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1

Development of mathematical and numerical models for the analysis of overlap laser beam welding of dissimilar materials

Domański Tomasz, Piekarska Wiesława, Saternus Zbigniew, Kubiak Marcin

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 2

15--26

EN

The welding process of dissimilar materials causes a lot of technological issues related to different properties of materials of joined elements. Thermal conductivity is one of most important factors influencing the deformation of the weld. The change of thermal conductivity in the function of the temperature can produce various strains that cannot be predicted during construction design. Different structures of materials appear during joining of dissimilar materials as well as different characteristic zones of the joint and its mechanical properties. The most important is the proper identification of joint zones and the size of deformation at the production stage of welded construction. This work presents the numerical analysis of physical phenomena in overlap welding of two sheets made of S355 carbon steel and 304 austenitic steel using a laser beam. A three-dimensional discrete model is developed taking into account thermophysical properties changing with temperature. Temperature distribution and the shape of the welding pool is predicted on the basis of performer computer simulations. The influence of thermal load on the formation of stress and strain fields is determined.

2

Analiza numeryczna wpływu wybranych parametrów spawania na stan naprężenia i deformacje w połączeniu zakładkowym spawanym laserowo

Saternus Z., Piekarska W., Kubiak M., Domański T., Goszczyńska-Króliszewska D.

Hutnik, Wiadomości Hutnicze

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2018

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Vol. 85, nr 1

32--37

PL

Praca zawiera analizę numeryczną zjawisk termomechanicznych występujących w procesie spawania laserowego złącza zakładkowego. W pracy analizowano wpływ parametrów procesu spawania na stan naprężenia oraz wielkość powstałych deformacji. Modelowanie numeryczne procesu spawania laserowego wykonano w pakiecie inżynierskim Abaqus FEA. Solver obliczeniowy programu Abaqus/Standard został uzupełniony o dodatkowe procedury numeryczne umożliwiające modelowanie rozkładu mocy ruchomego źródła spawającego. Obliczenia zostały podzielone na dwa etapy. Wstępnie została przeprowadzona analiza numeryczna zjawisk cieplnych w celu oszacowania kształtu strefy przetopienia. W drugim etapie obliczeń wyniki symulacji zjawisk cieplnych posłużyły do budowy modelu numerycznego, w którym uwzględniono kształt strefy przetopienia. Na styku łączonych elementów przyjęto odpowiednie warunki kontaktu między łączonymi elementami. Na podstawie przeprowadzonych symulacji numerycznych wyznaczono rozkład temperatury w spawanym połączeniu, określono kształt i wielkość strefy przetopienia oraz oszacowano uzyskane deformacje złącza spawanego dla różnych parametrów procesu spawania.

EN

The work concerns the numerical analysis of thermomechanical phenomena occurring in the laser welding process of the lap joint. The influence of the process parameters on the stress state and the value of deformation are analyzed. Numerical modeling of a laser welding process is performed in Abaqus/FEA engineering software. The Abaqus/Standard solver used in the analysis is supplemented by additional numerical subroutines which allowed the numerical modeling of a movable welding source. Calculations are performed in two steps. Numerical analysis of thermal phenomena is carried out in order to estimate the shape of the melted zone. Results of thermal phenomena are used in the second stage of calculations to perform a numerical modelling of mechanical phenomena, which take into account the shape of the melting zone. In the contact conditions between joined elements are taken into account in developed model. Temperature distribution, obtained on the basis of numerical simulations, allowed the determination of the shape and size of melted zone. Welding deformations are estimated for various welding parameters.

3

Discussion on the Methodology and Apparatus for Hot Distortion Studies

Ignaszak Z.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

141--145

EN

The paper refers to earlier publications of the author, on identification of properties of thermomechanical, chemically hardened core/mold sands. In that earlier period, first version of the original DMA apparatus, produced by a Polish company Multiserw-Morek, was used. The Hot Distortion (HD) study results, published by the author in 2008, referred to phenomena accompanying a thermal shock in real conditions of thermal interaction of a liquid alloy on a mold, in reference to a shock possible to obtain in laboratory conditions, without use of liquid alloy as a heat source, with analysis of solutions applied in the DMA apparatus. This paper presents author’s observations on testing a new, innovative version of the LRu-DMA apparatus, containing a module allowing the Hot Distortion (HD) study. Temperature of specimens achieved in the case of the gas burner heating reaches values definitely above 800°C on the heated side and 610°C on the other side. Using an electric radiator, with maximal temperature of 900°C allows obtaining temperatures in between 225-300°C.

