Characterization of Surface Defects Associated with Flash Butt-Welded Pearlitic Rails and their Contribution to Overload and Fatigue Failures

2009 ◽  
Vol 83-86 ◽  
pp. 1262-1269 ◽  
Author(s):  
Mostafa Mousavizade ◽  
Hassan Farhangi
Keyword(s):  
Surface Defects ◽  
Weld Zone ◽  
Welding Process ◽  
Electrical Heating ◽  
Main Concern ◽  
Zone Formation ◽  
Butt Welding ◽  
Fatigue Failures

Generally about 80 percent of railway tracks are welded by flash-butt welding that consists of electrical heating and hydraulic forging. Fracture of rails specially weld zone fractures are of main concern because of potential risk of a catastrophic derailment. In this paper, surface defects associated with flash butt welding process are examined. Metallographic and fractographic studies show various defects can be formed at the surface of weld zone. Formation mechanism of these defects and their contribution to the observed fatigue and overload weld failures are discussed. Fracture mechanics is also utilized to clarify the role of these defects in fatigue and overload failures.

scholarly journals Optical properties and carrier dynamics in Co-doped ZnO nanorods

2021 ◽  
Vol 3 (1) ◽  
pp. 214-222
Author(s):  
Aswathi K. Sivan ◽  
Alejandro Galán-González ◽  
Lorenzo Di Mario ◽  
Nicolas Tappy ◽  
Javier Hernández-Ferrer ◽  
...  
Keyword(s):  
Optical Properties ◽  
Crucial Role ◽  
Surface Defects ◽  
Zno Nanorods ◽  
Carrier Dynamics ◽  
Photoelectrochemical Characterization ◽  
Doped Zno ◽  
Co Doped

Optoelectronic and photoelectrochemical characterization of Co-doped ZnO nanorods revealing the crucial role of surface defects for enhanced photoresponse.

scholarly journals Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4841
Author(s):  
Aleksandra Królicka ◽  
Krzysztof Radwański ◽  
Aleksandra Janik ◽  
Paweł Kustroń ◽  
Andrzej Ambroziak
Keyword(s):  
Heat Treatment ◽  
Welded Joint ◽  
Construction Material ◽  
Weld Zone ◽  
Base Material ◽  
Welding Process ◽  
Solidification Structure ◽  
Hardness Distribution ◽  
Diffusion Type

One of the main limitations in application of nanostructured carbide-free bainite as a construction material is the difficulty of joining. This research presents a structural characterization of welded joints of medium carbon 55Si7 grade steel after the welding process with a regeneration technique as well as post welding heat treatment (PWHT). The hardness distribution of the welded joint with regeneration exhibit an overall decrease in hardness when compared to the base material and a significant decrease in hardness was observed in the heat-affected zone (HAZ). Unfavorable hardness distribution was caused by the presence of diffusion-type transformations products (pearlite) in the HAZ and bainite degradation processes. On the other hand, welding with the PWHT promotes the achievement of a comparable level of hardness and structure as in the base material. However, a slight decrease in hardness was observed in the weld zone due to the micro-segregation of the chemical composition caused by the indissoluble solidification structure. Based on the structural analysis, it was found that steel with relatively low hardenability (55Si7) should be welded using PWHT rather than a regeneration technique.

Effect of Different Welding Speeds on Mechanical Characterictics, Micro and Macrostructure in Dissimilar Friction Stir Butt Welding of AA6061-T6 and AA7075-T6

2009 ◽  
Author(s):  
Pouya Bahemmat ◽  
Mohammad Haghpanahi ◽  
Mohammad Kazem Besharati ◽  
Alireza Rahbari
Keyword(s):  
Welding Speed ◽  
Mechanical Characteristics ◽  
Microstructural Analysis ◽  
Weld Zone ◽  
Weld Strength ◽  
Microstructural Properties ◽  
High Quality ◽  
Butt Welding ◽  
Friction Stir

In this article, the effect of FSW process parameters on weldability and properties of two dissimilar aluminums joint, AA6061-T6 and AA7075-T6, is investigated. The experiments are conducted to study the role of different welding speeds. Weldability in each fabricated weld is evaluated using macrostructure for sound and defective welds. The mechanical characteristics are determined by comparing the ultimate strength, percentage of elongation for different welding speeds. Besides, microstructural analysis is performed for studying the influence of welding speed on microstructural properties in the weld zone. The results show that the welds were produced with 80 and 100 mm/min are free defects and the rest welds have some defects at SZ, however the weld strength made with 120 mm/min has superiority on the weld. Consequently, the optimum welding speed for fabricating the high quality welds is obtained in this research.

scholarly journals Study the effect of welding pass number on the mechanical and metallurgical properties of Aluminum type Al 1050 H14 produced by friction stir welding

2021 ◽  
Vol 28 (4) ◽  
pp. 1-13
Author(s):  
Najeeb Salman Abtan ◽  
Jawdat Ali Yagoob ◽  
Ayshan Mohammed Shukri
Keyword(s):  
Tensile Strength ◽  
Friction Stir Welding ◽  
Base Metal ◽  
Weld Zone ◽  
Welding Process ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Mechanical Mixing ◽  
Butt Welding ◽  
Friction Stir

