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1

The impact of corrosion on the fatigue strength of steel used in bridge structures

Wysokowski Adam

Ochrona przed Korozją

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2024

|

nr 1

2--8

EN

The phenomenon of corrosion, its processes and dependence on the physicochemical properties of the corroded material and the environment in which it occurs, as well as issues related to corrosion protection, are the subject of numerous research papers. Despite the preliminary recognition of the impact of corrosion pitting on the fatigue of structural steel elements, in particular, the impact of notches on the reduction of fatigue strength, appropriate coefficients have not yet been introduced in most of the standards for the design of steel bridges in the world, including Poland. The paper will present the results of the author’s research work on the estimation of the effect of corrosion on the fatigue capacity of rail and road steel bridge structures in service. The study was performed on two types of bridge steel commonly used in existing, in-service bridge structures. In order to determine the magnitude of the title phenomenon, an atmospheric corrosion simulation facility was set up for the tests. The experimental results unequivocally showed a significant decrease in the fatigue limit for both bridge steels and up to 50% of the initial condition.

PL

Zjawisko korozji, jej procesy oraz zależności od właściwości fizykochemicznych korodowanego materiału i środowiska, w jakim zachodzi, a także zagadnienia związane z ochroną antykorozyjną są tematem licznych prac badawczych. Pomimo wstępnego rozpoznania w zakresie wpływu wżerów korozyjnych na zmęczenie stali konstrukcyjnych, w szczególności wpływu karbów na obniżenie wytrzymałości zmęczeniowej, nie wprowadzono dotychczas odpowiednich współczynników w większości światowych, także polskich normatywów dotyczących projektowania mostów stalowych. Artykuł przedstawia wyniki autorskich prac badawczych nad oszacowaniem wpływu korozji na nośność zmęczeniową eksploatowanych stalowych konstrukcji mostowych – kolejowych i drogowych. Badania przeprowadzono na dwóch rodzajach stali mostowej powszechnie stosowanej w konstrukcjach eksploatowanych obiektów mostowych. W celu określenia skali wpływu korozji na wytrzymałość zmęczeniową stali stosowanej w konstrukcjach mostowych na potrzeby badań wykonano stanowisko do symulacji korozji w warunkach atmosferycznych. Wyniki badań jednoznacznie wykazały znaczny spadek granicy wytrzymałości zmęczeniowej w wypadku obu stali mostowych, i to nawet na poziomie 50% stanu wyjściowego.

2

The analysis of work shift patterns and risk of fatigue in aircraft maintenance personnel: a case study

Basaria Fransisca Tiur

Zeszyty Naukowe. Transport / Politechnika Śląska

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2023

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z. 118

5--16

EN

In response to the COVID-19 pandemic in 2020, PT. XYZ, the biggest aircraft maintenance, repair, and overhaul (MRO) company in Indonesia, implemented a new shift pattern for line-maintenance personnel. The new shift pattern allows maintenance personnel to have fewer working hours per day (7-hour shifts) in more shift varieties for 5 consecutive days. Maintenance personnel will have 2-morning shifts, 1-noon shift, and 2-night shifts followed by 3 rest days. This study aims to explore the risk of fatigue caused by the newly implemented shift pattern. Data were collected through electronic questionnaires from a total of 303 respondents. This study found that at the time of the survey, many respondents (78 of 303, 26%) felt tired and had difficulty concentrating, regardless of the shift they were in. Based on the duty time, the highest scores of level 6 (tired, difficult to concentrate) were discovered on night shift day 5. This result shows that although the organization had provided the maintenance personnel with the opportunity to obtain sleep during rest days, tiredness and fatigue were still experienced by the aircraft maintenance personnel. This study recommends necessary actions to be taken to prevent fatigue, especially from the noon shift afterwards, where fatigue level is increasing, and alertness level is decreasing.

