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EN
The paper presents results obtained from the destructive laboratory investigation conducted on materials from pressure vessels after long-term operation in the refinery industry. Tested materials contained structural defects, which arose from improper heat treatment during steel plate manufacturing. Detailed metallographic and chemical composition tests and static tensile tests were conducted. Next, complex tensile tests were conducted with simultaneous acoustic emission (AE) monitoring while observing microstructural changes by light microscopy. From the laboratory tests, the correlations between the AE signal parameters and material microstructural damage during the tensile tests were developed. The results will be used as a basis of new algorithms for the structural condition assessment of in-service pressure equipment.
2
Content available remote A parametric investigation of roller hemming operation on a curved edge part
EN
This study presents the roller hemming operation of a curved edge sheet metal which is critical in terms of dimensional accuracy and deformation. The investigation is focused on the process parameters such as bending angle, sheet thickness and roller diameter to observe their influence on roll-in, deformation, undesired wrinkling formation and hemming force which are directly related to material reliability and visual quality in the operation. A set of numerical simulations was designed and through the regression analysis of the results, the magnitude of each input parameter was investigated. The verification of the numerical model was carried out using experimental results. In the light of the results, the influence of input parameters was discussed for designing proper roller hemming operations for curved edge parts.
EN
In this paper, the analysis of the three-dimensional strain state for the hot cogging process of a steel tool with the application of the finite element method is presented. The results of work connected with the simulation of metal flow scheme, and fields of stress, strain and temperature in the material deformation process in the hot forging conditions are presented. The distribution of the effective strain, the effective stress, mean stresses and temperature on the surface of forging cross sections are determined. The numerical analysis was performed with the application of the programme DEFORM-3D. The theoretical results are subjected to experimental verification.
EN
In this paper an alternative material model using a generalized J2 finite-strain flow plasticity theory with isotropic hardening is presented. The model is based on a new nonlinear continuum mechanical theory of finite deformations of elasto-plastic media which allows for the development of objective and thermodynamically consistent material models. As a result, the constitutive equation, the evolution equation and even the ‘normality rule’, characterising the plastic flow in the material during return mapping, can be expressed in various forms, using several instances of the yield surface and corresponding pairs of stress measures and strain rates, respectively, which are conjugate with respect to the internal mechanical power and its arbitrary higher order time derivative. Therefore the results of the material model when used in numerical analyses are not affected by the description and particularities of the material model formulation. Here, we briefly outline the nonlinear continuum theory along with a detailed description of the material model and finally present the model in a numerical example using a cross-shaped specimen in biaxial tension.
EN
This paper discusses experimental results concerning the plastic deformation of the bonding zone in a two-layer AZ31/Al material subjected to compression loads. The specimens were fabricated by diffusion bonding method. The 50 μm thick transition zone at the AZ31/Al interface contained Mg–Al intermetallic phases. The physical modelling of the deformation behaviour of the intermetallic zone was performed using a Gleeble 3800 system. The compression tests were carried out at two temperatures (300 and 400 °C), two strain rates (0.1 and 1.0 s−1) and a true strain of 0.15 applied in one or two stages. The metallographic examinations and microhardness measurements were performed to assess the influence of the selected process parameters on the forming behaviour of the intermetallic zone. The experiments revealed that the main factors affecting the formability of the intermetallic zone in the two-layer AZ31/Al material were the strain rate and the temperature. It was found that when the deformation occurred at a strain rate of 0.1 s−1 and a temperature of 400 °C, there was no loss of continuity of the intermetallic transition zone; such conditions induced its plasticization.
EN
The present study investigates the possibility of enhancing the strength with ductility of dual-phase magnesium (Mg)-8 lithium (Li) alloy by the combination of alloying addition aluminium (Al) and suitable thermo-mechanical processing. Microstructural evolution, phase analysis and texture studies were performed for Mg-8Li-xAl (x = 0, 2,4 and 6) alloys with the help of scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is understood from the texture studies that the addition of Al to the Mg-8Li alloys activates the non-basal slip at room temperature. In turn, it facilitates the recovery process, hence a substantial improvement in plastic deformation after annealing of the alloys is observed. This is attributed to non-basal slip activity at room temperature. The presence of fine intermetallic compounds in the annealed Mg-8Li-xAl (x = 4 and 6) alloys leads to the higher ultimate strength (193 ± 7 MPa and 267 ± 9 MPa) and ductility (20% and 17%), respectively.
EN
Austenitic stainless steels are materials, that are widely used in various fields of industry, architecture and biomedicine. Their specific composition of alloying elements has got influence on their deformation behavior. The main goal of this study was evaluation of magnetic properties of selected steels, caused by plastic deformation. The samples were heat treated in different intervals of temperature before measuring. Then the magnetic properties were measured on device designed for measuring of magnetism. From tested specimens, only AISI 304 confirmed effect of plastic deformation on the magnetic properties. Magnetic properties changed with increasing temperature.
