Shell Strain Research Articles

Influence analysis of aging of spinal segment on the mechanical behavior of vertebral cortex

The risk of vertebral cortical shell fracture increases with aging. However, it remains unclear how aging contributes to cortex fracture at present. The aim of this study is to make understanding of the mechanism of how the spinal aging influences the cortical shell strain. Two finite element (FE) models of spinal segments (mildly and fully aged) were created, and then were compared to the FE models of the healthy spinal segment. The FE models of the aged spinal segments were generated by modifying both the geometry of the intervertebral disc (IVD) and the material properties of the spinal components. To find out under which case the cortical shell strain was influenced more, we created two types of FE model comparison methods: one with changes only in the spinal material properties and the other with changes only in the IVD geometry. The results showed that the cortical shell strains increased with aging and that compared to the changes of IVD geometry, the changes of spinal material property have a higher influence on the cortical shell strains. This study may suggest that for the prevention and treatment of vertebral cortex fracture, the augmentation of the vertebral body is a more effective treatment.

Vibrations of structurally orthotropic laminated shells under thermal power loading

On the basis of the linearized version of equations obtained in a geometrically nonlinear statement and describing the nonaxisymmetric strain of nonshallow sandwich structure orthotropic shells under thermal power loading, the Rayleigh–Ritz method with polynomial approximation of displacements and shear strains is used to solve the problem of small free vibrations of axisymmetrically thermally preloaded freely supported three-layer conical shell. The causes of dynamical fracture of the shell under study are revealed.

Heritability estimates for shell color-related traits in the golden shell strain of Pacific oyster (Crassostrea gigas) using a molecular pedigree

The Pacific oyster (Crassostrea gigas) is an important aquatic animal species with enormous production and economic benefits, but heritability estimation for shell color applying mixed-family approach and computer vision system has not been performed. In this study, heritability for shell color-related traits was estimated in the golden shell strain of Pacific oyster by fostering a single cohort of 30 families in a nested mating design consisting of 10 sires and 30 dams. After parentage assignment inference based on six microsatellite markers, 690 offspring were included in the subsequent analyses. Using an animal model, at 16months of age, heritability estimates were 0.10±0.12 for L⁎, 0.41±0.16 for a⁎, 0.23±0.15 for b⁎and 0.33±0.19 for ΔE. Genetic correlation between shell color-related traits and growth-related traits were generally inconspicuous ranging from −0.02 to 0.11. Conclusions can be obtained from our study that favourable improvement in aquatic selective breeding would be predictable for the genetic potential of the golden shell color in this strain of Pacific oyster, whereas independent selection conducted at the same time rather than correlative selection would be feasible in the improvement of both types of traits.

Genetic diversity and outlier loci detecting of shell color variation in the Pacific oyster (Crassostrea gigas) by SNP markers

Color polymorphism is relatively common in marine mollusks. Shell color affects the visual perception of products which, consequently, influences consumer preference and product value. To increase the value of the Pacific oyster (Crassostrea gigas ) for the half-shell market, four shell color strains (golden, white, purple, and black) of C. gigas have been developed through successive selective breeding. To investigate genetic variation and identify breeding signatures of C. gigas , the four shell color strains and three wild populations were assessed through using 133 single nucleotide polymorphism (SNP) markers. The genetic diversity analysis demonstrated that the shell color strain exhibited significant reduction in observed number of alleles in comparison with the wild population. However, there is no significant differences of observed heterozygosity and expected heterozygosity were identified among the seven populations. Based on three outlier tests, a total of 16 loci were identified under selection, and four common outlier loci (CgSNP82, CgSNP273, CgSNP646, and CgSNP1131) were detected based on all the methods. FST values showed significant genetic differentiation between shell color strains, as well as between shell color strains and wild populations. The information on the genetic variation and differentiation in shell color strains and wild populations of C. gigas is useful for setting up suitable guidelines for founding and maintaining of cultured stocks. The detected loci might benefit the breeding programs after being tested.