3

Consequences of using overlays on welded joints

Wojsyk Kwiryn, Nawrocki Jerzy

Welding Technology Review

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2023

|

R. 95

78--86

EN

The article refers to an earlier publication regarding "reinforcing" overlays on welded joints. In this context, the main principles of designing welded structures were reminded. To verify the principle of not using overlays on the welds, an FEM simulation of such a model was performed. Simulation proved that weld overlays used in plate girder structures are ballast, because they do not participate in stress transfer when tensile is dominant. In addition, they generate a stress concentration in the corner of the pad, which greatly reduces the time to fatigue failure of the structure. A list of the recommendations, requirements for the correct use of overlays on welded joints is given.

4

Effectiveness of a specific Reclaimed Asphalt Pavement (RAP) rejuvenating agent

Jurczak Robert, Mieczkowski Paweł, Merska Oliwia, Ratajczak Maria

Roads and Bridges - Drogi i Mosty

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2023

|

Vol. 22, no. 4

447--462

EN

Contemporary construction materials are expected to be recyclable in a closed-loop system, meaning they should allow reuse, after they have lost their original properties while being part of the original building product. This group of materials should undoubtedly include bituminous mixtures, which may be reclaimed during road renewal or alteration projects, and subsequently reused as Reclaimed Asphalt Pavement (RAP). Noteworthy, RAP performance depends on the properties of the binder it contains, whose visco-elastic behaviour has been affected by the ageing processes. Fortunately enough, these properties of bitumen may be effectively recovered by means of special chemical agents called rejuvenators. This paper presents the results of two-stage research project on this subject. The first stage included testing of the bituminous binder under analysis. It was a 50/70 pen-grade bitumen tested before and after short-term ageing (RTFOT + PAV) and aged binder tested after rejuvenation treatment. Spectroscopic and fractional composition analyses were carried out in addition to determining the basic properties i.e. penetration, softening point, dynamic shear modulus and phase angle. In the second stage of this research project a different material was tested: AC 16 W 50/70 asphalt concrete sourced from a hot-mix asphalt plant. The specimens were made from the fresh mix (control) and the same mix after short- and long-term ageing and after subsequent rejuvenation treatment. The determinations included density, bulk density, water sensitivity, stiffness modulus, resistance to fatigue and low temperature performance determined with the Thermal Stress Restrained Specimen Test (TSRST).The tests of RAP treated with oleyl alcohol ethoxylate phosphate ester carried out as part of this research showed improvement of the performance properties of aged bituminous binders, and thus confirmed the suitability of this agent in road paving applications

PL

Materiały stosowane w budownictwie powinny funkcjonować w obiegu zamkniętym, co oznacza ich ponowne wykorzystanie w momencie utraty właściwości w pierwotnym wyrobie budowlanym. Do tego typu materiałów należy zaliczyć mieszanki mineralno-asfaltowe, które w postaci destruktu asfaltowego pozyskiwane są z remontowanych lub przebudowywanych dróg. Ich funkcjonalność w dużym stopniu zależy od właściwości lepiszcza asfaltowego, które w wyniku procesów starzeniowych utraciło swoje właściwości lepkosprężyste. Poprawę tych właściwości można uzyskać poprzez zastosowanie specjalistycznych preparatów chemicznych zwanych rejuvenatorami. W artykule przedstawiono wyniki badań, które podzielono na dwa etapy. W pierwszym etapie badania wykonywano dla lepiszcza asfaltowego. Wykorzystano asfalt drogowy 50/70 przed i po starzeniu (RTFOT + PAV) oraz postarzone lepiszcze z dodatkiem rejuvenartora. Obok badań podstawowych (penetracji, temperatury mięknienia, zespolonego modułu ścinania i kąta przesunięcia fazowego) oznaczono skład grupowy asfaltów oraz wykonano analizy widmowe. W drugim etapie badania wykonano dla betonu asfaltowego AC 16 W 50/70, pozyskanego z WMB. Oznaczono podstawowe parametry mieszanki referencyjnej, po starzeniu technologicznym oraz eksploatacyjnym oraz z udziałem odświeżacza. W zakresie oznaczeń była gęstość, gęstość objętościowa, odporność na działanie wody, moduł sztywności, trwałość zmęczeniowa oraz parametry niskotemperaturowe mieszanki (TSRST). Przeprowadzone badania granulatu asfaltowego z udziałem esteru fosforowego alkoholu oleilowego, etoksylowanego świadczą, że substancja ta wpływa pozytywnie na zmiany właściwości zestarzonych lepiszczy asfaltowych, co pozwala z powodzeniem stosować ją w technologii drogowej

