Volume 54, Issue 2

Kurzfassung Der Vorgang der Erstarrung hat einen wesentlichen Einfluss auf die Mikrostruktur und die Hochtemperatureigenschaften von Stählen. Besonders bei Prozessen des Form- und Stranggusses ist die Gewinnung von Materialkennwerten an der Gussstruktur direkt nach dem Aufschmelzen und Erstarren von großer Bedeutung. Weiters kann man die Heißrissbildung im Laborversuch mit einer vorhergehenden Aufschmelzung realitätsnäher untersuchen. Es werden konventionelle Versuchsmethoden zur Bestimmung von Hochtemperatur-Materialkennwerten wie der Duktilität und Festigkeit von Stählen und eine neue Methodik zur Aufschmelzung von Heißzugproben vorgestellt. Die Aufschmelzung der Proben erfolgt bei dieser Testmethode ohne eine konventionelle Schmelzbadsicherung. Eine ungestörte Temperaturmessung während des ganzen Versuches ist damit gewährleistet.

The Laser Speckle Photometry is a newly developed non-contact non-destructive testing method which is based on the detection and analysis of thermal or mechanical activated characteristically speckle dynamics. The determination of the material damaged state is based on the understanding of structural changes on different scaling levels given by the physical mesomechanics. The hierarchical behavior of the mesomechanical structures (meso-structures) leads to the hypothesis of the fractal nature of the deformation structure. The fractal dimension D F is a suitable parameter to characterize the fatigued material state. In the case of the laser speckle photometry method the modified auto-correlation function from the pixel intensity changes of the speckles images was used for the computation of Parameter D F . The hardness or porosity of materials is defined by micro-structural variation and is combined with several thermal properties of the material. Therefore the speckle thermal diffusivity parameter K was determined using thermal conduction equation from the pixel intensity of speckle images changes during thermal activation. Afterwards correlation between the norm K and hardness and porosity, respectively was found. Results of this research will be presented in the present contribution.

In the present investigation, the AA1030 aluminium alloy and commercially pure copper plates were joined by friction stir welding. The effect of the processing parameters on the interface morphology, microstructure and strength of the joints was analyzed. The experimental results showed that some intermetallic compounds such as AlCu, Al 4 Cu 9 and Al2Cu cause the weld to crack during the friction stir welding process on the centerline of the weld. Especially at lower traverse speeds such as 60, 90, and 125 mm/min, some tunnels and voids were detected in the Aluminium close to the Al/Cu interface. The maximum tensile strength of the samples was obtained at a traverse speed of 160 mm/min getting by without cavity defects in the weld. In addition, the fracture morphology revealed both partially brittle and cleavage-like fracture.

The goal of this research is to describe how simulation and topology design can be used as a die design frame tool to introduce optimal die design structures with the desired maximum rigidity and minimum deformations using response surface methodology and differential evolution algorithms. In the simulation process, not only die deflection, but also press table deflection is taken into account in order to achieve more realistic results. The validation of the present approach is evaluated by a comparison of test and simulation results. In the experimental test, acceleration and strain data were measured from critical points of the die structure in order to obtain the maximum displacement and stress values. The optimal shape parameters for the die structure were obtained using response surface methodology and differential evolution as a fundamental optimisation technique. Significant results were obtained: The mass was reduced approximately about 24 %, and the current maximum stress decreased approximately about 72 %. By using this methodology in the design stage of die and sheet metal stamping, major improvements can be made to the vehicle development process, such as reducing the weight and the cost of die, reducing the labour costs during the tryout process and reducing the environmental damage and CO 2 emissions by reducing the amount of cast iron.

In this study, the effects of heat treatments and cooling rates on the properties of the steel X 38 CrMoV 5 3 were investigated. Heat treatments and cooling rates during the steel fabrication processes are critical parameters for the properties of tool steels, since the phases and the lattice structures change respectively. In the experiments, four different heat treatment processes and also, nitriding and carbonitriding processes were applied to specimens made from the investigated steel. For such experiments, two different austenitising temperatures with three different cooling rates were selected and the effects of the process para­meters on the mechanical strength were investigated. Microstructure evaluations were carried out by image analysis and by using a scanning electron microscope. To determine and compare the mechanical properties, Vickers hardness tests and three-point bending tests were applied.

The crushing energy for applications in the mineral processing industry is usually determined by an empirical bond index, regardless of the mechanical properties of a rock. Although several attempts have been made to obtain the comminution energy based on theoretical approaches, it would be beneficial to examine this relation based on a physical concept. In this paper, some Saudi samples of bauxite, kaolinite, granodiorite, magnetite, granite, feldspar and quartz were tested for hardness, abrasion, compressive strength as well as modulus of elasticity and the bond work index of these samples was estimated. The value of the bond work index of the above samples has shown a variation from 10.8 kWh ton -1 for bauxite (high abrasion value and low compressive strength) to 20.4 kWh ton -1 for granite (low abrasion value and high modulus of elasticity). The correlation between the abrasion value (X 2 ) and work index (W i ) is found to be W i = −1.8 Ln(X 2 ) + 11.5 with a correlation coefficient of 0.80.

Many experimental researches succeeded to improve fatigue properties of materials by treating their surfaces. In this study, the benefits of nanocomposite material are used to investigate the fatigue life of stainless steel specimens with different surface roughness. Nanocomposite coating was prepared with different concentrations (0.3 %, 0.5 %, and 0.7 %) of multi wall carbon nano tubes MWCNT. This coating was applied on stainless steel test specimens with four different values of the surface roughness (0.3, 0.8, 1.6, and 2.5). It turned out that fatigue life increased more than four times compared to the original material when using 0.5 % and 0.7 % MWCNT concentration in coating composition with the 0.3 surface roughness, while no significant difference was detected at another roughness.

Process capability indices are effective tools for both, process capability analysis and quality assurance. In quality assurance programs, process capability indices reflect the performance of key quality characteristics for a control process. Quality assurance in mass production is enabled by using statistical process control techniques. In this study, various statistical process control techniques were carried out using the measured values taken from the workpieces that represent the whole process in the medium sized company. The chances for using statistical techniques for quality estimation processes have been discussed. For this purpose, normal probability plots and histograms were prepared and the process capability indices were calculated. As a result of this study, it turned out that the process capability for the whole process was inadequate and the mass production was unstable. Some actions must be taken by engineers to improve the quality level by shifting the process mean to target value and reducing the process variation.

The aim of this study is the production of the metal tile core using waste paper. Paper which can be recycled many times is one of the most consumed materials in Turkey and all around the world. The reason behind the preference of paper usage is that 80 % of waste paper can be recycled. It has been noticed that recycled paper can be used in ceramic industry, as for instance for roof coverings and tiles, as a low cost raw material. A certain amount of waste paper was soaked with water and turned into pulp followed by a forging process to form the pulp into fibres. The mixture used as raw material for metal tile core production was composed of clay, quartz, and pulp. The raw material was shaped into tiles by slip casting and hand pressing. Tiles were dried, in a drying oven and coated with epoxy resin. Water absorption and bending tests were applied to the final samples.

The crystal of 1, 2-bis (ethoxycarbonyl) hydrazine was studied by XRD, FTIR and Raman spectroscopy. The ground-state geometries were optimized at B3LYP/6–31+G (d, p) level. These vibrational wavenumbers were calculated at the same level. The antibacterial activities have been screened for the compound against two bacteria: Staphylococcus aureus and Escherichia coli.