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1

Safety analysis of complex multistate ageing system

Kołowrocki Krzysztof

Safety and Reliability of Systems and Processes

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2023

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Summer Safety and Reliability Seminar 2023

79--98

EN

Recent developments of an innovative own earlier approach to safety analysis of a complex multistate ageing system impacted by its operation processes are presented. A safety function and other safety indicators are defined for a complex multistate ageing system changing its functional structure and consequently its safety structure and its components safety parameters during the operation and determined under the assumption that its components have piecewise exponential safety functions. Results are applied to examine safety of port and maritime transportation systems.

2

Investigating the ageing process of polymer modified bitumen using a modified Thin-Film Oven Test in the aspect of recycling purpose

Farid Miftah, Król Jan

Roads and Bridges - Drogi i Mosty

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2023

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Vol. 22, no. 4

379--386

EN

Polymer Modified Bitumen (PMB) is a widely used material for road construction. Commonly, PMBs are produced by mixing bitumen with various types of Styrene- Butadiene–Styrene (SBS) copolymers and, if necessary, with another additive such as a cross-linking agent to improve the material’s performance. The ageing process of PMBs is more complex than unmodified bitumen due to molecular interactions between the bitumen and the polymer. Previous studies suggest that the polymer modifier dominates the chemical degradation of PMBs during short-term ageing, while long-term ageing is dominated by bitumen oxidation. As a result, RAP containing PMB as its binder still contains polymer in its chemical composition, emphasizing the need for a comprehensive understanding of the ageing process of PMBs. In current practice, RAP is heated before being mixed with virgin materials to allow reactivation of its aged binder. This study proposes a modified Thin-Film Oven Test (TFOT) as an ageing simulation method, with variations in time and temperature to simulate ageing during the RAP mixing process. The bitumen oxidation phenomenon mostly dominates the ageing process. From quantitative indices analysis, under short duration and lower temperature conditions, the polymer degradation helps to resist ageing shortly. Moreover, the DSR test shows that ageing caused the PMB to increase in complex modulus while decreasing in phase angle, indicating hardening and shifting toward more elastic behaviour. The most prominent effect of ageing can be observed at lower test temperature for phase angle and higher test temperature for complex modulus. Generally, the ageing conditions’ temperature has a more significant role in dictating the ageing effect on PMB than the duration.

PL

Asfalt modyfikowany polimerami (PMB) to szeroko stosowany materiał do budowy dróg. Powszechnie asfalt modyfikowany polimerami wytwarzany jest poprzez mieszanie bitumu z różnymi rodzajami kopolimerów styrenowo-butadienowo-styrenowych (SBS) oraz, w razie potrzeby, z innym dodatkiem, takim jak środek sieciujący, w celu poprawy wydajności materiału. Proces starzenia asfaltów modyfikowanych polimerami jest bardziej złożony niż niemodyfikowanego asfaltu ze względu na interakcje molekularne między asfaltem a polimerem. Wcześniejsze badania sugerują, że modyfikator polimeru dominuje w degradacji chemicznej asfaltów modyfikowanych polimerami podczas starzenia krótkoterminowego, podczas gdy starzenie długoterminowe jest zdominowane przez utlenianie bitumu. W rezultacie destrukt asfaltowy zawierający asfalt modyfikowany polimerami jako spoiwo nadal zawiera polimer w swoim składzie chemicznym, co podkreśla potrzebę kompleksowego zrozumienia procesu starzenia asfaltów modyfikowanych polimerami. W obecnej praktyce destrukt asfaltowy jest podgrzewany przed zmieszaniem z materiałami pierwotnymi, aby umożliwić reaktywację jego starzejącego się spoiwa. W niniejszym badaniu zaproponowano metodę cienkiej warstwy (TFOT) jako metodę symulacji starzenia, ze zmianami czasu i temperatury w celu symulacji starzenia podczas procesu mieszania destruktu asfaltowego. Zjawisko utleniania bitumu przeważnie dominuje w procesie starzenia. Z analizy wskaźników ilościowych wynika, że w warunkach krótkiego czasu trwania i niższej temperatury degradacja polimeru pomaga w krótkim czasie ograniczyć proces starzenia. Co więcej, badanie DSR wykazało, że starzenie spowodowało wzrost złożonego modułu asfaltu modyfikowanego polimerami przy jednoczesnym zmniejszeniu kąta fazowego, co wskazuje na utwardzenie i przesunięcie w kierunku bardziej elastycznego zachowania. Najbardziej widoczny efekt starzenia można zaobserwować w niższej temperaturze testowej dla kąta fazowego i wyższej temperaturze testowej dla modułu zespolonego. Ogólnie rzecz biorąc, temperatura warunków starzenia odgrywa bardziej znaczącą rolę w dyktowaniu wpływu starzenia na asfalt modyfikowany polimerami niż czas jego trwania.

