scholarly journals An Upper Bound of Longitudinal Elastic Modulus for Unidirectional Fibrous Composites as Obtained from Strength of Materials Approach

2018 ◽  
Author(s):  
John Venetis ◽  
Emilio Sideridis
Keyword(s):  
Elastic Modulus ◽  
Upper Bound ◽  
Theoretical Models ◽  
The Novel ◽  
Fibrous Composites ◽  
Strength Of Materials ◽  
Fiber Concentration ◽  
Longitudinal Elastic Modulus ◽  
The Matrix ◽  
Specific Variation

In this paper, an upper bound of the longitudinal elastic modulus of  unidirectional   fibrous composites is proposed according to strength of materials approach, on the premise that the fiber is much stiffer than the matrix. In the mathematical derivations, the concept of boundary interphase between fiber and matrix was also taken into account and the main objective of this work is the attainment of an upper bound for the interphase stiffness with respect to fiber concentration by volume. The novel element here is that the authors have not taken into consideration any specific variation law to approximate the interphase modulus. The theoretical results arising from the proposed formula were compared with those obtained from some reliable theoretical models as well as with experimental data found in the literature, and a satisfactory agreement was observed.

scholarly journals An Upper Bound of Longitudinal Elastic Modulus for Unidirectional Fibrous Composites as Obtained from Strength of Materials Approach

Fibers ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 57
Author(s):  
John Venetis ◽  
Emilio Sideridis
Keyword(s):  
Elastic Modulus ◽  
Upper Bound ◽  
Intermediate Phase ◽  
Analytical Models ◽  
The Novel ◽  
Fibrous Composites ◽  
Strength Of Materials ◽  
Longitudinal Elastic Modulus ◽  
Theoretical Predictions ◽  
The Matrix

In this paper, the authors introduce an upper bound of the longitudinal elastic modulus of unidirectional fibrous composites to strength of materials approach, provided that the fibre is much stiffer than the matrix. In the mathematical derivations resulting in this bound, the concept of boundary interphase between filler and matrix was also taken into consideration. The novel element of this work is that the authors have not taken into account any particular variation law to approach the stiffness of this intermediate phase. The theoretical predictions were compared with those obtained from some accurate analytical models as well as with experimental data found in the literature, and a satisfactory accordance was observed.

A lower bound of longitudinal elastic modulus for three-phase fibrous composites

2017 ◽  
Vol 24 (1) ◽  
pp. 72-84
Author(s):  
J Venetis ◽  
E Sideridis
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Composite Materials ◽  
Lower Bound ◽  
Polymer Composite ◽  
Differential Calculus ◽  
Reasonable Agreement ◽  
Theoretical Models ◽  
Three Phase ◽  
Longitudinal Elastic Modulus

A lower bound of the longitudinal elastic modulus of polymer composite materials reinforced with unidirectional continuous fibres is obtained by means of a Differential Calculus approach. In the mathematical derivations, the concept of interphase between the fibre and matrix was also taken into consideration. The three phases are considered as isotropic. The results obtained from the proposed formula were compared with those arising from some reliable and accurate theoretical models as well as with experimental data found in the literature, and a reasonable agreement was observed.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

Gear transmission error outside the normal path of contact due to corner and top contact

1999 ◽  
Vol 213 (4) ◽  
pp. 389-400 ◽  
Author(s):  
R. G. Munro ◽  
L Morrish ◽  
D Palmer
Keyword(s):  
Dynamic Test ◽  
Theoretical Models ◽  
Transmission Error ◽  
Helical Gear ◽  
Gear Transmission ◽  
The Novel ◽  
Transmission Systems ◽  
Helical Gears ◽  
Tooth Stiffness ◽  
Top Contact

This paper is devoted to a phenomenon known as corner contact, or contact outside the normal path of contact, which can occur in spur and helical gear transmission systems under certain conditions. In this case, a change in position of the driven gear with respect to its theoretical position takes place, thus inducing a transmission error referred to here as the transmission error outside the normal path of contact (TEo.p.c). The paper deals with spur gears only, but the results are directly applicable to helical gears. It systematizes previous knowledge on this subject, suggests some further developments of the theory and introduces the novel phenomenon of top contact. The theoretical results are compared with experimental measurements using a single flank tester and a back-to-back dynamic test rig for spur and helical gears, and they are in good agreement. Convenient approximate equations for calculation of TEo.p.c suggested here are important for analysis of experimental data collected in the form of Harris maps. This will make possible the calculation of tooth stiffness values needed for use in theoretical models for spur and helical gear transmission systems.

scholarly journals The Algebraic Degree of Phase-Type Distributions

2010 ◽  
Vol 47 (03) ◽  
pp. 611-629
Author(s):  
Mark Fackrell ◽  
Qi-Ming He ◽  
Peter Taylor ◽  
Hanqin Zhang
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Polynomial Algorithm ◽  
Algebraic Degree ◽  
Nonnegative Matrices ◽  
Stieltjes Transform ◽  
Special Cases ◽  
Phase Type ◽  
Phase Type Distributions ◽  
The Matrix

This paper is concerned with properties of the algebraic degree of the Laplace-Stieltjes transform of phase-type (PH) distributions. The main problem of interest is: given a PH generator, how do we find the maximum and the minimum algebraic degrees of all irreducible PH representations with that PH generator? Based on the matrix exponential (ME) order of ME distributions and the spectral polynomial algorithm, a method for computing the algebraic degree of a PH distribution is developed. The maximum algebraic degree is identified explicitly. Using Perron-Frobenius theory of nonnegative matrices, a lower bound and an upper bound on the minimum algebraic degree are found, subject to some conditions. Explicit results are obtained for special cases.