Direct Investment Casting For Pattern Developed By Desktop 3D Printer

Development of RP technologies has encouraged rapid study on portable 3D Printer in which there are varieties of portable 3D printer machines in market. Nevertheless, less reports regarding its consumption of fabricated pattern to be used in direct investment casting. This study has focused on development of ABS P400 pattern in terms of collapsibility behaviour which has capability to be used as sacrificial pattern in direct investment casting. In addition, the internal built structures have been built into two designs such as square and polygon patterns respectively. The patterns were constructed in semi cylindrical geometry which comes with one side opened and one side closed together wrapped with 4 mm of ceramic shell. This experimental were conducted with variation temperature starting from 30°C until 150°C with increment of 5°C per minutes while for the numerical simulation, the temperature selected was between 30 °C to 120 °C with 10 °C increment per minutes. Moreover, the observation was made that glass transition temperature, Tg happened near 110°C. It was observed that the shell cracking happened on the ceramic shell. Other than that, the polygon pattern tends to collapsed inwardly rather than square pattern during the burnout process. A result also shows that, there is significant amount of stress reduction on both square and polygon which was 45 % respectively. Besides that, the amount of strain on pattern itself has shown about 9% reduction. Moreover, there is greater difference in terms of ceramic shell strain reduction which was 38% for square and polygon patterns respectively. Lastly, there is 11 % reduction of strain when compared square and polygon in terms of axial strain on ceramic shell

Development of a High-Temperature Tensile Tester for Micromechanical Characterization of Materials Supporting Meso-Scale ICME Models

A high-temperature tensile tester (HTTT) has been established for the evaluation of micro-mechanical properties of materials at the meso-scale. Metals and ceramics can now be tested at temperatures and strain rates between room temperature and 1200°C and 10−5 s−1 to 10−1 s−1, respectively. The samples are heated in a compact clam shell furnace and strain is measured directly in the sample gage with digital image correlation. The HTTT extracts representative mechanical properties, as evidenced by the similarity in the evaluated micro-tensile properties of a solid solution-strengthened Ni-base superalloy Ni-625 with that of the bulk. The effectiveness of the HTTT has also been demonstrated in evaluating the tensile and stress relaxation/short-term creep properties of a polycrystalline Ni-base superalloy Rene 88DT. The versatility in carrying out tensile, short-term creep, bend tests, and fracture toughness measurements makes the HTTT a robust experimental tool for small-scale and scale-specific benchmarking of multi-scale ICME models.

The experimental and theoretical analysis of high strains and limit states of elastoplasic cylindric shells under the complex loading of pressure and torsion

Nowadays, there are no techniques or software making it possible to simulate the high strains of shells under the combined complex loadings of internal pressure and torsion in the generalized axisymmetrical formulation. These problems are inherent for the experimental investigations of elastoplastic properties of metals and alloys on tubular samples. In this paper, we present the variation–difference method for solving similar problems with taking into consideration high strains and the conditions of an inhomogeneous stress–strain state. We conduct the numerical and experimental studies of the process of elastoplastic deformation and plastic strain localization under the combined loadings of internal pressure and torsion. The mutual influence of torsion on the shell forming under high strains is estimated. The loss of stability with axisymmetric and non-axisymmetric forms is analyzed by 2D and 3D modeling. The simulations results are finally validated by experiments.

Investigation of high elastoplastic straining of shells of revolution under complex tensile and torque loading

A method of the numerical solution of nonlinear unsteady problems of axisymmetric elastoplastic straining of shells of revolution with allowance for torque loading at high strains is proposed. The method is based on the geometrically nonlinear theory of the Timoshenko shells and the plasticity theory with due allowance for combined isotropic and kinematic hardening. The problem is solved with the use of the variational difference method. Results of numerical and experimental investigations of elastoplastic straining of cylindrical shells under proportional and sequential kinematic tensile and torque loading are reported.

Oxygen Reduction Reaction Activities for Various-Monolayer-Thick Pt Shells on Pt x Ni100-x (111)

