scholarly journals DETECTION OF MECHANICAL STRESS LIMITING EFFECTS OF CRANE STRUCTURE DEFORMATION

2021 ◽  
Vol 2021 (6) ◽  
pp. 5396-5402
Author(s):  
LEOPOLD HRABOVSKY ◽  
◽  
ZDENEK FOLTA ◽  

The paper presents a construction design and results of laboratory tests of so-called mechanical stress detectors, which can be used to detect the deformation of the steel structure of a crane and to amplify the mechanical signal from the effect of the so-called crane skewing, which is included among occasional loads acting on the crane. The values of the relative elongation of the detectors corresponding to the magnitude of the instantaneous tensile force were obtained by conducting experimental mechanical tests. Detectors of a known extent of deformation were installed on a two-girder overhead crane bridge, where they measured axial forces generated during the controlled deformation of the crane bridge. In practice, the instantaneous values of the axial forces recorded by the individual detectors make it possible to regulate the speed of the crane drive wheels and thus eliminate, in a relatively short time, the undesirable effects of deforming the crane bridge and friction of the crane wheels on the sides of the rail heads.

Author(s):  
Amin Loriemi ◽  
Georg Jacobs ◽  
Sebastian Reisch ◽  
Dennis Bosse ◽  
Tim Schröder

AbstractSymmetrical spherical roller bearings (SSRB) used as main bearings for wind turbines are known for their high load carrying capacity. Nevertheless, even designed after state-of-the-art guidelines premature failures of this bearing type occur. One promising solution to overcome this problem are asymmetrical spherical roller bearings (ASRB). Using ASRB the contact angles of the two bearing rows can be adjusted individually to the load situation occurring during operation. In this study the differences between symmetrical and asymmetrical spherical roller bearings are analyzed using the finite element method (FEM). Therefore, FEM models for a three point suspension system of a wind turbine including both bearings types are developed. These FEM models are validated with measurement data gained at a full-size wind turbine system test bench. Taking into account the design loads of the investigated wind turbine it is shown that the use of an ASRB leads to a more uniform load distribution on the individual bearing rows. Considering fatigue-induced damage an increase of the bearing life by 62% can be achieved. Regarding interactions with other components of the rotor suspension system it can be stated that the transfer of axial forces into the gearbox is decreased significantly.


2021 ◽  
pp. 002199832110115
Author(s):  
Shaikbepari Mohmmed Khajamoinuddin ◽  
Aritra Chatterjee ◽  
MR Bhat ◽  
Dineshkumar Harursampath ◽  
Namrata Gundiah

We characterize the material properties of a woven, multi-layered, hyperelastic composite that is useful as an envelope material for high-altitude stratospheric airships and in the design of other large structures. The composite was fabricated by sandwiching a polyaramid Nomex® core, with good tensile strength, between polyimide Kapton® films with high dielectric constant, and cured with epoxy using a vacuum bagging technique. Uniaxial mechanical tests were used to stretch the individual materials and the composite to failure in the longitudinal and transverse directions respectively. The experimental data for Kapton® were fit to a five-parameter Yeoh form of nonlinear, hyperelastic and isotropic constitutive model. Image analysis of the Nomex® sheets, obtained using scanning electron microscopy, demonstrate two families of symmetrically oriented fibers at 69.3°± 7.4° and 129°± 5.3°. Stress-strain results for Nomex® were fit to a nonlinear and orthotropic Holzapfel-Gasser-Ogden (HGO) hyperelastic model with two fiber families. We used a linear decomposition of the strain energy function for the composite, based on the individual strain energy functions for Kapton® and Nomex®, obtained using experimental results. A rule of mixtures approach, using volume fractions of individual constituents present in the composite during specimen fabrication, was used to formulate the strain energy function for the composite. Model results for the composite were in good agreement with experimental stress-strain data. Constitutive properties for woven composite materials, combining nonlinear elastic properties within a composite materials framework, are required in the design of laminated pretensioned structures for civil engineering and in aerospace applications.


Author(s):  
Наталія Юріївна Бондар

The article deals with the influence of the archetype of the way on the formation of the personality in the novel Paper Towns by John Green. The purpose of this article is to determine the originality of the image of an American teenager and to identify the influence of the archetype of the way on the formation of the personality, as well as to consider the archetype of the way as a real path of the character in the novel Paper Towns by John Green, taking into account the individual author’s interpretation. This object of research has been chosen because through it one can comprehend the specifics of the psychology of a teenager and define the artistic features that distinguish the author’s stylistics and worldview. The comprehensive research methodology has been used in the work: the synthesis of the comparative historical method, holistic analysis, elements of mythopoetic and hermeneutic methods. In the novel Paper Towns by John Green mythopoetic consciousness presupposes ontological ambivalent intentions in the archetype of the child / teenager (good and evil children). The metaphorical extension of the archetype of the child / teenager has been revealed in this article. All the images of teenagers are given in the development, on the way to growing up. The originality of the archetype of the way here lies in the fact that it merges with the concepts of Space and Chaos, confirming the idea of the unity of mankind. The metaphors themselves are also peculiar, associated with the archetype of the way: inanimate strings, gradually turning into living blades of grass, intertwined with roots with all that exists. During the search for Margo, Quentin grows up significantly, becomes more tolerant to their friends, and he learns to take responsibility for him. The image of Margo is the image of a rebel against any lack of freedom that it is inevitable in the “golden cage”. It is also revealed how Quentin is influenced by the new world opened during his trips, and his personal environment: for example, Radar opens his eyes to the fact that he does not need to demand too much from others. Both Margo is changed (from a “paper” girl – to a real one) and Ben and Radar are changed (false interests go into the background; everyone learns to expose himself to risks and troubles for the sake of friendship and human salvation). Ben and Radar are also shown in the development, in a short time they learn to understand each other and distinguish false values from true ones. These changes occur with all the teenagers, regardless of their skin color and nationality, and such an interpretation of the insignificance of formal differences is also a new word of the author.