3

Mechanical properties of Super 304H steel after long-term ageing at 650 and 700°C

Zieliński Adam, Sroka Marek, Purzyńska Hanna, Novy Frantisek

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 2

art. no. e144612

EN

The paper shows the degradation process of the modern austenitic Super 304H (X10CrNiCuNb18-9-3) steel which was subjected to long-term aging for up to 50,000 h at 650 and 700°C. The investigations include microstructure examination (SEM), identification and analysis of the precipitation process, and mechanical properties tests. The Super 304H steel has a structure characteristic of austenitic steels with visible annealing twins and single primary NbX precipitates. Long-term aging in the steel leads to numerous precipitation processes of M23C6, MX carbides, σ phase, Z phase, and ε-Cu phase. Precipitation processes lead to a decrease in plastic properties and impact energy as well as alloy over aging. Yield strength and tensile strength values after 50,000 h of aging were similar to those as delivered. The yield and tensile strength value strongly depend on the applied aging temperature.

4

Structure of the S304H Steel after 20,000 Hours of Ageing

Wersta Robert, Zieliński Adam, Sroka Marek, Puszczało Tomasz, Sówka Karol

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

487--493

EN

The S304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. The paper presents the results of the research on the microstructure after ageing for 20,000 hours at 650 and 700°C. The microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identifies using transmission electron microscopy. The influence of ageing time on microstructure changes and the precipitation process of the tested steel is described. The presented research results are an element of material characteristics of the new generation of steel, which are used in the design work of pressure devices of steam boilers and in diagnostic work during operation.

5

Structure of 22Cr25NiWCoCu Austenitic Stainless Steel After Ageing

Sroka Marek, Zieliński A., Puszczało T., Sówka K., Hadzima B.

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 1

175--180

EN

The 22Cr25NiWCoCu austenitic stainless steel was developed by AB Sandvik Material Technology in Sweden. Due to its high creep strength and good corrosion resistance, this material is well suited for use in superheaters in advanced coal-fired power boilers as well as in other types of steam boilers using various types of fuel. The examined material was subject to long-term ageing for the time of annealing up to 20 000 h at 700 and 750°C. Precipitation processes and microstructure stability as-received and after ageing were investigated. Examination of the microstructure was conducted using scanning electron microscopy. The identification of secondary phases was carried out by X-ray phase composition. Using the results of the investigations of precipitation processes in the microstructure, both within the grains and at the grain boundaries, their statistical analysis was carried out. To illustrate this impact, the following parameters were used: surface area and equivalent diameter of precipitates. Based on the surface area measurements, the percentage of the phase in the reviewed photo’s total area was calculated.

6

Safety analysis of critical infrastructure impacted by operation and climate-weather changes - theoretical backgrounds

Kołowrocki Krzysztof

Safety and Reliability of Systems and Processes

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2021

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Summer Safety and Reliability Seminar 2021

139--180

EN

The methodology and general approach to critical infrastructure safety and resilience analysis is proposed. The principles of multistate approach to critical infrastructure safety analysis are introduced. There are introduced the notions of critical infrastructure basic safety indicators like, the critical infrastructure safety function, the critical infrastructure risk function and the critical infrastructure fragility curve. The critical infrastructure safety and resilience indicators are proposed to be obtained using probabilistic approach to modelling of operation threats and extreme weather hazard impacts on its assets safety. There are proposed safety and resilience indicators, crucial for operators and users of the critical infrastructure, defined as a complex system in its operating environment. The safety of a critical infrastructure free of any outside impacts is discussed and modelled. The safety indicators of this critical infrastructure are defined. The safety of critical infrastructure impacted by its operation process is considered. The critical infrastructure operation process and its parameters are defined and its characteristics are determined. The safety and resilience indicators of the critical infrastructure related to the operation process impact are proposed. The safety of critical infrastructure impacted by the climate-weather change process at its operating area is considered. The climate-weather change process at the critical infrastructure operating area and its parameters are defined and its characteristics are determined. The safety and resilience indicators of the critical infrastructure related to the climate-weather change process at its operating area impact are proposed. The safety of critical infrastructure impacted by its operation process and climate-weather change process at its operating area is considered. The critical infrastructure operation process related to climate-weather change process at its operating area and its parameters are defined and its characteristics are determined. The safety and resilience indicators of the critical infrastructure impacted by the operation process related to climate-weather change process are proposed. Real critical infrastructures and their assets impacted by their operation processes related to climate-weather change process at their operating area are suggested to be examined and their safety and resilience indicators are proposed to be determined by the proposed methods.

