Band 61, Heft 1

The important role of grain boundaries for the mechanical properties of polycrystalline materials has been recognized for many decades. Up to now, the underlying deformation mechanisms at the nano- and micro scale are not understood quantitatively. An overview of the synthesis and subsequent mechanical testing of specific grain boundaries at the micro and sub-micro scale is discussed in the present contribution, including various methods for producing one or multiple specific, crystallographically well-defined grain boundaries. Furthermore, established micromachining methods for isolating and measuring local dislocation-grain boundary interactions are portrayed. Examples of the techniques described are shown with to the aid of copper grain boundaries.

The paper presents experimental studies using a complex technique for diagnostics of the structural-mechanical state of the base metal and welded joints. Application of the metal magnetic memory (MMM) method, the main task of which is detecting local SCZs, i.e, sources of damages development, for practical diagnostics is demonstrated. SCZs are areas where the processes of metal damaging develop most intensively. The results of laboratory studies for the most representative metal specimens, determined by the MMM method in industrial conditions, are presented.

Epoxy resins are highly moisture absorbant when exposed to weather and environmental factors, which brings about a deterioration of durability and of mechanical properties in epoxy composites. In this paper, the effect of humidity on the durability and mechanical properties of epoxy resin and its composites was thoroughly studied for various time durations. It was found that moisture absorption increases linearly to the square root of time, following Fick's second law. Due to the resulting moisture absorption, the flexural strength and modulus of epoxy resin are impaired compared to dry samples. However, the strength retention rate of epoxy resin cast at a relative humidity of 60 % and 70 % are better than those of samples at relative humidity of 100 % and 90 %, a promising observation for assuring favorable application in high humidity environments. It is believed that this research will be beneficial for a wide and safe application of certain epoxy resin systems in harsh service environments.

This paper focuses on the optimal design of connecting rods and optimal design of a particle sensor system in diesel engines in order to save material, reduce costs and enhance quality. Optimization is very significant for developing better designs and means less material, lower costs and better conditions. Topology and topography optimization are new but likewise very important optimization approaches for the automotive industry. One of the aims of this study is to create an optimal design for connecting rod components and to use these components in diesel engines to comply with new emission regulations. An analysis of the connecting rods of an existing model was conducted using mathematical data obtained from numerical formulas in order to determine if the part was suitable for topology optimization. According to the results obtained from the topology optimization of the existing model, a new design was created. A comparison of the new design with the existing one showed that the mass of the model was reduced by 18 %, while all product expectations were me. Another purpose of the study is to provide an optimal design for a particle sensor system and utilize this system in automobiles to achieve the new emission values required by Euro-Norm 6c regulations. Within the scope of this optimization study, a specific particle measurement system foreseen for Renault 1.5 dCi engines was considered and designed optimally. According to the output of the topology and topography optimization methods, the particle sensor system was designed optimally, and the mass of the system was reduced by 26.7 %.

In this study, Hardox450+FeW reinforced metal matrix composites (MMCs) were alloyed on AISI1020 substrate materials by the plasma arc welding (PAW) process. Microstructural characterizations of the coating layers were carried out by optic microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffractometer (XRD) and microhardness measurements. The results showed that there was a good bond between the substrate and the coating. The microstructural studies of the coating layer revealed the presence of a mixed dendritic phase structure of ferrite (α). The microhardness and the size of dendrites formed on the coated surfaces changed depending on the amount of FeW. The XRD results showed that Hardox450+FeW coatings were mainly composed of Fe 3 W 3 C, Fe 2 W, Cr 3 C 2 and Fe 7 W 6 phases. The Hardox450+25 wt.-%FeW composite coating represented the most appropriate combination in terms of microhardness.

In this work, the digital image correlation (DIC) procedure is applied to experiments involving the tearing behavior of membranes under the effect of initial crack length, to obtain the displacement and corresponding strain results image and data of the tensile process, which intuitively shows the changes in the tearing process of the membrane. The experimental results and the analytical solution of the displacement of the orthotropic material in the fracture mechanics are compared and analyzed to verify the reliability of the theoretical model. Based on the theoretical model and the displacement values measured, mixed-mode (I, II) stress intensity factors at different angles of the crack tip are analyzed. This will make it possible to analyze the crack propagation law of the membrane and also provide a more effective measurement method and calculation method for a tearing test of orthotropic material under tensile loading.

This study deals with the effect of different quantities of aluminum (Al) on the wear resistance and machinability in AM series cast magnesium alloys. Changes in the quantity of Al in these alloys (containing 0.5 wt.-% Mn) and their effect on hardness, wear resistance and machinability with respect to cutting force were analyzed. To this purpose, AM series cast magnesium alloys (AM20, AM40, AM60, and AM90) in varying amounts of Al from 2 to 9 wt.-% were used. It was observed that the intermetallic phases Mg 17 Al 12 and Al 8 Mn 5 found in the microstructure had an effect on their wear resistance, hardness and machinability (with respect to cutting force), flank build-up, chip formation and surface roughness. AM90 alloy manifested the highest values in terms of hardness, wear resistance and surface quality among these alloys. On the other hand, AM90 alloy had the lowest machinability properties.

In this study, the ferromagnetic Heusler alloy Al-Cu-Fe was aged at a temperature of 300 °C for 0.5 h, 1 h, 1.5 h, 2 h and 2.5 h, respectively. The mechanical and structural properties, residual stress state and wear performance of the specimens were investigated. The results show that precipitation has a crucial influence on the mechanical properties and wear performance of a Heusler alloy. The hardness and wear resistance of the specimens improve with an increase of precipitation density. These precipitates are associated with Cu-rich and Al-Cu lamellar structures. The density of these precipitates reveal two certain Al 2 Cu peaks at an aging time of 90 minutes, and 150 minutes for the annealed specimens.

