Authors: Slaviša Djačić, *Srbislav Aleksandrović, Dušan Arsić, Marko Delić, Vukić Lazić

Abstract

Comparison of application of constant and variable lateral force in strip ironing process with double side thinning are presented in the paper. Given are the experimental results for single and multiphase ironing process with constant lateral force during the course of particular process. Material used was mild steel DC04. Stripes were 20 mm wide and 2.5 mm thick. Constant lateral force intensities were 5, 10 and 15 kN. Lubrication was with appropriate mineral oil and grease. In other side given is analysis of idea of possibility to apply variable lateral force during the strip ironing process and consequences of this action. Expected is control of strip thickness variation with difficulties because of contact and other appearances influence.

Key words: ironing process, strip sliding test, variable lateral force;

DOI: 10.24867/ATM-2021-2-001

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Authors: Nitai S. Dasa, Hillol Joardara, Matruprasad Routb, Bikash C. Beheraa, Kalipada Maity

Abstract

This paper outlines the salient features of the “generalized upper bound” technique and uses it to derive upper bounds for plane strain compression and extrusion of metals in the presence of Coulomb friction (τ = µp). For compression the velocity field is established by reformulating the same proposed earlier by Lee and Altan so as to be compatible with the interface Coulomb friction condition. For extrusion, the upper bound velocity field is derived from a stream function for flow through a smooth die of wedge angle (α+λ) where, α is the semi-wedge angle of the rough die, and λ is the friction angle (tanλ = µ). Analysis for this case is also presented assuming the flow to be radial. The analytical results are compared with those obtained from, the slip-line field and finite element analyses and from the rigid triangle velocity fields. These are also validated by some e experimental results available in literature.

Key words: Coulomb friction; Upper bound; Plain strain; stream function compression; extrusion; Finite element modelling

DOI: 10.24867/ATM-2021-2-002

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Authors: Slobodanka Boljanović, Strain Posavljak, Stevan Maksimović

Abstract

Fatigue-induced flaws play an important role in safety-integrity performances of large moving systems. Therefore, the present research work proposes a computational model to gain insight into such surface stress raisers. The analysis shows that a combination of damage-tolerance design with fracture mechanics-based concept is a key to generating relevant relationships between fatigue life and stress intensities.

Key words: fatigue design, residual life, stress intensity analysis, surface flaw

DOI: 10.24867/ATM-2021-2-003

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Authors: Svetomir Simonović

Abstract

Because of the continuing miniaturization of integrated circuits it appears that quantum phenomena will play a more and more dominant role in their design and functioning. Therefore, the work exposes concise quantum mechanical and mathematical background of quantum phenomena based computing through the introduction of concepts such as Hilbert space, qubit, Bloch sphere, quantum gate and measurement. Recent improvements in ion- trap technology based computing suggest ion- trap technology as the most promising one for use in quantum computing. So, the paper describes the ion- trap based technology, its use in quantum computation and its latest applications in quantum computing. It turns out that recent ion- trap technology based computers dramatically improves on all of the Vincenzo’s criterions.

Key words: miniaturization; Hilbert space; qubit; Bloch sphere; measurement; ion-trap technology.

DOI: 10.24867/ATM-2021-2-004

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Authors: Matic Lešnjak, Borut Kosec, Blaž Karpe, Goran Janjić, Mirko Gojić, Jure Bernetič, Gorazd Kosec

Abstract

Steels from the group PROTAC are distinguished by good mechanical properties and excellent armour properties even at small thicknesses. The mechanical properties of PROTAC 600 steel are known, while data on thermal properties (thermal conductivity, specific heat and temperature conductivity) are not available, so in the frame of our work we determined its thermal properties. As the first part of the work, a study and evaluation of the operation of the device for determining the thermal properties of Hot Disk TPS 2200, today one of the more modern and high-quality instruments for determining thermal properties. In the second part of the work, we performed measurements of thermal properties in accordance with the standard ISO 22007- 2 at ambient temperature. The values of thermal properties of PROTAC 600 steel at ambient temperature (approximately 22 °C) are: thermal conductivity 28.69 W/mK, specific heat 3.94 MJ/m3K, and temperature conductivity 7.29 mm2/s. We found that steel PROTAC 600 has more than 10% higher heat conductivity in comparison with the steel of previous generation PROTAC 500.

Key words: armour steel, properties, thermal properties, measurements;

DOI: 10.24867/ATM-2021-2-005

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Authors: Dušan Petković, Miloš Madić, Goran Radenković

Abstract

Biomaterials are a special class of contemporary materials used to make prostheses, parts of organs or to replace entire organs. They are used to replace soft and hard tissues. Metal biomaterials are mostly used to replace hard bone tissues and joints. There is no ideal substitution for natural biological material, but each of the biomaterials has a number of advantages and disadvantages. The problem of choosing the most favorable biomaterial is a complex process of multi‐criteria decision‐ making, which requires a lot of knowledge and experience. In order to help decision makers in solving this complex task, a decision support system named MCDM Solver is proposed. MCDM Solver is used in decision‐making process to rank the biomaterials with respect to several criteria. In this paper, MCDM Solver was used to select knee prosthesis material.

Key words: biomaterial selection, multi‐criteria decision making (MCDM), MCDM Solver, decision support system, knee prosthesis;

DOI: 10.24867/ATM-2021-2-006

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Authors: Srđan Bulatović, Vujadin Aleksić, Ljubica Milović, Bojana Zečević

Abstract

In many production processes, as well as in the exploitation of machine components and structures, materials are exposed to impact loads. In structures made of welded joints of high strength low-alloy steels with their constituents (parent metal, weld metal and heat-affected-zone), the toughness test determines the tendency of steel to brittle fracture, respectively the tendency to increase brittleness during exploitation. The strain rate is high and the material manifests much more brittle behavior than is shown by tensile testing. Toughness as a mechanical property is an important factor that is defined as the energy that needs to be spent in order to achieve fracture. Parameters obtained by testing the properties of plasticity are the basis for the design of structures in order to achieve strengths under applied load. The test results of high strength low-alloy steel toughness assessment at different test temperatures show that temperature significantly affects the impact toughness of steels and their alloys. At higher temperatures the impact energy on fracture is high (the material shows the properties of plasticity) while at lower temperatures the impact energy is small (the material is brittle).

Key words: impact toughness, high strength low-alloy steel, welded joint;

DOI: 10.24867/ATM-2021-2-007

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