Volume 56, Issue 5

This study presents the effects of seawater and distilled water immersion time periods on mechanical properties of unidirectional glass reinforced epoxy composites. Tension, compression, and shear test specimens exposed to seawater and distilled water were prepared according to ASTM standards. After tests, SEM imaging of fracture surface of specimens was made. Results showed that seawater and distilled water immersion time affects significantly mechanical properties and strength values of glass-epoxy composites.

In this study the effect of refined boron product borax on friction and wear performance of various brake friction couples were investigated. Different amounts of borax were used in the mix with other regular ingredients in the respective brake pad. Newly formulated brake pad material with nine different ingredients was tested using friction assessment and screening test (FAST). Among such specimens, only half of the samples (shown with H indices) were heat treated for 4 h at 180 °C. The friction coefficient as well as the wear rate were determined and the friction surfaces were examined by scanning electron microscope (SEM) to assess the performance of these samples. The heat treated sample that was reinforced with 12 % borax exhibited the optimum friction and wear behaviour. With increasing friction surface temperature, a reduction of the friction coefficient of the samples was observed. The lowest reduction of the friction coefficient was observed the 8 % and 12 % borax reinforced and heat treated samples.

In this study, the influence of using compatibilizer as tie-layer between fiber matrix interfaces in continuous aramid fiber reinforced high density polyethylene (HDPE) composites was investigated. Maleic anhydride (MAH) grafted polyethylene and ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) terpolymer were used as compatibilizers at varying layer numbers. Adhesion strength was determined by T-peel test, and tensile test was carried out. It was found that higher MFR (Melt Flow Rate) valued matrix and compatibilizer application increased the mechanical performance. The maximum strength values were obtained with EMA-GMA applications. In observations of peeled parts and cross-sectional slices, interface adhesion was investigated and failure patterns were determined. It was seen that the samples with compatibilizer had more wetted portions especially the EMA-GMA tie-layered ones.

The surface roughness is one of the major parameters for determining the level of machining quality. The cutting parameters and conditions have great importance to achieve the desired values during the turning process. In the present work, a new approach was considered for modelling the effect of various turning process parameters and conditions on surface roughness. The experimental studies about the surface roughness after the turning process documented in the literature were collected and compiled into a model based on a genetic learning algorithm. As input parameters for modeling the work piece alloy type, tool type, tool tip radius, tool coating type, cooling conditions, cutting speed, feed rate, and cut depth were used in the study and were comprehensivly compiled.

In this experimental study, the alloys AA6061 and AA7075 which have different properties but common usage areas such as aviation, space, and defence industry are difficult and problematic to be welded by conventional fusion welding methods. However, friction welding represents a modern and alternative joining method. For such welded joints, rotation speed was used as variable parameter, and so joints with different mechanical and microstructural properties were obtained. The crosssectional microstructure of friction welds were examined by optical microscopy. In order to determine the mechanical properties, microhardness and tensile tests were performed on the welded samples. Fracture surfaces obtained as a result of tensile tests were examined by scanning electron microscopy (SEM) and fracture type as well as fracture surface characteristics were investigated.

The main aim of non-destructive testing (NDT) with ultrasounds (US) is the materials defect detection with respect to their main data, i. e. size, shape, and position. Inspectors carry out this task by attention to the reflected signal in the material and by comparison of the signals obtained at a specific defect with those of the defect-free material. In this way, the existence or absence of heterogeneities to be attributed to a specific defect can be determined. Inspectors are trained using specimens of the same material in which artificial defects are created, in order to establish a hypothetical appearance as natural defects. Such to be tested material specimens can be really expensive, and the total cost is particularly increased by the defect incorporation with the main scope to create the ideal size defects. The main purpose of this study is the detection of defects in metallic specimens by simulation of ultrasonic propagation in order to reduce the high cost of ultrasound protocol tests by comparing simulated and experimental results. It turned out that the good correlation between both methods allows using ultrasonic simulation as training method.

In this study, the plasma arc welded cladding of FeCrC and B 4 C powder mixtures alloyed with 70 wt.- % Cr on the surface of AISI 316 stainless steel was investigated. Application of the Taguchi method revealed respective effects on the abrasive wear resistance of the cladding layer on the stainless steel. The abrasive wear behaviour of the AISI 316 stainless steel surfaces coated with Fe-Cr-C and with 10 wt.-%, 15 wt.-%, 20 wt.-%, and 25 wt.-% B 4 C was investigated by using four loads and four distances for the 220 mesh SiC abrasive. Results were analyzed by variance analysis using ANOVA, and effects of parameters on the wear rate were determined as percentage rate. Furthermore, the error ratio was statistically evaluated. The experimental results were analyzed by the respective analysis of means and variance which is discussed in detail.