5

A comprehensive review of polymer materials and selective laser sintering technology for 3D printing

Jabri F. E., Ouballouch A., Lasri L., Alaiji R. El

Journal of Achievements in Materials and Manufacturing Engineering

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2023

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Vol. 118, nr 1

5--17

EN

Purpose This review analyses different approaches used to study selective laser sintering (SLS) technology of polymer materials. These main approaches concern: thermal behaviour, fatigue and surface roughness. Design/methodology/approach Regarding the first behaviour, researchers extensively studied the impact of process parameters, including scan speed, laser, power and laser energy density, on the thermal behaviour of 3D printed parts. Numerical and experimental analyses are used to conduct process parameter evaluations. Findings Laser power and scan speed are the most significant parameters of the laser energy density. For the second, according to test protocols and quantitative analysis performed, the authors concluded that the combination of small and large laser energy density particles generates higher sintering and better fatigue resistance. Moreover, tensile analysis in different environments showed that testing in the water decreased the fatigue life of polymer samples. The influence of process parameters on the mechanical properties and surface roughness of 3D parts is also analysed. In addition, the investigators found that the additives increase the surface roughness of 3D printed parts. Practical implications This review shows that researchers can focus on creating a combination of these approaches to expand the use of this process for industrial part production. Originality/value All these investigations have made it possible to determine the optimal process conditions to ensure higher quality, optimal surface quality and better fatigue strength.

6

Steam turbines for flexible operation

Biesinger Frank, Huáscar Lorini, Banaszkiewicz Mariusz

Energetyka

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2023

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nr 12

706--713

EN

The demand for more flexible operation of power plants has increased significantly in the last few years. Increased numbers of starts, operating hours and ramp rates result in accelerated lifetime consumption of the steam turbine components. Nowadays, one of the major tasks is to assess the capabilities of existing steam turbine units in terms of more flexible operation. New concepts are developed to allow improved flexible operation with associated thermal stress protection of components. New calculation methods support this approach and help to best utilize the remaining lifetime for future operation. The current lifetime status has to be established first and the remaining lifetime is then available to be utilized and distributed for future operation. The assessment of components is done by using the Finite Element Method with creep and transient calculations. Implementation of a state-of-the-art thermal stress control system allows adjustment of the stress calculator settings to the needs of the re-allocated remaining life. There are also options available to enhance flexible operation within an existing steam power plant, e.g. a reconditioning of the existing rotor with particular focus on the first blade groove or exchange an existing component for one with superior properties.

PL

W ostatnich kilku latach znacząco wzrosło zapotrzebowanie na elastyczną eksploatację elektrowni zawodowych. Zwiększona liczba rozruchów, godzin pracy oraz wyższe tempa zmian mocy skutkują przyspieszonym zużyciem elementów turbin parowych. Obecnie jednym z głównych zadań jest ocena możliwości poprawy elastyczności eksploatacji aktualnie pracujących bloków parowych. Opracowano tutaj nowe koncepcje zwiększające elastyczność pracy z jednoczesnym zabezpieczeniem elementów od naprężeń termicznych. Umożliwiły to nowe metody obliczeniowe, które jednocześnie wspomagają jak najlepsze wykorzystanie trwałości resztkowej w dalszej eksploatacji. W pierwszym kroku określa się aktualny stan żywotności a następnie dostępną żywotność resztkową rozkłada się na dalszą eksploatację. Ocena żywotności elementów wykonywana jest za pomocą metody elementów skończonych wykorzystywaną w obliczeniach pełzania i zmiennych warunków pracy. Implementacja nowoczesnego systemu kontroli naprężeń termicznych umożliwia dostosowanie jego nastaw do potrzeb realokowanej trwałości resztkowej. Dostępne są również inne opcje poprawy elastyczności istniejących bloków, np. odnowa wirnika ze szczególnym uwzględnieniem pierwszego wrębu łopatkowego lub wymiana elementu na nowy o lepszych własnościach.

