Abstract
The preparation of highly efficient and low cost abrasive stones has gained considerable interest in the last few years from the industrial and academic research societies. Meanwhile, ...composition of such abrasive stones material has played a significant role on its physicochemical, mechanical properties and cost. In this work, series of magnesium oxychloride cement samples were prepared by adding MgCl
2
solutions to magnesia, where H
2
O/MgCl
2
was 13:1, 15:1, and 17:1, while MgO/ MgCl
2
molar ratio was fixed at 7:1 for all samples. During mixing, two grades of SiC were added separately in proportions of 20, 25, and 30 mass percentage. A comprehensive characterization including bulk density, compressive strength, abrasion resistance, and polishing performance were carried out to the prepared composites samples. This was followed by studying their mineral composition and the possible use in grinding and polishing processes of marble slabs. Interestingly, the obtained characterization results demonstrated that among the different prepared composite materials, 25 mass percent SiC‐containing samples showed the best physicochemical and mechanical properties. Notably, the degree of fineness of SiC has affected the overall properties of SiC composite. When very fine SiC type was used and the water content was reduced, consequently, the samples bulk density and abrasion resistance increased. Phase 5 (5Mg(OH)
2
.MgCl
2
.8H
2
O) and silicon carbide, as the main phases with a minor amount of magnesia, were detected in the samples. From the economic point of view, the obtained result in our study is promising for its high performance‐low cost for grinding and polishing of marble slabs in the industrial fabrication.
The rescue excavations in Bataševo in central Serbia showed that it was a multi-layer site, on which occupation traces dated from the Early Neolithic, and then from the Bronze Age and the Roman ...period to the Middle Ages. The most valuable findings and data in the Early Neolithic settlement were provided by the excavations in Makedonska Street, in trenches 2/ 06, 1/ 07 and 2/ 07 where an Early Neolithic layer 1– 1.5 m thick was discovered. According to the archaeological material (stone tools, pottery and cult items, objects made of bone, fauna) and dug-in features and houses, it is very certain that during the Early Neolithic period Bataševo was a well-developed settlement, whose inhabitants, aside from husbandry and agriculture, also took part in the production of items made of stone, bone, pottery etc. Ground and abrasive stone tools, according to the choice of the raw materials, manner of making and consumption, repairing and recycling of tools, completely reflects the Early Neolithic technology of production and manner of tool use observed elsewhere in the territory of the Central Balkans. The only remarkable trait is the great fragmentation of the tools, already mentioned, which has been noted so far only at the site of Aria Babi in the Iron Gates, as well as the existence of specialised grindstones for processing stone tools. On the basis of the small area researched so far (35 m2), it is not possible to conclude if there was a specialisation of production of certain groups of artefacts, since no workshop was discovered.
Cercetările arheologice preventive de la Bataševo în centrul Serbiei au indicat prezența unui sit pluri-stratificat, cu urme de locuire pornind din neoliticul timpuriu până în epoca bronzului și apoi din perioada romană până în evul mediu. Cele mai importante descoperiri și informații atribuite neoliticului timpuriu provin din strada Makedosnka, secțiunile 2/ 06, 1/ 07 și 2/ 07, unde a fost descoperit un nivel neolitic timpuriu de 1– 1,5 m grosime. Materialul arheologic (piese de piatră, ceramică și obiecte de cult realizate din os, precum și resturi faunistice) și complexele și structurile de locuire sugerează că pe durata neoliticului timpuriu Bataševo era o așezare bine dezvoltată ai cărei locuitori se ocupau alături de creșterea animalelor și agricultură, și de producția de obiecte de piatră, os, ceramică etc. Piesele aparținând industriei pietrei șlefuite, împreună cu materiile prime folosite, modul de producere și de consum, repararea și reciclarea lor, oferă o imagine completă a tehnologiei neolitice timpurii și a modului de utilizare a uneltelor, asemănătoare cu cea observată în alte părți din zona de centru a Balcanilor. Singurele caracteristici remarcabile sunt gradul mare de fragmentare al uneltelor (observat și la Aria Babi, Porțile de Fier) și existența unor piese de piatră specializate pentru producerea uneltelor de piatră. Dată fiind aria relativ mică investigată până acum (35m2) nu putem vorbi despre specializarea producției pentru un anumit tip de piese, întrucât nu a fost descoperit nici un atelier.
Антоновић Драгана, Dimić Vidan. Ground and abrasive stone tools from the Early Neolithic site of Bataševo (Serbia). In: Materiale şi cercetãri arheologice (Serie nouã), H-S 2021. pp. 413-428.
In the present paper, residual stresses induced by honing processes on hardened steel cylinders were determined. Cubic boron nitride (CBN) abrasives were employed. Both surface measurements and depth ...profiles were obtained by means of XRD. SEM observations were performed on samples’ surface. Roughness and material removal rate were also measured. Compressive residual stresses, which are known to increase fatigue life of components, were reported both in the axial and in the tangential direction. Shearing stresses were negligible. If only rough honing is taken into account, as a general trend, the lower cutting conditions used, the higher surface stresses are. A similar situation was found when only semifinish or only finish honing is considered. In most cases studied, stress profiles similar to those obtained in grinding processes, in which compressive stresses decrease with depth, were observed. However, in rough honing at hard cutting conditions, a typical hook-shaped profile was found with maximum compressive stress at 80-μm depth. Such shape is usual in turning processes. In order to obtain high surface stresses a rough, semifinish or finish honing operation with low cutting conditions is recommended. However, if stresses are to be obtained at a certain depth, rough honing at high cutting conditions is to be selected.
