scholarly journals Laboratory research on functioning of bridge structures reinforced with induction brazing

2019 ◽  
Vol 6 (2) ◽  
Author(s):  
Sergey Bokarev ◽  
Andrei Usoltsev
Keyword(s):  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
High Strength ◽  
Laboratory Research ◽  
Induction Brazing ◽  
Research Institution ◽  
Bridge Span ◽  
Metal Plates ◽  
Bridge Structures ◽  
Bridge Spans

Welded metal bridge spans are one of the most wide-spread types of bridge spans, several thousand of them being in operation along motorways and in city areas in Russia. Similar to other welded structures they are prone to fatigue cracking which is usually repaired using metal plates fixed with high-strength bolts. The Siberian Research Institution of Bridges located in Siberian Transport University has developed the structure and technology of welded bridge span reinforcement using round metal plates fixed by induction brazing. To prove the efficiency of the technology a laboratory research and testing of girders reinforced with round metal plates fixed by induction brazing has been conducted. The research shows that after the induction brazing enforcement the bridge structures that have fatigue cracks obtain strength parameters 25 per cent higher compared to those of completely new unreinforced samples without fatigue cracks. The article is part of the dissertation research Usoltseva A.M.

scholarly journals PREVENTION OF METAL BRIDGE SPANS FROM FATIGUE CRACKING

2019 ◽  
Vol 21 (4) ◽  
pp. 181-193
Author(s):  
S. A. Bokarev ◽  
A. M. Usoltsev ◽  
A. I. Sluzhaev
Keyword(s):  
Fatigue Cracking ◽  
Crack Mouth ◽  
Railway Network ◽  
Residual Welding Stress ◽  
Welding Stress ◽  
Bridge Span ◽  
Metal Plates ◽  
Cracking Process ◽  
Bridge Spans ◽  
Further Development

At present, more than four thousand metal bridge spans are in operation all over the Russian railway network. Through the years of operation, about thirty types of fatigue cracking were identified. The dynamics of the types Т-9 and Т-10 cracks formation has increased significantly in recent years. The formation and growth of fatigue cracking is influenced by such factors as residual welding stress, stress-strain state of the bridge structure, defects, damages, and non-observing the operation and maintenance standards, bridge location and bridge span structure. At present, neither measures nor repair are performed to prevent fatigue cracking not exceeding 20 mm in length. Only when a creak reaches a certain length, the regulatory documents require to drill a hole at a crack mouth in order to prevent its further development. The hole diameter should be equal approximately to the doubled wall thickness. In order to prevent further crack growth and cover the hole, a high-tensile bearing type bolt is fixed into it, creating a volume stress. As a rule, such a repair is not enough to stop the cracking process. The article suggests a number of measures based on induction heating that allows to prevent cracking (including forging reducing gaps between connecting plates and horizontal sheets in a truss), to carry out repair (crack mouth soldering) and reinforcement (fixing metal plates onto a wall with a hole).

Fatigue Life of Welded Joints of High-Strength Structural Steel S960QL

2016 ◽  
Vol 250 ◽  
pp. 169-174 ◽  
Author(s):  
Tomasz Slezak ◽  
Lucjan Sniezek
Keyword(s):  
Fatigue Life ◽  
Structural Steel ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
High Strength ◽  
Propagation Rate ◽  
Total Strain Amplitude ◽  
Fatigue Life Analysis

The article presents the results of research on low cycle fatigue strength of welded joints of structural steel S960QL. Two types of butt welds were analysed: I-joints and V-joints. The tests were performed under load controlled using the total strain amplitude εac. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. High concordance was found of the adopted description model with experimental results. Studies have shown differences in the fatigue life of the various joints analysed, wherein I-joints showed about 20-50% higher fatigue life. Fractographic tests of fatigue fractures in joints revealed the details of fatigue cracking and differences in the propagation rate of fatigue cracks.

Effect of Corrosion on Crack Development and Fatigue Life

1998 ◽  
Vol 1624 (1) ◽  
pp. 110-117 ◽  
Author(s):  
John W. Fisher ◽  
Eric J. Kaufmann ◽  
Alan W. Pense
Keyword(s):  
Fatigue Life ◽  
Weld Metal ◽  
Fatigue Cracking ◽  
High Strength ◽  
Time Dependent ◽  
Structural Behavior ◽  
The Past ◽  
Fatigue And Fracture ◽  
Bridge Structures

Fatigue and fracture as well as loss of section caused by corrosion are time-dependent performance characteristics that have the potential to jeopardize the integrity of bridge structures. During the past 25 years these conditions have developed in a number of bridges, resulting in loss of service, costly repairs, and concern about the safety of these structures. A review of the experience with such time-dependent damage since 1970 is presented. The experience is grouped into three categories: fatigue cracking resulting from changes in structural behavior as a result of corrosion, fatigue cracking resulting from development of corrosion notches in members, and stress corrosion of high-strength steel and weld metal. The examples cited illustrate the role of corrosion phenomena in bridge service and the need to control the corrosion conditions on bridge structures.

