A review on mechanical properties of aluminium-based metal matrix nanocomposites

Industrial production today requires new improved materials to meet market demands, which leads to the production of new materials with improved properties. One kind of response to those requirements is the development of metal matrix composites (MMCs) with the aim of obtaining materials with better properties when compared to conventional metals and alloys. Nowadays, metal matrix nanocomposites (MMnCs) are being increasingly investigated due to the possibility of achieving better machinability, high fracture toughness and improved ductility when compared to conventional composites. Considering the pace of development and the huge perspective of different classes of materials, this research aims to provide insight into the mechanical properties of aluminium nanocomposites. Aluminium nanocomposites are attracting a lot of attention due to their high strength-to-weight ratio, wear resistance and low costs, when compared to matrix alloy. In this paper, an attempt is made to review other research reports and make a connection between the characteristics of the microstructure and the mechanical properties, which are dependent on the method of fabrication and type and content of reinforcement.https://www.tribomat.net/archive/2023/2023-03/2023-03-04.htm

Influence of materials on the efficiency of worm gear transmission

This paper presents the results of experimental research of efficiency of a worm gearbox which was designed for that purpose. The gearbox housing is of a welded construction with side openings, which enables simple assembly and disassembly of worm pairs, bearings and other elements. Two worm pairs with the same geometric characteristics were used for testing, where the worms are made of improved steel 42CrMo4 and the worm gears are made of zinc-aluminum alloy ZA12 and aluminum alloy A356. The values of the efficiency were determined at different operating modes of the gearbox (loads and rotational speeds), where mineral oil with a viscosity of 460 mm2/s was used as a lubricant. According to the previously defined working conditions, the power losses and friction coefficient of the worm gear pairs were calculated. Based on the test results, it is concluded that the values of the efficiency of the worm gear pair 42CrMo4/ZA12 are significantly higher compared to the worm gear pair 42CrMo4/A356, which is the result of lower power losses and lower values of the coefficient of friction

EVALUATION OF HEALING EFFECTS OF NEW HERBAL FORMULATION ON VENOUS LEG ULCER: PILOT STUDY

Venous leg ulcers represent a significant public health problem that will increase as the population ages. A wide variety of agents are available for the treatment of venous leg ulcers, including ointments and dressings. Numerous herbs and their extracts are potentially conducive to wound healing, including the ability to serve as an antimicrobial, antifungal, astringent and etc.The aim of the study was to establish the healing effects of herbal therapy on non-infected venous leg ulcers. The major components of the DermaplantG were extract of Allii bulbus, Hyperici herba and extract of Calendulae flos. In the study were included 18 patients with venous leg ulcers treated by DermaplantG herbal therapy. Our investigation focused on the five controls (baseline, 1st , 3rd, 5th 7th weeks) of the parameters changes important for ulcer healing: wound surface area and reduction of venous leg ulcer score (fibrin deposits, exudation and eczema). Within-treatment analysis showed that, following DermaplantG herbal treatment, there was a significant decrease in surface leg ulcer and venous leg ulcer score after 7th treatment week (P < 0.05). The results of this pilot study demonstrate healing and antimicrobiologic efects of herbal therapy on non-infected venous leg ulcer