Abstract. A steel structure is naturally lighter than a comparable concrete construction because of the higher strength and firmness of steel. Nowadays, the growth of steel structures in India is enormous. There are so many advantages in adopting the steel as structural members. Almost all high-rise buildings, warehouses & go-downs are steel structures and even some of the commercial buildings are made of steel. Tension members are the elements that are subjected to direct axial load which tends in the elongation of the structural members. Even today bolted connections play a major role in the connection of hot rolled structural steel members. In this experimental study the behavior of tension members (TM) such as plates, angles & channels have been studied under axial tensile force. There is strong relation between pitch and gauge (with in the specified limit as per IS 800:2007) in determining the rupture failure plane. In this study we intensively tested the behaviour of TM for different fasteners pattern by changing the pitch, gauge, end & edge distance and by adopting the different patterns or arrangements of bolted connection in it.


Author(s):  
Leopold Hrabovský ◽  
Daniel Čepica ◽  
Karel Frydrýšek

2006 ◽  
Vol 5 (3) ◽  
pp. 234-242 ◽  
Author(s):  
Nobuaki Tsukamoto ◽  
Takeshi Maeda ◽  
Hiromasa Miura ◽  
Seiya Jingushi ◽  
Akira Hosokawa ◽  
...  

Object Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed. Methods The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically. After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein–2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans. Conclusions The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.


2019 ◽  
pp. 128-148 ◽  
Author(s):  
Miriam Noël Haidle

Cumulative culture is widely seen as a uniquely human characteristic involving distinct cognitive and behavioral performances. In searching for its origin, different factors have been suggested as crucial, based on comparative studies, and dates proposed as to when cumulative culture may have emerged in human evolution. This chapter reviews possible factors, suggesting that several are necessary, not only in the social sphere but also in the individual and environmental spheres. These interdependent factors have developed in three developmental dimensions (evolutionary-biological, ontogenetic-individual, and historical-social) in interaction with the specific environment. The interplay of basic factors and developmental dimensions shows a slow and gradual development of cumulative culture from its basis to simple and advanced donated culture. The onset of cumulative culture is concluded not to have been a single-trait event that occurred in a relatively short time but rather, the result of multifactorial and gradual processes that unfolded over millions of years.


2019 ◽  
Vol 13 ◽  
pp. 117822181882297 ◽  
Author(s):  
Megan E Patrick ◽  
Yvonne M Terry-McElrath

High-intensity drinking (HID; ie, having 10+ drinks in a row) is a recognized public health concern due to the individual and public risks (eg, alcohol-related injuries, alcohol poisoning, memory loss, sexual risk) associated with consumption of a large quantity of alcohol over a relatively short time period. Using nationally representative samples of US 8th, 10th, and 12th grade students, and follow-up of subsamples of 12th graders, we present overall and sex-specific prevalence estimates of past 2-week HID from 29 966 individuals at the modal ages of 14 to 30 in 2016-2017. Similar data for the more commonly studied measure of binge drinking (having 5+ drinks in a row) is provided for comparison. HID prevalence ranged from 1% to 11.5% and was significantly higher for males than females at all ages other than modal age 14 (8th grade). Binge drinking prevalence ranged from 3.5% to 32.5%; males reported a higher prevalence than females at approximately half of the ages examined. Peak binge drinking and HID age for males was earlier (modal age 21/22) than that for females (modal age 21-24 for binge drinking and 25/26 for HID). The observed rapid increase in HID from adolescence through the early to mid-20s highlights the importance of prevention and intervention efforts targeted to these ages.


Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1498
Author(s):  
Miroslawa Prochon ◽  
Anna Marzec ◽  
Oleksandra Dzeikala

Buffing Dust Collagen (BDC) is a hazardous waste product of chromium tanning bovine hides. The aim of this study was to investigate whether BDC has the desirable properties required of modern fillers. The microstructural properties of BDC were characterized by elemental analysis (N, Cr2O3) of dry residue and scanning electron microscopy (SEM). The BDC was applied (5 to 30 parts by weight) to styrene butadiene rubber (SBR), obtaining SBR-BDC composites. The physicochemical properties of the SBR-BDC composites were examined by Fourier transform infrared analysis, SEM, UV–Vis spectroscopy, swelling tests, mechanical tests, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The biodegradability of the SBR-BDC composites and their thermo-oxidative aging were also investigated. The filler contributed to increase the cross-link density in the elastomer structure, as evidenced by enhanced mechanical strength. The introduction of a filler into the elastomer structure resulted in an increase in the efficiency of polymer bonding, which was manifested by more favorable rheological and mechanical parameters. It also influenced the formation of stable interfacial bonds between the individual components in the polymer matrix, which in turn reduced the release of compact chromium in the BDC filler. This was shown by the absorption bands for polar groups in the infrared analysis and by imaging of the vulcanization process.


2017 ◽  
Vol 270 ◽  
pp. 246-252
Author(s):  
Zbyněk Špirit ◽  
Michal Chocholoušek ◽  
Marek Šíma

This paper describes the testing of thin-walled tubes made of oxide dispersion-hardened steels based on yttrium oxides. Series of mechanical and metallographic tests were carried out on the steels to evaluate the basic material properties. These steels are the candidate materials for the manufacture of the fuel cladding for generation IV nuclear reactors. Mechanical tests were performed on miniature specimens of Fe-9Cr and Fe-14Cr steels at 20 °C, 500 °C, and 625 °C under vacuum. Metallographic, fractographic and EBSD analyses were used to describe microstructure and fracture mechanism of the tested materials.


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