Wyniki wyszukiwania - BazTech

1

The influence of storage conditions on the physicochemical properties and dimensional accuracy of the alginate impressions

Żelezińska K., Nowak M., Żmudzki J., Krawczyk C., Chladek G.

Journal of Achievements in Materials and Manufacturing Engineering

|

2018

|

Vol. 87, nr 2

68--76

EN

Purpose: Alginate impression materials are the most commonly used masses for taking impressions. They are characterized by good relation of properties to the price. However, the main problem associated with use of the impression masses is dimensions stability. Manufacturers of alginate masses recommend storage impression without any source of moisture, but dentists frequently store impressions wrapped in a wet materials. This may be the a reason of changes in dimensions and other properties. Moreover, it is recognized, that casting the model in the soon after making impression guarantee better dimensional accuracy. However, models are made usually after 24h. For some masses producers claim unequivocally, that the impressions can be stored for up to 168 h without changing the dimensions. So in this study was investigates how storage conditions affect chosen properties of alginate mass, including the accuracy of the models. Design/methodology/approach: Samples were prepared according to the manufacturer instruction and divided into 5 groups. Measurements were made 20 min after taking the impression and after 24h/168h of storage with/ without the resource of moisture. The measurements of Shore A hardness, tensile strength, mass changes and dimensional changes were made. Accuracies of the dental stone models were investigated with models manufactured after 20 min and 168 h after impressions, in comparison to the master model. Findings: The study showed that the storage conditions and time of storage had influence on properties of alginate impression mass. The resource of moisture has got an influence on dimensions and mass changes, tensile strength, elongation and shore A hardness. The results show that the use of the resource of moisture may be a cause of unfavourable changes in the gypsum model dimensions. Research limitations/implications: The storing of the alginate impressions with the resource of moisture is commonly practiced by the doctors, but it inconsistent with the manufacturer's recommendation. Practical implications: The method storing of the alginate impressions determined not only the materials properties, but also the clinical properties of final products like dentures. Originality/value: The significant of the method of the storing of alginate impression materials on the chosen properties of the materials and the accuracy of the dental stone models were shown.

2

The influence of chemical composition of nanofluids on dimensional changes of hardened constructional steel

Gęstwa W.

Journal of Achievements in Materials and Manufacturing Engineering

|

2017

|

Vol. 85, nr 1

5--11

EN

Purpose: The possibility definition of utilization of the quenching from the nanofluids group is to the hardened of elements created from constructional steels. The definition of influence size of nanofluids on the dimension changes of the element created from low carbon constructional steel is also the important aspect of this work. Design/methodology/approach: Methodology used during investigations enclosed two areas. First area enclosed the investigation of quenching mediums propriety in the support about the English method, which permitted estimate of their warmth receipt ability in the support about cooling curved in the arrangement the temperature – the time or the cooling speed. Second area enclosed the investigations of the hardened element which let define dimension changes and hardness on the transverse section. The formed structure was also estimated on the cross section in the support about the light microscope. Findings: of this article is show the possibility obtainment of minimum dimension changes the element of the cooled in nanofluids near the retained of hardness and structure on the level which was got in the quenching mediums until now used for the studied material. The summery up the use of quenching mediums of the nanofluids group at the base of distilled water, ammoniac water and Al2O3 nanoparticles causes decrease of dimension changes near keep on the same of hardness of hardened elements from constructional steel. Research limitations/implications: Research limitations result from the quantity of the quenching mediums used in the investigations which one can use as the point of the reference for nanofluids. This arose from initial investigations over this aspect, which is the dimension change of elements. It should also use real the parts of machines or tool in farther investigations. Practical implications: of results presented in this article, we will get in the range of the construction projecting of steel elements, where should consider technological surpluses for this element and material proprieties which has to which meet. For full utilization in the practice, however you should conduct additional investigations still both in the laboratory scale, how and industrial. Originality/value: Originality of this article is the performance of the influence of quenching mediums from the group nanofluids on the dimension changes of hardened steel elements.

3

Dimensional Changes, Microstructure, Microhardness Distributions And Corrosion Properties Of Iron And Iron-Manganese Sintered Materials

Kupková M., Hrubovčáková M., Zeleňák A., Sułowski M., Ciaś A., Oriňáková R., Morovská Turoňová P., Žáková K., Kupka M.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2A

639--642

EN

Iron samples and Fe-Mn alloys with Mn content of 25 wt.% and 30 wt.% were prepared by blending, compressing and sintering with the aim to study their dimensional changes, microstructure, microhardness distribution and primarily the electrochemical corrosion behaviour in a simulated body environment. The light microscopy (LM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness measurements revealed a microheterogeneous multiphase structure of sintered Fe-Mn samples. The potentiodynamic tests have demonstrated that the corrosion rates of such Fe-Mn alloys immersed in Hank’s solution were higher than those for a pure iron, and also higher than the rates reported for homogeneous Fe-Mn alloys.

PL

Próbki żelazne oraz stopy Fe-Mn, zawierające 25 i 30% mas. Mn, przeznaczone na biomateriały, zostały przygotowane na drodze mielenia, prasowania oraz spiekania w celu zbadania ich zmian wymiarowych, mikrostruktury, rozkładu mikrotwardości oraz odporności korozyjnej w skumulowanych w warunkach laboratoryjnych, panujących w ciele człowieka. Badania z wykorzystaniem mikroskopii optycznej i skaningowej, wraz z EDX oraz pomiary mikrotwardości ujawniły mikroniejednorodność wielofazowej struktury spiekanych stopów Fe-Mn. Testy potentiometryczne wykazały, że współczynniki korozji spieków Fe-Mn były wyższe niż spieków wykonanych z czystego żelaza oraz z jednorodnych stopów Fe-Mn.