Solid propellants for micro-thruster are required to have high thermal sensitivity and a lower critical condition of ignition as well as excellent filling properties. The energy properties of ammonium perchlorate (AP)/ hydroxy-terminated polybutadiene (HTPB), AP/nitrocellulose (NC), lead styphnate (LS)/NC and LS/dibasic lead stearate (SQ-2) were obtained from thermodynamic calculations. Thermal decomposition characteristics of LS/NC and LS/SQ-2 mixtures were investigated for different species ratios. The formula ratio of LS to NC was tested for 1 : 1, 6 : 4, and 7 : 3, and the ratio of LS to SQ-2 was tested for 4 : 6, 1 : 1, 6 : 4, and 7 : 3, respectively. Ignition powers of LS/NC and LS/SQ-2 were measured, the formula ratio of LS to NC and LS to SQ-2 was 1 : 1, 6 : 4, 7 : 3, and 8 : 2, respectively. Micro-impulse tests were carried out for micro-thrusters with a charge of 0.08 mg and 0.1 mg, respectively, and compared with the thrust and impulse obtained by simulations. Results indicated that the thermal stability of LS is decreased by adding NC or SQ-2 to it, meanwhile, the energy produced is promoted. The addition of NC is more effective. The ignition power is 2.16 W when the proportion of LS to NC is 1 : 1. The average thrust peak from 0.08 mg propellant is measured as 0.1543 N, the average impulse is about 6.34 × 10 −5 N × s. The thrust peak is 11.89 % higher than the calculated simulation value, while the total impulse is 17.99 % higher. The measured average thrust peak of 0.1 mg is 0.1789 N, which is 18.3 % higher than the calculated value, while the average impulse is about 7.48 × 10 −5 N × s and 16.6 % higher than the calculated value.

Research and development of nano/micro-sized objects and systems have received considerable interest in the last few decades and were accelerated in the last decade due to the emergence of nanotechnology. Compliant mechanisms have made an enormous contribution in the design process of various fields such as for adaptive structures, hand-held tools, components in transportations, electronics, and surgical tools, respectively. The use of compliant mechanisms will help reducing the number of components, which therefore decrease manufacturing cost and additionally increase the performance. Topology optimization has proven to be a powerful method for the conceptual design of structures and mechanisms. Topology optimization is the technique that finds the optimal layout of the structure within a specified design domain. This paper presents the angular compliant mechanism of a micro/nano table which can realize a planer angular movement of the objects. The topology optimization is applied for designing two-dimensional micro/nano table angular compliant mechanism. The optimization algorithm is implemented using interface between Matlab and ANSYS. The final optimal topology configuration of the micro/nano angular table is shown and discussed.

A three-step batch-type indium recovery method was developed to prove feasibility of recovering indium powders from highly acidic dilute indium chloride solution prepared by dissolving indium tin oxide (ITO) electrodes of waste liquid crystal display (LCD) panels in concentrated hydrochloric acid (HCl) solutions. More specifically, a batch-type three-step indium recovery by cementation and subsequent electro co-deposition process was designed and performed and its individual experimental parameters were varied to get insights in the engineering feasibility of validation experiments. Significant proportion of copper and tin was removed by cementation with cobalt powder. Residual copper and tin ions were further removed by primary electro co-deposition directly from the highly acidic etching waste solution recovered from cementation process. Synergistic effect of cobalt electro co-position on indium electro-reduction was observed during secondary electro co-deposition, which warrants additional electro-refining process for selective removal of indium from cobalt-indium metal mixture and its purification. Ionic and metallic species thus obtained from the validation experiments were further characterized using various analytical tools such as inductively coupled plasma/atomic emission spectroscopy (ICP/AES), X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray fluorescence (XRF).

Studies have been carried out to investigate the performance of silane-siloxane based hydrophobic emulsion coatings and of special amino alcohol based organic and inorganic mixture inhibitor coatings. The coated and uncoated concrete specimens were subjected to accelerated corrosion to determine the time-to-corrosion-initiation. The accelerated corrosion test results clearly showed that the specimens coated with the silan-siloxane based hydrophobic emulsion performed better than concrete specimens coated with special amino alcohol based organic and inorganic inhibitor mixture.