7

Stand testing of springs for drum brake systems

Drożyner Przemysław, Brodecki Adam, Szymczak Tadeusz

Diagnostyka

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2023

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Vol. 24, No. 4

art. no. 2023414

EN

The paper concerns the study of changes in responses of spring for drum brake systems, due to fatigue cycles conducted at operational regimes of vehicles with respect to the number of kilometers. Three types of springs from two manufacturers were examined i.e. double cylindrical, single cylindrical, and conical helical. The springs were subjected to a durability test up to 1×106 loading cycles, covering 300-500 thousand kilometers traveled. Tensile test was used for collecting differences between results for the tested object in the as-receive state and after fatigue. Values of the Pearson correlation coefficient were used to indicate differences between tested objects before and after loading cycles. They show that the obtained results expressed a very strong correlation, which means that the elastic response of the springs during operation over a distance of 300-500 thousand kilometers did not change significantly. Taking into account the recommendations of brake system manufacturers regarding the replacement of brake drums after 150,000 and 50,000 kilometers, respectively, it can be concluded that brake springs are the most durable and reliable element of such a brake system.

8

Microstructure formation and fatigue performance of duplex stainless steel 2205 welded joints by electric resistance welding

Dong Zhilong, Xie Xue-fang, Li Jingwen, Wan Yu, Wang Chaolei

Archives of Civil and Mechanical Engineering

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2023

|

Vol. 23, no. 3

art. no. e180, 2023

EN

The electric resistance welding of thin-thickness duplex stainless steel (DSS) has an outstanding attraction in the plate-fin heat exchanger which is widely used in power machinery, diesel locomotive and other fields, but its structural integrity is threatened seriously by fatigue failure. Therefore, in this research, the formation of the heterogeneous microstructure of DSS electric resistance welding joints (ERWJ) was analyzed by the optical microscope (OM) and electron back-scattered diffraction (EBSD) observations, and the uniaxial tensile and fatigue tests were subsequently executed to disclose their mechanical properties. The intrinsic relevancy between phase-related characteristics and failure behavior was extensively analyzed. The results show that the ferrite was dominating at whole ERWJ, particularly at the energized area, accounting for up to 72%. More than 45% of high-angle boundaries (HABS) and the highest kernel average misorientation (KAM, 2.46° for austenite and 1.52° for ferrite), which indicates greater plastic deformation and residual stress, were observed at the weld edge. In addition, the failure occurred as a tear along the weld edge regardless of the monotonic and cyclic loadings under the deterioration of residual stress and island-like austenite. The distribution of fatigue life with cyclic amplitude performed an obvious turning point of 19.5 MPa due to the different failure mechanisms, providing a permissible range of the stress amplitudes and reinforcement strategies for the plate-shell heat exchanger ERWJ in the engineering.