7

Ocena jakości estetycznej włóknisto-cementowych prefabrykatów elewacyjnych z betonu

Woyciechowski Piotr, Jackiewicz-Rek Wioletta

Materiały Budowlane

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2021

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nr 9

32--35

PL

Przedmiotem artykułu jest metodyka oceny estetyki elewacyjnych płyt cementowo-włóknistych. Przedstawiono propozycję kryteriów takiej oceny, a także propozycję metody badawczej, umożliwiającej prognozowanie zachowania estetyki takich płyt w czasie eksploatacji, na podstawie przyspieszonego badania starzeniowego.

EN

The subject of the article is a methodology for assessing the aesthetics of fiber-cement facade flat-sheets. A proposal of criteria for such an evaluation was presented, as well as a proposal of a research method that would enable the prediction of the aesthetic behavior of such elements during exploitation, based on an accelerated aging test.

8

Microstructure of cast MgBi6X0.5 (X = Ca, Mn, Zn) alloys in peak-aged condition

Gryc Adam, Dybowski Bartłomiej, Jarosz Robert, Kiełbus Andrzej

Journal of Metallic Materials

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2021

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Vol. 73, no. 3

23--28

EN

Cast magnesium alloys are characterised by the lowest density among commercially used structural metals. They are applied mainly in the transportation industry and small, lightweight electronic devices. Due to the low operating temperature of the most widely used alloys from the Mg-Al system, alloys containing rare earth elements with the maximum working temperature reaching 300°C have been developed. However, these alloys are extremely expensive due to the low availability of RE elements. The Mg-Bi system is a promising candidate for the new magnesium-based alloys, as it reveals limited solubility of Bi in Mg enabling precipitation hardening and a high melting point of the Mg3Bi2 phase. The paper presents the results of the analysis of MgBi6 and MgBi6X0.5 (X = Ca, Mn, Zn) alloys’ microstructure in the peak-aged condition. The microstructure of the analysed alloys in the as-cast condition consists of α-Mg solid solution dendrites and Mg3Bi2+α-Mg eutectic compound. Solutionising conducted at 525°C for 8 h, followed by water quenching leads to the dissolution of the intermetallic phases in all of the investigated alloys apart of the MgBi6Ca0.5 alloy. In this case, fine intermetallic phases containing Mg, Bi, and Ca have been found after solutionising. The ageing of the alloys at 200°C results in peak hardness after 120-44 h. The heat treatment leads to the formation of fine strengthening phases within the α-Mg solid solution, characterised by a variety of morphologies -needle, platelet- or lathlike and cuboid. The needle- and platelet- or lathlike phases are found in two sizes -large, with length reaching hundreds of nanometres, and smaller, not exceeding 100 nm. Cuboid particles are found with sizes not higher than 100 nm. The addition of Mn and Zn increases precipitate volume fraction after the heat treatment. Additionally, in the case of the MgBi6Zn0.5 alloy, particles forming an angle of 120° were found, which indicates their presence at the prismatic planes of α-Mg HCP crystal lattice.

