Wyniki wyszukiwania - Biblioteka Nauki

1

Lateral impact of tubular structure – theoretical and experimental analysis. Part 1 – Investigation of single tube

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Lipa S. , Kotełko M.

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tom Vol. 51 nr 4

873--882

EN

If a thin-walled member is subjected to dynamic load, the estimation of its structural behaviour has to count for the strain-rate influence upon stress-strain material characteristics. It is particularly important when a thin-walled member works as an energy absorber. In the paper, the problem of collapse load, post-failure behaviour and energy dissipation of a tubular structure subjected to lateral impact load is presented. The analytical solution of the problem of initial collapse load and post-failure behaviour of a single tube is discussed. The analysis is limited to the “dynamic progressive crushing”, which means that we take into account the strain-rate but neglect inertia effects. The solution is based on the yield-line analysis and takes into account the impact velocity and strain rate, using the Cowper-Symonds constitutive relation. The same problem concerning both the single tube and multi-member tubular structure subjected to lateral bending impact load is solved using Finite Element (FE) simulation, which also takes into account the impact velocity and strain rate, using the corresponding to Cowper-Symonds Perzyna material model. Results of numerical calculations are compared with those obtained from the quasi-dynamic tests performed at different loading velocities on single tubes. The results are shown in load-deformation diagrams and diagrams of deformation patterns.

2

Impact behaviour of spot-welded thin-walled frusta

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Kotełko M. , Mołdawa A.

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tom Vol. 10, no. 4

280--284

EN

In the paper the dynamic response of thin-walled, spot-welded prismatic frusta subjected to axial impact load is investigated. The parametric study into the influence of several parameters on the energy absorption capability, expressed by some crashworthiness indicators is performed, using Finite Element simulations. FE model is validated by experimental results of quasi-static and dynamic (impact) tests. Results of initial study concerning influence of spot welds are presented. Some conclusions are derived from the parametric study into the influence of frustum angle and wall thickness upon the energy absorption capability.

3

Stochastyczna analiza wrażliwości nośności dźwigara skrzynkowego

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Lis P. , Kotełko M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2013

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tom z. 101

69--70

PL

W ostatnich latach deterministyczne podejście w projektowaniu konstrukcji cienkościennych jest często zastępowane podejściem probabilistycznym. Również niektóre normy obliczeniowe, szczególnie w inżynierii lądowej, traktują zagadnienie niezawodności i nośności konstrukcji, jako probabilistyczne. Zakładając, że parametry konstrukcyjne (wymiary geometryczne, parametry materiałowe, imperfekcje wstępne, etc.) są zmiennymi losowymi, można przeprowadzić stochastyczną analizę wrażliwości nośności konstrukcji [1].

4

Analiza parametryczna nośności ściskanych płyt sandwiczowych z rdzeniem ulowym

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Kotełko M. , Mania R.

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tom Vol. 8, No. sp.

257--265

PL

Praca zawiera wyniki analizy parametrycznej nośności płyty sandwiczowej z rdzeniem ulowym poddanej równomiernemu ściskaniu. Analizowano wpływ różnych parametrów płyty na jej nośność i stosunek nośności do ciężaru własnego. Do oszacowania dolnego nośności zastosowano modele zastępcze jednorodnych płyt jednowarstwowych oraz metodę elementów skończonych dla płyty trójwarstwowej z rdzeniem homogenizowanym, do oszacowania górnego - metodę kinematyczna, w odniesieniu do płyty trójwarslwowcj z rdzeniem o zerowej sztywności. Przedstawiono wybrane wyniki obliczeń i wnioski wynikające z analizy parametrycznej.

EN

The parametric study of the load-carrying capacity of the honeycomb sandwich plate subject to uniform compression is presented in the paper. Influence of different geometrical and material parameters of the plate upon the load-carrying capacity and load-capacity to weight ratio are examined. The lower-bound estimation of ultimate loads is conducted using the equivalent single plate approach as well as finite element analysis. The upper-bound estimation of ultimate loads is performed using the kinematical method - plastic mechanism approach. Exemplary results of numerical calculations are presented in diagrams. Conclusions concerning the appiicability of the above methods and an influence of some basic parameters upon the load-capacity of the examined plate are derived.

5

Konstrukcje cienkościenne jako absorbery energii - najnowsze trendy i wyniki badań

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Kotełko M. , Lipa S.

