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EN
Fatigue and sleepiness are two major factors that have been reported to contribute to road crash and accidents in Indonesia. Fatigue among commercial drivers is probably a common phenomenon, particularly during long-duration driving. This study aimed at characterizing fatigue and sleepiness during long-duration driving. Nine commercial drivers were recruited in this field study and were requested to drive a multipurpose vehicle for three trips back and forth between two major cities. Each trip was completed within 4 hours, with about 3 to 3.5 hours of continuous driving (and 0.5 to 1 hour of rest). Fatigue was assessed by utilizing the Psychomotor Vigilance Task (PVT), which was administered for 5 minutes immediately following the completion of each trip. A video camera was employed to capture blink frequency, and for each trip, this measure was determined during 5 minutes after two hours of driving. Subjective ratings were also collected during the task and included the Swedish Occupational Fatigue Inventory (SOFI) and the Karolinska Sleepiness Scale (KSS). The results of this study demonstrated a consistent increase in the blink rate and subjective measures of fatigue. A significant association was also found between the blink rate and SOFI measures, indicating an association between those objective and subjective measures. Although not statistically significant, there were also changes in PVT parameters associated with driving duration. However, no significant association was found between PVT parameters and the subjective measures. This study found that a minimum of six hours of intermittent driving was adequate in inducing fatigue and sleepiness, despite the seemingly sufficient amount of rest break. Based on the findings of this study, it is suggested that long-duration driving be limited to a maximum of 12 hours, and that a minimum of 30 minutes of rest be provided after 3 to 4 hours of driving. This finding should be used as a basis for scheduling drivers and for finding the appropriate intervention strategy for mitigating fatigue and sleepiness risks during prolonged driving tasks.
2
Content available remote Fatigue risk management of the operator based on selected examples
EN
The article presents issues related to methods of risk management related to operator fatigue. An organization that wants to safely carry out operational tasks need effective methods and tools for risk assessment in safety system to increase the chances and likelihood of the organization achieving its goals. In this case, it is about identifying the risk of fatigue at work, controlling it and minimizing its negative effects. The article presents, on the example of a pilot, the possibilities of managing the risk of fatigue at work, both in the reactive, proactive and predictive dimensions, using selected examples of methods and tools. The summary emphasizes the need for a systemic risk management related to fatigue at work.
PL
W artykule przedstawiono zagadnienia związane z metodami zarządzania ryzykiem związanym ze zmęczeniem operatora. Organizacja, która chce bezpiecznie realizować zadania operacyjne potrzebuje efektywnych metod i narzędzi do szacowania ryzyka w systemie bezpieczeństwa, aby zwiększyć szanse oraz prawdopodobieństwo osiągnięcia przez organizację celów. W tym przypadku chodzi o rozpoznanie ryzyka związanego ze zmęczeniem w pracy, sterowanie nim i zminimalizowanie jego negatywnych skutków. W artykule przedstawiono, na przykładzie pilota, możliwości zarządzania ryzykiem jego zmęczenia w pracy, zarówno w wymiarze reaktywnym, proaktywnym, jak i predyktywnym, wykorzystując wybrane przykłady stosowanych metod i narzędzi. W podsumowaniu podkreślono konieczność podejścia systemowego do zarządzania ryzykiem związanym ze zmęczeniem.
PL
Projektowanie konstrukcji smukłych o dużych rozpiętościach lub wysokościach, znacząco obciążonych, wymaga analizy i rozwiązania wielu zagadnień projektowych. Są to m.in.: konieczność oceny wrażliwości konstrukcji na wzbudzenia aerodynamiczne od obciążeń dynamicznych oraz analiza wpływu obciążeń wysokocyklowych na zmęczenie konstrukcji. Przedstawiono wybrane przykłady takich konstrukcji.
EN
Designing slender structures with large spans or heights, and at the same time heavily loaded, poses additional challenges for designers. These are for example the need to assess the structure’s susceptibility to aerodynamic excitation from dynamic loads and the analysis of the impact of high-cycle loads on fatigue. This article presents selected examples of such structures.