PL

Odlewnicze stopy magnezu charakteryzują się najniższą gęstością wśród wszystkich komercyjnie stosowanych stopów konstrukcyjnych. Znajdują zastosowanie głównie w przemyśle transportowym oraz małych, lekkich urządzeniach elektronicznych. Z uwagi na niską temperaturę eksploatacji najpowszechniej stosowanych stopów z układu Mg-Al, opracowano stopy, zawierające pierwiastki ziem rzadkich, znajdujące zastosowanie w temperaturach do 300°C. Jednak stopy z tej grupy są niezwykle drogie, z uwagi na ograniczoną dostępność pierwiastków ziem rzadkich. Obiecującą alternatywę stanowią stopy z układu Mg-Bi, który z uwagi na ograniczoną rozpuszczalność bizmutu w magnezie oraz wysoką temperaturę topnienia fazy Mg3Bi2 umożliwia ich umocnienie na drodze utwardzania wydzieleniowego. W artykule przedstawiono wyniki badań mikrostruktury stopów MgBi6 oraz MgBi6X (X = Ca, Mn, Zn) po starzeniu. Mikrostruktura badanych stopów w stanie lanym składa się z dendrytów roztworu stałego α-Mg oraz mieszaniny eutektycznej Mg3Bi2+α-Mg. Przesycanie, przeprowadzone w temperaturze 525°C przez 8 h z chłodzeniem w wodzie doprowadziło do rozpuszczenia faz międzymetalicznych we wszystkich badanych stopach, z wyjątkiem stopu MgBi6Ca0,5. W jego przypadku po przesycaniu zidentyfikowano w strukturze drobne fazy międzymetaliczne, zawierające Mg, Bi i Ca. Maksymalną twardość stopów po starzeniu w temperaturze 200°C osiągnięto po 120÷144 h. Zastosowana obróbka cieplna doprowadziła do utworzenia się wewnątrz ziaren roztworu stałego α-Mg drobnych faz umacniających o zróżnicowanej morfologii -od iglastej, przez płytkową, po prostopadłościenną. Zaobserwowano dwa typy wydzieleń iglastych i płytkowych -większe, o długości rzędu kilkuset nanometrów oraz mniejsze, nieprzekraczające 100 nm długości. Wydzielenia prostopadłościenne charakteryzowały się rozmiarami, nieprzekraczającymi 100 nm. Dodatek Mn oraz Zn spowodował wzrost udziału objętościowego wydzieleń po obróbce cieplnej. Dodatkowo, w przypadku stopu MgBi6Zn1,5, wydzielenia tworzyły kąt 120°C, co wskazuje na ich obecność na płaszczyznach pryzmatycznych komórki elementarnej α-Mg.

9

Mechanical properties of P91 and PB2 steel after long-term ageing at 620°C

Golański Grzegorz

Journal of Metallic Materials

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2021

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Vol. 73, no. 3

2--6

EN

The article presents the results of research on mechanical properties of martensitic steels, X10CrMoVNb9-1 (P91) and X13CrMoCoVNbNB9-2-1 (PB2), as-received and after 50,000 hours of ageing at 620˚C. The scope of the tests of mechanical properties included a Vickers hardness test, Charpy impact test, and static tensile test. As received, the investigated steels were characterised by relatively high mechanical properties. The long-term effect of temperature and time contributed to a relatively slight decrease in the strength properties and hardness of the tested steels. However, a considerable decrease in the ductility of these alloys was observed. The decrease in mechanical properties after long-term ageing was smaller in the case of the PB2 steel, which was attributed to the beneficial effect of microalloying boron.

PL

W artykule przedstawiono wyniki badań właściwości mechanicznych stali martenzytycznych X10CrMoVNb9-1 (P91) i X13CrMoCoVNbNB9-2-1 (PB2) w stanie dostawy oraz po 50 000 godzinach starzenia w temperaturze 620˚C. Zakres badań właściwości mechanicznych obejmował pomiar twardości metodą Vickersa, próbę udarności oraz statyczną próbę rozciągania. W stanie dostawy badane stale charakteryzowały się względnie wysokimi właściwościami mechanicznymi. Długotrwałe oddziaływanie temperatury i czasu przyczyniło się do względnie niewielkiego spadku właściwości wytrzymałościowych i twardości badanych stali. Obserwowano natomiast znaczące obniżenie ciągliwości tych stopów. Spadek właściwości mechanicznych po długotrwałym starzeniu był mniejszy w przypadku stali PB2, co przypisano korzystnemu działaniu mikrododatku boru.

10

Effect of accelerated ageing on some surface properties of UV-coated hackberry (Celtis australis L.) wood parquet

Ayata Ümit, Esteves Bruno, Gürleyen Levent, Çakicier Nevzat, Ferreira Jose, Domingos Idalina, Türk Mutlu

Drewno : prace naukowe, doniesienia, komunikaty

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2021

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vol. 64, nr 208

17--33

EN

The importance of UV-curable coatings is currently increasing. In the parquet industry, where UV systems are applied, it is beneficial to investigate new tree species as potential raw materials. This study was carried out to determine the effect of accelerated ageing on some surface properties of hackberry (Celtis australis L.) wood treated with UV system parquet varnish. UV system parquet varnishes were applied to hackberry wood surfaces in three and five layers, according to the requirements of industrial applications. The varnished surfaces were then exposed to UV rays for 252 and 504 h using UVA-340 lamps in a QUV ageing device. Glossiness, colour parameters, pendulum hardness and adhesion strength (pull-off) (MPa) were determined for the coated samples before and after ageing, and the results for the aged and unaged test samples were compared. Analysis of variance showed that the results were significant for all tests. The results for all tests varied by ageing time.