In this study, characteristics of automobile disc brake linings produced by three different manufacturers were compared experimentally, these being original parts (OEM), subsidiary industrial production parts (SIPM), and brake linings of Turkish production (TM). These brake linings which vary in composition, components, wear and friction characteristics, as well as mechanical and physical properties were investigated. In addition, their environment and their usage were compared. For the ensuant chemical analyses, scanning electron microscopy (SEM), EDS (energy dispersive spectroscopy) system and XRF (X-ray fluorescence) were used. TG (thermo gravimetric analysis) was performed to determine the mass losses in the brake lining materials. Wear friction tests of the brake linings carried out according to the JIS D 4411 standard. Apart from these, the hardness, density and internal shear strength values of the brake linings were measured.

In the present contribution, the impact properties of clay and silica nanoparticles for strengthening an intraply carbon/aramid fiber reinforced epoxy composite have been investigated. Five clay and silica nanoparticles, containing 2, 4, 6, 8 and 10 wt.-% and 0.5, 1.0, 1.5, 2.5 and 3.0 wt.-%, respectively, were used to produce the hybrid composite specimens. The Charpy impact results indicate that the impact energy and strength were improved for all clay and silica nanoparticles specimens, as compared to the unmodified carbon/aramid fabric reinforced epoxy composite. The images of the damaged specimens show a significant fiber pullout with delaminated layers at the impacted and edge surfaces. SEM investigations revealed a good interfacial adhesion of the clay and silica nanoparticles to the carbon/aramid fiber reinforced epoxy composite.

The effects of turning process parameters on surface roughness, tool vibration and temperature were investigated for an AISI316Ti steel. The parameters were optimized by the Taguchi method. Experiments were performed using the L 9 orthogonal array (Ti, Al) N + TiN coated carbide cutting tools in dry conditions. ANOVA and S/N ratio were used to optimize the cutting parameters. The most dominant factor affecting tool vibration and tool temperature was determined as cutting speed and the most dominant factor affecting surface roughness was feed rate. The optimum parameter combination developed by the Taguchi method was confirmed with the help of confirmation tests. As a result, with the help of optimization, the surface roughness was reduced from 1.421 μm to 1.204 μm and the tool vibration was reduced from 0.01454 mm to 0.00758 mm.

As a result of the rapid development of industry, the heavy metal contamination of landfill leachate has become more serious. Adsorption is an effective method that can remove heavy metal ions from landfill leachate. Na-bentonite was selected as the adsorbent for the adsorption of heavy metal ions (lead, cadmium, copper) from landfill leachate in both single and competitive systems. Batch experiments were conducted to study the effects of contact time, pH value, temperature, and initial concentration on adsorption efficiency. Adsorption behavior was investigated by means of adsorption isotherms, adsorption kinetics, and adsorption thermodynamics. The study results show that: 1. The amount of heavy metal ions adsorbed by Na-bentonite increases with increasing contact time, pH value, temperature, and initial concentration of heavy metal ions. 2. Adsorption behavior is suitable for modeling with the Langmuir isotherm and a pseudo second-order kinetic model. 3. The adsorption of lead and cadmium are thermodynamically spontaneous, the adsorption of copper is not spontaneous, and the adsorption processes of lead, cadmium and copper are all endothermic using thermodynamic analysis. 4. Competitive adsorption between lead, cadmium, and copper occurs in competitive systems.

A batch-type and lab-scale germanium recovery method was developed with proprietary emphases placed on electro-winning (EW) to investigate the mass-production capability and feasibility of economical and facile recovery of a germanium-enriched acidic leachate solution product from non-electrochemical hydrometallurgical recycling. Considering the inherent limitation of germanium recovery from an aqueous solution by electro-winning, an ICP-OES method was also applied as a supplement to provide quantitative information on germanium contents recovered over time. A 24-h electro-winning period under optimized conditions resulted in a 40 % recovery with an estimated area-specific metallic germanium deposition rate of 9.89 × 10 −6 g × (cm 2 × h) −1 . However, the electro-winning rate declined after 8 h, a phenomenon attributed to the dual effects of hydrogen evolution and the inherently slow kinetics of the electro-deposition of germanium. This short communication proprietarily contains technical contents on the electrodeposition method, procedure, and results which supplement and cast engineering insight into a previously published MP article on the optimization of germanium enrichment from waste optical fibers using a hybrid approach.

Weight reduction and improved fuel efficiency have been attained in automobiles by means of the introduction of aluminum alloys into the steel structural parts of vehicles. The difference in the physical, mechanical and metallurgical properties of Al and steel pose a great challenge to obtaining good weld quality. In this study, a 2.0 mm thick EN-5005-H24 aluminum alloy was welded to zinc coated 0.65 mm thick BH 20/34 +Z galvanized steel by cold metal transfer (CMT) with the aim of optimizing and obtaining a sound weld. Taguchi's L16 orthogonal array was employed for the experimental plan/run while the welding parameters included wire feeding speed, pre-setting gap and post-treatment duration. The mechanical properties of the dissimilar joint was determined using a scanning electron microscope (SEM) integrated to an energy dispersive spectroscopy (EDS) and the three zones of the joints, galvanized steel side, intermetallic compound (IMC) layer and aluminum alloy side were investigated. The optimum parameters for the dissimilar robotic CMT welded BH 20/34+Z galvanized steel and EN-5005-H24 aluminum alloy investigated in this study were determined to be as follows: a wire speed of 5.5 m/min; 0.3 mm pre-setting gap and no post weld. Experimental results indicated that the intermetallic layer thickness in the CMT welds plays a critical role in achieving relatively high weld strength. Increasing the pre-setting gap also has a positive effect on increasing weld strength due to decreasing welding porosity.