9

Cracks Development Formed as a Result of Cyclic Micro-Impacts on the Surface of Anti-Wear Coatings

Krupa Jolanta, Zimowski Sławomir

Tribologia

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2022

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nr 1

33--41

EN

Fatigue tests are commonly used to define the mechanical properties of materials intended for responsible components operating in various conditions. The fatigue strength of monolithic materials is most often determined during bending, tensile, compression, or torsion tests. The growing area of thin, hard coatings application forced the researchers to extend the fatigue tests to the coating-substrate systems. Since the behaviour of complex, modern materials are not subject to general rules, it is necessary to conduct investigation and analyses and generalise the results of these tests for given groups of materials. In this article, micro- impact fatigue tests were performed to analyse the behaviour of single- and double-layer chromium and chromium nitride coatings. The microhardness and elastic modulus obtained by an indentation method were used to determine the influence of mechanical properties of the coatings on their fatigue wear. After the fatigue tests, the deformation of the coating/substrate system was examined, taking into account the geometry of the craters, and the forms of coating wear caused mainly by cracking were analysed.

PL

Badania zmęczeniowe są powszechnie stosowane do określenia właściwości mechanicznych materiałów przeznaczonych na odpowiedzialne elementy pracujące w różnych warunkach. Wytrzymałość zmęczeniowa materiałów monolitycznych wyznaczana jest najczęściej podczas testów zginania, rozciągania, ściskania lub skręcania. Zwiększenie obszarów zastosowania cienkich, twardych powłok wymusiło na badaczach rozszerzenie testów zmęczeniowych na układy powłoka–podłoże. Ponieważ zachowanie złożonych, nowoczesnych materiałów nie podlega znanym regułom, konieczne jest prowadzanie badań i analiz oraz dążenie do uogólnienia wyników tych badań dla danych grup materiałów. W artykule przeprowadzono mikroudarowe badania zmęczeniowe w celu analizy zachowania przeciwzużyciowych jedno- i dwuwarstwowych powłok chromu i azotku chromu. Przeprowadzone pomiary mikrotwardości i modułu sprężystości metodą indentacyjną pozwoliły na określenie wpływu właściwości mechanicznych powłok na ich zużycie zmęczeniowe. Po testach zmęczeniowych zbadano odkształcenie układu powłoka/podłoże ze względu na geometrię kraterów oraz dokonano analizy form zużycia powłok, którego główną przyczyną było pękanie.

10

Czy zmęczenie jest nam potrzebne? Cz. I

Gembalska-Kwiecień Anna

Promotor BHP

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2022

|

nr 9

66--72

PL

Każda osoba aktywna zawodowo spotkała się w swoim życiu z uczuciem zmęczenia. Jakie są rodzaje i objawy zmęczenia?

11

Crack growth diagnostic of ball bearing using vibration analysis

Belaidi S., Lecheb S., Chellil A., Mechakra H., Safi B., Kebir H.

International Journal of Applied Mechanics and Engineering

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2022

|

Vol. 27, no. 1

35--45

EN

It is known that supported ball bearings have great effects on the vibrations of the gear transmission system, above in all the presence of local faults as well as the crack growths. For this purpose, this paper focuses on shock and vibration crack growth diagnostic of ball bearing using vibration analysis. Our work is devoted first to a study the static behaviour of the ball bearing by determining the stress, strain and displacement, then its dynamic behaviour by determining the first four natural frequencies. Secondly, a dynamic analysis study of the bearing was carried with defects as a function of crack size and location. The obtained results clearly show that the natural frequencies decrease in a non-linear way with the growth of the length of the crack, on the other hand the stress increases with the presence of the singular points of the crack. Finally, this residual decrease in natural frequencies can be used as an indicator of the state of failure, as well as a parameter used for the diagnosis and screening, and to highlight the fatigue life of the bearing.

