Influence of temperature and specimen orientation on the impact toughness of microalloyed steel

NIOMOL 490 microalloyed steel, used for welded pressure vessels subjected to dynamic loads and operating at sub-zero temperatures, exhibits acceptable toughness. This paper presents the experimental analysis, which includes an impact toughness test. The analysis resulted in impact energy values and represents the first phase of a comprehensive investigation into behavior of NIOMOL 490 steel. the aim was to determine the effects of temperature and the effects of specimen orientation with respect to rolling direction on impact toughness and the relationship between its components

Primena georadara pri proceni stanja prethodno napregnutnih mostova

Procena i održavanje armiranih i prednapregnutih betonskih mostova od ključnog su značaja za očuvanje integriteta i produženje njihovog veka trajanja. Georadar (GPR) postao je neophodna nedestruktivna metoda za evaluaciju ključnih parametara pri proceni stanja, poput rasporeda armature, geometrije i prisustva defekata kao što su korozija ili delaminacija kao i za lociranje kablova za prednaprezanje (određivanje položaja i podužnih šipki armature i kablova). U ovom radu pokazana je primena georadara (Proceq GP8800), profometra (Proceq 650 AI) i ultrazvučni tomograf (Proceq Pundit PD8000) na primerima projekata prednapregnutih konstrukcija železničkog mosta (Želežnička stanica Novi Beograd) i drumskog mosta (granični prelaz Karakaj - Mali Zvornik). Nedavne studije naglašavaju važnost primene antena visoke frekvencije radi poboljšanja detekcije anomalija, posebno u identifikaciji oštećenja uzrokovanih korozijom armature delova nosive konstrukcije mosta. Simulacije su pokazale da izbor optimalne radne frekvencije značajno utiče na tačnost detekcije. Pored toga, starenje prednapregnutih betonskih mostova suočava se sa izazovima poput pojave prslina, korozije, delaminacije i smanjenja krutosti, što zahteva aktivno praćenje i održavanje kako bi se usporila degradacija nosive konstrukcije. Studije slučaja ističu prednosti i ograničenja različitih metoda inspekcije, naglašavajući njihov značaj u očuvanju bezbednosti, smanjenju troškova i ekološkog uticaja, dok se istovremeno obezbeđuje trajnost ovih ključnih infrastrukturnih objekata

Cavitation resistance of refractory coatings

In this study, the resistance to the cavitation effect of three types of refractory samples based on talc with the addition of 10%, 15% and 20% cordierite was investigated. Talc has a fine structure, low hygroscopicity, insensitivity to temperature changes, low coefficient of thermal conductivity, low coefficient of linear thermal expansion, great ability to stick and coat surfaces, good grindability, low hardness. Cordierite has high refractoriness, high hardness, high density, low value of dielectric constant, low coefficient of thermal conductivity, low coefficient of linear thermal expansion, high resistance to thermal shock, relatively high melting temperature with the possibility of application up to 1380°C, high inertness towards liquid metal. Cordierite was added in order to improve properties, primarily to increase resistance to the effect of cavitation. The prepared mixtures of refractory powders were pressed under a pressure of 1 MPa and sintered at 1200°C.To evaluate the cavitation resistance properties of the investigated refractory samples, the ultrasonic vibration method with a stationary sample was applied. The change in the mass of the samples as a function of the cavitation time was monitored and the cavitation speed was determined. The formation and development of damage to the surface of the samples was monitored using a scanning electron microscope. The mechanism of degradation and resistance to the effect of cavitation of the tested samples was monitored by measuring the mass loss and morphological analysis of the pits formed on the surface of the tested samples. Research has shown that the addition of cordierite in the composition of the tested samples based on talc significantly improves the properties of resistance to the effect of cavitation.http://www.serbianceramicsociety.r

Techno-economic analysis in the service of traditional ceramic industry. The first review

The traditional ceramics industry uses large amounts of raw materials and energy while significantly contributing to the CO2 footprint. The improvements, primarily in the first two areas, will contribute to sustainable development and answer the emerging questions of decreasing a gas-release footprint. These are topics of high importance considering European Union goals, and thus, on the contrary, there is yet only scarce available literature on the subject. This paper describes the state and future perspectives of the traditional ceramics industry through the techno-economic lens. Many options are detected that save resources (waste materials), energy consumption (reparation or modification of kilns, usage of dry pressing in ceramic tiles production, etc.), and control of flue gas composition (changing the fuel, etc.). Further intensified research is needed to widen the knowledge and compare the results. In the first place, the composition of flue gas should be determined by the same methods and presented using unified units. The lowest energy consumption and flue gas composition are determined in ceramic tiles production by the dry route. Using a downdraft gasifier of biomass in brick manufacturing increases the internal rate of return if a longer tunnel kiln is applied. The expected payback period is from 4 to 8 years

