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1
Content available remote The impact of corrosion on the fatigue strength of steel used in bridge structures
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.
EN
The durability of bearing units of large machines depends mainly on the condition of their welded joints. With this in mind, we developed numerical models of the analyzed bearing units, for which we performed FEM simulations of the stresses in welded joints inseveral basic load cases. In each of the respective variants the technical condition of the bearing nodes was different and it corresponded to the severity of the degradation processes. Different positions of the superstructure in relation to the undercarriage were also taken into account. The simulations used the hot-spot method dedicated to FEM analyses of complex welded structures. We discovered that the loads have a significant influence on the values and distribution of von Mises principal stresses and their axial components. Based on the carried out analyses, we identified the most unfavorable load cases that generate the highest stresses in the welded joints of the assessed nodes. We also demonstrated that the applied method effectively assesses the stresses of welded joints subjected to variable working loads.
EN
The paper presents the results of fatigue tests of the 6060 aluminum alloy. The test material was taken from the profiles used for the production of side windows and external doors of the passenger trains by the RAWAG company. The tests were carried out for cyclic loads with pure bending, pure torsion, and two combinations of bending and torsion. Fatigue tests were performed at zero mean values. Using scanning electron microscopy, a fractographic analysis was made, which is a supplementary basic for considerations about the mechanism of initiation and development of fatigue cracks. Based on the appearance of individual zones and the characteristics of cracks, a picture of the behavior of the material under specific conditions was obtained. Finally, the plastic property of fatigue cracks was indicated.
EN
To construct resilient structures, systems and sustainable buildings, capable of enduring fatigue, inclement weather, and seismic activity, researchers are actively seeking effective solutions to minimize vibrations and cyclic loading. Although these factors may not have immediate effects, they contribute to residual deformation in structures that gradually grows over time. For this reason, shape memory alloy (SMA) can be used as a perfect damper to dissipate the mechanical load in structures construction and buildings. The SMA actuators characterized by several thermo-mechanical functions, they are generally used in different applications as Mechatronics, Biomedical, Mechanical engineering and building systems. This study aims to adapt SMA actuator with structures for construction and buildings, in order to ensure a high displacement and vigilance taking into account fatigue phenomena to repulse mechanical fatigue and fretting. Accordingly, a thermomechanical analysis has been developed using finite element techniques to describe shape memory alloys' behavior and can integrate these material as a thermomechanical actuator dampers in building engineering systems. Furthermore, the suggested model elucidates the actuator's thermomechanical response, showcasing its adaptable behavior to both superelasticity and the shape memory effect within the desired structure in the building. Thus, the numerical findings affirm the efficacy of the proposed design that based on shape memory materials in addressing thermomechanical fatigue within buildings, concurrently enhancing structural resilience against mechanical fatigue. The primary outcome of this study is the successful preservation of the Ni-Ti superelastic response within the proposed system. This preservation is validated through cycling variations of up to 7.6% strain, significantly surpassing the requirements typically mandated for applications in earthquake engineering.
EN
In this paper, an attempt to estimate the stage of the fatigue process using the Barkhausen noise method is studied. First, microstructural and static tensile tests were carried out and, subsequently, fatigue tests up to failure were conducted. After determination of the material behaviour in the assumed static and dynamic conditions, the interrupted fatigue tests were performed. Each specimen was stressed up to a different number of cycles corresponding to 10%, 30%, 50%, 70% and 90% of fatigue lifetime for the loading conditions considered. In the next step of the experimental programme, the specimens were subjected to the Barkhausen magnetic noise measurements. Various magnetic parameters coming from the rms Barkhausen noise envelopes were determined. The linear relationship betweenthe full-width at half-maximum (FWHM) of the Barkhausen noise envelope and the number of loading cycles to fracture was found. Specimens loaded up to a certain number of cycles were also subjected to a tensile test to assess an influence of fatigue on the fracture features.
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.
7
Content available Consequences of using overlays on welded joints
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.