12

Significance of a new preliminary treatment method of the Pen206_18 borehole penetrometer’s pressure readouts for a reliable analysis of rock stress-strain parameters

Pierszalik Rafał

Archives of Mining Sciences

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2022

|

Vol. 67, no. 1

159--178

EN

This article describes some selected aspects of a preliminary treatment of measurement cycle results obtained by a new Pen206_18 type hydraulic borehole penetrometer (a borehole jack type), a tool of an in situ determining of mechanical properties of rocks. The pre-treatment of the measurement cycle results is a necessary step to prepare the data for a following appropriate analysis of stress-strain parameters of rocks. Aforementioned aspects are focused mainly on a pre-treatment of hydraulic pressure readouts. The Pen206_18 type penetrometer is a modified version of a standard Pen206 type penetrometer. The standard version, based on a digital measurement of a critical hydraulic pressure, has been in use in polish hard coal mines for almost 15 years to determine various rock strength parameters. In contrary, the Pen206_18 type penetrometer now provides simultaneous recording of two main measurement cycle parameters (hydraulic pressure and a head pin stroke) during the whole measurement cycle duration. A recent modification of the penetrometer has given an opportunity to look closer at various factors having an influence on the measurement cycle data readouts and, as a consequence, to lay a foundation for a development a new penetrometric method of determining stress-strain parameters of rocks. In this article it was shown that just before a main stage of the measurement cycle, a transitional stage could occur. It complicates a determination of the beginning of an useful set of measurement cycle data. This problem is widely known also in other static in situ methods of determining stress-strain parameters. Unfortunately, none of various known workouts of this problem were sufficiently adequate to the pre-treatment of the penetrometric measurement cycle results. Hence, a new method of determining the beginning of the useful set of pressure readouts has been developed. The proposed method takes into account an influence of an operational characteristics of the measuring device. This method is an essential part of a new pre-treatment procedure of the Pen206_18 measurement cycle’s pressure readouts.

13

Synthesis of functionalized HAp-surface on β-Ti alloy using ball-burnishing assisted EDC process for biomedical application

Prakash Chander, Kotecha Ketan, Pramanik Alokesh, Basak Animesh, Shankar S.

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 4

art. no. e192, 2022

EN

The current research develops functionalized biocompatible hydroxyapatite (HAp)-rich surface on TNTZ alloy using a novel ball-burnishing assisted electric discharge cladding (BB-EDC) has been presented. The biomechanical properties of HAp-layer, such as mechanical properties, fatigue performance, in-vitro corrosion resistance, and bioactivity, have been investigated. The results showed that EDC-modified surfaces comprised discharge craters, globules, splats structures, and high ridges of redeposited metal. However, the BB-EDC process produced a relatively flat, smooth, dense surface with an average roughness value of 0.75 µm. The HAp-cladded layer by EDC and BB-EDC process featured an irregular surface range 25–30 µm thick and compact layer ranging 5–7 µm thick, respectively. The ball burnishing subjected caused plastic deformation on the developed layer that produced fine microstructure that increased surface hardness from 2.8 to 8.7 GPa. The functional HAp-cladded layer obtained by BB-EDC exhibit excellent corrosion properties. The dense and compact layer comprised a deformed microstructure with high residual stresses that offered high resistance to crack imitation propagation, thus resulting in better fatigue performance of β-phase TNTZ alloy. Furthermore, in-vitro bioactivity results showed that BB-EDC modified exhibit anti-inflammatory surface and promoted cell growth. The findings of the current research work offer up new possibilities for biomedical, automobile and aerospace industries to utilize the potential of BB-EDC as a new surface engineering technology to develop functionalized surfaces with improved surface characteristics and mechanical properties.

14

Effect of plasma nitriding process on the fatigue and high temperature corrosion resistance of Inconel 740H nickel alloy

Kopec Mateusz, Gorniewicz Dominika, Kukla Dominik, Barwinska Izabela, Jóźwiak Stanisław, Sitek Ryszard, Kowalewski Zbigniew L.