ANTIMICROBIOLOGICAL EFFECTS OF NEW NATURAL ANTISEPTIC FORMULATION ON NON-INFECTED VENOUS LEG ULCER: PILOT STUDY

Venous leg ulcers represent a significant public health problem that will increase as the population ages. Numerous herbs and their extracts are potentially conducive to wound healing, including the ability to serve as antimicrobial, antifungal, astringent etc. The aim of the study was to establish the in-vivo antimicrobial effects of herbal hydrogel formulation DermaplantG. The major components of the DermaplantG were the extracts of Allii bulbus, Hyperici herba and extract of Calendulae flos. A total of 12 patients with non-infected venous leg ulcers were treated twice daily, for 5 weeks, with new hydrogel formulation. All ulcers showed clinical signs of contamination or colonization without signs of systemic infection. Premoistening the swab with sterile saline was considered when the surface of the wound was dry. The tip of the swab was rolled on its side in a zigzag pattern for at least one full rotation. Standard methods for isolation and identification of aerobic and anaerobic bacteria were used. On baseline assessment, a large number of different types of bacteria were detected in all venous leg ulcers. S. aureus and P. aeruginosa were isolated from almost all controls.On baseline, mixed bacterial flora (50%) was isolated in six venous leg ulcers (five ulcers with S. aureus-P. aeruginosa and one ulcer with E.coli-Enterobacter spp-P.aeruginosa). At the end of the treatment in DermaplantG group in 8 venous ulcers were detected S. aureus (66.66%) and P. aeruginosa (16.66%), and one venous leg ulcers was detected as sterile (8.33%). The number of different types of isolated bacterial species decreased significantly (P<0.05) after the use of DermaplantG herbal preparations. Therapy in DermaplantG group was administered without any side effects.The preliminary results of this pilot study demonstrate potential antimicrobial effects of herbal therapy on non-infected venous leg ulcers

Surface texturing for tribological applications: a review

Surface texturing is one of the surface modification techniques which deliberately change the texture of the surface, in order to improve, among other things, its tribological performance. This is obtained through different patterns, which can be on micro or nano scale, created on the contact surfaces. The performance of a textured surface depends on the shape, geometry and pattern of the surface texture and the operating condition of the components in contact. There is a number of various techniques for surface texturing, among which laser surface texturing is most often used. The different surface texture shapes, different textured area ratios and patterns, different lubrication regimes with different contact geometries and materials have been subject of theoretical and experimental research for many years. This paper reviews the state-of-the-art of researches that consider various surface texturing for tribological application, as well as its effect on performance enhancement. Conclusions of this paper may provide guidance for optimal design of surface textures in practical engineering applications

Kriveljski kamen - Bunar: Necropolis of urnfield culture in the vicinity of Bor

U neposrednoj blizini lokaliteta Čoka lu Balaš kod Krivelja, arheološka ekipa Muzeja rudarstva i metalurgije u Boru otkrila je nekropolu urnenfelder kulturne grupe, iz poznog bronzanog doba. Pored grobnih konstrukcija, u kulturnom sloju je nađena keramika iz poznog eneolita i starijeg gvozdenog doba. Ova nekropola sa spaljenim pokojnicima donosi nove podatke o funerarnim tradicijama metalurških zajednica koje su u bronzanom dobu naseljavale metalogenetski region između Bora i Majdanpeka.Site Kriveljski Kamen - Bunar is located few hundred meters eastward of the hillfort settlement Čoka lu Balaš dating from the Middle and Late Eneolithic. Underneath medieval inhumation burials have been encountered circular stone structures with pottery urns, which are devastated by additional later burials. Prehistoric necropolis at the site Bunar considering the method of construction bears greatest resemblance to the necropolis Trnjane. Four structures with one urn each have been recorded during the excavation campaign. They were built on the rocky ground of marl where first the urn was dug in and then broken local gray stone was arranged making circular platform. Funerary structure 2 had in central zone also few flat limestone pebbles of rather large size that probably with its bright white color create the contrast with gray local stone. Within structures 3 and 4 besides gray local stone there were also rather large pieces of chalcopyrite rock and one rectangular piece of marl with natural netlike cracks. Although structure 4 is mostly devastated the urn was still preserved in situ in its bedding. Pottery finds in the cultural layer under and around these structures date from the Eneolithic period, i.e. from Coţofeni-Kostolac cultural circle and from the Basarabi culture of the Early Iron Age. Anthropological analysis revealed that in the urns had been deposited cremated remains of three adult individuals (urns 1, 3 and 4) and also skeletal remains of one juvenile (female?) individual (urn 3). Most interesting is certainly urn 3 where cremated and non-cremated bones were placed together. Their weight was almost identical (cremated bones are weighing 11.6 g and non-cremated 10.9 g), so it is possible that because of some unknown reason special care was taken that non-cremated bones are approximately of the same weight as cremated bones. This unusual ritual will probably be explained more precisely by future physicochemical analysis of the material. Necropolis Bunar near Krivelj belongs to the group of urnfield necropoleis where members of Late Bronze Age population in the Crni Timok river basin had been buried. It bears more resemblances to the necropoleis Trnjane and Hajdučka Česma near Brestovačka Banja and less to the necropolis Magura near Romuliana. Considering the geographic area of its location it probably belonged to the Bronze Age metallurgical communities, which inhabited territory between Bor and Majdanpek, i.e. the area richest in mineral raw materials in northeastern Serbia

