Volume 56, Issue 2

The paper presents a comparison of fatigue characteristics of twenty selected materials. The compared models were proposed by Wöhler, Basquin, Stromeyer, Corson, and Bastenaire. The determination coefficient was calculated for each material in order to define the best fitting to the empirical data. After analysis authors evaluated which characteristics best describes the course of the destruction of the specimens during fatigue tests.

Kurzfassung Bei der thermografischen Prüfung von Widerstandspunktschweißverbindungen wird die Emissivität der Fügeverbindung bisher als Störgröße angesehen und – wenn möglich – unterdrückt. Nachfolgende Arbeit untersucht, ob eine für diese Prüfung nutzbare Korrelation zwischen Emissionsgrad des Kappenabdrucks und Schweißpunktdurchmesser besteht. Dazu werden 60 Blechproben in drei praxisrelevanten Materialkombinationen und mit unterschiedlicher Anbindungsqualität vermessen. Über die thermografische Grundgleichung kann die Emissivität bestimmt werden. Der Punktdurchmesser wird zerstörend ermittelt. Die Ergebnisse zeigen eine Korrelation der beiden Messwerte auf, die umso höher ausfällt, je geringer die Emissivität des Grundwerkstoffes ist. Abschließend wird ein Ausblick auf die Verwendbarkeit dieses Zusammenhangs in der thermografischen Schweißpunktprüfung gegeben.

In this study, kinetic examinations on boronized X45NiCrMo4 (DIN 1.2767) and 90MnCrV8 (DIN 1.2842) steel samples are described. Samples were boronized in indirect heated fluidized bed furnace at 1123 K, 1223 K, and 1323 K for 1 h, 2 h, and 4 h. Morphologically and typically examinations of borides formed on the surface of the steel samples were studied by optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD). Boride layer thickness formed on the steel X45NiCrMo4 ranges from 45 μm to 382 μm and for the material 90MnCrV8 ranges from 33 μm to 471 μm. The hardness of the boride layer formed on the steel X45NiCrMo4 varied between 1713 HV 0.1 and 2111 HV 0.1 and for the steel 90MnCrV8 between 1716 HV 0.1 and 2761 HV 0.1 . Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature. The kinetics of the reaction has been determined with K = K o exp (-Q/RT) equation. Activation energy (Q) of the borided steel X45NiCrMo4 was determined as 156 kJ/mol and that of the steel 90MnCrV8 was determined as 179 kJ/mol.

Cooling slope casting process is one of the methods used to produce feedstock material having non-dendritic structure for thixocasting of A357 aluminum alloy. In the present work, the effect of various pouring distances of cooling slope on the microstructure of A357 aluminum alloy was investigated. For this purpose, the molten metal at 630 °C superheat temperature was poured on the surface of water-cooled slope. Reheating of feedstock ingots at a temperature of 572 °C with various holding times was also performed to achieve a spheroidal microstructure. Experimental results showed that optimum spheroidal microstructure of thixocasted A357 ingots having a cell size of 45 μm and a shape factor of 0.60 of primary Al were obtained when a pouring distance of 350 mm on the cooling slope is used. A holding time of 5 min at 572 °C reheating temperature of feedstock ingots with 350 mm pouring distance provided optimum thixotropic properties.

The objective of the present work was to determine whether deformation of samples of barrier materials which protect from chemical permeation has an effect on breakthrough time. The tested materials included gloves made of chloroprene rubber, a fabric coated with butyl rubber, and a membrane made of butyl rubber. Permeation resistance was determined for 2 solvents, cyclohexane and ethyl acetate. It was found that depending on the type of material and solvent, the application of different tensile forces leads to different effects. The use of deformation variants (with tensile forces of 100 N or 200 N) did not significantly affect the breakthrough time of cyclohexane through the chloroprene membrane. On the other hand, the cyclohexane breakthrough time for the fabric coated with butyl rubber decreased by about 20 % at 200 N.

In this study, powder metal (P/M) compacts were prepared by mixing iron powder with 0–1 wt.-% Al, 2–3 wt.-% Cu and 0.2–0.8 wt.-% graphite. The 16 different P/M compacts compositions were prepared with 0.8 wt.-% zinc stearate as lubricant. The compacts' dimensions were 10 × 10 × 55 mm. All compacts were pressed at 600 MPa and sintered at 1120 °C for 30 minutes using a conventional sintering furnace and then boronizing, steaming and carbonitriding heat treatments were applied. The results of all the compacts in regard of the effects of corrosion endurance, density, and HV microhardness results were compared.

