The combined finite element method and the maximum principal stress analysis gave insight into the fracture mechanisms of teeth with two-surface composite restorations followed by root canal preparation. Removal of tooth tissue, despite its subsequent restoration with dental materials, weakened the tooth by changing the stress intensity and distribution through tooth structures. Access cavity preparation had the greatest influence on tooth strength whilst canal enlargement did not contribute to this process substantially.

Purpose The purpose of this paper is comparison of experimental values of the drawing forces to numerical values in different contact conditions, taking into account the appearance of galling which occurs due to of difficult drawing process conditions. Design/methodology/approach The following two research approaches are used in this paper – the physical modeling, realized by the laboratory experiment, and the numerical simulation of the ironing drawing process. By analyzing the obtained results, the technique of physical modeling, with help of the laboratory equipment and numerical simulation by application of the finite element method, can be successfully used in studying the thin sheet ironing – strip drawing process. Findings It is significant to compare values of the deformation forces obtained by physical experiment to values obtained by the numerical simulation. In that way, it is possible to compare applied contact conditions (four lubricants in that case) and estimate matching of experimentally and numerically obtained results of the deformation forces. Presented results point out very good technological characteristics of ecologically friendly lubricant (single-bath) and grease based on MoS2. Significant decrease of the deformation force was achieved by its application, as well as maintaining of the lubricant’s layer during the forming process and almost complete elimination of galling on the contact. Practical implications Numerical analysis of stresses in the working piece wall, during the thin sheet strip drawing, requires precise values of the friction coefficient. It is an important indicator because one can define the contact conditions as the input data for the numerical simulation, based on its values for each type of lubricants and each value of the compressive lateral force. Originality/value The environmentally friendly lubricant tested exhibits a more favorable distribution of the drawing force during the process, mainly in experimental case. Grease based on MoS2 has good lubricating properties but that lubricant is conventional and environmentally unacceptable. Ecologically friendly lubricant can be successfully used in real ironing strip drawing process especially for high values of holding force achieving an increased tool life.

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Purpose The purpose of this study is to show which filler metal is the best for hard facing. Because the quality of the surface layer has a great influence on the working life of parts, the purpose was to extend the working life of parts exposed to intensive wear. The tested hard-faced models were made of low carbon steel to save the expensive base metal and to analyze the possibilities of extending the service life of existing structural parts. Design/methodology/approach Samples were prepared from plates hard faced with various filler metals. Samples were then subjected to experimental testing – testing of tribological properties and hardness and microstructure. Testing was done in conditions similar to real ones – with a sliding speed of 0.25, 0.5 and 1 m/s and with a load of 50, 75 and 100 N and in most rigorous dry conditions. Research was done by using a combination of experimental and theoretical approaches. Findings The paper shows the results of the experimental testing of four different filler metals aimed for hard facing of parts exposed to highly intensive wear. Results shown that CrWC 600 alloy is the most favorable filler metal for hard facing of parts such as those of construction mechanization and those subjected to intensive abrasive wear at stone mines. Practical implications All obtained results are real and fully applicable, as there is a huge industrial need for these types of technologies. With the application of these technologies, beside money savings, the working life of parts can be significantly extended. Originality/value The research presented in this paper was conducted because of the lack of results from this area in Serbia and because of the necessity for application of obtained results in companies for road maintenance and stone excavation in the region of Šumadija, Serbia.

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Ïðåäñòàâëåíû ðåçóëüòàòû ðàñ÷åòíî-ýêñïåðèìåíòàëüíîãî àíàëèçà âëèÿíèÿ òåìïåðàòóðû íà ìåõàíè÷åñêèå ñâîéñòâà âûñîêîïðî÷íîé êîíñòðóêöèîííîé ñòàëè S690QL. Îïðåäåëåíà ìàêñèìàëüíàÿ òåìïåðàòóðà ïðè ñòàòè÷åñêèõ èñïûòàíèÿõ íà ðàñòÿaeåíèå, ïðè êîòîðîé äàííàÿ ñòàëü ñîõðàíÿåò âûñîêèå ìåõàíè÷åñêèå õàðàêòåðèñòèêè. Ñòàòè÷åñêèå èñïûòàíèÿ íà ðàñòÿaeåíèå ïðîâîäèëèñü ïðè ïÿòè ðàçëè÷íûõ òåìïåðàòóðàõ â äèàïàçîíå 20…550°Ñ. Ïîëó÷åííûå ýêñïåðèìåíòàëüíûå äàííûå ñðàâíèâàëèñü ñ ðåçóëüòàòàìè êîíå÷íîýëåìåíòíûõ ðàñ÷åòîâ ïóòåì ïîñòðîåíèÿ ñîîòâåòñòâóþùèõ êðèâûõ óïðî÷íåíèÿ ñòàëè.Êëþ÷åâûå ñëîâà: ñòàëü S690QL, òåìïåðàòóðà, ìåõàíè÷åñêèå ñâîéñòâà, êîíå÷íîýëåìåíòíûé ÷èñëåííûé àíàëèç, ýêâèâàëåíòíîå íàïðÿaeåíèå, ýôôåêòèâíàÿ äåôîðìàöèÿ.Introduction. With constant advancements in the field of construction engineering, there is a growing need for high strength construction steels such as the steel grade S690QL, which is analyzed in this paper. These steels should have good mechanical properties which would make the construction reliable and light. The steel grade S690QL is used for producing high responsible constructions such as cranes, dynamic loaded parts for millitary vehicles and battle assemblies, etc [1]. When complex constructions are made, especially the ones made of steels of wide cross sections, the steel is often heated (preheated, additionally heated and tempered), and the process engineers and designers often find themselves in a dilemma concerning the maximum temperatures allowed for this process. In the literature, wide ranges of these temperatures can be found, depending on the thickness. The aim of this paper is to determine experimentaly and numericaly the maximum working temperatures at which S690QL steel keep thier high strength values.In order to determine dependance of mechanical properties of the S690QL steel on the temperature, numerous investigations has been carried out [2][3][4][5][6][7]. Most of the investigations dealt with properties of base metal S690QL, but some papers show results of investigation of welded joints made of mentioned steel [2]. The aim of investigations was to determine

Influence of the contact pressure in the deep drawing processes is a very actual research topic in the metal forming technology. Within this research the tribological model of the strip sliding in the flat die was developed. The original experimental computerized apparatus for testing of the strip sliding in the variable contact pressure conditions was developed, as well. The complex, multi-factor experiment was performed by application of the Al thin sheet, with the contact elements of various roughnesses, with different lubricants application and with the variable contact pressure. Besides the description of the developed apparatus, the theoretical way for determination of the pressure dependences was also presented. Based on the theoretical changes of pressure, set in advance, the real influence of the contact pressure was obtained, for each of the given conditions. That makes possible to determine the influence of the tribological factors on the actual pressure. The obtained real contact pressure has verified the reliability of the experimental apparatus, namely the degree of the theoretical pressure dependences deviation from the real ones.

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