Repository of the Institute for Material Testing (RIMS)
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Geometric optimization of transition zones based on biomimetics principles
Get PDFThe basic definitions and a history of the development of biomimetics as a discipline that
considers nature-inspired design are presented in this paper. The discussion and the results of the
application of principles of nature-inspired design in machine elements design are given. The fact
that transition zones that Nature chose and designed on trees in many cases survived for more
than a hundred years, resisting on the various and variable external loads and other external
conditions, is considered. Presented case study used the nature-inspired transition shapes in the
research of innovative design and geometric optimization of transition zones of high-loaded
shafts. The comparative Finite Element Analysis is performed for a particular transition zone with
traditional engineering design, as well as with nature-inspired design. The conclusions about the
increase of load capacity that is obtained with innovative biomimetics design are discussed
Komparacija rezultata dobijenih ispitivanjem šipova koji su izvedeni različitim tehnologijama u istim geološkim uslovima
No full textU radu je prikazana komparacija rezultata ispitivanja šipova, opitom statičkog probnog opterećenja na vertikalnu silu pritiska za objekat “GRINFILD” postrojenja za proizvodnju čokolade u Novom Sadu. Prikazana su tri ispitivanja šipa izvedena u istoj geološko geotehničkoj građi terena koji su izvedeni različitim tehnologijama. Razmatraće se CFA šip prečnika Ø600 mm, SDP šip prečnika Ø510mm i Franky šip prečnika Ø520mm. Dužine ispitivanih šipova iznose L= 16.0 m
The characterization and pollution status of the surface sediment in the Boka Kotorska Bay, Montenegro
No full textSurface sediments collected from twelve stations in the Boka Kotorska Bay were analyzed for the level and distribution of twenty-six elements and ten oxides, grain sizes, organic matter, and carbonate content. Potentially toxic elements (Al, Fe, Mn, Cr, Zn, Ni, Cu, Pb, As, Co, U) were determined to assess the contamination status and potential environmental risk according to the single-element indices (enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (CF)), and combined index (pollution load index (PLI)). The single-element indices EF and CF revealed that the surface marine sediment was moderately polluted with Pb, Cu, and Cr, while Igeo indicated moderate pollution with Ni > Cr > Zn > Cu > As and moderate to heavy pollution with Pb, as a result of the anthropogenic factors. The method of the combined effect of toxic elements, PLI, showed the highest pollution rate at the shipyard location in the Bay of Tivat. Pearson's correlation coefficient (r), principal component analysis (PCA), and cluster analysis (CA) were applied to highlight similarities and differences in the distribution of the investigated elements in the Bay, confirming the claim obtained by the pollution indices. The sediment contamination with most heavy metals, such as Cr, Zn, Ni, Cu, Pb, and As, has been identified in the Tivat Bay area
J-integral Analysis of the Simulated Heat-affected Zone of the Elevated-temperature Martensitic Steel
No full textDue to its superior strength at high temperatures P/T91 steel is often applied in the chemical, petrochemical and fossil-fired power generation industries. The high strength is achieved by a suitable martensitic microstructure after appropriate heat treatment procedure. Welding is the most important process of joining the components in such plants, and the heat-affected zone is often the weakest part of these structures. Having in mind that the welded joint is the weakest area, it is necessary to know its properties and assess the level of its degradation. It was found that the life-limiting factor in case of P/T91 steel welded structures are the cracks located in the heat affected zones, more precisely in its intercritical region. In present paper the results of the fracture toughness measurement carried out on simulated P91 steel ICHAZ specimens produced using a weld simulator has been presented. The tests were done on two types of simulated specimens, those subjected to the subsequent PWHT and with those left untreated (without PWHT), at room temperature and 600 degrees C. For the J-integral estimation pin-loaded SEN(T) specimens were tested in plane stress conditions using the unloading compliance method of deriving a single specimen resistance curve and the eta-method
An Artificial Neural Network-based Prediction Model for Utilization of Coal Ash in Production of Fired Clay Bricks: A review
Get PDFThis study analyzed the last 20 years' data available on power plant coal ashes used in clay brick production. The statistical analysis has been carried out for a total of 302 cases based on the relevant parameters reported in the literature. The chemical composition of the clays and coal ashes, percentage incorporation and maximum particle size of ash, size of fired samples, peak firing temperature, and the corresponding soaking time were selected as inputs for modeling. The product characteristics i.e. open porosity, water absorption, and compressive strength was taken as output parameters. An artificial neural network model has been developed and showed a satisfactory fit to experimental data and predicted the observed output variables with the overall coefficient of determination (r(2)) of 0.972 during the training period. Besides, the reduced chi-square, mean bias error, root mean square error, and mean percentage error were utilized to check the correctness of the obtained model, which proved the network generalization capability. The sensitivity analysis of the model suggested that the quantity of Na2O coming from brick clays, the percentages of SiO2 and K2O coming from ashes, and MgO coming from clays were the most influential parameters in descending order for the ash-clay composite bricks' quality, mostly owing to the influence of fluxes during firing
Comparative analysis of current standards for testing thermal protection of facade carpentry
Get PDFThe low level of energy efficiency in buildings results in increased energy
consumption for heating and cooling and high carbon dioxide emissions. Insufficient
thermal protection of the exterior of a building contributes to a high value of thermal
transmittance of external walls and facade carpentry.