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tom Z. 28

33-43

PL

Praca ma charakter przeglądowy. Zawiera omówienie szeregu publikacji dotyczących szeroko pojętych zagadnień konstrukcji cienkościennych pracujących jako absorbery energii. Omawia podstawowe rozwiązania konstrukcyjne takich absorberów. Przedstawia wyniki badań autorów, dotyczące zastosowania krótkich, ściskanych profili cienkościennych jako absorberów energii, a także układów rur cienkościennych poddanych promieniowemu zgniotowi.

EN

The paper contains a review of several works carried out in the wide range of problems concerning thin-walled structures used as energy absorbers. Basic types of design of such structures are discussed. The results of works carried out by the authors are presented. The research was devoted to the investigation of the applicability of short thin-walled profiles as energy absorbers and also to the investigation into the crushing behaviour of thin-walled tube systems subject to lateral crushing load.

6

Load-capacity of combined steel/aluminium members under bending action - experimental study

80%

MacDonald M. , Rhodes J. , Kotełko M.

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2002

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tom Vol. 6, nr 2

41-47

EN

The analysis of the load-capacity and failure behaviour of combined steel/aluminium members subject to bending is presented in the paper. Members are formed from an extruded aluminium box-section into which a cold formed plain steel channel is inserted. The results of FE analysis both for an elastic and elasto-plastic-buckling stage are shown. Tests performed on cantilever beams with riveted and unriveted component members are described. The failure behaviour of the combined members under investigation is presented on the basis of FE results and experimental tests. The work is completed with a comparison of equivalent FE results, British Standard calculations and experimental work performed. An influence of riveting is discussed.

PL

W referacie przedstawiono analizę zagadnienia nośności granicznej i nośności w fazie zniszczenia cienkościennych prętów o przekroju złożonym. Pręt taki budowany jest z pręta aluminiowego o przekroju skrzynkowym, wewnątrz którego umieszczono stalowy ceownik zimno walcowany. Przedstawiono wyniki analizy metodą elementów skończonych (MES) w stanie sprężystym i sprężysto-plastycznym z uwzględnieniem wyboczenia. Opisano eksperyment przeprowadzony na belkach wspornikowych o przekroju złożonym, z elementami nitowanymi i nie nitowanymi. Przedstawiono zachowanie się badane] konstrukcji w fazie zniszczenia, na podstawie wyników analizy numerycznej MES, a także wyników eksperymentu. Przeprowadzono porównanie wyników MES z wynikami obliczeń według Normy Brytyjskiej (BS) i wynikami eksperymentu. Opisano wpływ nitowania na nośność graniczną konstrukcji.

7

Numerical simulation of energy absorption in polyurethane foams under impact

80%

Jankowski M. , Czechowski L. , Kotełko M.

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tom Vol. 19, No. 4

245-252

EN

Selection of proper mechanical characteristics of the padding material of the head rest, namely polyurethane foam, is particularly important in the design process of the vehicle seat head restraint. In the paper the code of numerical simulation of flexible polyurethane foam absorber response against impact of a rigid body (passenger's head) is presented. The code is based on the lump mass method. Basics of the numerical algorithm based on this method are presented. Material constitutive model of flexible polyurethane foam (FPF) derived on the basis of former experimental tests and used in the algorithm is described. Comparative results of numerical simulations together with results of experiments carried out on drop hammer rig with flat impact or are shown. The results are presented on diagrams of deceleration versus time. Also comparative Finite Element simulations are carried out. The FE simulation was performed using the implicit analysis, taking into account the multi-linear, hyper-elastic material model and large strain (non-linear geometric relations). The influence of damping coefficient on the deceleration characteristics was investigated. Some final conclusions concerning the applicability of the numerical code based on the lump mass method, as well as its advantages in comparison with the FE software are derived.

8

Plastic mechanisms for thin-walled cold-formed steel members in eccentric compression

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Ungureanu V. , Kotełko M. , Grudziecki J.

Acta Mechanica et Automatica

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2016

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tom Vol. 10, no. 1

33--37

EN

The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections.

9

Energy absorbing effectiveness – different approaches

80%

Kotełko M. , Jankowski J. , Ferdynus M.

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tom Vol. 12, no. 1

54--59

EN

In the paper the study of different crashworthiness indicators used to evaluate energy absorbing effectiveness of thin-walled energy absorbers is presented. Several different indicators are used to assess an effectiveness of two types of absorbing structures, namely thin-walled prismatic column with flaws and thin-walled prismatic frustum (hollow or foam filled) in both cases subjected to axial compressive impact load. The indicators are calculated for different materials and different geometrical parameters. The problem of selection of the most appropriate and general indicators is discussed.