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 1

art. no. e57, 2022

EN

The paper presents a comparison of microhardness, fatigue and high temperature corrosion of Inconel 740H nickel alloy in its as-received state and the same material with nitrided surface layers. The nitrided layers were produced using traditional glow discharge nitriding (specimens nitriding on the cathode potential) and an active screen (specimens nitriding at the plasma potential). A microstructure of the layers was characterized through the scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction analysis. Mechanical properties of the nitrided Inconel 740H alloy were examined using microhardness measurements and standard fatigue tests. It was found that Inconel 740H with a nitrided surface exhibited an improved fatigue response of 50 MPa in the whole range of stress amplitudes from 350 to 650 MPa and almost 325% increase of hardness for plasma modified surface and 250% for cathode modified surface. Additionally, the application of cathode nitriding enhanced the corrosion resistance of the alloy in question and effectively protected it against a high temperature oxidation.

15

Road safety for cyclists based on the calories needed

Bosurgi Gaetano, Pellegrino Orazio, Wachnicka Joanna, Okraszewska Romanika

Transport Problems

|

2021

|

T. 16, z. 1

113--126

EN

Cyclists are a vulnerable group of road users, especially when no separate infrastructure for cyclists is provided. Then, road factors such as distance and altitude differences can indirectly affect cyclists' safety. Therefore, the authors proposed a procedure based on the geometric characteristics of the road that can determine riding difficulties for cyclists. The proposed procedure can be used both by the public authorities who manage cyclists' safety and as a method of classifying the road network for cycling. The proposed procedure, based on the use of pattern recognition techniques, analyses data from a sample of nine riders who travelled on rural roads within the Municipality of Messina (Italy) to classify the roads according to their cycling difficulty. For each rider, duration, distance, road slope, altitude difference and spent calories have been measured and analysed. The collected data were used for the development of a model capable of predicting the cyclist’s physical effort as a function of the road alignment itself. Knowing the effort required to cycle along a route can contribute to a more complete assessment of road classification, commonly defined according to motor vehicles. Moreover, it may constitute a measure determining the safety of cycling by encouraging cyclists to travel along roads compatible with their physical abilities.

16

Nowoczesne koncepcje konstrukcji nawierzchni

Błażejowski Krzysztof, Wójcik-Wiśniewska Marta

Materiały Budowlane

|

2021

|

nr 4

70--72

17

Berlik Marcin, Ewertowski Tomasz

Journal of KONBiN

|

2021

|

Vol. 51, iss. 3

75--86

EN

The purpose of this publication is to discuss the issues related to the operator sleep deficiency, its effects and the resulting risk. The issue is discussed on the example of a pilot, as a position in which the probability of occurrence of the phenomenon is high, with consequences of its occurrence that can be very severe. Despite the fact, the authors try to present the issues in a universal way enabling reference to a wide spectrum of different types of operators. In the article, concepts such as risk and fatigue are characterized. Furthermore, short and long-term fatigue are discussed, as well as the impact of shift work on human health and reliability. The second part presents methods of fatigue monitoring useful in aviation. The summary emphasizes the need for a holistic approach to the issue of crew fatigue in the management and the need for actions before commencing with work.

PL

Celem publikacji jest omówienie zagadnień związanych z niedoborem snu operatora, jego skutków oraz wynikającego z nich ryzyka. Powyższe zagadnienie omawiane jest na przykładzie pilota jako stanowiska, na którym prawdopodobieństwo wystąpienia zjawiska jest wysokie, a konsekwencje jego wystąpienia mogą nieść za sobą bardzo dotkliwe skutki. Mimo to autorzy starali się przedstawić problematykę w sposób uniwersalny, umożliwiając odniesienie treści do szerokiego spektrum różnego rodzaju operatorów. W pierwszej części artykułu scharakteryzowane zostały takie pojęcia jak ryzyko i zmęczenie. Omówiono także rodzaje zmęczenia: krótkotrwałe i długotrwałe oraz wpływ pracy zmianowej na stan zdrowia i niezawodność człowieka. W drugiej części zaprezentowano metody monitorowania zmęczenia użyteczne w lotnictwie. W podsumowaniu podkreślono konieczność holistycznego podejścia do zagadnienia zmęczenia załóg w zarządzaniu oraz podejmowania działań jeszcze przed rozpoczęciem wykonywania pracy.