8
Content available remote Effectiveness of a specific Reclaimed Asphalt Pavement (RAP) rejuvenating agent
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
EN
Failure starts with creation of a crack, then the propagation of the crack and eventually the fracture of the material. Furthermore, material selection, geometry, processing and residual stresses are critical factors that may contribute to uncertainty and prospective failure mechanisms in engineering. These issues may also arise in computational analysis, a problematic model, for instance, a three-dimensional surface fracture that may necessitate numerous degrees of freedom during analysis. However, considering the multiple incidents of material failure, detailed analysis and efforts to prevent premature material failure for safety and engineering integrity can be carried out. Thus, the objective of this study is to model crack growth in a surface-cracked structure. Aluminium alloy 7075-T6 was the material of interest in this study. The S-version finite element method (SFEM) was used to study fracture propagation. The numerical approach developed in this research was the probabilistic SFEM. Instead of mesh rebuilding, a typical finite element approach, the SFEM uses global–local element overlay method to create a fatigue crack growth model, which was then used for crack research. Empirical computation and previous experimental data were used to evaluate the stress intensity factor (SIF), surface crack growth and fatigue life. The SIF was determined using a virtual crack closure method (VCCM). In addition, the probabilistic approach is also a critical method to generate random parameters, such as Monte Carlo and bootstrap methods. The SIF, fatigue life and surface crack growth were validated and deemed to be within the acceptable range.
10
Content available Fatigue life testing of the round link mining chains
EN
The material fatigue phenomenon consists of progressive material damage through the appearance and development of fractures under the influence of variable, periodically recurring stresses. Engineers designing machinery and structures to be fatigue resistant can gain useful insights about design and material properties by reviewing the literature. In this way, we can avoid costly research, but in the case of complex loading phenomena and the interaction of components, we must carry out such research. Fatigue strength calculations are less accurate than simple static calculations. The wear of link chains is concentrated in three areas, depending on the installation location and function of the individual links, namely: in the joints (the points of contact between two links), on the outer surfaces of the arches and on the outer surfaces of the straight sections of the links. During operation, chains are particularly vulnerable to wear through abrasion, corrosion and fatigue. These ageing factors, which act with varying intensity depending on the properties of the deposit, determine the service life of the chain, unless other unforeseen damage occurs, e.g. "hard" blockage of the chain. In many cases, users are guided by their own subjective criteria for assessing the technical condition of chains, which does not always lead to fully rational decisions regarding the continued use of used chains. To date, there have been no attempts to transfer the results of chain fatigue tests to behaviour of real objects. This paper presents issues related to mining chain fatigue testing. The test results presented are for both new and used chains. The experimental tests conducted at GIG made it possible to solve the problem of applying fatigue test results in industrial practice.
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.
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.
13
Content available Stand testing of springs for drum brake systems
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.
EN
In this study, the effect of calcium treatment on the mechanical properties and fatigue behavior of low carbon steel material is investigated. By applying calcium treatment after aluminum deoxidation for steel cleanliness, the aim is to transform the inclusions into harmless structures and produce cleaner liquid steel. As a result of the study, calcium treated material’s tensile strength slightly increases while fatigue life decreases. SEM studies were conducted to evaluate the results and it was observed that while elongated inclusions were observed as well as spherical shapes in the untreated sample, the inclusions generally had a spherical shape in the calcium treated sample. After the steel cleanliness process, the mechanical properties of the samples were improved. The tensile strength of the calcium treated sample increased slightly. However, a significant decrease in fatigue strength was observed depending on brittle inclusions that occur as a result of the calcium treatment process.
EN
Self-hardening aluminium alloys represent a new and interesting group of aluminium alloys. They have the advantage that they do not need to be heat treated, which is an important advantage that contributes to a significant reduction in production costs of some components and in the amount of energy used. The present paper deals with the possibility to replace the most used heat treatable AlSi7Mg0.3 cast alloys with a self-hardened AlZn10Si8Mg cast alloy. In this study, microstructural characterization of tensile and fatigue-tested samples has been performed to reveal if this replacement is possible. The results of fatigue tests show that AlSi7Mg0.3 alloy after T6 heat treatment and self-hardened AlZn10Si8Mg has comparable values of fatigue properties. The self-hardening alloy has slightly lower strength, ductility, and hardness.