11

Novel Composite Solid Propellant with High Resistance to Thermo-oxidative Degradation Reactions, Extended Shelf Life, and Superior Combustion Characteristics

Elbasuney Sherif, Elsaka Eslam, Elbeih Ahmed, Mostafa Hosam E.

Central European Journal of Energetic Materials

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2021

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Vol. 18, no. 1

143--158

EN

Hydroxy-terminated polybutadiene (HTPB) pre-polymer is the main constituent that is responsible for conferring high mechanical properties on composite solid propellants. However, HTPB pre-polymer suffers from oxidative degradation reactions that diminish its mechanical properties and shelf life. Composite solid propellant formulations based on an advanced stabilizing agent (anti-oxidant), Flexzone 6-H, with different curing ratios, 0.7 and 1.1, were developed via mixing and casting under vacuum. The developed formulations were subjected to artificial ageing using Vant Hoff,s formula by isothermal heating at 80 °C for up to 35 days. The change in strain with ageing was evaluated using a uni-axial tensile test. The propellant formulation based on a curing ratio of 0.7 demonstrated a high ageing resistance coefficient and an extended service life of up to 15 years, compared with 5 years for higher curing ratio. A propellant grain is considered to be ‘aged out’ at 30% reduction in its maximum strain value. The propellant formulation based on the 0.7 curing ratio exhibited superior thermal stability as it offered a minimum decrease in heat released after ageing using DSC. Additionally, the 0.7 curing ratio formulations exhibited a minimum change in burning rate and pressure exponent with ageing time. It can be concluded that the propellant with 0.7 curing ratio can maintain its mechanical, thermal, and ballistic properties with ageing.

12

Assessment of the Shelf Life of Composite Solid Propellants in Air and Nitrogen Atmospheres through Thermal Ageing

Keshavarz Mohammad Hossein, Hosseini Seyyed Hesamodin, Mehran Karimi

Central European Journal of Energetic Materials

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2021

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Vol. 18, no. 1

25--45

EN

This work introduces dynamic mechanical thermal analysis (DMTA) as an efficient method for the assessment of the shelf life of solid composite solid propellants in air and nitrogen atmospheres. The samples were aged at three temperatures 323.15, 333.15, and 343.15 K for 60, 120, and 180 days. The two different methods of Arrhenius and Berthelot were used to compare the effects of air and nitrogen atmospheres on the ageing of composite solid propellants. Damping (Tan δ) of composite solid propellants was used to determine the shelf life of the samples based on the loss of half of the physical property Tan δ (50% drop in damping). For the air atmosphere, the calculated activation energy for the degradation reactions of the samples was 86.26 kJ·mol–1. Both models, Arrhenius and Berthelot, confirmed that the shelf lives of the samples under the nitrogen atmosphere are more than four times those in an air atmosphere.

13

Analysis of the precipitation process of secondary phases after long-term ageing of the S304H steel

Zieliński Adam, Wersta Robert, Sroka Marek

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

|

Vol. 69, nr 5

art. no. e137520

EN

S304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. The paper presents the results of research on the microstructure following ageing for 30,000 hours at 650 and 700°C. Microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identified using transmission electron microscopy. The paper analyses the precipitation process and its dynamics depending on the temperature and ageing time in detail. MX carbonitrides and the ε_Cu phase were proved to be the most stable phase, regardless of the test temperature. It was also showed that the M₂₃C₆ carbide precipitates in the tested steel and the intermetallic sigma phase (σ) may play a significant role in the loss of durability of the tested steel. This is related to their significant increase due to the influence of elevated temperature, and their coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quantitative identification of the secondary phase precipitation processes described in the study is important in the analysis of the loss of durability of the tested steel under creep conditions.