4

Dynamiczne zjawiska geo-termo-mechaniczne jako źródło inicjałów dyskretnych zapłonu metanu

Trenczek S.

Mechanizacja i Automatyzacja Górnictwa

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2006

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R. 44, nr 1

33-42

PL

W artykule podano charakterystyczne zjawiska będące następstwem zapłonu metanu. Przypomniano podstawowe czynniki wpływające na poziom zagrożenia zapłonu metanu: czynniki termogazowe oraz inicjalne, z wyszczególnieniem inicjałów jawnych i dyskretnych. Przytoczono przykłady zapaleń i wybuchu metanu oraz niektóre wyniki badań związane z niszczeniem struktury twardych skał stropowych. Scharakteryzowano grupę inicjałów dyskretnych zapłonu metanu związanych z występowaniem dynamicznych zjawisk geo-termo-mechanicznych. W oparciu o zaistniałe w Polsce zapłony metanu spowodowane inicjałami dyskretnymi podano czynniki górniczo-geologiczne tworzące tzw. "grupę ryzyka" dla ścian zawałowych. Na koniec określono rodzaj badań niezbędnych dla pełnej analizy zagrożenia zapłonu metanu. W konkluzji pokazano wyzwanie jakie stoi przed automatyczną aerometrią górniczą, dla rozwiązania systemowego monitorowania tego zagrożenia.

EN

The characteristic phenomena resulted from the ignition of methane have been given in the paper. The essential factors influencing the level of methane ignition hazard, it means the thermo-gas and initial factors, specifying the open and discrete initiations have been reminded. Examples of methane ignitions and explosions as well as some research results relating to destroy of structure of the hard roof rocks have been given. A group of initiations of discrete methane ignition related to occurring of dynamical geo-thermo-mechanical phenomena has been characterized. Basing on the ignitions of methane, which happened in Poland and have been caused by the discrete initiations, the mining-geological factors, so called "risk group" for heavy roof falls, have been given. Finally it has been determined a kind of research being indispensable to make a complete analysis of methane ignition hazard.In conclusion it has been issued a challenge to the automatic mining aerometry in order to implement a monitoring system of this hazard.

5

The analysis of thermo-mechanical and diffusion phenomena in the process of ceramic-metal friction welding.

Włosiński W., Zimmerman J.

Archives of Materials Science

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2006

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Vol. 27, nr 1

5-27

EN

In this paper a physical model of friction welding of elastic materials and plastic metals is presented. The model has been practically verified in the process of friction welding of corundum ceramics, containing 97.5% of Al2O3, and Al as well as in the process of friction welding of the same ceramics and Cu. In the process of Al2O3-Al welding the following conditions, i.e. values of the process parameters were applied: diameter of cylindrical bonded elements - 10 mm, pressure in the stage of friction heating - 18 MPa, rotational speed of the ceramic element - 14500 r.p.m., heating time - 0.85 s. pressure in the stage of forging - 46 MPa, time of Al forging - 3.5 s. Mechanical strength of the acquired welded joints was sufficient. Also, diffusion of Al into Al2O3 was observed in the bonding zone. The mathematical modelling of the friction welding process is also demonstrated. Simulation of the process was performed by means of finite element (FEM) method using two FEM systems, namely ADINA-T and ADINA. The process conditions in the numerical simulation were the same as those in the technological process. In ADINA-T the temperature field, which changed with time, was determined. The field was then superimposed onto the mechanical one (ADINA). The simulations made it possible to observe the thermo-mechanical phenomena that take place during the process. The obtained results show that the pressure and temperature distribution on the contact surfaces of the bonded elements is non-homogeneous. This fact has a significant influence on the quality of the welded joint. The performed calculations and studies on the influence of the diffusion phenomena on the welding process showed that the diffusion depth is approx. 4 micrometres and the calculated diffusion coefficient of Al into Al2O3 is 1.8x10 to the -13 square metres/s. Diffusion of Al into Al2O3 generates also internal stresses in the intermediate layer between the welded elements.