EN
The research article address, the mechanical properties such as fatigue, impact strength and tribological properties of Austempered ductile iron (ADI) has been investigated. The samples of ADI iron were austenitized at 927°C for 2 hrs and later it was under austempering process for 2 hrs at a temperature range of 240°C to 400°C. Experiments under axial loading has been carried out on three different compositions (without Ni(X), 0.22wt.%Ni(X1), 0.34wt.%Ni(X2). Fabricated test bars were converted in to as per ASTM standard samples for different tests. In order to study the influence of chunky nickel morphology studies on fatigue life and impact strength were carried out on a second set of specimens without any microstructural defect. Metallurgical analyses were performed on all the samples of heat treated samples (AF - Ausferrite, MB - Mixed bainite, M - Martensite, RA - Retained Austenite and N - Nodule) were found and compared. It was found that a mean content of 22% of chunky nickel in the microstructure (with respect to total Ni content) influence considerably the fatigue and impact strength properties of the cast iron. Moreover tribological properties of the specimens were also studied under dry sliding conditions at various sliding speed and load. The wear resistance and coefficient of friction were found to increase with increase in load and sliding speed.
EN
The article will be focused on analysis of properties of aluminum alloy for the casting of type Al-Mg. As an experimental material was used aluminum alloy EN AC 51200, supplied in a cast state without a heat treatment. It was produced by the continuous casting method. Experiments deal with microstructural material analysis, fractographic analysis, mechanical and fatigue tests. The microstructure of the testing sample was examined using an optical microscope Neophot 32. Fatigue properties of aluminum alloy was tested by three-point bending cyclic loading. The fracture surface of the testing sample was examined using scanning electron microscopy (SEM), where sample was observed on various stages of the fatigue process, its characteristics and differences of fracture surfaces.
EN
Presented work is primarily oriented on the experimental verification of the influence of fatigue on the psychological condition of the flying personnel, using psychological and performance tests. For the evaluation of a pilot performance, the 24 hours experiment was conducted. In total, eight subjects participated in the experimental measurements. Eight participants went through several tests, including simulator flights, to investigate the effects of the fatigue on the results of psychological measurements. Measurements included workload evaluation, using NASA task load evaluation concept and performance testing, using the so-called OR-test. Significant statistical differences between measurements performed during 24 hours were not found in the case of NASA task load Scores. In the case of OR-test, Friedman ANOVA and subsequent post-hoc analysis show that the greatest decrease in performance was observed in approximately 22 hours of wakefulness, i.e. approximately in half of the measuring process. The concept of 24-hour measurements for the quantification of fatigue is not commonly used yet as well as objectivization using performance testing. As the apparent effect of fatigue is mainly on performance testing results, it can be argued that this work could serve as a basis for further studies on fatigue. Also, it could serve as a support for introducing new pilots' psychological testing procedures in the future, which could contribute to current efforts to improve aviation safety.
EN
In recent years, the research of nodular cast iron has been focused on increasing fatigue resistence. In the paper, two types of alloyed nodular cast irons have been investigated – SiMo-nodular cast iron alloyed by 4% of silicon and 1% of molybdenum and SiCu-nodular cast iron alloyed by 4% of silicon and 1.5% of copper. SiMo-nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines. SiCu-nodular cast iron is used in various components of tribotechnical units. These components are often loaded by fatigue. The mechanical and fatigue behaviour of both nodular cast iron types has been studied by means of tensile test, impact bending test, hardness test and fatigue tests. Fatigue tests were realised at low frequency cyclic push-pull loading up to 10 million cycles. The relationship between the amplitude of stress and number of cycles to failure was investigated and the fatigue strength was determined. Mechanical and fatigue properties of both nodular cast iron types are correlated with the microstructure of specimens.
EN
The article presents the results of the research conducted within the framework of the project entitled WIND-TU-PLA (ERA-NET, MARTEC II), the general aim of which was to design and analyse supporting structures for wind turbines intended for operation on the South Baltic area. The research part described in the article aimed at developing a preliminary design for a jack-up platform which can operate on water areas with depth of 40 m. The main task was to determine optimal dimensions of platform legs and the radius of their spacing. Two jack-up platform concepts differing by spacing radius and hull dimensions were designed with the intention to be used as a supporting structure for a 6-MW offshore wind turbine. For each concept, the parametric analysis was performed to determine optimal dimensions of platform legs (diameter Dleg and plating thickness tleg). Relevant calculations were performed to assess the movements of the platform with parameters given in Table 1 in conditions simulating the action of the most violent storm in recent 50 years. The obtained results, having the form of amplitudes of selected physical quantities, are shown in comprehensive charts in Fig. 6 and 7. Based on the critical stress values (corresponding to the yield stress), the area was defined in which the impact strength conditions are satisfied (Fig. 14). Then, the fatigue strength analysis was performed for two selected critical leg nodes (Fig. 12). Its results were used for defining the acceptable area with respect to structure’s fatigue (Fig. 14). Geometric parameters were determined which meet the adopted criteria, Table 6. The decisive criterion turned out to be the fatigue strength criterion, while the yield point criterion appeared to be an inactive constraint.
