Influece of the austempering temperature on the tensile strength of the austempered ductile iron (ADI) samples

Austempered Ductile Iron (ADI) is a class of ductile iron subjected to a two-step heat treatment process – austenitization and austempering. The heat treatment gives to ADI a high value of tensile strength and an especially good strength-to-weight ratio. However, designers in most cases are unfamiliar with this material that can compete favorably with steel and aluminum castings, weldments and forgings. The high tensile strength of ADI is the result of its unique ausferrite microstructure. In this paper, an investigation of the influence of the austempering temperature on the tensile strength of the ADI samples is presented

Physical modelling and numerical finite element method (FEM) simulation of forging in open die of alloy AIMgSi0,5

This paper researches the process of forging in open die of gradual axial-symmetric workpiece made of alloy AIMg-Si0,5. The physical modelling was carried out, for which an original method for physical discretisation and numerical FEM analysis was developed. The components of tensor were determined: strain, strain rate, stress and the corresponding effective parameters. The results obtained experimentally and through a numerical FEM simulation were compared and analysed

Analiza pęknięć koła pasowego układu wciągarki Wysięgnika koła czerpakowego

This paper presents the results of the pulley fracture analysis. Experimental investigations confirmed that the chemical composition and basic mechanical properties of the pulley material, except the impact energy at a temperature of –20°C, meet the requirements of the corresponding standard. The impact energy value at the temperature of –20°C is for ≈45% lower than the prescribed value which has considerable influence on the appearance of the brittle fracture, especially having in mind the fact that the bucket wheel excavators operate at low temperatures. Metallographic examinations as well as magnetic particle inspections indicated that initial cracks in the welded joints occurred during the manufacture of the pulleys. Characteristic levels of the rope load cycle are obtained by using in-house software which includes the dynamic effects of the resistance-to-excavation. The FEA results pointed out that in the representative load cases the combinations of the mean stress and the alternating stress in the pulley critical zone lie considerably below the limit line of the modified Goodman’s diagram. The conclusion, based on the presented results, is that the fracture of the pulley appeared as the result of the ‘manufacturing-in’ defects.Artykuł przedstawia wyniki analizy pęknięć koła pasowego. Badania doświadczalne potwierdziły, że skład chemiczny oraz podstawowe właściwości mechaniczne materiału, z którego zostało wykonane koło pasowe, za wyjątkiem energii udaru w temperaturze –20°C, były zgodne z odpowiednią normą. Wartość energii udaru w temperaturze –20°C była o ≈45% niższa od wartości zalecanej, co ma znaczący wpływ na występowanie pękania kruchego, zwłaszcza gdy weźmie się pod uwagę fakt, że koparki kołowe są przeznaczone do pracy w niskich temperaturach. Badania metalograficzne oraz badania magnetyczno-proszkowe wykazały, że pęknięcie pierwotne w połączeniu spawanym pojawiło się już w fazie produkcji koła pasowego. Charakterystyczne poziomy cyklu obciążenia liny uzyskano stosując własne oprogramowanie, które uwzględnia dynamiczne oddziaływanie odporności na urabianie. Wyniki MES pokazały, że w przypadku obciążeń reprezentatywnych, wartości średniego naprężenia w funkcji naprężenia zmiennego w strefie krytycznej koła pasowego były znacznie niższe niż wartości graniczne wyznaczone na podstawie zmodyfikowanego wykresu Goodmana. Na podstawie otrzymanych wyników stwierdzono, że pęknięcie koła pasowego powstało wskutek wad produkcyjnych

Influence of austempering heat treatment on mechanical and corrosion properties of ductile iron samples

Mechanical properties and corrosion resistance of metals are closely related to the microstructure characteristics of the material. The paper compares the results of these two sets of properties after investigating samples of base ductile iron and heat-treated samples of the base austempered ductile iron (ADI). The basic material is perlite ferritic iron alloyed with copper and nickel. To test the corrosion rate of the base material (ductile iron) and the heattreated samples (ADI), electrochemical techniques of potentiostatic polarization were used (the technique of Tafel curves extrapolation and the potentiodynamic polarization technique)

Physical modelling and numerical finite element method (FEM) simulation of forging in open die of alloy AIMgSi0,5

This paper researches the process of forging in open die of gradual axial-symmetric workpiece made of alloy AIMg-Si0,5. The physical modelling was carried out, for which an original method for physical discretisation and numerical FEM analysis was developed. The components of tensor were determined: strain, strain rate, stress and the corresponding effective parameters. The results obtained experimentally and through a numerical FEM simulation were compared and analysed