4

Wpływ struktury na zmiany wymiarowe i wybrane właściwości węgloutwardznej stali C20

Gęstwa W., Wypych A., Przyłęcka M.

Inżynieria Materiałowa

|

2008

|

Vol. 29, nr 6

795-799

PL

W pracy przedstawiono wyniki badań strukturalnych, mikrotwardości, zmian wymiarowych oraz obliczone naprężenia własne w węgloutwardzanej stali C20. Stal C20 nawęglono gazowo w temperaturze 930°C przez 7 h przy zmiennym potencjale węglowym. Nawęglone próbki były hartowane jednokrotnie, podwójnie w dwóch ośrodkach chłodzących o różnym stężeniu polimeru oraz wymrażane lub odpuszczane. Ośrodkiem chłodzącym podczas procesów hartownia był wodny roztwór poliakrylanu sodu (ACR) o różnych stężeniach polimeru. Dla zastosowanych stężeń polimerów w ośrodkach chłodzących wyznaczono wartość współczynnika przejmowania ciepła (HTC), który wykazał, że wzrost zawartości stężenia polimeru w wodnym roztworze powoduje obniżenie jego wartości. Wraz ze wzrostem stężenia polimeru również maleje twardość i grubość warstwy węgloutwardzonej. Natomiast po procesach hartowania i wymrażania lub odpuszczania uzyskano grubsze warstwy utwardzone przy zbliżonej wartości twardości na powierzchni. Struktura uzyskana w tych próbkach w warstwie to martenzyt z austenitem szczątkowym, a w rdzeniu: martenzyt - bainit - austenit szczątkowy. Ilość austenitu szczątkowego wykazała, że wzrost stężenia polimeru w ośrodku chłodzącym podczas hartowania powoduje wzrost udziału austenitu szczątkowego. Wyniki obliczeń naprężeń własnych w próbkach węgloutwardzanych wykazały występowanie naprężeń ściskających w warstwie wierzchniej, a rozciągających w rdzeniu. Zmiany wymiarowe zbadane zostały na próbkach Navy C-pierścień. Najmniejsze zmiany wymiarowe uzyskano dla próbek hartowanych i wymrażanych a największe dla próbek hartowanych jednokrotnie w 10% wodnym roztworze poliakrylanu sodu (ACR).

EN

In work it were introduced the results of structural investigations, microhardnesses and dimension changes as well as the calculated of residual stresses in hardened carburized C20 steel. The C20 steel was gas carburized ab temperature 930°C by 7 h and by changing carbon potential. The carburized samples was single hardened, doubly hardened in two different quenching mediums as well as sub-zero treatment or tempered. The quenching mediums during hardened processes was the water solution of sodium polyacrylate (ACR) about different concentrations polymer. The value of heat transfer coefficient (HTC) was calculated for quenching mediums about different polymers concentration, which it showed, that the content growth of polymer concentration in water solution polimer causes lowering his value. The hardness and the thickness of hardened carburized layer diminishes together with growth of polymer concentration In quenching mediums. However it was got was fatter layers hardened near approximate value of hardness on surface after hardened and sub-zero treatment or tempered processes. The structure obtained in these samples in layer then martensite with retained austenite, and in core: martensit - bainite - retained austenite. The value of retained austenite showed, that the growth of polymer concentration In quenching mediums during hardened causes the growth of retained austenite part. The calculations results of residual stresses showed the occurrence the compressive stresses in surface layer and tensile stresses in core of hardened carburized samples. The dimension changes were examined on the Navy C-ring samples. The smallest dimension changes were obtained for hardened and sub-zero treatment carburized samples and the largest for one hardened samples in 10% water solution of polyacrylate of sodium (the ACR).

5

Monitoring the dimensional changes of castings in the process of solidification

Nova I., Hošek Z., Nováková I., Bradáč J.

Archiwum Odlewnictwa

|

2005

|

R. 5, nr 15

285--291

EN

The article deals with measurements of linear changes of castings from foliated graphite cast iron and Al-alloys during their solidification. For this purpose the measuring apparatus, which applies a dilatometer of Polish provenience, was built up. Dilatation curves of graphite cast iron and Al-alloys were acquired during the casting process. In the case of Al-alloys the influence of chemical composition and metallurgical treatment (use of refining salts) on linear changes during solidification and on the dimension of shrinkage originating was observed.

PL

Artykuł dotyczy pomiarów zmian liniowych wymiarów odlewów z żeliwa szarego i stopów aluminium podczas krzepnięcia. Do tego celu zbudowano aparaturę pomiarową zawierającą dylatometr skonstruowany w Polsce. Krzywe dylatacyjne żeliwa szarego i stopów aluminium wyznaczane były w trakcie procesu odlewania. W przypadku stopów aluminium zaobserwowano wpływ składu chemicznego i obróbki metalurgicznej (użycie soli rafinujących) na liniowe zmiany podczas krzepnięcia i na rozmiar skurczu.