Parameter optimization in milling of glass fiber reinforced plastic (GFRP) using DOE-Taguchi method

Introduction: Optimization of machining parameters is essential for improving expected outcome of any machining operation. Case Description: The aim of this work is to find out optimum values of machining parameters to achieve minimal surface roughness during milling operation of GFRP. Discussion and Evaluation: In this machining operation speed, depth of cut and feed rate are considered as parameters affecting surface roughness and Design of Experiment (DOE)-Taguchi method tool is used to plan experiments and analyse results. Conclusion: Analysis of experimental results presents optimum values of these three parameters to achieve minimal surface roughness with speed as a major contributing factor. Speed—200 rpm, depth of cut—1.2 mm and feed—40 mm/min are an optimal combination of machining parameter to produce minimal surface roughness during milling of GFRP

Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing

Potential therapeutic applications of microbial surface-activecompounds

Numerous investigations of microbial surface-active compounds or biosurfactants over the past two decades have led to the discovery of many interesting physicochemical and biological properties including antimicrobial, anti-biofilm and therapeutic among many other pharmaceutical and medical applications. Microbial control and inhibition strategies involving the use of antibiotics are becoming continually challenged due to the emergence of resistant strains mostly embedded within biofilm formations that are difficult to eradicate. Different aspects of antimicrobial and anti-biofilm control are becoming issues of increasing importance in clinical, hygiene, therapeutic and other applications. Biosurfactants research has resulted in increasing interest into their ability to inhibit microbial activity and disperse microbial biofilms in addition to being mostly nontoxic and stable at extremes conditions. Some biosurfactants are now in use in clinical, food and environmental fields, whilst others remain under investigation and development. The dispersal properties of biosurfactants have been shown to rival that of conventional inhibitory agents against bacterial, fungal and yeast biofilms as well as viral membrane structures. This presents them as potential candidates for future uses in new generations of antimicrobial agents or as adjuvants to other antibiotics and use as preservatives for microbial suppression and eradication strategies

Studying the microstructural effect of selective laser melting and electropolishing on the performance of maraging steel

Selective laser melting is one of the additive manufacturing technologies that have been known for building various and complicated shapes. Despite numerous advantages of additive manufacturing technologies, they strongly influence the microstructure and typically show a relatively high surface roughness. In this study, maraging steel was produced by selective laser melting (SLM), and its microstructure, hardness and corrosion behavior before and after heat treatment were studied and compared to traditionally manufactured ones (wrought, forged samples). In addition, the effect of electropolishing on the surface roughness was evaluated. The microstructural study was carried out by scanning electron microscopy equipped with electron backscattered diffraction in three different sections: parallel to the top surface (xy), transverse cross section (xz) and longitudinal cross section (yz). The same characterization was applied to heat-treated samples, austenitized and quenched as well as the aged ones. The results showed that selective laser melting produced a fine grain martensitic structure (in the as-printed condition) with a surface roughness (Ra) of about 10 µm. There was no sign of preferred texture or anisotropy in the microstructure of as-print SLM materials. The SLM microstructure was similar in all 3 sections (xy, xz and yz). Despite finer microstructure, nano-hardness and corrosion behavior of SLM and conventional wrought maraging steel in heat-treated conditions were similar. Aging resulted in the maximum nano-hardness and the minimum corrosion potential values. Precipitation has the main role in both hardness and corrosion behavior. Electropolishing was optimized and reduced the surface roughness (Ra) by 65%.Open access funding provided by Jönköping University.http://link.springer.com/journal/11665hj2021Materials Science and Metallurgical Engineerin

Formations of AZ91/Al2O3 nano-composite layer by friction stir processing

Composite layers containing ~0.8 %vol Al2O3 nanoparticles were produced on AZ91 magnesium alloy by friction stir processing (FSP). The treated layers were characterized using optical and scanning electron microscopes, as well as microhardness and wear testing units. It was noticed that, by reducing the rotational speed and increasing the travel speed, the grain size of the treated layer reduces and its hardness increases. In addition, the presence of nano Al2O3 reduces the grain sizes of the layers further and increases their hardness. Furthermore, FSP of AZ91 with Al2O3 particles improved the wear resistance significantly and changed the wear mechanism from oxidation and adhesive mode in the as-received AZ91 to oxidation and abrasive in the FSPed specimens. Finally, the rotational speed of 800 rpm and the travel speed of 40 mm/min were the optimum parameters for achieving a suitable composite layer with the highest hardness and wear resistance among the treated layers

A study on microstructure development and mechanical properties of pure copper subjected to severe plastic deformation by the ECAP-Conform process

Commercially pure copper rod was successfully subjected to severe plastic deformation by applying the continuous equal channel angular pressing (ECAP-Conform) method at room temperature. Microstructural characterizations of copper rod samples at various stages of plastic deformation were carried out by optical microscopy and electron backscatter diffraction methods. X-ray diffractometry and Kernal average misorientation were used for dislocation density estimations. Microstructural evaluations revealed grain size change of 30 μm for the initial annealed copper rod to less than 5 μm and even 100 nm for severely deformed samples. Mechanical behaviors of samples after different deformation stages were characterized using tensile and hardness tests. The ultimate tensile strength of the severely deformed copper rod was increased threefold by ECAP-Conform while elongation halved in comparison to the initial annealed copper. Low-temperature annealing of severely plastic deformed samples led to bi-modal grain size distribution and lowering of strength accompanied by the increase of elongation. Tensile properties of severely deformed and then annealed copper samples showed around a 40% increase in both ultimate tensile strength and elongation in comparison to the initial annealed copper rod

Taguchi optimization of process parameters in friction stir processing of pure Mg

Taguchi experimental design technique was applied to determine the most influential controlling parameters of FSP such as tool rotational speed, travel speed, tilt angle and penetration depth on hardness value of Mg. In this case, 9 combinations of these 4 essential processing parameters were set and Taguchi's method followed exactly. Signal to noise ratio (S/N) analysis showed that maximum hardness achieved when rotational and travel speeds, penetration depth and tilt angel were chosen as 1600 rpm, 63 mm/min, 0.1 mm and 2°, respectively. In addition, analysis of variance (ANOVA) technique indicated that tilt angle and rotational as well as travel speed are the significant influential parameters in the hardness value of the treated samples, respectively. Finally a model for hardness values based on FSP parameters was calculated by design expert which was also confirmed by experimental results