EN
Delamination crack growth is a major source of failure in composite laminates under static and fatigue loading conditions. In the present study, damage mechanics based failure models for both static and fatigue loadings are evaluated via UMAT subroutine to study the delamination crack growth phenomenon in Glass Fiber Reinforced Plastic (GFRP) composite laminates. A static local damage model proposed by Allix and Ladev`eze is modified to an non-local damage model in order to simulate the crack growth behavior due to static loading. Next, the same classical damage model is modified to simulate fatigue delamination crack growth. The finite element analysis results obtained by the proposed models are successfully compared with the available experimental data on the delamination crack growth for GFRP composite laminates.
10
Content available Fatigue life of butt weldments made of S1100QL steel
EN
Fields of application for quenched and tempered advanced high-strength steels are mainly ground-moving, mining equipment, commercial vehicles, and truck cranes. One of the main aspects determining range of applicability for the high strength steels is the possibility to obtain welded joints with the given fatigue strength. Information about fatigue behaviour of the weld joints strongly increases the operational safety of the structures. Factors influencing mechanical properties of the joints can be related to the welding parameters, i.e. welding current, voltage, and interpass and preheat temperatures. Thermo-mechanical process (fusion welding) also causes the diversification of the microstructure in the weld and heat affected zones. Microstructure changes induce residual stress, influencing the fatigue behaviour of the weld joint. The main topic of the paper are results of the experimental fatigue tests performed for S1100QL butt welds produced with two different technological parameter setups. Technological parameters configurations were selected on the basis of experimental tests carried out for sheets with a thickness of 12 mm. The low and high welding parameters differed due to energy introduced into the system. The energy was controlled by current parameters and the preheating of joined elements. In both configurations, it was possible to make welded joints that meet regulatory requirements but differ in the level of introduced internal stresses and microstructural properties in heat affected zone sizes. The joints were additionally subjected to standard strength and microstructural tests.
PL
Obszar zastosowania stali ulepszanych cieplnie to głównie maszyny służące do robót ziemnych, urządzenia górnicze, pojazdy użytkowe oraz żurawie samochodowe. Jednym z głównych aspektów określających zakres stosowalności stali wysoko wytrzymałych jest możliwość uzyskania połączeń spawanych o zadanej minimalnej wytrzymałości zmęczeniowej. Informacje na temat zjawisk zmęczeniowych zachodzących w złączach spawanych znacznie zwiększają bezpieczeństwo eksploatacyjne konstrukcji. Czynniki wpływające na właściwości mechaniczne złączy mogą być związane z parametrami spawania, tj. prądem spawania, napięciem, temperaturą międzyściegową i temperaturą wstępnego podgrzewania. Proces termomechaniczny, jakim jest spawanie łukiem elektrycznym, powoduje również zróżnicowanie mikrostruktury w samych spoinach i strefach wpływu ciepła. Zmiany mikrostruktury wywołują między innymi naprężenia szczątkowe wpływające na trwałość zmęczeniową złącza spawanego. Głównym tematem artykułu są wyniki eksperymentalnych testów zmęczeniowych wykonanych dla spoin doczołowych S1100QL wytworzonych przy użyciu dwóch różnych konfiguracji parametrów technologicznych. Połączenia zostały dodatkowo poddane standardowym testom wytrzymałościowym i mikrostrukturalnym. W artykule zaprezentowano również symulację propagacji wzrostu pęknięć zmęczeniowych.
PL
Omówiono zagrożenia kabli w użytkowanych mostach podwieszonych oraz przedstawiono konkluzje z prowadzonych w świecie badań nad metodami oceny stanu tych kabli i ze studiów nad racjonalnymi rozwiązaniami ich systemów. Poinformowano o wynikach międzynarodowej ankiety na temat systemów kabli mostów podwieszonych, problemów ich projektowania, kontroli i utrzymania przeprowadzonej przez Transportation Research Board (Washington) wśród administratorów mostów podwieszonych i specjalistów odpowiedzialnych za ich utrzymanie. Podano przykłady mostów z kablami podwieszającymi w złym stanie.