Surface texturing for tribological applications: a review

Surface texturing is one of the surface modification techniques which deliberately change the texture of the surface, in order to improve, among other things, its tribological performance. This is obtained through different patterns, which can be on micro or nano scale, created on the contact surfaces. The performance of a textured surface depends on the shape, geometry and pattern of the surface texture and the operating condition of the components in contact. There is a number of various techniques for surface texturing, among which laser surface texturing is most often used. The different surface texture shapes, different textured area ratios and patterns, different lubrication regimes with different contact geometries and materials have been subject of theoretical and experimental research for many years. This paper reviews the state-of-the-art of researches that consider various surface texturing for tribological application, as well as its effect on performance enhancement. Conclusions of this paper may provide guidance for optimal design of surface textures in practical engineering applications

Funerary Traditions of the Bronze Age Metallurgical Communities in the Iron Gates Hinterland

Metallurgical communities in the Iron Gates hinterlands are best presented through necropolises, for which traditions of Urnfield Culture influences can be recognized. Only four necropolises have been noted for being clearly connected with the metallurgical communities so far. Anthropological analyses were made on a smaller number of osteological finds, but even these data are sufficient to help reach new conclusions regarding the funerary traditions and relationship towards the deceased, characteristic for the period of the Late Bronze Age. Apart from the osteological analyses, this paper shall also present the results obtained through scanning electronic microscopy, contributing to the confirmation of some earlier theories proposed by the authors regarding the cremations of the deceased during the Bronze Age

Comparison of expert, deterministic and Machine Learning approach for landslide susceptibility assessment in Ljubovija Municipality, Serbia

Landslide Susceptibility Assessment is becoming a very productive re-search area, wherein different modeling approaches are practiced to delineate zones of the high-low likelihood of landslide occurrence. However, there is no strong consensus on which approach is the most adequate. The reason behind the lack of the general view on the performance of different approaches could be partially explained by the particularity of each study. To evaluate the effi-ciency of different approaches they need to be applied under the same conditions for the same study area. Herein, we examined three different approaches, in-cluding expert, deterministic and Machine Learning, on the example of Ljubo-vija Municipality in western Serbia. The study area has been known as suscep-tible to landslides, and represents good ground for assessing the chosen methods. It is represented by complex geology, prone to landslides that are commonly hosted in thick weathering crust of Paleozoic formations, composed of schists and meta-sediments. Under extreme triggering conditions, such as the one that unfolded in May 2014, these thick weathering crusts saturate, and give way to a variety of landslide and flash-flood processes that we will be focusing on in this study. The application of the expert-approach, through Analytical Hierarchy Process provided a rough assessment map. The deterministic model, which couples simple infinite slope and hydrological model, provided us with lower quality results, when compared to the expert-based one. This could be explained by the assumptions used in the model are too simplistic to generically model a wide range of landslide typology. Finally, Machine Learning approach, using the Random Forest algorithm, provided significantly better results and showed that it can cope with versatile landslide typology over larger scales. Its AUC performance is about 0.75 which is considerably outperforming the AUC values of the other two models, which were up to 0.55, i.e. at the level of random gues

Wear of A356/Al2O3 nanocomposites and optimisation of material and operating parameters

The aim of this study was optimization of wear of nanocomposites with A356 alloy as a matrix. Different percentages of Al2O3 particles (0.2, 0.3 and 0.5 wt. %), with two average size (25 and 100 nm), were dispersed in the A356 matrix and fabricated by compocasting process. The tribological tests were conducted by the orthogonal L24 matrix. By application of the RSM method, a mathematical model was developed that best describes wear dependence on the observed factors and it was found that all considered factors have a significant impact on the wear of nanocomposite