The features of inclusions and microstructure for Ti-added carbon structural steel (C: 0.26 wt.-%) were studied by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). After etching, it has been found that the titanium oxide can act as nucleation site for acicular ferrite. Moreover, from the SEM-EDS mapping images, it can be seen that the MnO-SiO 2 phase occupies the core of nucleation inclusion, and the titanium oxide precipitates on them. This result can be explained by theoretical calculation, and this kind of precipitation does not lead to inclusion coarsening. Furthermore, the element sulfur accumulates on the periphery of nucleation oxides, which implies the absorption of MnS plays an important role for the acicular ferrite formation. These results confirm that titanium oxide precipitate can also induce the acicular ferrite formation, and may gain new insights in the oxide metallurgy.

Iron based materials manufactured by powder metallurgy (P/M) method are widely used in industry. These materials are very important in applications where no machining is required, they can also be used as journal bearing material due to their self-lubricated property, and can be used for applications in the medical industry. In this study, powder metal parts were manufactured from composites based on FeCu-graphite by P/M method. Fatigue test was carried out on manufactured samples, which were only treated by boronizing or boronizing and shot peeing. The fatigue properties of these parts were investigated by a rotating bending fatigue test rig.

Red mud is a waste generated by the aluminium industry and its disposal is a major problem. Red mud waste from Eti Seydişehir aluminium plant of Turkey was considered as a hazardous waste for the environment and human health. The storage of the red mud is difficult due to its high amount of various metal oxides, elements and caustic content. In this study, the environmental compliance tests of the produced construction products of red mud were done and evaluated according to the >Regulation on Regularly Storage of Waste in Turkey<. According to the test results red mud, a hazardous waste alone, can be used in the construction products production. The construction products produced with red mud do not contain hazardous substances and thus, fit the requirements of the >Regulation on Regularly Storage of Waste in Turkey<.

The dynamic compaction method was used to analyze the consolidation of the railway foundation. Based on the physical characteristics of sands, an extended model was proposed by soil tests. This model is powerful for investigations of mechanical behaviour of sands under the dynamic compactions. By comparing with the experimental results, it is indicated that the dynamic compaction was an effective method for understanding the consolidation of railway foundations, moreover, the numerical model based on the infinite element analysis was a powerful tool to find the practical conditions without boundary reflection under the dynamic compactions.

In this study, a mineral fiber composite of stone wool-reinforced high density polyethylene (HDPE) with different weight percentages was tested. For preparation of the samples a hot pressing technique was used. Significant improvement of the tensile strength was observed for composites of stone wool HDPE with a fiber content of 20 wt-%. The fracture surfaces of the samples were analyzed for their inter layer bounding by scanning electron microscopy (SEM).

Beneficiation of a deslimed, +0.038/−0.25 mm in size, phosphate ore containing carbonate fluorapatite (francolite), calcite, dolomite, and quartz by froth flotation is accomplished by a special approach based on conditioning the ore with a micro-emulsion consisting of 20 wt.- % Custafloat AR27 (collector, blend of fatty acid soaps and sulfates), 55 wt.- % No. 5 fuel oil and 25 wt.- % water at 70 wt.- % solid content and subsequent flotation after pulp dilution with water to 25 wt.- % solids. A good selectivity of separation was achieved at pH 8.5 and after 1.5 min conditioning time with micro-emulsion and flotation of the diluted pulp in the next 2 min. The maximum curvature of the upgrading Halbich grade-recovery curve indicated that the most efficient separation for the deslimed phosphate ore having 16.86 wt.- % P 2 O 5 in the feed occurred at 0.6 kg/Mg providing concentrates containing 33 wt.- % P 2 O 5 with P 2 O 5 recovery equal to 70 wt.- %. The same flotation reagents used in a traditional way provided much worse concentrates containing 27 wt.- % P 2 O 5 with recovery of 60 wt.- % at 0.9 kg/Mg of reagents.

In this paper the mechanical behaviour of double lap joints (DLJs) bonded with adhesive was analyzed. The stress-strain behaviour was investigated along the overlap length and adherend thickness in DLJs subjected to tensile loads. The stress analyses were performed by finite element method (FEM). The FEM calculations were performed using ANSYS (12.0.1). Experimental results were compared with the FEM results and were found to be quite reasonable. The results show that the failure loads are increased with an increase in adherend thickness. The stress-strain behaviour changes depending on adherend thickness and overlap length. Both FEM stress analyses and experimental results revealed that failure occurred around the edge zones of the overlap length due to the effect of shear stresses, while the failure at the edges of the adhesive layer originated from the peel stress in tensile.