8
EN
This work deals with the fractography analysis of nickel-base superalloy Inconel 718 fatigued at 700°C in air atmosphere in the high cycle region. During cyclic loading of this alloy at high temperatures some different mechanisms compared to cyclic loading at ambient temperature take place. Cyclic plastic deformation at high temperatures causes some structural changes, which could have some influence.
PL
Opisano dotychczas stosowane rozwiązania w zakresie pomiaru odkształcenia i naprężenia w warstwie wierzchniej elementów umacnianych poprzez zgniot. Przedstawiono nowy, zgłoszony do opatentowania, sposób pomiaru podatności metalowych struktur cienkościennych na miejscowe, powierzchniowe odkształcenie plastyczne. Polega on na porównaniu czasu styku elementu nagniatającego z obrabianym przedmiotem cienkościennym oraz przedmiotem o dużej sztywności. Eksperyment zweryfikowano metodą elementów skończonych.
EN
This paper describes existing solutions for measuring deformations and stress in the surface layer of strain-hardened parts. It also presents a new, patent pending method of measuring susceptibility of metal thin-walled structures to a local, plastic deformation on their surface. This method compares the time of contact of an impacting element with the thin- -walled workpiece and a high-rigidity object. The experiment was verified using the Finite Element Method.
10
PL
Artykuł dotyczy opracowania metody analitycznej obliczania siły stosowanej do zginania wyrobu w kształcie pierścienia podczas zgrzewania doczołowego z uwzględnieniem obecności odkształceń plastycznych w strefie bocznikowania. Zbadano reguły odkształcania sprężysto-plastycznego prętów krzywoliniowych w wyniku zginania oraz opracowano podstawy teoretyczne określania przemieszczeń w tych prętach. Uzyskano równania analityczne, który łączą wielkość siły zginania z przemieszczeniami ruchomych szczęk mocujących zgrzewarki, parametrami geometrycznymi i własnościami fizyko-mechanicznymi materiału zgrzewanego wyrobu pierścieniowego. Na przykładzie szeregu wręgów wykazano, że uwzględnienie odkształceń plastycznych posiada istotny wpływ na wielkość siły zginania. Wyniki obliczeń wielkości siły zginającej z zastosowaniem opracowanej metody analitycznej są zbieżne z wynikami obliczeń numerycznych. Za pomocą odpowiednich wzorów opisano granice obszarów sprężystych i plastycznych strefy bocznikowania przy jej zginaniu podczas zgrzewania doczołowego. Określono wielkość krytyczną siły zginającej, przy osiągnięciu której wymagany kształt geometryczny zgrzewanego wyrobu pierścieniowego zostaje zniekształcony.
EN
The article is concerned with the development of an analytical method enabling the calculation of force used for the bending of a ring-shaped product during the butt welding allowing for the presence of plastic strains in the shunting zone. The research involved the investigation of principles governing the plastic-elastic strain of curvilinear bars subjected to bending and the development of theoretical foundations enabling the identification of displacements in such bars. The research-related investigation led to the obtainment of analytical equations combining bend force with movements of welding machine fixing clamps, geometrical parameters and physico-mechanical properties of a ring-shaped product material subjected to welding. Using a number of frames as an example, it was demonstrated that plastic strains significantly affected the value of bend force. The calculation results concerning the volume of bend force obtained using the above named analytical method converged with the results obtained using numerical calculations. Appropriate formulas were used to describe the boundaries of elastic and plastic areas of the shunting zone subjected to bending during butt welding. The research resulted in the determination of the critical value of bend force, the exceeding of which led to the deformation of the required geometrical shape of a ring-shaped product subjected to welding.
PL
Przedstawiono wyniki badań eksperymentalnych odkształceń plastycznych metali wywołanych impulsem laserowym. Badania przeprowadzono na laserze Nd:YAG o długości fali promieniowania 1064 nm i czasie impulsu laserowego 10 ns. Indukowaną impulsem laserowym falę uderzeniową wykorzystano do wywołania lokalnego odkształcenia plastycznego powierzchni materiałów. Przeprowadzono analizę możliwości wykorzystania badanego procesu do opracowania nowej metody pomiaru twardości dynamicznej materiałów.
EN
The paper presents experimental data of surface plastic deformation of 304 steel and two aluminum alloys caused by nanosecond laser pulse. The experiments were conducted on Nd:YAG laser on 1064 nm wavelength and 10 ns. The pressure wave was use to induced local surface plastic deformation of materials. The analysis of the possibilities of using the process to develop a new method for measuring dynamic hardness of materials under very high strain rate is shown.