Introduction Pt-M (M = Fe, Co, Ni, Pd and Cu) core-shell nanoparticles have been intensively studied as oxygen reduction reaction (ORR) catalysts for polymer electrolyte fuel cells (PEFCs). As for the core-shell catalysts, core elements M strongly modify the electronic properties of outermost Pt shell layers, leading to enhanced ORR activities [1]. From electrocatalytic perspectives, however, discussion of ORR enhancement mechanisms is intricate, because the activity enhancements depend on many factors, such as particle sizes, electronic and/or strains of Pt shells, the shell thickness, etc. In this study, we fabricated various-monolayer-thick Pt (111) epitaxial layers on PtxNi100-x (111) (x = 75, 50, 25) substrates model core-shell catalysts by using molecular beam epitaxy (MBE) and discussed Pt/Ni-composition-dependent ORR activity enhancements of the surface Pt shells. Experimental First, PtxNi100-x (111) single crystal substrates were cleaned by Ar+ sputtering and annealing at 1173 K in ultra-high vacuum (UHV). Then, 2 ML-thick Pt was deposited on the cleaned PtxNi100-x (111) substrates by using an electron-beam evaporation method at room temperature, followed by UHV-annealing at 673 K for 10 minutes to flatten the room-temperature-prepared surfaces. The resulting surface structures were verified by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The UHV-fabricated samples were transferred to electrochemical evaluation systems set in a N2-purged glove box without air exposure. CV and LSV measurements were conducted in N2-purged and O2-saturated 0.1 M HClO4, respectively. The ORR activities were evaluated from j k values at 0.9 V vs. RHE by using Koutecky-Levich equation. Results and Discussion STM images of as-prepared Pt2ML/PtxNi100-x (111) surfaces are summarized in Fig. 1(a). Pt2ML/Pt50Ni50 (111) and Pt2ML/Pt25Ni75 (111) surfaces exhibit Moire-like height modulations of the topmost surfaces that probably derived from large lattice mismatches between the 2 ML-Pt (111) shells and PtxNi100-x (111) substrates. In contrast, such a height modulation is absent on the image of Pt2ML/Pt25Ni75 (111). These results suggest that the 2 ML-thick Pt shell layers on the Pt50Ni50 (111) and Pt25Ni75 (111) substrates are subjected to larger compressive strain than that on the Pt75Ni25 (111). Corresponding CV curves of the Pt2ML/PtxNi100-x (111) and Pt (111) are presented in Fig. 1(b). Depending upon the Pt/Ni alloy compositions of the substrates, QHupd were markedly suppressed and OHads regions shifted positively in comparison to those for clean Pt (111). Especially, sharply-peaked “butterfly” features at 0.8 V that might stem from formation of an ordered overlayer of OH-related species on surface Pt (111) lattices [2] disappear for the Pt2ML/Pt50Ni50 (111) and Pt2ML/Pt25Ni75 (111). Initial ORR activities for the Pt2ML/PtxNi100-x (111) and Pt (111) are summarized in Fig. 1(c). The activities increased with increasing the substrate Ni compositions (100-x): the Pt2ML/Pt25Ni75 (111) exhibit 25 fold higher activity relative to that of Pt (111). The results obtained in this study suggest that, with increasing Ni compositions of the Pt-Ni substrates, compressive strains of the Pt shell layer become large, leading to remarkable ORR activity enhancements, in particular, for the Pt2ML/Pt25Ni75 (111) (× 25 vs. Pt (111)). Acknowledgement This study was supported by New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Isothermal Pneumatc Molding of Dome-Shaped Parts of Anisotropic Material in Short-Time Creeping Mode

Studying isothermal straining of dome-shaped shells with the aim of evaluating kinematics of the material flow, stress and strained conditions, force conditions, geometrical dimensions of shells and possibility frontier of straining. The theoretical study of the isothermal straining processes has been performed on the basis of the theory of short-time creeping of anisotropic material. There has been revealed the influence of technological parameters, conditions of loading, and geometry of working tools on the kinematics of material flow produced by friction conditions on the blank and tool contact surfaces, stress and strain states, force conditions, possibility frontiers of form-shaping of operations of isothermal deforming of dome-shaped shells made out of high-strength anisotropic materials. Conclusions. The equations obtained can be used for theoretical analysis of operations of isothermal straining of dome-shaped shells in the mode of short-time creeping.

Impact of an elastic spherical shell on a thin fluid layer

The axisymmetric problem of the impact of a spherical shell on a thin layer of an ideal incompressible fluid is considered. The strains of the spherical shell are described by means of the normal mode method, a decomposition of the fluid flow zone onto subzones proposed in [1] being used for the hydrodynamic analysis and determination of the radius of the wetted surface. The connected problem of hydroelasticity is reduced to an evolutionary system of differential equations and calculations of the features of impact are carried for various parameters of the problem. It is shown that vibrations corresponding to the higher modes develop in the lower part of the shell during the impact on the fluid surface. This is in agreement with experiments and proves the inconsistency of the models in which a few number of modes are taken into account. The thinner is the fluid layer, the higher are the hydrodynamic loads and the amplitude of elastic vibrations of the shell during the impact.