EN
Threats to cables in used cable-stayed bridges were discussed and conclusions were presented from world-wide research on methods for assessing the condition of these cables and from studies on rational solutions of their systems. The results of an international questionnaire on stay-cable bridges problems of their design, control and maintenance, carried out by the Transportation Research Board (Washington) among the administrators of stay-cable bridges and specialists responsible for their maintenance were announced. Examples of bridges with stay cables in poor condition are given.
PL
W artykule zaproponowano zintegrowane środowisko graficzne do zestawiania metod przetwarzania sygnału EKG celem separacji załamków R. Współczesne systemy automatyzacji i informatyzacji pola walki zaczynają dotyczyć nie tylko środków bojowych ale również załóg i obsług wysoce specjalistycznego oprzyrządowania. W artykule opisano efektywność algorytmów przetwarzania sygnału EKG, na potrzeby elektronicznych urządzeń medycznych i biomedycznych, w których zaawansowane sensory i algorytmy mają nieprzerwanie monitorować wydolność i gotowość do prowadzenia działań bojowych przez żołnierzy. Autor opisuje efektywności dobieranych doświadczalnie algorytmów oraz ograniczenia i wyzwania w procesowaniu sygnałów EKG, w odniesieniu do stosowanych metod.
EN
The article proposes an integrated graphical environment for the compilation of ECG signal processing methods for the separation of R-waves. Modern automation systems and computerization of the battlefield begin to deal not only with combat assets but also crews and the handling of highly specialized instrumentation. The article describes the efficiency of the ECG signal processing algorithms, for the needs of electronic medical and biomedical devices, in which advanced sensors and algorithms are to continually monitor the efficiency and readiness to conduct combat operations by soldiers. The author describes the effectiveness of experimentally selected algorithms as well as limitations and challenges in ECG signal processing in relation to applied methods.
EN
The article presents an analysis of the change in air voids in asphalt mixtures subjected to fatigue tests at three temperatures of 0°C, 10°C and 25°C. The X-ray computerized tomography imaging method, XCT, was used to identify the air voids in the samples. The research allowed to determine changes in the content of air voids in subsequent fatigue cycles in the sample area. The relationship between air voids volume and the stiffness modulus value was also determined during fatigue for three temperatures. The largest changes were found in samples with notches at 0°C. The analysis of the change in the content of air voids showed that the micro-cracking nucleation processes develop with the number of fatigue cycles. Using the numerical model finite element method we determined the distribution and change in fatigue damage in the extreme areas of the sample during various stages of fatigue. We found clear relationship between the damage and the increased content of air voids.
PL
Współczesne badania wskazują na brak pozytywnego wpływu na zdrowie dużych obciążeń fizycznych w pracy zawodowej, zwłaszcza w połączeniu z deficytem aktywności fizycznej rekreacyjnej w czasie wolnym od pracy. Kobiety, ze względu na uwarunkowania fizjologiczne, nie są w stanie wykonywać wszystkich czynności w pracy na równi z mężczyznami. Dotyczy to zwłaszcza prac związanych z wysiłkiem fizycznym i transportem ciężarów oraz wymuszoną pozycją ciała. W przypadku kobiet starszych, oprócz fizjologicznych różnic podyktowanych płcią, dochodzą zmiany funkcjonalne zachodzące w organizmie ludzkim wraz z wiekiem, które również istotnie obniżają możliwość wykonywania pracy fizycznej. Lekceważenie przez pracodawców problemu ciężkiej pracy fizycznej prowadzi do niekorzystnych skutków, zarówno dla pracowników, jak i dla firmy. Nadmierne obciążenie i związane z nim zmęczenie pracownika jest przyczyną gorszej jakości i wydajności pracy oraz zwiększenia absencji chorobowej. Dlatego oczywista wydaje się konieczność dostosowywania stanowisk i warunków pracy do potrzeb pracownic fizycznych w starszym wieku.
EN
Contemporary studies indicate the lack of a positive impact of high physical effort in professional work on health, especially in connection with the deficit of recreational physical activity during leisure time. Women, due to physiological conditions, are not able to perform all activities at work equally with men. This applies in particular to work related to physical effort, transport of weights and forced body position. In the case of older women, apart from the physiological differences dictated by gender, functional changes occurring in the ageing human body, which also significantly reduce the ability to perform physical work, are added. The problem of employers disregarding hard physical labour leads to adverse effects for both them and their companies. Excessive work toad and, associated with it, fatigue of employees result in inferior quality and work efficiency and the increase in sick leave due to ailments and illnesses. Therefore, it seems obvious to adapt the work station and working conditions to the needs of older women that perform physical work.