EN
This paper presents the calculation results obtained on the basis of three formal simplifications (derived in Part I) gradually led into the main components of the generalized model of strain where suitable simplifications of the 1st, 2nd and 3rd type have been obtained. The paper also presents the results of considerations on the wall thickness distribution in the vertex point of the elongated layers of the bent elbow, and values of main components of the strain state and intensity of the strain (equivalent strain) depending on the bending angle for the generalized strain scheme and three simplified methods. The results are shown in the form of graphs and table.
EN
The paper contains two parts. In the first part, basic relationships were derived and some problems connected with stability loss during hydraulic forming of round metallic drawpieces with liquid pressure were discussed. The aim of the considerations is to test drawability of sheets by estimation of acceptable values of plastic strains and the corresponding heights of spherical shells. The analysis was based on some selected real conditions of stability loss. The influence of the coefficient of material hardening for the drawpiece, the coefficient of normal anisotropy and coefficients of plane anisotropy on acceptable values of plastic strains and heights of the formed drawpieces corresponding to the given condition of stability loss was also tested.
EN
This part of the paper contains the calculation results presented in the form of suitable diagrams and tables. The calculations were made according to the relationships obtained in Part I devoted to a laboratory test of hydraulic forming for some chosen engineering conditions of stability loss. The influence of the coefficient of material hardening, the coefficient of normal anisotropy and the coefficients of plane anisotropy on acceptable plastic strains and heights of the formed drawpieces corresponding to a given condition of stability loss was tested, too.
EN
In the paper the complex model of hardening of the hot-work tool steel is presented. Model of estimation of phase fractions and their kinetics is based on the continuous heating diagram (CHT) and cooling diagram (CCT). Phase fractions which occur during the continuous heating and cooling (austenite, pearlite or bainite) are described by Johnson-Mehl (JM) formula. To determine of the formed martensite the modified Koistinen-Marburger (KM) equation is used. Model takes into account the thermal, structural, plastic strains and transformation plasticity. To calculate the plastic strains the Huber-Mises plasticity condition with isotopic hardening is used. Whereas to determine transformations induced plasticity the Leblond model is applied. The numerical analysis of phase compositions and residual stresses in the hot-work steel (W360) element is considered.
PL
W pracy przedstawiono kompleksowy model hartowania stali narzędziowej do pracy na gorąco. Model szacowania ułamków faz oraz ich kinetyki oparto na wykresach ciągłego nagrzewania (CTPA) oraz chłodzenia (CTPc). Ułamki faz powstałych podczas ciągłego nagrzewania i chłodzenia (austenit, perlit lub bainit) wyznaczane są równaniem Johnsona- Mehla. Do określenia tworzącego się martenzytu wykorzystano zmodyfikowane równanie Koistinena i Marburgera. W modelu uwzględniono odkształcenia cieplne, strukturalne, plastyczne oraz odkształcenia transformacyjne. Do wyznaczania odkształceń plastycznych zastosowano warunek plastyczności Hubera-Misesa ze wzmocnieniem izotropowym, natomiast do wyznaczenia odkształceń transformacyjnych wykorzystano model Leblonda. Dokonano analizy numerycznej składu fazowego oraz naprężeń hartowniczych w elementach wykonanych ze stali narzędziowej do pracy na gorąco (W360).
EN
Development of microstructure in two-phase α+β titanium alloys is realized by thermomechanical processing – sequence of heat treatment and plastic working operations. Analysis of achieved results indicates that hot plastic deformation – depending on deformation degree – causes significant elongation of α phase grains. Following heat treatment and plastic deformation processes lead to their fragmentation and spheroidization. Characterization of microstructure morphology changes during thermomechanical processing of quenched Ti-6Al-4V and Ti-6Al-2Mo-2Cr alloys is presented in the paper. The effect of martensitic phase α’(α”) on microstructure development in plastic deformation process was confirmed.
PL
Kształtowanie mikrostruktury dwufazowych stopów tytanu α+β realizowane jest w procesie cieplno-plastycznym będącym sekwencją operacji obróbki plastycznej i przeróbki plastycznej. Analiza uzyskanych wyników badań wskazuje, że odkształcanie plastyczne na gorąco – w zależności od stopnia odkształecenia - powoduje wydłużanie ziarn fazy α. Kolejne operacje obróbki cieplnej lub odkształcania plastycznego prowadzą do ich fragmentacji i sferoidyzacji. W pracy przedstawiono charakteryzację zmian morfologii składników mikrostruktury stopów Ti-6Al-4V oraz Ti-6Al-2Mo-2Cr poddanych przechładzaniu na początkowym etapie procesu cieplno-plastycznego. Potwierdzono oddziaływanie fazy martenzytycznej α’(α”) w badanych stopach na przebieg procesu kształtowania ich mikrostruktury podczas odkształcania plastycznego.