Measurement of strain in InGaN/GaN nanowires and nanopyramids

The growth and optoelectronic properties of core–shell nanostructures are influenced by the strain induced by the lattice mismatch between core and shell. In contrast with planar films, nanostructures contain multiple facets that act as independent substrates for shell growth, which enables different relaxation mechanisms. In this study, X-ray diffraction data are presented that show that InαGa1−αN shells grown on GaN cores are strained along each of the facets independently. Reciprocal space maps reveal multiple Bragg peaks, corresponding to different parts of the shell being strained along the individual facet planes. The strained lattice constants were found from the positions of the Bragg peaks. Vegard's law and Hooke's law for an anisotropic medium were applied in order to find the composition and strain in the InGaN shells. A range of nanowire samples with different InGaN shell thicknesses were measured and it is concluded that, with an In concentration of around 30%, major strain relaxation takes place when the thickness reaches 23 nm. InGaN shells of 6 and 9 nm thickness remain nearly fully strained biaxially along each of the \{10{\overline 1}0\} facets of the nanowires and the \{10{\overline 1}1\} facets of the nanopyramids.

Facile Synthesis of Carbon Supported Pd3Au@Super-Thin Pt Core/Shell Electrocatalyst with a Remarkable Activity for Oxygen Reduction

Aiming at developing a highly active electrocatalyst with high platinum utilization efficiency, we report a facile synthesis of carbon supported Pd3Au@Pt electrocatalyst by chemical reduction of K2PtCl4, K2PdCl4, and aq NaAuCl4 with ascorbic acid (AA) under ambient conditions in the absence of surfactants. The resultant Pd3Au@Pt/C electrocatalyst comprises of a thin platinum layer less than 1 nm in thickness deposited on the outer surface of Pd3Au alloy core with an average diameter of 3.4 nm. Remarkably, Pd3Au@Pt/C exhibited a high mass activity (MA, 939 mAmg(Pt)(-1)) toward oxygen reduction reaction (ORR), which is 4.6 times that of commercial Pt/C (203 mAmg(Pt)(-1)). The durability of Pd3Au@Pt/C is close to that of commercial Pt/C. According to X-ray diffraction (XRD) patterns, the lattice constant of the Pd3Au alloy supported on carbon is determined to be 3.950 angstrom close to yet slightly larger than that of Pt/C (3.920 angstrom), inducing a lateral tensile strain of the platinum shell. Meanwhile, electrons from the Pd3Au core appear transferred to the platinum shell as evidenced by X-ray photoelectron spectroscopy (XPS). We propose that the lateral tensile strain (geometric effect) and the electron transfer (electronic effect) as well as the high platinum utilization efficiency have contributed to the significantly improved electrocatalytic activity of Pd3Au@Pt/C. The coexistence of the lateral tensile strain and the electron transfer in the electrocatalyst with a high ORR activity has not been reported prior to this study.

Strain effects on optical properties of tetrapod-shaped CdTe/CdS core–shell nanocrystals

The exciton states of strained CdTe/CdS core–shell tetrapod-shaped nanocrystals were theoretically investigated by the numerical diagonalization of a configuration interaction Hamiltonian based on the single-band effective mass approximation. We found that the inclusion of strain promotes the type-II nature by confining the electrons and holes in nonadjacent regions. This carrier separation is more efficient than that with type-II spherical nanocrystals. The strain leads to a small blue shift of the lowest exciton energy. Its magnitude is smaller than the red shift induced by increasing the shell thickness. Moreover, the larger arm diameter reduces the influence of both shell thickness and strain on the exciton energy. Considering the broken symmetry, a randomness induced carrier separation was revealed which is unique to a branched core–shell structure. The calculated shell thickness dependence of the emission energy agrees well with available experimental data.

Influence of fiber slippage coefficient distributions on the geometry and performance of composite pressure vessels

In this article, the effects of several slippage coefficient distributions on the geometry, fiber trajectories, and the structural efficiency of non‐geodesic domes are evaluated for composite pressure vessels. Several functions, which ensure C1 continuity of the winding trajectories, are respectively used to describe the slippage coefficient distributions along the fiber paths. With the aid of the fiber slippage law and the optimality condition of equal shell strains, the differential equations that govern the non‐geodesics–based dome shapes and related fiber trajectories are formulated. The meridian profiles and winding angle developments of the carbon–epoxy domes are obtained based on the given slippage coefficient distributions; their structural performances are then determined and compared with each other. The results conclude that the non‐geodesic dome designed using the maximum constant slippage coefficient exhibits better performance than those using other slippage coefficient distributions; this is mainly triggered by maximum utilization of the longitudinal strength of the laminate. It is also revealed that the structural efficiency of domed pressure vessels can be improved using non‐geodesics that provide higher degrees of freedom in the design of filament wound structures. POLYM. COMPOS., 315–321, 2016. © 2014 Society of Plastics Engineers