Friction Stir Welding (FSW) is a solid-state welding technique with non-fusible rotary welds. Heat is generated by the friction produced between the weld tool and the two opposite surfaces of the two welded parts and the tool works on mechanical mixing with the presence of heat, pressure, and heat generated, reaching approximately (80-90%) of the melting point of the metal to be welded. In this study, Al 1050 H14 aluminum with a thickness of (6mm) was used for the purpose of welding it by means of the friction stir welding process in a butt welding method to obtain similar welding joints. A set with a square stitching tool Made of alloy steel was used by using a milling machine, with fixed (rotational speed of 1008 rpm and linear velocity of 40mm / min), an inclination angle of (2o), and counterclockwise rotation. The efficiency of welded joints was evaluated through static mechanical tests. Tensile tests, microscopic hardness, and visual examination. The results for all welds showed that the mixing zone (NZ) consists of fine grains of equal axes compared to the base metal. When welding on one side and in one path, the microstructure of HAZ was similar to the base metal. TAMZ was a transition region between HAZ and NZ. As for welding on one side, with two paths and three paths, the structure turned into a fine crystalline structure. By increasing the number of paths per side, the welding efficiency of the welded sample increased as the best efficiency was from one side and three paths (76.215%). Through the results, the tensile strength increases with the increase in the number of paths, as the best tensile strength was obtained when conducting the welding process from one side and by three paths, which is (93.653 MPa). It is equivalent to 76.21% of the tensile strength of the base metal. The hardness value in the weld zone (NZ) is higher than the other two zones (HAZ, TMAZ) due to the occurrence of dynamic recrystallization, which results in very fine and equiaxial crystals, but the hardness value in the weld zone remains less than the hardness value of the base metal.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Effects of bottom plate in friction stir welding of AA6061-T6

2020 ◽  
Vol 118 (1) ◽  
pp. 108
Author(s):  
M.A. Vinayagamoorthi ◽  
M. Prince ◽  
S. Balasubramanian
Keyword(s):  
Mechanical Properties ◽  
Axial Load ◽  
Weld Zone ◽  
Welding Process ◽  
Bottom Plate ◽  
Welding Parameters ◽  
Nugget Zone ◽  
Friction Stir ◽  
Weld Joints ◽  
Fine Grain

The effects of 40 mm width bottom plates on the microstructural modifications and the mechanical properties of a 6 mm thick FSW AA6061-T6 joint have been investigated. The bottom plates are placed partially at the weld zone to absorb and dissipate heat during the welding process. An axial load of 5 to 7 kN, a rotational speed of 500 rpm, and a welding speed of 50 mm/min are employed as welding parameters. The size of the nugget zone (NZ) and heat-affected zone (HAZ) in the weld joints obtained from AISI 1040 steel bottom plate is more significant than that of weld joints obtained using copper bottom plate due to lower thermal conductivity of steel. Also, the weld joints obtained using copper bottom plate have fine grain microstructure due to the dynamic recrystallization. The friction stir welded joints obtained with copper bottom plate have exhibited higher ductility of 8.9% and higher tensile strength of 172 MPa as compared to the joints obtained using a steel bottom plate.

Consideraciones en torno a la reducción solipsista

1970 ◽  
Vol 11 ◽  
Author(s):  
Natalia Carolina Petrillo

ResumenEn el presente trabajo se intentará mostrar que la fenomenología no conduce a una postura solipsista. Para ello, se caracterizará en qué consiste el solipsismo. Luego, se intentará refutar a lo que se ha de llamar “solipsismo metafísico” y “solipsismo gnoseológico”, con el objetivo principal de poner de manifiesto el fundamento de motivación para la salida de la ficción solipsista.Palabras claves:Phenomenology – solipsim – empatía - HusserlAbstractWith the aim of showing that phenomenology does not lead in solipsism, I will first attempt a characterization of it. Then, I will attempt a refutation of the so-called “metaphysical” and “epistemological” solipsisms. Finally, the nature and role of Husserl´s solipsistic fiction is examined, and the grounds that motivate the overcoming of this standpoint are disclosed.key wordsFenomenología – solipsismo - empathy – Husserl

ART STUDIOS – A WAY TO DEVELOPE CHILDREN’S IMAGINATION

2020 ◽  
Vol 11 (1) ◽  
pp. 144-148
Author(s):  
Liuba Zlatkova ◽  
Keyword(s):  
Fairy Tale ◽  
Psychological Effects ◽  
Complete Product ◽  
The Arts ◽  
The Creation ◽  
Role Of Parents

The report describes the steps for creating a musical tale by children in the art studios of „Art Workshop“, Shumen. These studios are led by students volunteers related to the arts from pedagogical department of Shumen University, and are realized in time for optional activities in the school where the child studies. The stages of creating a complete product with the help of different arts are traced – from the birth of the idea; the creation of a fairy tale plot by the children; the characterization of the fairy-tale characters; dressing them in movement, song and speech; creating sets and costumes and creating a finished product to present on stage. The role of parents as a link and a necessary helper for children and leaders is also considered, as well as the positive psychological effects that this cooperation creates.

Sign in / Sign up

Export Citation Format

Share Document