17
Content available Impact Load of Welds after Micro-Jet Cooling
EN
Micro-jet cooling is an innovative method of forced cooling. It could be used to cooling after welding immediately. It allows to obtain welds with better properties in comparison to ordinary welding method. Favourable structure of weld metal deposit (WMD) with higher content of acicular ferrite (AF) could be obtained. These properties can be controlled by several variables (e. g. type of cooling gas, number of jets). Plastic properties are particularly important in case of impact load. This type of strength is very dangerous for the structure and for safety of users (ex. car body during car crash). This article presents the influence of the cooling gas and the number of jets on plastic properties of the weld joint for impact load. It is described by restitution coefficient and plastic strain.
PL
Chłodzenie mikrojetowe to innowacyjna metoda wymuszonego chłodzenia. Może ona być wykorzystywana do chłodzenia spoin natychmiast po spawaniu. Umożliwia to uzyskanie spoiny o lepszych właściwościach w porównaniu do spoin wykonywanych w typowych metodach spawania. Powodem tego jest pojawienie się korzystnej struktury stopiwa o dużej zawartości drobnoziarnistego AF (acicular ferrite). Właściwości spoiny mogą być przy tym sterowane przez kilka zmiennych, takich jak rodzaju gazu chłodzącego oraz ilość chłodzących mikro strug. Własności plastyczne stopiwa są szczególnie ważne w przypadku obciążeń udarowych. Ten rodzaj wymuszeń jest bardzo niebezpieczny dla samej konstrukcji spawanej oraz dla bezpieczeństwa jej użytkowników (np. nadwozia samonośnego samochodu podczas wypadku samochodowym). Artykuł przedstawia wpływ rodzaju gazu chłodzącego i ilości mikro strug na własności plastyczne spoiny przy obciążeniach udarowych. Własności plastyczne zostały opisane przez współczynnik restytucji i odkształcenia plastyczne.
EN
Magnesium alloys are the lightest structural materials, which makes them particularly suitable for use in the aircraft and automotive industry. However, due to hexagonal close-packed crystal structure, resulting in insufficient number of independent slip systems, magnesium alloys exhibit poor formability at room temperature. Conventional methods of work hardening of magnesium alloys requires the temperature about 300°C, which favours simultaneously processes of thermal recovery and grain growth, but decreases beneficial microstructure strengthening effect. Thus, it is a crucial to undertake development of a technology for semi-finished magnesium alloys elements, which will ensure better mechanical properties of the final products by forming desirable microstructure. In the paper we present the development of crystallographic texture of the Mg-based alloy (Mg-AZ31) in the form of pipe extruded at 430°C and subjected to pilger rolling at relatively low temperature.
PL
Stopy magnezu należą do najlżejszych materiałów konstrukcyjnych, co czyni je szczególnie użytecznymi w przemyśle lotniczym i samochodowym. Jednakże ze względu na strukturę heksagonalną zwartą, skutkującą niewystarczającą liczbą systemów poślizgu, stopy magnezu wykazują złą plastyczność w temperaturze pokojowej. Konwencjonalne metody umocnienia poprzez zgniot wymagają temperatury około 300°C dla tych stopów, co sprzyja jednocześnie procesom zdrowienia i rozrostu ziarna, ale obniża sam efekt umocnienia. Zatem kluczowe jest rozwinięcie technologii dla półproduktów ze stopu magnezu, która zapewni lepsze właściwości mechaniczne końcowych produktów poprzez uformowanie korzystnej mikrostruktury. W pracy przedstawiono rozwój tekstury krystalograficznej stopu na bazie magnezu (Mg-AZ31) w formie rury wyciśniętej w temperaturze 430°C i poddanej walcowaniu pielgrzymowemu we względnie niskiej temperaturze.
EN
In this research, effect of the various mechanical milling process on morphology and microstructural changes of nano and micron Al-powders was studied. The milling of Al-powders was performed by both high energy and low energy ball milling process. The influence of milling (pulverizing) energy on the structural changes of Al-powders was studied. Al-nanoparticles were agglomerated during the MA and its size was increased with increasing milling while micron Al-powder gets flattened shape during high energy ball milling due to severe plastic deformation. Meanwhile, structural evolution during high energy ball milling of the nano powder occurred faster than that of the micron powder. A slight shift in the position of X-ray diffraction peaks was observed in nano Al-powders but it was un-altered in macro Al-powders. The variation in lattice parameters was observed only for nano Al powders during the high energy ball milling due to lattice distortion.
20
EN
The study deals with failure criteria for S235JR steel subjected to spatial stress states. The predictions were made using the modified Gurson–Tvergaard–Needleman (GTN) material model, which takes into account the effect of microstructural damage. The relationship between the material strength parameters and the microstructural changes caused by plastic deformation was established by analyzing the void volume fraction. The microstructural failure criteria determined for S235JR steel refer to the moment of decrease in strength and rupture.
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