Developing of the optimal shape and reinforcement structure of the specimen for adequate determination of the tensile strength in unidirectional composites

Unidirectional composites exhibit the highest strength when stretched along the fibers. However, the proper determination of the strength faces great methodological difficulties. The main problems of tensile testing of polymer composites consisted in developing of the specimen shape and the method of specimen fixation which ensure the minimum impact of the stress concentration near the grips on the strength measurements. A conventional shape of the specimen with fillets is unsuitable for unidirectional polymers due to the splitting occurred in the fillet zones upon loading. Therefore, the specimens are usually standardized in the form of rectangular strips fixed using pads or special grips which provide constant transverse forces. However, with such a specimen shape, a significant stress concentration inevitably occurs at the edge of grips and the lower the ratio of the interlayer shear modulus to the longitudinal Young’s modulus, the greater the stress concentration impact. For the purpose of the most correct determination of the strength we propose to use specimens with smoothly varying dimensions at the same cross-sectional area which ensures keeping the total number of unbroken fibers in each section. The specimen thickness decreases when moving from the working part of the specimen to the gripping part, whereas the width (while maintaining the section area) grows to prevent the specimen collapsing resulting from transverse forces in standard self-tightening grips. Analytical and FEM modeling is performed to select a rational contour shape. Technological equipment has been developed and a procedure of manufacturing testing specimens has been worked out. The tensile test of specially manufactured curvilinear reinforced specimens showed higher strength values compared to standard rectangular strips or specimens with semicircular fillets.

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Experimental Determination of the Effective Resolution Limit in Thick Specimens at High Voltages

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100116942 ◽

1975 ◽

Vol 33 ◽

pp. 664-665

Author(s):

Mircea Fotino

Keyword(s):

Experimental Approach ◽

Chromatic Aberration ◽

Resolving Power ◽

Biological Research ◽

Specimen Thickness ◽

Resolution Limit ◽

High Voltage Electron Microscopy ◽

Voltage Electron ◽

Resolution Level

The use of thick specimens (0.5 μm to 5.0 μm or more) is one of the most resourceful applications of high-voltage electron microscopy in biological research. However, the energy loss experienced by the electron beam in the specimen results in chromatic aberration and thus in a deterioration of the effective resolving power. This sets a limit to the maximum usable specimen thickness when investigating structures requiring a certain resolution level.An experimental approach is here described in which the deterioration of the resolving power as a function of specimen thickness is determined. In a manner similar to the Rayleigh criterion in which two image points are considered resolved at the resolution limit when their profiles overlap such that the minimum of one coincides with the maximum of the other, the resolution attainable in thick sections can be measured by the distance from minimum to maximum (or, equivalently, from 10% to 90% maximum) of the broadened profile of a well-defined step-like object placed on the specimen.

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Problems in Thin-Film X-ray Quantification

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135897 ◽

1990 ◽

Vol 48 (2) ◽

pp. 458-459

Author(s):

J N Chapman ◽

W A P Nicholson

Keyword(s):

Thin Film ◽

Specimen Thickness ◽

X Rays ◽

Characteristic Peak ◽

Local Composition ◽

X Ray ◽

Measured Ratio ◽

Path Lengths ◽

Composition Changes

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.

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Gender determination of caucasoid hair using image analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146928 ◽

1993 ◽

Vol 51 ◽

pp. 216-217

Author(s):

T.B. Ball ◽

W.M. Hess

Keyword(s):

Image Analysis ◽

Cross Sections ◽

Scalp Hair ◽

The Body ◽

Equivalent Diameter ◽

Cross Sectional ◽

Hair Samples ◽

Length Width ◽

Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

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Profil Penyakit Malaria Di Rumah Sakit Islam Siti Rahmah Padang Tahun 2018

Health & Medical Journal ◽

10.33854/heme.v2i2.546 ◽

2020 ◽

Vol 2 (2) ◽

pp. 08-15

Author(s):

Rahma Triyana ◽

Salmi Salmi

Keyword(s):

