Authors: Alkiviadis Tsamis

Abstract

Aortic disease (AoD) is a leading cause of mortality in developed countries. Two of the most common forms of AoD are aneurysm (widening) and dissection (tear in inner wall). Aneurysm and dissection often associate with bicuspid aortic valve (BAV) instead of the normal tricuspid aortic valve, and BAV aneurysms of ascending thoracic aorta have the tendency to bulge asymmetrically towards the greater curvature of aorta. Multiphoton microscopy can help us image collagen and elastin fibres, which are considered as main load-bearing constituents of the aortic wall, in order to investigate potential role of fibre microstructure in ascending thoracic aortic aneurysm or dissection. Regional differences in fibre microstructure may be driven by distinct mechanisms of vascular remodelling, and, combined with mechanical tests, could improve our understanding of the biomechanical mechanisms of aortic aneurysm and dissection potential. Should we wish to investigate the effect of microstructure in soft tissue formation and organ development, we would have to consider a rapidly growing process. In that process, the cells are the main load-bearing components, which cooperate to produce tissue-level forces that shape tissue formation. Our understanding of this phenomenon, called mechanotransduction, has advanced significantly over the past years, to the point where it is now clear that nearly every biological process is modulated by how these forces are decoded intracellularly. It is therefore important to create our own fluorescently-labeled matrix that could integrate into the tissue and enable tracking of these forces in-vivo. A new 3D optical nanomechanical biosensor (NMBS) based on fluorescent fibronectin fibres was developed based on integrated photolithography and micro-contact printing technology. NMBS was successfully validated under uniaxial tensile test of biologically relevant materials for microscopic vs. macroscopic mechanical strains. In the future, biomimetic 3D scaffolds could be fabricated by assembly of 2D fibre constructs based on the NMBS technology, in order to analyse the effect of selected set of load-bearing microstructural components on both mechanical and functional response of soft biological materials.

Key words: Aortic aneurysm, Biosensor, Cell, Fibre microstructure, Soft tissue formation;

DOI: 10.24867/ATM-2022-2-001

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Authors: Tomaž Vuherer

Abstract

The heat-affected zone (HAZ) is the part of the weld that is affected by the heat generated by the welding process during welding. The microstructure of the HAZ is very heterogeneous and consists of different zones such as the coarse-grained HAZ, the fine-grained HAZ, the intercritical HAZ, and the over-tempred HAZ [1]. All these zones are very narrow and their properties are slightly different. These properties affect the integrity of the entire weld, so in many cases the HAZ may be the worst part of the weld. Another challenge is determining the properties of the individual HAZ regions, since the entire HAZ is very narrow and inhomogeneous. For this reason, many properties cannot be determined accurately, with the exception of a few, such as hardness, for which only a small region is sufficient for measurement. Therefore, it is important to know how to produce the individual microstructure of a HAZ in a wider range of the material in order to determine the actual properties of such a HAZ. One of the ways is to measure the welding parameters during welding to determine the actual influence of the thermal cycle on the formation of the invidual microstructure of HAZ in the weld. Moreover, it is crucial to repeat this weld thermal cycle in an unaffected base metal on a thermal welding simulator to obtain a suitable microstructure of the HAZ [1,2]. The second option is to prepare the microstructure in the furnace by slow heating which is followed by rapid cooling [1,3]. Both processes must be precise and accurate to obtain suitable HAZ microstructures. This article addresses the challenges of producing HAZ microstructures on the high-alloy steel CT781, which is widely used in the automotive industry for parts subjected to high dynamic loads.

Key words: Fatigue growth test, Heat Affected Zone, Mechanical testing, Welds;

DOI: 10.24867/ATM-2022-2-002

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Authors: Sebastian Baloš, Dragan Rajnović, Danka Labus Zlatanović, Miroslav Dramićanin, Petar Janjatović, Mirjana Trivković, Milan Pećanac, Leposava Šidjanin

Abstract

In this paper, a case study of pitting corrosion of austenitic stainless steel weld of a pipe in brewing industry is presented. Pitting corrosion caused leakage and the cause of corrosion was sought to be found. After a comprehensive investigation, comprising of visual inspection, chemical composition, hardness, tensile and metallographic testing. It was found that there are two reasons that influenced the occurrence of pitting corrosion, both related to welding process. The first is the unnecessary cleaning of the inside of the pipe by wire brush tool on the power drill, introducing creases that held the acidic cleaning agent. The concentration of the acid rose after evaporation that caused the corrosion, aided by the tinting of the weld zone. Tinting was caused by insufficient oxygen purging from the inside of the pipe by shielding gas. After welding, no passivation was performed, which left the heat tinting layer with compromised corrosion resistance.

Key words: Brewery, Pipe, Corrosion, Welding

DOI: 10.24867/ATM-2022-2-003

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Authors: Tomasz Węgrzyn, Bożena Szczucka-Lasota, Wojciech Tarasiuk, Piotr Cybulko, Adam Jurek, Adam Döring, Aleksandar Kosarac

Abstract

The stainless steel must be treated as good material used to construction of antenna mounts. The duplex steel 1.4462 steel has a very good resistance to corrosion in an ambient and also in an elevated temperatures. The duplex steel is rather good weldable, although it is prone to various types of welding incompatibilities. Many factors influence quality of the weld. The goal of the paper is to study of the influence of main MAG welding parameters on creation of proper welds. A novelty in an article is the use of shielding gas mixtures with a very limited amount of oxygen (below 1% O2) in MAG welding. Welding duplex steels with a shielding gas mixture with a very low oxygen concentration was difficult until recently. It could be expected that new technological solution will allow to obtain a duplex joint with good corrosion resistance and good mechanical properties, which is important in antenna structures. The mechanical properties of several tested joints were investigated and the relationship between the oxygen content in the gas mixture and the oxygen content in the weld was determined.

Key words: Welding, MAG, 1.4462 steel, Experiment, Thermal conditions

DOI: 10.24867/ATM-2022-2-004

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Authors: Nikola Kostić, Saša Ranđelović, Sandra Stanković

Abstract

The simulation of the clutch lever forging process was carried out using Qform software, which is based on numerical and finite element methods, while the tool itself was modeled in SolidWorks CAD software. The stress-deformation state of the workpiece in the process of hot forging in an asymmetric dies for forging with excess material, which represents one of the most common technologies in modern industrial processes of the metalworking industry was analyzed and monitored in this paper.

Key words: Hot forging, FEM, Stress, Strain, Die;

DOI: 10.24867/ATM-2022-2-005

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Authors: Nada Ratković, Živana Jovanović Pešić, Dušan Arsić, Miloš Pešić, Dragan Džunić

Abstract

FSW is a solid-state joining process. It is widely used for joining hard alloys like steel, titanium, and aluminium which are very difficult to join by fusion welding. FSW joint quality is mainly influenced by shoulder and pin geometry, its diameter, tool material, tool rotation speed, and linear traveling speed. The paper presents a brief overview of the tools used during the FSW procedure. The influence of the tool pin on the material flow and mixture was analysed in detail. In addition, the primary and secondary material flow and how it is affected by the shape and dimensions of the tool pin are also discussed.

Key words: FSW, FSW tool, Material flow

DOI: 10.24867/ATM-2022-2-006

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