierstrass elliptic functions. The equilibrium equation in the fibre domain is solved in closed form by applying the theory of hypergeometric functions, for new wide classes of grading profiles defined in terms of special functions. The effectiveness of the present analytical procedure is proved by convergence analysis and comparison with finite element solutions. A parametric analysis investigating the influence of microstructural and material features on the effective moduli is presented. The feasibility of mitigating the shear stress concentration in the composite by tuning the fibre grading profile is shown.

The Meibomian puzzle: combining pieces together.

The purpose of this review was to summarize the available information on lipidomic analysis of human meibum and tear film, and critically evaluate the pertinent past and present analytical procedures and results obtained in various laboratories. Human meibum was shown to be a very complex mixture of lipids of various classes. For decades, their exact structures have remained elusive. Because of the limitations of the then-current techniques, most of the complex lipids that constitute meibum could not be analyzed as whole molecules and required prior hydrolysis and/or transesterification of the entire lipid pool. These procedures effectively made it very difficult, and often impossible, to reconstruct the complete structures of the original intact compounds, which prompted us to call this The Meibomian Puzzle. Modern techniques such as high-performance liquid chromatography in combination with mass spectrometry help in solving this puzzle by allowing a researcher to detect and analyze intact molecules of complex lipid compounds, even if present in extremely low concentrations. This current de-facto standard procedure in lipidomic analysis of natural lipids and their mixtures is compared with other experimental techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, gas chromatography, and thin layer chromatography, among the others. The results obtained by older techniques, and their limitations and deficiencies are discussed. It appears that some of the earlier findings did not withstand a scrupulous re-evaluation and need to be modified and/or corrected. The most intriguing development is the virtual absence in meibum of typical phospholipids - an important group of amphiphilic compounds whose role in the human tear film was thought to be to stabilize the entire tear film structure. Instead, another group of previously unidentified compounds, very long chain (O-acyl)-omega-hydroxy fatty acids, appears to be a stabilizing factor which might be related to tear film stability and deterioration. Thus, these compounds may become an important target in biochemistry and (patho)physiology of ocular surface and dry eye research.