18

Mechanical properties and fatigue life detection of copper particle filled polyester composite material under rotating bending load

Hamzah Ahmed Fadhil, Al-Turaihi Ali S., Hunain Mustafa Baqir, Fadhel Essam Zuheir

Diagnostyka

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2021

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Vol. 22, No. 3

35--42

EN

In the present investigation, the fatigue life detection of composite material by adding copper particle of about than 25 μm diameter with 5, 10, 15 % volume fraction, as a reinforcements into the unsaturated polyester polymer composite material on fatigue life detection of composite material were studied experimentally and numerically. Composites were made using hand lay-up technique and evaluated for mechanical and fatigue properties in accordance with ASTM standards. The experimental results of the tensile test showed that adding 15% of copper particle in unsaturated polyester gives maximum ultimate tensile stress. Fatigue tests including test rod specimens made of composite materials under completely reversed cyclic loading in a rotating cantilever reversed bending machine. It is found that, the fatigue life and fatigue strength increase with increasing in the copper percentage volume fraction in unsaturated polyester resin compared with pure polyester composites. The experimental work was compared with numerical work, which was done by using ANSYS/19 and good agreement has been found. The maximum overall difference between the experimental and numerical work was around 9 %.

19

Experimental and numerical studies of fatigue properties of carbon/glass fiber/epoxy hybrid composites enhanced with nano TiO2 powder

Hunain Mustafa Baqir, Abass Basim A., Akhudair Jaafar Musa

Diagnostyka

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2021

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Vol. 22, No. 2

75--84

EN

The present work deals with the fatigue behavior of hybrid nanocomposites consisting epoxy strengthen by unidirectional carbon fibres, and/or woven roving glass fiber and TiO2 nanofillers. For this purpose, nanocomposite material was manufactured by mixing TiO2 nanoparticles with the epoxy using an ultrasonic mixer to insure complete dispersion of such particles in the base material. Different particle concentrations (1, 3, and 5) % wt. of TiO2 nanoparticles have been added to the epoxy. Different types of hybrid nano composite materials were manufactured by adding three layers of carbon fibers and/or woven roving glass fiber to the prepared epoxy nanocomposite materials with a constant weight fraction of 30%. The laminated hybrid nanocomposite materials were then prepared using hand lay-up technique using a vacuum device. For experimental purposes tensile and fatigue test specimens have been manufactured according to ASTM-D3039 and ASTM D 3479/D 3479M-96, respectively, while ANSYS19 program was used to analyze the fatigue behavior of such materials numerically. Tensile tests were carried out at room temperature while fatigue tests has been carried out at constant stress ratio (R=-1). Scanning electron microscope (SEM) was used to identify the underlying mechanisms for fatigue failure and the progressive of damage growth. For each test, three specimens were tested and the average magnitude for each property was taken. The results obtained indicated that the hybrid nanocomposite (EP+C/C/C+3% TiO2) has the highest fatigue limit and tensile strength in comparison with the other tested material, while the SEM results showed that the composite failed by a brittle way. It has been also generally observed that the addition of (TiO2) nanoparticles has a positive effect on the fatigue behaviour of the such materials.

20

Study of mechanical behaviour in three-point bending of fatigue-stressed composite laminates

Khelifa Noureddine, Bey Kamel, Mzad Hocine

Composites Theory and Practice

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2021

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R. 21, nr 3

107--113

EN

The aim of this work was to conduct an experimental investigation of the mechanical behaviour in the three-point bending of fatigue-stressed cross-ply laminated composites. A 3-point static bending study was carried out on two types of laminated composite materials to determine their mechanical characteristics as well as to assess the influence of the test speed and the effect of the stacking sequence on their mechanical behaviour. Different damage modes leading to the rupture of these materials were highlighted to determine their types.