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1
Content available An Improved Approach in the Application of an Elastic-Plastic Contact Force Model in the Modelling of Multiple Impacts
Warzecha Mariusz, Grzejda Rafał
Tribologia
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2023
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nr 1
85--97
EN
This paper presents the modelling of a simultaneous multiple collision occurring between several bodies of a kinematic chain. An algorithm is proposed that when used with an elastoplastic contact model, allows the phenomena that can occur during a multiple-body collision to be taken into account. These phenomena include the transition of the collision state from the restitution phase directly to the compression phase or successive collisions occurring along the same normal. The proposed algorithm can be used with any elastoplastic contact model. This paper presents its use with a selected model in a three-body system. Numerical calculations based on the model have been verified using the Finite Element Method (FEM). The use of the proposed improved approach reduces the post-collision velocity prediction error by 2.34% compared to the baseline description of collisions known from the literature.
PL
W artykule przedstawiono modelowanie symultanicznego zderzenia wielokrotnego zachodzącego pomiędzy kilkoma ciałami łańcucha kinematycznego. Zaproponowano algorytm, który wykorzystany z elasto-plastycznym modelem kontaktu pozwala na uwzględnienie zjawisk, które mogą wystąpić w trakcie zderzenia wielokrotnego. Do zjawisk tych zaliczyć można przejście stanu zderzenia z fazy restytucji bezpośrednio do fazy kompresji czy też kolejne zderzenia zachodzące wzdłuż tej samej normalnej. Zaproponowany algorytm może zostać wykorzystany z dowolnym, elasto-plastycznym modelem kontaktu. W artykule przedstawiono jego wykorzystanie z wybranym modelem w modelu składającym się z trzech ciał. Obliczenia numeryczne przeprowadzone na podstawie modelu zostały zweryfikowane za pomocą Metody Elementów Skończonych (MES). Zastosowanie zaproponowanego, ulepszonego podejścia pozwala na zmniejszenie błędu przewidywania prędkości po zderzeniu o 2.34% w porównaniu z opisem bazowym zderzenia znanym z literatury.
2
Content available Concept of an innovative technological line for the processing of linear profiles
Gustowski Tomasz, Kurek Waldemar, Grzejda Rafał
Production Engineering Archives
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2023
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Vol. 29, Iss. 1
7--13
EN
The paper presents the concept of an innovative technological line intended for the processing of long linear profiles used in engineering steel and aluminium structures, which can be both hollow and open section profiles. The line is set up with seven main sections: profile loading system, input roller conveyor, plasma arc cutting section, circular saw cutting section, robot welding section, output roller conveyor and profile packaging system. The assumptions adopted to create the concept of the techno-logical line were specified. A block diagram of the line and drawings showing the structure of its selected elements were depicted. The features of the technological line documenting its product and process innovativeness were indicated. The proposed technological line is built in the AGICO Group company, but it can also be successfully implemented in other companies dealing with the processing of long linear profiles.
3
Content available Prototyp przecinarki z frezem tarczowo-piłkowym mocowanym od spodu przedmiotu obrabianego
Gustowski Tomasz, Kurek Waldemar, Samsonik Krystian, Grzejda Rafał
Systemy Wspomagania w Inżynierii Produkcji
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2022
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Vol. 11, iss. 2
57--65
PL
W artykule przedstawiono prototyp przecinarki tarczowej z narzędziem mocowanym od spodu przedmiotu obrabianego. Układ przeznaczony jest do obróbki długich profili liniowych stosowanych w stalowych konstrukcjach inżynierskich. Umożliwia cięcie profili o zamkniętych lub otwartych przekrojach poprzecznych na zadany wymiar. Układ jest częścią innowacyjnej linii technologicznej do automatycznego cięcia plazmowego, cięcia frezem tarczowo-piłkowym oraz spawania z wykorzystaniem robotów spawalniczych.
EN
In the paper, a prototype of a circular saw with a tool fixed from the bottom of the workpiece is introduced. The system is intended for the processing of long linear profiles used in engineering steel structures. It enables cutting profiles with closed or open cross-sections to a given size. The system is part of an innovative technological line for automatic plasma cutting, circular saw cutting and welding with use of welding robots.
4
Content available Thermal strength analysis of a steel bolted connection under bolt loss conditions
Grzejda Rafał
Eksploatacja i Niezawodność
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2022
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Vol. 24, no. 2
269--274
EN
The aim of the paper is to analyse an exemplary bolted connection under the conditions of loss of bearing capacity of some fasteners in the connection. The presented tests are numerical and concern an asymmetric bolted connection. The joined elements in the connection were modelled as 3D finite elements, and the fasteners were treated as hybrid models consisting of rigid heads and nuts, and flexible beams between them. The bolted connection was first preloaded according to six different tensioning orders using a standardised force. After all bolts were tensioned, the selected bolts were removed, simulating bolt damage. The connection was then tested for external loads with temperatures ranging from 20 to 600°C. The influence of loosening the connection on the load in the remaining bolts at the operational stage of the connection was investigated. The calculation results were compared with the test results for a healthy bolted connection. It was shown that the bearing capacity of the connection in the damaged state decreased by 13%.