Autonomni modularni sistem za dinamičko ispitivanje šipova

Broj prijave: MP-2023/0028 Link do baze patenata: https://reg.zis.gov.rs/patreg/?t=

Cement zasnovan na bio-otpadu za održivu građevinsku praksu

Industrial byproducts are being increasingly used as raw materials in the cement clinker production. This can help to address the issue of huge amounts of eggshell waste that are discarded into the environment. This bio-waste has a trigonal-calcite structure and similar behaviour as limestone. In this study, cement clinker is synthesized at 1300 °C using eggshell waste in place of limestone. The raw materials are mechanically activated in a high-energy mill. The sintering kinetics are calculated using the results of differential ther-mal analysis. Mechanical activation modified the spatial distribution of Al, Si, Ca, and Fe, thereby improving the reactivity which in turn decreased the sintering temperature of the clinker. The study demonstrated that eggshell waste is a suitable replacement for limestone in the production of ordinary Portland cement

Electromagnetic property selection for GPR modelling in corrosive concrete environments

Understanding the mechanisms that alter the ground penetrating radar (GPR) electromagnetic wave propagation as a result of reinforcement corrosion is pivotal for accurate assessment of the corrosion of reinforced concrete (RC) structures. Nevertheless, the behaviour of the GPR signal during the complex corrosion process is not thoroughly understood. In this study, finite-difference time-domain (FDTD) modelling was used to analyse the effects of corrosion-related parameters, i.e., moisture, chlorides, and corrosion products, on the electric field strength. This study aims to expand the database on numerical simulations of GPR signal behaviour in corrosive environments. It also addresses the knowledge gap in modelling the frequency-dependent properties of concrete and iron oxides. Modelling approach adopted in the study was validated with experimental data obtained on laboratory specimens that correspond to the numerical models in terms of geometry and condition

Neutron shielding parameters of selected types of concrete

In this scientific research, the definition of appropriate neutron shielding parameters is presented and the results of calculations or measurements of these parameters are presented for four selected types of concrete that are used in protection against neutron radiation. A method for calculating the fast neutron effective removal cross section is considered, which has its own specificities because it takes into account different types of interactions of fast neutrons with the materials from which the selected types of concrete are made. In addition, the values of macroscopic neutron absorption cross section for thermal neutrons, macroscopic neutron scattering cross section and total macroscopic neutron attenuation cross section, which includes scattering of fast neutrons and absorption of thermal neutrons, are presented for the selected types of concrete. Based on the analysis of neutron shielding parameters, type of concrete with coarse-fine aggregate limonite-limonite has a higher level of ability to protect against neutron radiation compared to concrete with coarse-fine aggregate magnetite-limonite and concrete with barite-barite.ceo rad na CD UDK: 539.12/.16:666.97

Corrosion Damages of Pipelines Assessment by Using the Finite Element Method

In order to ensure pipeline safety during their service life, all relevant construction, testing and safety requirements must be met. Corrosion damage is a major hazard to the steel pipeline as a whole, and it is necessary to comply with inspections and adequate maintenance so that destruction with catastrophic consequences would be avoided. In this paper, the standard calculation for determining the maximum acceptable corrosion damage length according to the RSTRENG method is presented using the calculation of the corrosion-damaged structure of the ammonia (NH3) transfer pipeline. After that, the methodological approach to calculation using the finite element method (FEM) is presented in accordance with the methods defined by the new and general approach to standardization and technical harmonization for pressure equipment (Pressure Equipment Directive). The aim of the work was to present advanced modeling techniques of corroded surfaces based on FEM in order to develop a procedure for evaluating the residual strength of steel pipelines in the chemical industry

Application of waste raw materials as a reinforcement for protective coatings based on pyrophyllite

In this study, pyrophyllite was used for the first time in the composition of protective refractory coatings together with supplementary waste resources. The proposed refractory coatings are applicable for metallic and non-metallic structures, with the option of using them to protect machinery components in the chemical industry, metallurgy, and mining. Given that pyrophyllite has a low hardness, the goal was to improve the coating's resistance to cavitation erosion by adding 20 wt.% of hard refractory materials, i.e., crushed and micronized waste bricks based on mullite and corundum, respectively. Previous studies have demonstrated that protective coatings using a pyrophyllite filler have refractory qualities but insufficient resistance to cavitation erosion. As a result, the composition of refractory coatings, the preparation techniques, and the coating manufacturing process were altered. This study presents a simple method for combining conventional coatings made of refractory fillers (primary resource: pyrophyllite) with waste materials (mullite brick and corundum brick) used as reinforcement in protective refractory coatings for metal and non-metal structural elements that are highly resistant to cavitation erosion