EN
Effects of charge composition on microstructure, mechanical and fatigue properties of nodular cast irons have been studied. For experiments, five melts of nodular cast iron were used – three types of unalloyed nodular cast irons (with different ratio of steel and pig iron in a charge and different additives for regulation of the chemical composition) and two types of alloyed nodular cast irons (SiMo- and SiCu- nodular cast iron). The microstructure of the specimens was evaluated according to a norm and by automatic image analysis. The mechanical properties were investigated by the tensile test, impact bending test and Brinell hardness test. The fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The best mechanical properties were reached in the nodular cast iron alloyed by Si and Cu, what is related to its microstructure.
EN
In this research work, Ti6Al4V alloy material was subjected to electric discharge machining (EDM) and its fatigue life was investigated at low cycle fatigue mode. In order to evaluate the influence of recast layer generated during the machining process on the fatigue life, samples prepared using end milling process were also subjected to similar tests and a comparative analysisis presented. Data were observed in the fully reversed fatigue mode at room temperature using samples fabricated as per ASTM standard E606. The specimen were machined on a spark electric discharge die sink machine which were subjected to fatigue, and the recorded fatigue lives were compared with the fatigue life of end milled specimen. The machined surfaces were examined through optical and scanning electron microscopes, and the roughness was measured with a standard profilometer. It was observed that when the discharge current is augmented, the recast layer formed was in the range of 20 to 70 μm thick. From the results, it is being concluded that fatigue life of the samples fabricated by EDM is less for various load conditions when compared with that of the end milled sample. The milled sample at 160 MPa load exhibited 2.71×105 cycles, which is 64% more when compared to EDM sample.
EN
Sound joint of hollow-extruded 6005A-T6 aluminum alloy was achieved by friction stir welding and its high cycle fatigue performance was mainly investigated. As a result, the joint fatigue limit reaches 128.1 MPa which is 55% of the joint tensile strength. The fatigue fracture mainly occurs at the boundary between the stir zone and thermo-mechanically affected zone due to the large difference in the grain size. This difference is caused by the layered microstructure of the base material. The shell pattern with parallel arcs is the typical morphology in the fracture surface and the distance between arcs is increased with the increase of stress level. The specimen with the fracture located in the stir zone possesses a relatively low fatigue life.
EN
7N01-T4 aluminum alloy was welded by metal inert gas welding and the influence of V-groove angle on joint fatigue properties was investigated. The results indicate that the volume of fusion zone (FZ) and the grains in FZ become small when the groove angle decreases to 50° from 70°. Most pores distribute at the FZ edge and fewer pores are formed in the small angle joint. The fatigue crack mainly initiates at the transition region between the weld passes due to the pore concentration. The small angle contributes to increasing joint fatigue properties, especially at the low stress level. The fatigue strength of 50° joint is 103.06 MPa which is 15.3% higher than that of 70° joint.
EN
The present work has the objective of studying the effect of shot peening with glass microspheres on SAE 1020 steel in its resistance to fatigue. Fatigue tests were carried out by rotary bending with load control and loading on balance in specimens with and without shot peening. A rotation speed of approximately 750 rpm (12.5 Hz) was employed in the fatigue tests. Vickers microhardness tests were performed in order to verify the surface hardening produced by shot peening with glass microspheres. Analysis of the steel surface and fatigue fractures was performed using scanning electron microscopy (SEM). Fatigue tests were performed in order to obtain S-N curves (Wöhler curves). It was observed that shot peening with glass microspheres improved the fatigue strength of the steel at high cycle.
EN
Aluminum alloys are widely used for fabrication of aircraft, civil structures, and space vehicles. Fatigue life consideration of a material is the most important design criteria in many such critical applications. In this research work, a widely used Aluminum alloy AA2219-T87 was TIG welded using AA2319 as a filler material. The effect of natural aging on Fatigue Crack Propagation Rate (FCPR) of welded and non-welded compact tension (CT) specimens (AA2219˗T87) is studied. The relationship between stress intensity factor (ΔK) and crack ratio (a/W) for different value of the crack length in base metal and the welded zone is presented. Paris curves for both welded and non-welded specimens and compared to study the effect of natural aging (NA) on FCGR and compared with non-aged specimens. The results obtained provide a base for the development of Structural Health Monitoring systems for the propagation of crack growth in such components.
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