5
Content available Mechanical properties of the porcine pericardium extracellular matrix cross-linked with glutaraldehyde and tannic acid
Dąbrowska Karolina Zofia, Turek Artur, Grzejda Rafał, Kobielarz Magdalena
Acta of Bioengineering and Biomechanics
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2022
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Vol. 24, no. 3
21--31
EN
The aim of this study was to determine the influence of factors such as temperature and glutaraldehyde (GA) concentration on the mechanical properties of porcine pericardia, in order to propose the recommended optimal conditions of a cross-linking process. It was also to verify whether tannic acid (TA), a natural cross-linking agent that stabilizes collagenous tissues by a different mechanism than GA, may positively influence the strength of pericardium. Methods: The samples were incubated at various temperatures (4, 22, and 37 °C) and GA concentration solutions (0.6, 1.5 and 3%) for 7 days. Three series were selected and additionally cross-linked with 0.3% TA for another 7 days. Mechanical properties of cross-linked pericardium samples, i.e., ultimate tensile strength (UTS) and elastic modulus (E) were measured in uniaxial tensile testing. The hyperelastic model for incompressible materials – isotropic by Ogden [24] and anisotropic by Fung [7] were utilized to describe the mechanical behaviour of treated pericardium. Results: The temperature has an influence on cross-linking effects; the lowest values of UTS were reported for specimens cross-linked at 22 °C, while the mechanical properties of series treated at 4 °C or 37 °C were comparable. At a particular temperature of incubation, the GA concentrations have not affected the mechanical properties of tissues. The dependence between mechanical parameters and agent concentration was only observed for specimens treated with GA at 37 °C. Conclusions: The conditions of the cross-linking process affect the mechanical properties of the porcine pericardium. Room temperature (22 °C) and the concentration of 1.5% GA occurred to be ineffective. The mechanical properties of GA-treated pericardium were improved by an additional TA cross-linking.
6
Content available Finite Element Modelling of a Pair of Flexible Elements Contact Preloaded and Externally Loaded with an Arbitrary Force
Grzejda Rafał
Advances in Science and Technology. Research Journal
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2020
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Vol. 14, no 3
118--124
EN
In the paper, the numerical tests of the contact of a pair of flexible elements were presented. The non-linear phenomena occurring in the contact zone of two elements have been considered separately for the assembly and operational condition of the joint. The physical and mathematical models of the contact joint created using the finite element method were proposed. The contact joint is treated as a system composed of the subsystems: two of them are joined elements and the third one is the contact layer between the elements. The calculations results for the selected contact joint were given.
7
Content available remote Study of the distribution of normal contact pressure between parts joined in a multi-bolted system under operational loads
Grzejda Rafał
Engineering Transactions
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2019
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Vol. 67, iss. 2
147--155
EN
Modelling and calculations of unsymmetrical multi-bolted connections treated as a system for different bolt models and contact layer models between the joined parts are presented. The modelling refers to preloaded and externally loaded connections. The systemic models of the connection for two substitute models of bolts are shown. Between the joined parts two types of the Winkler model of a contact layer are taken into consideration. Calculations were made for an exemplary unsymmetrical connection. Its models were preloaded and externally loaded with normal forces. As a result of the calculations, distributions of normal contact pressure at the interface of the parts joined in the connection are shown.
8
Content available Determination of Bolt Forces and Normal Contact Pressure Between Elements in the System With Many Bolts for its Assembly Conditions
Grzejda Rafał
Advances in Science and Technology. Research Journal
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2019
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Vol. 13, no 1
116--121
EN
The paper put forward a thesis that modelling dissymmetric non-linear multi-bolted connections as a system is possible. Modelling of the systems composed of four subsystems on the assembly state was presented. These subsystems included: a couple of joined elements (a flange and a support), a contact layer between them, and bolts. The physical model of the system was described considering the tightening of bolts according to a specific sequence. In this model: the flange and the support were built using spatial finite elements, the contact layer was formed as the non-linear Winkler model, and the bolts were replaced with simplified models made of flexible beams. The calculation model which can be applied to determine the changes in bolt forces, as well as in the normal contact pressure between the joined elements during the tightening of the system and at its end, was presented. The results of sample calculations for the selected multi-bolted system were shown.
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