14

Funkcjonalność szpitala i ergonomia pracy personelu w obliczu starzenia

Szuba Paulina

Zeszyty Naukowe Politechniki Poznańskiej. Architektura, Urbanistyka, Architektura Wnętrz

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2020

|

Z. 2

157--167

PL

Ostatnie dekady wskazują na potrzebę istotnych zmian w organizacji i zarządzaniu szpitalami. Obowiązująca definicja szpitala, jaką jest budynek z odpowiednią infrastrukturą techniczną, kreujący przestrzeń niezbędną do realizacji procedur (Tomanek 2015) staje się niewystarczająca. Istnieje wyraźna relacja pomiędzy skutecznością leczenia i efektywnością pracy personelu, lecz przy obecnym niedoborze i starzejącej się populacji personelu medycznego, dotkniętego często przypadłością wypalenia zawodowego, jest ona teoretyczna. Starania o sprawne działanie służby zdrowia są warte szczególnej uwagi, gdyż stawką jest zapewnienie równego dostępu do opieki zdrowotnej, ochrona społeczeństwa przed konsekwencjami utraty zdrowia, obrona populacji przed zagrożeniem zdrowia oraz poprawa stanu zdrowia jednostki, rodziny i społeczności (WHO 2010).

EN

Recent decades show significant changes in the organization and management of hospitals. The definition of a hospital, which is “a building with appropriate technical infrastructure, which creates space adjusted to the implementation of medical procedures”, becomes deficient. There is a clear relationship between the effectiveness of treatment and the work efficiency of staff, but in the current situation of medical personnel shortage and an aging population of medical staff, that is often suffering from work burnout, it is theoretical. Efforts for efficient work of the health services are worth special attention, while it must ensure equal access to health care, protect society against the consequences of health loss, defend the population against health threats, and improve the health of the individual, family and community.

15

Safety analysis of multistate ageing car wheel system with dependent components

Kołowrocki Krzysztof

Safety and Reliability of Systems and Processes

|

2020

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Summer Safety and Reliability Seminar 2020

101--116

EN

An innovative approach and a new significant theoretical result are proposed for the safety analysis of multistate ageing systems that consider their components’ dependency. A safety function and a risk function are defined and determined for a multistate ageing system with independent and dependent components. As a special case, the safety of a series system is modelled using its components’ piecewise exponential safety functions. Results are applied to examine and characterize safety of an exemplary car wheel system.

16

Safety analysis of car wheel system impacted by operation process

Dąbrowska Ewa

Safety and Reliability of Systems and Processes

|

2020

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Summer Safety and Reliability Seminar 2020

61--75

EN

A practically important approach is proposed for the safety analysis of multistate ageing systems that considers the influence of their operation processes on their safety. The system operation process semi-Markov model is introduced and its characteristics are determined. The system safety function is defined and determined for a multistate ageing complex system impacted by its operation process. As a special case, the safety of a series system is modelled using its components’ piecewise exponential safety functions and the results are applied to examine and characterize safety of an exemplary car wheel system.

17

Wpływ warunków starzeniowych na podatność tworzyw sztucznych na degradację

Dziechciarz Anna, Małozięć Daniel, Bąk Damian, Klapsa Wojciech

Przemysł Chemiczny

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2020

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T. 99, nr 7

1054--1057

PL

Większość powszechnie stosowanych tworzyw sztucznych wykazuje bardzo dobre właściwości termo- i elektroizolacyjne i są one powszechnie wykorzystywane w urządzeniach elektrycznych i elektronicznych. W długim okresie użytkowania tych urządzeń właściwości tworzyw nie powinny ulegać pogorszeniu. Badaniom poddano wybrane rodzaje powszechnie stosowanych tworzyw sztucznych (PE 300, PPH i PVC) zarówno „nowych”, jak i poddanych procesowi starzenia. Stwierdzono, że starzenie przeprowadzone zgodnie z wymaganiami określonymi w dokumentach normatywnych dla urządzeń elektrycznych nie pogarsza w znaczący sposób parametrów rozkładu tych tworzyw.

EN

Com. polyethylene, hard polypropylene and poly(vinyl chloride) 2–3 mm thick plates were thermally aged under std. conditions: SO2 + air, humidity 75% at 25°C, air, humidity 93% at 40°C or dry air at 70°C. The aged samples were studied by thermogravimetry. No substantial changes of characteristics decompn. temps. and rates were obsd. after ageing.