In the present work, the mixing process of different components of abrasive stones of cubic boron nitride used for rough honing was studied. Stones are made by the sintering process of abrasive ...grains, a metallic bond, and a humectant that favors covering of each abrasive grain by the bond. Incorrect mixing of abrasive grains with the bond and humectant can result in stones with nonuniform abrasive grain distribution. As the abrasive stone wears out, grain distribution will vary and modify efficiency of the honing operation. Tin is the metal having the lowest melting point among metals in the bond. By means of a scanning electron microscope and energy-dispersive X-ray microanalysis, tin segregation was discarded, which could have led to abrasive grain segregation. Later, mixing tests of the different components of the stones were performed at different mixing times. Both homogeneity degree of the abrasive content of different samples in a mix and covering degree of abrasive grains by bond were determined through two new parameters introduced in the present study. It was noted that use of a chain to accelerate the mixing process excessively reduces covering degree of abrasive grains even at initial mixing times. The highest quantity of humectant is recommended in order to get better covering degree. Mixing time should be high enough to assure homogeneity degree of the mix but low enough to avoid excessive reduction of covering degree.
The objective of this investigation is to clarify a new and high efficient mirror machining process with using ultrasonic and low frequent vibrations, that has been named "superposition ...superfinishing (SSF process)". In the first report, it was confirmed that a stock removal rate of superposition vibration cutting as cutting process on this SSF process can be higher than that of low frequent superfinishing, and that a high efficient mirror machining can be practically achieved. In the second report, by analysis and consideration on superposition cutting track, it was found that cutting length of this superposition vibration cutting strongly influence on a stock removal amount. In this report, as one reason of obtaining a high stock removal rate, we have adopt equivalent grade characteristics of ultrasonically vibrated abrasive stone. It has be shown that the grade of abrasive stone decreases according as amplitude incleases. On the result of some experiments, it is found that this phenomenon can be controlled by an amplitude value of ultrasonic vibration, and that a rate of abrasive stone ware per one meter of superposition superfinishing is lower than that of low frequent superfinishing in the case of large maximum cross angle.
The objective of this investigation is to clarify a new and high efficient mirror machining method with using ultrasonic and low frequent vibrations, that has been named superposition superfinishing ...(SSFmachining). At first report, it was confirmed that stock removal could be increased by providing simultaneously 20650 Hz low frequent vibration and 28 kHz ultrasonic vibration on # 3000 fine abrasive stone, and that high efficient mirror machining on this new process could be practically achived. On this report, Average cutting speed and maximum cross angle can be calculated with analyzing the abrasive cutting track on superposition machining. And on the several experiments with changing rotational frequency, and vibration speed of abrasive stone, it is found that stock removal amount on this superposition superfinishing is strongly influenced by the cutting length better than the maximum cross angle, because the maximum cross angle is constantly made large.
The objective of this investigation is to clarify a new and high efficient mirror machining method with using ultrasonic and low frequent vibrations, that has been named superposition superfinishing ...(SSFmachining). At first report, it was confirmed that stock removal could be increased by providing simultaneously 20〜50Hz low frequent vibration and 28kHz ultrasonic vibration on #3000 fine abrasive stone, and that high efficient mirror machining on this new process could be practically achived. On this report, Average cutting speed and maximum cross angle can be calculated with analyzing the abrasive cutting track on superposition machining. And on the several experiments with changing rotational frequency, and vibration speed of abrasive stone, it is found that stock removal amount on this superposition superfinishing is strongly influenced by the cutting length better than the maximum cross angle, because the maximum cross angle is constantly made large.
In this investigation a high efficient mirror machining process with providing above 20kHz ultrasonic vibration and 20-50Hz low frequent vibration to fine abrasive stone, has been created and named ..."Superposition superfinishing (SSF process)". This machining process consists of the first cutting process (SVC process: superposition vibration cutting) and the second mirror machining process (SF process: superfinishing). To finally obtain a high efficient and high precision mirror surface with smoothness, more fine uneven surface roughness on first cutting process is desired, because the mirror finishing time on second process can be reduced. Until now, in several experiments it was practically observed that surface roughness by superposition vibration cutting is smaller than that by superfinishing without stone loading. In this report, some experiments have been examined to confirm this inproving effect in detail. Experimental conditions are as follows: Rotational frequency of work: 60-950min^<-1>, Work diameter (material): φ35mm (SKS3, H_RC47), Frequency F and Amplitude A of Low frequent vibration: 0-25Hz, 0-1mm, Frequency f and Amplitude a of ultrasonic vibration: 0-46kHz, 0-7.5μm, Stone Pressure P: 24.5-196kPa, Stone: WA(600-3000)RH(20-80)V, Machining fluid: Light oil. In this paper, it is confirmed with analyzing and experiments that surface roughness by SVC process can be improved in comparison with SF process without stone loading.
The objective or this investigation is to clarify a new and high efficient mirror machining, that can be named superposition superfinishing (SSF process) using a fine abrasive stone. In this ...machining, at first process (SVC process: superposition vibration cutting) high efficient cutting is achieved with simultaneously providing (20〜50Hz) low frequent vibration and ultrasonic vibration above 20kHz on fine abrasive stone, and at next process (SF process: superfinishing) mirror surface can be obtained in a short time with only low frequent vibration. In this report, it is shown that basic machining characteristics and possibility of high efficient mirror machining on this new process are practically confirmed by several experiments.
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