Wyniki wyszukiwania - BazTech

1

Composite material components damaged by impact loading: a methodology for the assessment of their residual elastic properties

Belingardi G., Cavatorta M. P., Paolino D. S.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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Vol. 87, nr 1

18--24

EN

Purpose: Detection and evaluation of damage due to impact or fatigue loading in components made by composite materials is one of the main concern for automotive engineers. We focus on damage due to impact loading on long fibre, plastic matrix composite, as they represent one of the most interesting development solution for automotive components toward lightweight structure that in turn means reduction of fuel consumption and of Green House Gas emissions. Design/methodology/approach: An innovative simplified methodology is proposed, based on the impact and repeated impact behaviour of composite material, for the evaluation of the induced damage and of material residual elastic properties. The investigated composite laminate is made of eight twill-wave carbon fabrics impregnated with epoxy resin. The methodology consists of two phases: at first the identification of the impact response. Composite plates have been impacted at different energy levels and residual elastic properties measured through standard tensile tests. The relationship between impact energy and residual elastic properties is obtained. Then the exploration impact load is identified, large enough to give a well-defined picture of the suffered damage but soft enough to do not induce further damage in the composite laminate. Findings: This exploration impact test and the Damage Index (DI) value, as interpretation key, leads to a prediction of the local residual elastic properties in the damaged area. The proposed methodology has been validated on plate specimens. A strict correlation is found between the predicted and the actual residual elastic properties of the damaged composite plate. Practical implications: Subsequently it has been applied to a composite beam, with a omega shape transverse section, that can be considered as a demonstrator for a typical beam used in the car body frame. Originality/value: A selection on the following alternatives will be possible: a – don’t care the damage is not affecting the structure performance; b – repair is needed but will be sufficient; c – substitute the damaged component as soon as possible.

2

Distribution of surface pressure of avocado fruit at impact loads

Stopa R., Komarnicki P., Młotek M.

Agricultural Engineering

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2014

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Vol. 18, No. 2

163--174

EN

The paper presents the results of measurements of surface pressure of Fuerte avocado with the use of Tekscan system in impact loading conditions were presented. Contour lines of thrusts for two variants of loading which differ with speed and energy in the moment of crash were determined. Average values measured during the test were determined and statistical analysis was carried out for them. It was determined that the increase of speed and energy results in the increase of value of the maximum surface pressure but does not influence significantly their distribution on the resistance surface. It was proved that in the central area of contact mainly elastic strains appeared at the lack of plastic strains of tissue.

PL

W pracy przedstawiono wyniki pomiarów nacisków powierzchniowych avocado odmiany Fuerte przy pomocy systemu Tekscan w warunkach obciążeń udarowych. Wyznaczono warstwice nacisków dla dwóch wariantów obciążenia różniących się prędkością i energią w momencie zderzenia. Wyznaczono średnie wartości wielkości mierzonych podczas testu i przeprowadzono dla nich analizę statystyczną. Ustalono, że wzrost prędkości i energii zderzenia powoduje zwiększenie wartości maksymalnych nacisków powierzchniowych, ale nie wpływa w istotny sposób na ich rozkład na powierzchni oporowej. Wykazano, że w centralnej strefie styku występowały głównie odkształcenie sprężyste przy braku odkształceń plastycznych tkanki.

3

Rozkłady nacisków powierzchniowych jabłek przy obciążeniach udarowych

Stopa R., Komarnicki P., Młotek M.

Inżynieria Rolnicza

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2013

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R. 17, nr 3, t. 1

363--374

PL

Przedstawiono wyniki pomiarów nacisków powierzchniowych jabłek odmiany Ligol przy pomocy systemu Tekscan w warunkach obciążeń udarowych. Wyznaczono warstwice i rozkłady nacisków w dwóch wzajemnie prostopadłych kierunkach dla dwóch wariantów obciążenia różniących się energią zderzenia jabłka z powierzchnią oporową. Wyznaczono średnie wartości wielkości mierzonych podczas testu i przeprowadzono dla nich analizę statystyczną. Ustalono, że wzrost energii zderzenia wpływa na wartość i rozkład maksymalnych nacisków w miejscu styku jabłka z powierzchnia oporową. Wykazano, że w centralnej strefie styku nastąpiły odkształcenia plastyczne tkanki jabłka w wyniku jej uszkodzenia objawiające się niskimi wartościami nacisków powierzchniowych. Maksymalne wartości nacisków powierzchniowych znajdują się w strefie granicznej powierzchni styku.

EN

Results of measurements of surface pressure of Ligol apples with the use of Tekscan system in impact loading conditions were presented. Contour lines and distribution of pressure in two mutually perpendicular directions for two variants of loading differing with the energy of apple collision with the area of resistance were determined. Average values measured during the test were determined and statistical analysis was carried out for them. It was determined that the growth of collision energy influences the value and distribution of maximum pressures in the area of the apple contact with the area of resistance. It was proved that in the central contact zone, plastic deformations of the apple tissue occurred as a result of its damage appearing with low values of surface pressure. Maximum values of surface pressure are in the border zone of the contact area.

4

Process description of piercing when using degenerated model

Jamroziak K.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 26, nr 1

57-64

EN

Purpose: The material piercing process is an extremely complex phenomenon for the theoretical analysis. This is connected with the fact that the materials used mainly for ballistic shields may not be treated as isotropic media. The description of piercing of ballistic shields made of light weight composite materials, on the basis of the Hooke's model and the Young's module reflects the too low result effectiveness for practical applications. The purpose of this article is the mathematical description of the impact phenomenon of a bullet of the speed ca. 400 m/s, with the use of a degenerated model. Design/methodology/approach: In the study, an attempt has been made to apply an untypical model for the piercing phenomenon analysis. Basing on the model, the theoretical analysis of the piercing phenomenon in quasistatic and dynamic load conditions, in the impact load form, has been carried out. Findings: This analysis enabled derivation of significant conclusions useful in the design process of effective ballistic shields. Research limitations/implications: In the study, the concept has been assumed that a dynamic model simple as possible, that may be analyzed not only by numerical methods but also (at least approximately) with the mathematical analysis methods, may provide significant directions concerning material piercing. Practical implications: The use of so called degenerated model allows to describe the phenomenon in more detail at various piercing speeds what extends the possibilities in the sphere of designing the optimum ballistic shields and of identification of the properties of materials applied for construction of shields. Originality/value: The proposed method of identification of material properties in the piercing process, within the relation: force – deformation, is a novel one since the essence of the identification is the standard rheological model in an adequate plastic component describing the viscous attenuation with dry friction.