A Yield Criterion of Porous Materials With Anisotropy Caused by Geometry or Distribution of Pores

1991 ◽  
Vol 113 (4) ◽  
pp. 425-429 ◽  
Author(s):  
T. Hisatsune ◽  
T. Tabata ◽  
S. Masaki
Keyword(s):  
Velocity Field ◽  
Porous Materials ◽  
Upper Bound ◽  
Volume Fraction ◽  
Yield Criterion ◽  
Longitudinal Direction ◽  
Axisymmetric Deformation ◽  
The Other ◽  
The Matrix ◽  
Spherical Cells

Axisymmetric deformation of anisotropic porous materials caused by geometry of pores or by distribution of pores is analyzed. Two models of the materials are proposed: one consists of spherical cells each of which has a concentric ellipsoidal pore; and the other consists of ellipsoidal cells each of which has a concentric spherical pore. The velocity field in the matrix is assumed and the upper bound approach is attempted. Yield criteria are expressed as ellipses on the σm σ3 plane which are longer in longitudinal direction with increasing anisotropy and smaller with increasing volume fraction of the pore. Furthermore, the axes rotate about the origin at an angle α from the σm-axis, while the axis for isotropic porous materials is on the σm-axis.

Fabrication and Mechanical Properties of Dense/Porous β-Tricalcium Phosphate Bioceramics

2007 ◽  
Vol 330-332 ◽  
pp. 907-910
Author(s):  
Fa Ming Zhang ◽  
Jiang Chang ◽  
Jian Xi Lu ◽  
Kai Li Lin
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Exponential Growth ◽  
Weight Bearing ◽  
Area Ratio ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Matrix ◽  
Porous Bioceramics

Attempt to increase the mechanical properties of porous bioceramics, a dense/porous structured β-TCP bioceramics that mimic the characteristics of nature bone were fabricated. Experimental results show that the dense/porous structured β-TCP bioceramics demonstrated excellent mechanical properties with compressive strength up to 74 MPa and elastic modulus up to 960 MPa, which could be tailored by the dense/porous cross-sectional area ratio obeying the rule of exponential growth. The interface between the dense and porous bioceramics is connected compactly and tightly with some micropores distributed in the matrix of both porous and dense counterparts. The dense/porous structure of β-TCP bioceramics may provide an effective way to increase the mechanical properties of porous bioceramics for bone regeneration at weight bearing sites.

Investigation of Thermochemical Hydrogen Production via the Novel Thermo-Mechanical Stabilized Iron Oxide-Zirconia Porous Structure

2013 ◽  
Author(s):  
Ayyoub M. Mehdizadeh ◽  
Kelvin Randhir ◽  
James F. Klausner ◽  
Nicholas AuYeung ◽  
Fotouh Al-Raqom ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Porous Structure ◽  
Chemical Reactivity ◽  
Thermal Reduction ◽  
The Novel ◽  
Concentrated Solar Energy ◽  
The Matrix ◽  
Unique Method ◽  
Laboratory Scale Reactor ◽  
The Stability

In this study we have developed a unique method for synthesizing very reactive water splitting materials that will remain stable at temperatures as high as 1450 °C to efficiently produce clean hydrogen from concentrated solar energy. The hydrogen production for a laboratory scale reactor using a “Thermo-mechanical Stabilized Porous Structure” (TSPS) is experimentally investigated for oxidation and thermal reduction temperatures of 1200 and 1450 °C, respectively. The stability and reactivity of a 10 g TSPS over many consecutive oxidation and thermal reduction cycles for different particle size ranges has been investigated. The novel thermo-mechanical stabilization exploits sintering and controls the geometry of the matrix of particles inside the structure in a favorable manner so that the chemical reactivity of the structure remains intact. The experimental results demonstrate that this structure yields peak hydrogen production rates of 1–2 cm3/(min.gFe3O4) during the oxidation step at 1200 °C and the 30 minute thermal reduction step at 1450 ° C without noticeable degradation over many consecutive cycles. The hydrogen production rate is one of the highest yet reported in the open literature for thermochemical looping processes using thermal reduction. This novel process has strong potential for developing an enabling technology for efficient and commercially viable solar fuel production.

scholarly journals Breach of Contact: An Intercultural Reading of China Miéville's 'The City and The City'

2014 ◽  
Vol 11 (2) ◽  
Author(s):  
Barbara Elizabeth Hanna ◽  
Peter Cowley
Keyword(s):  
Theoretical Models ◽  
The Other ◽  
Intercultural Training ◽  
The Novel ◽  
Intercultural Encounters ◽  
Training Courses ◽  
City States ◽  
City Relations ◽  
The City ◽  
Two Populations

China Miéville’s 2009 'Weird' detective novel The City and The City is a tale of two city states, culturally distinct, between which unpoliced contact is forbidden. While residents of each city can learn about the other’s history, geography, politics, see photographs and watch news footage of the other city, relations between the two are tightly monitored and any direct contact requires a series of protocols, some of which might seem reasonable, or at least familiar: entry permits, international mail, international dialing codes, intercultural training courses. What complicates these apparently banal measures is the relative positioning of the two cities, each one around, within, amongst the other. The two populations live side by side, under a regime which requires ostentatious and systematic disregard or 'unnoticing' of the other in any context but a tightly regulated set of encounters. For all that interculturality is endemic to everyday life in the 21st century, what is striking is that critical and popular uptake of this novel so frequently decries the undesirability, the immorality even, of the cultural separation between the two populations, framing it as an allegory of unjust division within a single culture, and thus by implication endorsing the erasure of intercultural difference. We propose an alternative reading which sees this novel as exploring the management of intercultural encounters, and staging the irreducibility of intercultural difference. We examine how the intercultural is established in the novel, and ask how it compares to its representations in prevalent theoretical models, specifically that of the Third Place.

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