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Number of results: 7
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Abstract

A simple resistance-based method was used to study the epoxy-carbon composite material. Measurement of changes of the resistance between contacts, located on the composite specimens, allows detecting the damage process in quasi-static and fatigue tests. The method can be useful to determine the margin of safety of composite elements.

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Authors and Affiliations

Paweł Pyrzanowski
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Abstract

In the paper, the author presents experimental analysis of propagation of plastic zones in two-dimensional models with different stress concentrators. The experimental tests were carried out by photoelastic coating method on duralumin stripes loaded by tensile stresses. For various levels of loading, the photographs of isochromatic pattern were taken under loading and after removing loading. On the basis of isochromatic pattern recorded for loaded models, the boundaries of plastic zones were determined using the Treska-Coulomb yield condition. The isochromatic pattern taken for the unloaded, but previously partly plastified elements, show the picture of the residual strain remaining in the material. A discussion of the results is presented.

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Authors and Affiliations

Barbara Kozłowska
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Abstract

In the paper, author presents the analysis of the elastic-plastic residual stresses and the boundaries of plastic zones in two-dimensional model with central circular hole. The experimental testing was carried out by photoelastic coating method. The duralumin model was loaded within the overelastic range by uniformly distributed tensile stresses. For various levels of loading, the photographs of isochromatic pattern were taken. The residual stresses along the axis of symmetry perpendicular to the stretching direction were calculated by the characteristics method, using multisectional schematization of ϭ-ε relation for the material. The boundaries of plastic zones in the loaded model were obtained on the basis of the Treska-Coulomb yield condition directly from the isochromatic pattern. The analysis and discussion of the test results is presented.

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Authors and Affiliations

Barbara Kozłowska
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Abstract

In the paper, the author presents the application of thermography method for investigation of elastic-plastic states in two-dimensional models. The experimental testing was carried out on the duralumin elements with different stress concentrators loaded by uniformly distributed tensile stresses. The changes of temperature distribution on the surface of the models during loading process were recorded by a thermovision camera. On the basis of calibrating test carried out on the stretched element, the relationship between loading, temperature increment and specimen elongation was determined. Quantitative temperature distribution in chosen cross-sections of the models was determined using thermograms received for various levels of loading. On the basis of the obtained results, the author estimated the accuracy of the method as well as its usability for investigation of the plastic zones' localization and propagation.

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Authors and Affiliations

Barbara Kozłowska
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Abstract

The paper presents the results of experimental investigations into variations of the stress tensor components due to both the interaction between subsurface fatigue crack faces and rolling contact. The load assumed represents real interaction between the railway wheel and rail. The Grating Holographic Interferometry (GHI) method was employed. The results obtained were compared with those resulting from numerical simulations performed using FEM. The results reveal a strong influence exerted by shape, crack thickness distribution and roughness of the crack faces, respectively, on the distribution of displacement and stress tensor component fields. A new concept consisting in application of the effective crack thickness was proposed. The best agreement between experimental and numerical results was achieved in the case when the real crack shape, effective crack thickness and the friction coefficient of 0.3 were assumed.
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Authors and Affiliations

Paweł Pyrzanowski
ORCID: ORCID
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Abstract

In this paper, an experimental method was utilized to investigate acoustic emission (AE) characteristics and to identify emission sources of the nonlinear AE signal on the cylinder body of a large low-speed two-stroke marine diesel engine in real-working conditions on the sea in misfiring and normal firing modes. Measurements focused on the AE signal acquired in a transverse direction in low-frequency (20–80 kHz), medium-frequency (100–400 kHz) and high-frequency (400–900 kHz) ranges. The collected signals were analyzed on the crank angle and crank angle-frequency domains. The results showed that all potential sources of the nonlinear AE signal could be mapped in the low-frequency range. However, only the AE signal caused by the combustion process at around the top dead center could be well-observed in the medium-to-high-frequency range. The findings also revealed that in normal firing conditions, the AE energy radiated by friction in the down-stroke period was smaller than in the up-stroke process due to gas-sealing forces. Moreover, the AE energy in the misfiring condition was higher than in the normal firing state. These outcomes considerably contributed understandings to characteristics of friction and wear around the mid-stroke area of the cylinder on a two-stroke marine diesel engine.
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Authors and Affiliations

Xuan Thin Dong
1
Manh Hung Nguyen
1

  1. Vietnam Maritime University Hai Phong, Vietnam
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Abstract

In this study, the optimization of air gap magnetic flux density of open slotted axial flux permanent magnet (AFPM) machine which was developed for wind turbine has been obtained using the Taguchi experimental method. For this, magnetic analyzes were performed by ANSYS Maxwell program according to Taguchi table. Then the optimum values have been determined and the average magnetic flux density values have been calculated for air gap and iron core under load and no-load conditions with ANSYS Maxwell. Traditionally, 15625 analyzes are required for 6 independent variables and 5 levels when experimental method is used. In this study, optimum values are determined by 25 magnetic analyzes, which use L25 orthogonal array. For this purpose, both factor effect graph and signal to noise ratios are used, according to the factors and levels which are obtained from the factor effect graph and the signal to noise ratio. Parameters are re-analyzed by Maxwell. The optimum factors and levels are determined. For optimized values, the air gap magnetic flux density is improved by 65.7% and 173.26%, respectively, according to the average value and the initial design. Therefore, the variables are optimized in a shorter time with Taguchi experimental design method instead of the traditional design method for open slotted AFPM generator. In addition, the results were analyzed statistically using ANOVA and Regression model. The variables were found to be significant by ANOVA. The degree of influence of the variables on the air gap magnetic flux density was also determined by the Regression model.

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Authors and Affiliations

E. Hüner

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