Regulations and standards in the field of energy efficiency in Serbia are going to be
harmonized with European documents, which is an integral part of the EU accession
process. Before placing construction products on the market, it is necessary to examine
product performances of products so that the thermal transmittance of facade carpentry
can be tested according two valid Serbian standards: SRPS U.J5. 060 from 1984 and
SRPS EN ISO 12567-1, which were adopted in 2012. These types of testing can only be
performed in accredited laboratories.
The paper presents a comparative analysis of those two standards for testing thermal
transmittance of external carpentry, the testing method, measuring equipment, the
obtaining of results that prove the performance of the product
High strength low alloy steels impact toughness assessment at different test temperatures
Get PDFIn 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)
Optimize, upgrade or invest in novel dryer? – A brick factory case study
No full textDrying has an enormous impact on the quality of final masonry clay elements. The accumulated knowledge about modeling the drying process, as well as the registered progress in computing the coupling between the heat and mass transfer during the last decade has reached the applicative industrial level. The available novel commercial drying solutions have dropped the drying cycle to 5 hours for hollow clay products and up to 9 hours for clay blocks of large size and weight. The ability to speed up the drying process also strongly depends on the properties of the raw materials. The decision on optimization of the existing dryer and its upgrade or investment in a novel drying facility must be experimentally validated. Results of the one-month monitoring and analysis of the production process in one Serbian brick factory including the material and energy balances are given in this paper. Based on the collected data, raw material limitations and costs of the novel dryer the existing tunnel dryer upgrade and the minimization of the "false" ambient air into the dryer are proposed
Recycling of waste coal dust for the energy-efficient fabrication of bricks: A laboratory to industrial-scale study
Get PDFIn this study, an optimal mixture of loess brick clays and waste coal dust in laboratory hollow blocks production is determined with the aim of promoting sustainable development in terms of saving resources and energy. The novelty of the work lies in the first-time utilization of waste coal dust in combination with loess soil brick-making thus bolstering European effort on waste utilization. The mentioned is also in line with UN sustainable development goals, SDG 12 and 9. The chemical and mineralogical contents of the clays were obtained using various chemical characterization methods, and thermal behavior by using dilatometry and simultaneous DSC/TG analysis. The important ceramic and technological characteristics of the extruded brick clay and waste coal dust composite samples during molding, drying, and firing were obtained. The chosen mixture of 70 % calcareous clay and 30 % plastic clay to 3 % of high-calorie waste coal dust is found optimal. Industrial-scale optimal blocks (250x190x190 mm(3)) with 60 % of vertical voids were fired in a tunnel kiln, and the firing regime was recorded. It is determined that the regime must be corrected in the firing and cooling zone since the differences measured by thermo-couples were up to 180 degrees C. The industrial prototype was found to be of satisfactory quality meeting the requirements of water absorption and compressive strength as per European and other international standards. The study was first of a kind detailed characterization of the industrial size bricks encompassing waste coal dust and loess brick clays, with the emphasis on the usability in the industry, and additionally recording and correcting of the firing regime in a tunnel kiln. The product is recyclable and can be disposed of safely after the end of life