EN
The aim of this paper is to evaluate the fatigue resistance of austenitic nodular cast iron and to compare it with other types of nodular cast irons. The austenitic nodular cast iron, used for the experiments, was alloyed by 13% nickel and 7% manganese (EN-GJSA-XNiMn13-7) to obtain an austenitic matrix. The microstructure was studied using light metallographic microscopy. Mechanical properties were investigated by tensile test, impact bending test and Brinell hardness test. Fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The results of fatigue tests were compared with the fatigue properties of ferrite-pearlitic nodular cast iron and pearlite-ferritic nodular cast iron. Experimental results show that NiMn-type of austenitic nodular cast iron has lower tensile strength and hardness, but higher elongation and absorbed energy than the compared types of nodular cast iron. However, austenitic nodular cast iron has lower fatigue limit.
EN
The aim of this publication was to propose a method to determine changes in fatigue in selected muscle groups of the lower extremity during dynamic and cyclical motion performed on a rowing ergometer. The study aimed to use the discrete wavelet transform (DWT) to analyze electromyographic signals (EMG) recorded during diagnostic assessment of muscle and peripheral nerve electrical activity (electroneurography) using an electromyography device (EMG). Methods: The analysis involved implementing calculations such as mean frequency (MNF) and median frequency (MDF) using the reconstructed EMG signal through DWT. The study examined the efficacy of DWT analysis in assessing muscle fatigue after physical exertion. Results: The study obtained a negative regression coefficient for DWT analysis in all muscles except for the right gastrocnemius (GAS). The results suggest that DWT analysis can be an effective tool for evaluating muscle fatigue after physical exertion. Conclusions: The use of DWT in the analysis of EMG signals during rowing ergometer exercises has shown promising results in assessing muscle fatigue. However, additional investigations are necessary to confirm and expand these findings. This publication addresses the literature gap on the determination of muscle fatigue considering motion analysis on a rowing ergometer using the discrete wavelet transform. Previous studies have extensively compared and analyzed methods such as the Fourier transform (FFT), short-time Fourier transform (STFT), and wavelet transform (WT) for muscle fatigue analysis. However, no previous work has specifically examined the assessment of muscle fatigue by incorporating DWT analysis with motion analysis on a rowing ergometer.
EN
: The aim of the study was to assess static postural stability under fatigue in subjects with chronic ankle instability – “copers” in comparison with healthy controls. Methods: We conducted a prospective study on a group of 60 young, physically active subjects, divided into 3 groups: I – 14 subjects with unilateral ankle instability, II – 15 subjects with bilateral ankle instability, III – 31 healthy subjects, without ankle instability. The fatigue trial was based on modified Short-Term Fatigue Protocol. Static stabilography was performed with the use of HUR platform. Results: showed an increase in the value of COP trace length after fatigue test in study population I. The level of COP trace length Z before fatigue was significantly lower than after fatigue. Subjects from study population I had higher levels of COP trace length Z in comparison with the control group. The main effect for the group also proved to be significant. Study population I had higher levels of COP trace length Z in comparison with the control group. For the measurement after fatigue, there was significant difference only between the study population I and the control group. Conclusions: The incidence of structural ankle instability was not correlated with functional instability. Subjects with ankle instability, or “copers”, had good functional levels, enabling them to perform sports activities. “Copers” had weakened proprioception in static stabilography tests. Short and intense fatigue protocol weakened the ability to maintain balance in static stabilography test with eyes closed.
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.
20
Content available The evolution of the shape of composite dowels
EN
Composite dowels have opened new possibilities for engineers designing composite structures. The fundamental and most important characteristic of composite dowels is the shape of the cutting line. It is important to understand why only one particular shape of the cutting line is used in bridge engineering, while so many different shapes have been investigated by many researchers. The essential part of the process of developing composite dowels – the development of the shape of the cutting line – is presented in this paper. The influence of the steel web thickness is presented, and technological problems of steel fabrication are highlighted. The role of empirical experience from the first bridges, push-out tests, and finite element simulations is presented. Assumptions for numerical procedures are given. The distinction between the steel failure and concrete failure modes is introduced for composite dowels. The paper presents how the concept of “shape” was divided into “shape,” “ratio,” and finally “size,” and how, because of the fatigue problems in bridges, all the three factors have emerged to result in the form of shapes that can satisfy the requirements for bridges. Research leading to the invention of the first version of the clothoidal shape is presented.
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