18

Simulation modeling for predicting hospital admissions and bed utilisation

Hajłasz Maria, Mielczarek Bożena

Operations Research and Decisions

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2020

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Vol. 30, No. 3

5--19

EN

Demographic research of the world population shows that societies are ageing. The ongoing changes in the population structure will require appropriate quantitative and qualitative adjustments in health services to meet the needs of society. Simulation methods turn out to be helpful in these kinds of analyses. In this paper, the authors present a case study on using discrete event simulation (DES) to support decision-making in the field of hospital bed management in the light of demographic changes. The case study was elaborated for one of the Polish district hospitals. A DES model was built to simulate admissions to two hospital wards: paediatric and geriatric. A series of experiments were carried out as based on real data extracted from the hospital database and forecasted demographic trends elaborated by the Central Statistical Office of Poland (CSO). The influence of demographic changes on hospital admissions in the chosen age-gender cohorts was explored, examining different variants of hospital bed availability. The results of the experiments show that demographic trends significantly influence healthcare admission and bed utilisation. The reduction in the number of admissions to the paediatric ward by about 6% results in a change in average bed utilisation from 57.90% to 54.06%. With about 12% more admissions to the geriatric ward, the change is from 68.88% to 75.59%.

19

Impact of long-term ageing on σ phase precipitation process in steels with austenitic matrix

Zieliński Adam

Journal of Metallic Materials

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2020

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Vol. 72, no. 4

31--39

EN

Super 304H, HR3C and Sanicro 25 grade austenitic matrix steels are used in the construction of pressure components of boilers with supercritical operating parameters. The article presents the results of microstructure examination in delivery condition and after ageing for up to 50,000 hours at 700°C. The microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identified using transmission electron microscopy. In particular, the study analysed the σ phase precipitation process and its dynamics depending on the ageing time. It has been shown that the intermetallic σ phase plays a significant role in the loss of durability of the tested steel. It is related to its significant increase due to the influence of high temperature, and its coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quantitative identification of the intermetallic σ phase precipitation process described in the study is important in the analysis of the loss of durability of the tested steels under creep conditions.

PL

Stale o osnowie austenitycznej w gatunkach Super 304H, HR3C i Sanicro 25 stosowane są w budowie elementów ciśnieniowych kotłów o nadkrytycznych parametrach pracy. W pracy zaprezentowano wyniki badań mikrostruktury w stanie dostawy oraz po starzeniu do 50 000 godzin w temperaturze 700°C. Badania mikrostruktury wykonano wykorzystując skaningową i transmisyjną mikroskopię elektronową. Identyfikację występujących wydzieleń przeprowadzono przy użyciu transmisyjnej mikroskopii elektronowej. W pracy w szczególności analizowano proces wydzieleniowy fazy σ i jego dynamikę w zależności od czasu starzenia. Pokazano, że międzymetaliczna faza σ odgrywa istotny wpływ na utratę trwałości badanej stali. Związane jest to z jej znacznym wzrostem wskutek oddziaływania wysokiej temperatury, a jej dynamika koagulacji i koalescencji zależy silnie od poziomu temperatury starzenia/eksploatacji. Identyfikacja jakościowa i ilościowa opisanego w pracy procesu wydzieleniowego międzymetalicznej fazy σ ma istotne znaczenie w analizie utraty trwałości badanych stali w warunkach pełzania.

20

Degradation of welded joint made of T91 steel with different additional materials

Wojsyk Kwiryn, Klimaszewska Klaudia, Golański Grzegorz

Welding Technology Review

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2019

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R. 91, nr 7

55--60

EN

The aim of the research was to analyse the processes of degradation observed in a similar welded joint of T91 steel. The analysis was performed for welded joints after long-term annealing for up to 8000 hours at the temperature of 600 °C. Microstructural analysis and hardness testing were performed. The purpose of the tests was to evaluate the effect of annealing time at the temperature of ageing on formation and properties of the decarburized zone in the inter-bead area of the welded joint. The study presents the results of physical examinations of the joint welded using two different filler materials (similar welded joint) after long-term effect of high temperature.

PL

Celem badań była analiza procesów degradacji obserwowanych w złączu spawanym ze stali T91. Analizę wykonano dla połączeń spawanych po długotrwałym wyżarzaniu do 8000 godzin w temperaturze 600°C. Przeprowadzono analizę mikrostrukturalną i badania twardości. Celem badań była ocena wpływu czasu wyżarzania w temperaturze starzenia na powstawanie i właściwości strefy odwęglonej w obszarze międzyściegowym złącza spawanego.