Observational Study ◽

Frequency Distribution ◽

Cross Section ◽

Laboratory Tests ◽

Age Group ◽

Normal Range ◽

Cross Sectional ◽

West Sumatra ◽

Severity Of The Disease

Malaria is one of the health problems in Indonesia, especially West Sumatra. Determination of the description of Malaria disease in an area is needed to determine the spread and severity of the disease. This study aims to determine the frequency distribution according to age, sex and place of residence, description of the types of Plasmodium causes of Malaria and hematological features in Malaria patients at Siti Rahmah Padang Hospital in 2018. This type of research is a descriptive observational study with an approach or design cross section (cross sectional). The frequency distribution of Malaria sufferers in Siti Rahmah Padang Hospital in 2018 according to the highest age was in the age group 21-30 years as many as 28 cases (36.8%), the highest sex among men was 46 (60.5%) and the highest number of residences was found in Koto Tangah sub-district there were 31 cases (40.8%). The type of Plasmodium found in Malaria cases in Siti Rahmah Padang Hospital in 2018 was P. vivax (73 cases (96.05%)) and P. falciparum (3 cases (3.95%)). The results of laboratory tests on Hb, hematocrit, platelet and leukocyte levels in Malaria positive patients in Siti Rahmah Padang Hospital in 2018 were in the normal range.

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Profil Penyakit Malaria di Rumah Sakit Islam Siti Rahmah Padang Tahun 2018

Health & Medical Journal ◽

10.33854/heme.v2i2.452 ◽

2020 ◽

Vol 2 (2) ◽

pp. 08-15

Author(s):

Rahma Triyana Y ◽

Salmi Salmi

Keyword(s):

Observational Study ◽

Frequency Distribution ◽

Cross Section ◽

Laboratory Tests ◽

Age Group ◽

Normal Range ◽

Cross Sectional ◽

West Sumatra ◽

Severity Of The Disease

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Numerical Modeling of Stress Concentration Around Failed Fibers in Unidirectional Composites

AIAA Scitech 2021 Forum ◽

10.2514/6.2021-0087 ◽

2021 ◽

Author(s):

Francisco Lopez Jimenez

Keyword(s):

Numerical Modeling ◽

Stress Concentration ◽

Unidirectional Composites

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DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

Izvestia Ufimskogo Nauchnogo Tsentra RAN ◽

10.31040/2222-8349-2020-0-4-19-24 ◽

2020 ◽

Vol 0 (4) ◽

pp. 19-24

Author(s):

I.M. UTYASHEV ◽

◽

A.A. AITBAEVA ◽

A.A. YULMUKHAMETOV ◽

◽

...

Keyword(s):

Cross Sectional Area ◽

Variable Cross ◽

Sectional Area ◽

Longitudinal Vibrations ◽

Cross Sectional ◽

Method Error ◽

Various Boundary Conditions ◽

Elastic Fixation ◽

Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

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Determination of stress concentration factors for shafts under tension

Materials Testing ◽

10.3139/120.111500 ◽

2020 ◽

Vol 62 (4) ◽

pp. 413-421 ◽

Cited By ~ 1

Author(s):

Murat Tolga Ozkan ◽

Fulya Erdemir

Keyword(s):

Stress Concentration ◽

Concentration Factors ◽

Stress Concentration Factors

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Circulating bioactive sclerostin levels in an Austrian population-based cohort

Wiener klinische Wochenschrift ◽

10.1007/s00508-021-01815-0 ◽

2021 ◽

Author(s):

Katharina Kerschan-Schindl ◽

Ursula Föger-Samwald ◽

Andreas Gleiss ◽

Stefan Kudlacek ◽

Jacqueline Wallwitz ◽

...

Keyword(s):

Serum Levels ◽

Population Based ◽

Negative Regulator ◽

Total Serum ◽

Mineral Density ◽

Cross Sectional ◽

Robust Parameter ◽

Austrian Population ◽

Different Levels

Summary Background Circulating serum sclerostin levels are supposed to give a good estimation of the levels of this negative regulator of bone mass within bone. Most studies evaluating total serum sclerostin found different levels in males compared to females and in older compared to younger subjects. Besides an ELISA detecting total sclerostin an ELISA determining bioactive sclerostin has been developed. The aim of this study was to investigate serum levels of bioactive sclerostin in an Austrian population-based cohort. Methods We conducted a cross-sectional observational study in 235 healthy subjects. Using the bioactive ELISA assay (Biomedica) bioactive sclerostin levels were evaluated. Results Serum levels of bioactive sclerostin were higher in men than in women (24%). The levels correlated positively with age (r = 0.47). A positive correlation could also be detected with body mass index and bone mineral density. Conclusion Using the ELISA detecting bioactive sclerostin our results are consistent with data in the literature obtained by different sclerostin assays. The determination of sclerostin concentrations in peripheral blood thus appears to be a robust parameter of bone metabolism.

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