The onset of plasticity of a Zr-based bulk metallic glass

The deformation behaviors of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glassy alloy under step-controlled tensile loads have been studied in situ and systematically using scanning electron microscopy and synchrotron X-ray diffraction. A circular hole, as a stress concentrator, was introduced in the middle of the gauge length of the sample to facilitate the creation of shear bands in a controllable way at the edge of the hole in situ imaging and diffraction studies could be carried out at the identical loads in a quasi-steady state manner. Pair distribution function was used to calculate the strains of different atomic coordination shells and the relative change of the bond lengths of different atomic pairs. The combined imaging and diffraction studies revealed that (1) the extension of solvent–solvent (Zr–Zr) atomic pairs under tension causes the nucleation of shear bands, and (2) the compressive stress field around the shear band tip effectively slows down the fast propagation of shear bands.

A preliminary study for identification of candidate AFLP markers under artificial selection for shell color in pearl oyster Pinctada fucata

Pearl oyster Pinctada fucata is widely cultured to produce seawater pearl in South China, and the quality of pearl is significantly affected by its shell color. Thus the Pearl Oyster Selective Breeding Program (POSBP) was carried out for the shell color and growth traits. The black (B), gold (G), red (R) and white (W) shell strains with fast growth trait were achieved after five successive generation selection. In this study, AFLP technique was used to scan genome of four strains with different shell colors to identify the candidate markers under artificial selection. Eight AFLP primer combinations were screened and yielded 688 loci, 676 (98.26%) of which were polymorphic. In black, gold, red and white strains, the percentage of polymorphic loci was 90.41%, 87.79%, 93.60% and 93.31%, respectively, Nei's gene diversity was 0.3225, 0.2829, 0.3221 and 0.3292, Shannon's information index was 0.4801, 0.4271, 0.4825 and 0.4923, and the value of FST was 0.1805. These results suggested that the four different shell color strains had high genetic diversity and great genetic differentiation among strains, which had been subjected to the continuous selective pressures during the artificial selective breeding. Furthermore, six outlier loci were considered as the candidate markers under artificial selection for shell color. This study provides a molecular evidence for the inheritance of shell color of P. fucata.

Core/shell CdS/ZnS nanoparticles: Molecular modelling and characterization by photocatalytic decomposition of Methylene Blue

Core/shell CdS/ZnS nanoparticles were modelled in the Material Studio environment and synthesized by one-pot procedure. The core CdS radius size and thickness of the ZnS shell composed of 1–3 ZnS monolayers were predicted from the molecular models. From UV–vis absorption spectra of the CdS/ZnS colloid dispersions transition energies of CdS and ZnS nanostructures were calculated. They indicated penetration of electrons and holes from the CdS core into the ZnS shell and relaxation strain in the ZnS shell structure. The transitions energies were used for calculation of the CdS core radius by the Schrödinger equation. Both the relaxation strain in ZnS shells and the size of the CdS core radius were predicted by the molecular modelling.The ZnS shell thickness and a degree of the CdS core coverage were characterized by the photocatalytic decomposition of Methylene Blue (MB) using CdS/ZnS nanoparticles as photocatalysts. The observed kinetic constants of the MB photodecomposition (kobs) were evaluated and a relationship between kobs and the ZnS shell thickness was derived. Regression results revealed that 86% of the CdS core surface was covered with ZnS and the average thickness of ZnS shell was about 12% higher than that predicted by molecular modelling.

Функции Коши—Крылова в расчетах на прочность пластин и оболочек

Функции Коши—Крылова в расчетах на прочность пластин и оболочек

A Simple Design-Oriented Model for FRP-Confined High-Strength Concrete

This paper presents a study on the axial compressive behavior of fiber reinforced polymer (FRP)-confined high-strength concrete (HSC). A large experimental test database assembled from the published literature was used to investigate and quantify factors influencing the compressive behavior of FRP-confined HSC. The database consisted of 976 test data having unconfined concrete strength ranging from 6.2 to 169.7MPa. Based on the analysis results of the database, it was found that the threshold confinement stiffness increases significantly with an increase in concrete strength, which in turn adversely affects the strength enhancement of confined concrete. It was also observed that the hoop rupture strain of FRP shell decreases with an increase in concrete strength. Existing confinement models that are applicable to FRP-confined HSC were assessed using the database. Finally, a new simple design-oriented model for FRP-confined HSC developed on the basis of the database is presented.