Fatigue crack detection method using analysis of vibration signal

2017 ◽  
Vol 1 (20) ◽  
pp. 63-74 ◽  
Author(s):  
Arkadiusz Rychlik ◽  
Krzysztof Ligier
Keyword(s):  
Crack Detection ◽  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
Vibration Signal ◽  
Technical Condition ◽  
Visual Methods ◽  
Signal Characteristics ◽  
Fatigue Crack Detection ◽  
Sample Structure ◽  
Change Identification

This paper discusses the method used to identify the process involving fatigue cracking of samples on the basis of selected vibration signal characteristics. Acceleration of vibrations has been chosen as a diagnostic signal in the analysis of sample cross section. Signal characteristics in form of change in vibration amplitudes and corresponding changes in FFT spectrum have been indicated for the acceleration. The tests were performed on a designed setup, where destruction process was caused by the force of inertia of the sample. Based on the conducted tests, it was found that the demonstrated sample structure change identification method may be applied to identify the technical condition of the structure in the aspect of loss of its continuity and its properties (e.g.: mechanical and fatigue cracks). The vibration analysis results have been verified by penetration and visual methods, using a scanning electron microscope.

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

scholarly journals Regulation of dynamic characteristics of bridge spans in the conditions of the changing impact of the temporary moving load

2021 ◽  
Vol 1 ◽  
pp. 4-19
Author(s):  
Vladimir Mikhailovich Kartopoltsev ◽  
◽  
Andrey Vladimirovich Kartopoltsev ◽  
Keyword(s):  
Dynamic Characteristics ◽  
Moving Load ◽  
Musical Instrument ◽  
Oscillatory Process ◽  
Natural Oscillations ◽  
Structural Content ◽  
Bridge Structures ◽  
National Programs ◽  
And Control ◽  
Bridge Spans

It is known that an unregulated structure is likened to an unadjusted musical instrument [7]. The adjusted dynamic stress-strain state of the bridge spans will be adequate to the parameters of the design and operational state as a result of the introduction of regulation and control of fl uctuations in the conditions of the changing impact of the temporary mobile load. Methods for regulating dynamic characteristics by changing the frequency of natural oscillations of the system, taking into account energy dissipation, as well as introducing into the oscillatory process a transformed form of intense oscillations in the process of artifi cial or selective resonance, in which the oscillations of the system either damp or cease to be dangerous, are especially carefully considered. Attention is focused on the infl uence of the defectiveness of the roadway with an increase in the mass and speed of a temporary moving load. For this purpose, a classifi er of bridge deck defects has been developed to clarify the boundaries of the eff ect of a defect on the dynamic operation of a structure [1, 3]. Analysis of the structural content and criteria for determining shows the insuffi ciency of the components assessing the eff ect of the temporary mobile load on the span under non-stationary oscillations, and also reveals contradictions in the assessment of the dynamic additive . The practical use of the research results is advisable by the Ministry of Transport Construction in the implementation of state national programs and projects for improving structures, calculation methods, design and operation of bridge structures

scholarly journals Wilson–Konovalov disease: acute onset, course, diagnosis and treatment (clinical case)

2021 ◽  
pp. 76-81
Author(s):  
Yu.I. Alekseeva ◽  
◽  
Ji. V. Turkin ◽  
О.B. Synoverskaya ◽  
L.Ya. Ivanyshyn ◽  
...  
Keyword(s):  
Clinical Picture ◽  
Clinical Case ◽  
Local Level ◽  
Acute Onset ◽  
Left Lobe ◽  
Diagnostic Methods ◽  
Laboratory Research ◽  
Disease Etiology ◽  
Research Institution ◽  
Body Tissues

The article presents information on the main etiology and pathogenesis of Wilson–Konovalov disease, as hepato-lenticular degeneration associated with excessive accumulation of copper in body tissues due to an inherited autosomal recessive defect of a protein that transports copper. A rare case of the onset and course of the disease in a patient who was examined and treated at the Ivano-Frankivsk Regional Children's Clinical Hospital is described. The main focus is on the acute, atypical onset of the disease, in particular the signs of severe intoxication syndrome caused by manifestations of hepatic encephalopathy, steroid-induced diabetes, anemia of complex genesis, coronavirus disease, pyoderma. The difficulties of diagnosing the disease against the background of delayed manifestation of the main pathognomonic manifestations and the absence of reliable signs of the disease are shown. The clinical picture of this clinical case, features of the course are described, the indicators of the main clinical and laboratory research methods are given, the results of instrumental diagnostic methods and genetic examination methods are shown, both in laboratories of Ukraine and abroad, which confirmed the diagnosis of Wilson–Konovalov disease. The treatment of this clinical case is described in detail not only at the local level but also in the main leading research institution of Ukraine «OHMATDYT» and «National Institute of Surgery and Transplantology named after O.O. Shalimov». Recommendations for further observation and treatment of the child at the place of residence after orthotopic transplantation of the left lobe of the liver from a living family donor. The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: Wilson-Konovalov disease, etiology, pathogenesis, clinical picture, diagnosis, examination, treatment.

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