In this paper, the effects of different weight percentages of silica nano-particles on the wettability and optical properties of polymer based surfaces were investigated. The Polydimethylsiloxane (PDMS)-SiO2 nano-composites containing 0.5, 1, 2, 3 and 4 wt% silica were prepared and coated on the fabric surfaces by immersion technique at the ambient conditions. Then, the characterization of nano-composite coated samples was carried out by water contact angle technique, scanning electron and atomic force microscopes and diffuse reflectance spectroscopy. It was found that increasing the silica content caused to increase the water contact angle of sample to 158° which results in an improvement in the water repellency property. This can be due to the aggregation of silica nano-particles which led to higher surface roughness of sample. The AFM and SEM images validated the results of surface roughness. However, Silica-PDMS composite coated sample exhibited a lower transmittance value (57%) in comparison to the uncoated sample (90%). This can be ascribed to the light scattering by silica nano-particles. پرونده مقاله

Various parameters can affect shot peening such as the number of particles and distance between particles and the surface layer. In this computational study, these parameters' effects on the creation of residual stress and mechanical behavior of Ti-6Al-4V alloy were described. For this purpose, Molecular Dynamics (MD) method is applied in two main steps. First, the simulated titanium surface was equilibrated for 1 ns. Next, the shot peening process was done on the equilibrated surface by using the various numbers of particles and distance. MD simulation results indicated, that by increasing the number of particles from 1 to 5, the mechanical behavior of the titanium surface was improved, and residual stress and hardness of the surface increased and reached 452.02 MPa and 494.46 HV in model 1 (Lj potential between particle and titanium surface), respectively. Furthermore, the results indicated that decreasing the distance from 15 Å to 5 Å led to increasing compressive residual stress and hardness of titanium surface mechanical. Numerically, by decreasing the shot peening distance from 15 Å to 5 Å, residual stress and hardness of titanium surface layer increased and reached -419.63 MPa and 510.83 HV in model 1, respectively. پرونده مقاله

This study evaluated the effects of peening angle and time on the microstructure and wear behavior of AZ31 alloy subjected to the shot peening process. The samples were shot peened at 30° and 45° for 20 and 80 min with steel pellets. The microstructures and grain sizes of the shot peened samples were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, the samples were characterized through hardness and wear measurements. The results showed that shot peening time had a greater effect on grain refining than shot peening angle. In addition, the hardness was increased to 206% for the sample shot peened at 45° for 80 min. This can be ascribed to reduced grain sizes on the surface (crystallite size of 169 Å) and increased micro-strains. The wear test revealed that the wear resistance of the sample was increased with increasing the peening angle and time. Furthermore, the mechanisms of adhesive and abrasive wear were observed for untreated and shot-peened specimens. پرونده مقاله

در این تحقیق، بهینه سازی پارامترهای فرآیند بر تخلخل و استحکام کششی سیم های کامپوزیتی زمینه آلومینیوم AA1050/SiC تولید شده به روش اکستروژن اصطکاکی اغتشاشی صورت پذیرفت. در این راستا، نمونه های کامپوزیتی زمینه آلومینیوم AA1050 تقویت شده با ذرات سرامیکی SiC، با استفاده از فرآیند اکستروژن اصطکاکی اغتشاشی تولید شدند. همچنین به منظور طراحی آزمایش، از روش سطح پاسخ استفاده شد. سرعت دورانی ابزار، نیروی اکستروژن و ذرات تقویت کننده به عنوان متغیرهای ورودی فرآیند و درصد تخلخل و استحکام کششی نهایی نمونه‌های کامپوزیتی تولید شده به عنوان متغیرهای پاسخ تعیین شدند. به منظور آنالیز داده‌های حاصله از آنالیز واریانس و تحلیل رگرسیون استفاده گردید. نتایج نشان داد که سرعت دورانی، نیروی اکستروژن با تاثیرات مرتبه دوم و درصد تقویت کننده با تأثیرات خطی بر استحکام کششی و تخلخل نمونه‌های کامپوزیتی موثر بودند. همچنین بهینه‌سازی پارامترهای فرآیند FSEبه منظور رسیدن به حداقل درصد تخلخل و حداکثر استحکام کششی نهایی به کمک روش مطلوبیت انجام گرفت. در انتها، با اجرای آزمون صحه‌گذاری، نتایج بهینه‌سازی مورد ارزیابی قرار گرفت. با دستیابی به مقدار بیشینه تابع مطلوبیت (9852/0)، شرایط بهینه متغیرهای ورودی فرآیند با سرعت دورانی برابر باrpm 787، نیروی اکستروژن برابر باkN 7/11 و درصد تقویت کننده برابر با %86/3 جهت دستیابی همزمان به مقادیر بیشینه استحکام کششی نهاییMPa) 4/155) و کمینه درصد تخلخل(%45/0) انجام پذیرفت. همچنین مقادیر حاصل از بهینه‌سازی با مقادیر تجربی مقایسه شده و صحت نتایج در استحکام کششی و تخلخل به ترتیب با%57/2 و% 78/6 خطا مورد تایید قرار گرفت. پرونده مقاله

This study introduced a method based on magnetic field assisted finishing mechanism for micromachining the inner surfaces of Aluminum tubes. In this approach, using the alternating magnetic field of an AC electromotor, abrasive particles were formed as Magnetic Rods (Magnetic Clusters) and surface micromachining was carried out by the dynamic particular pattern made by an alternating magnetic field. The aim of this process was to improve machining efficiency of Aluminum tubes based on surface roughness and dimensional tolerance. Continuously, the effects of parameters such as tube inner diameter, abrasive particles weight, current frequency and machining time on changes of surface roughness were assessed by DOE technique. Taguchi standard orthogonal method (L9 (34)) was used to analyze the process factors. Moreover, the output results derived from experiments were analyzed by two most widely used analytical techniques including Signal to Noise ratio (S/N) and Analysis of Variance (ANOVA). Finally, by considering the results of analysis and plotted graphs, abrasive particles weight and current frequency were identified as significant factors and the optimum conditions of process including tube inner diameter of 55 mm, abrasive particles weight of 1 g, frequency of 40 Hz and machining time of 60 s were obtained. پرونده مقاله

The recycling of mine stone waste has been interesting for the creation of employment opportunities and added value and the prevention of environmental pollution. The present study examined the effects of the physicomechanical properties on the abrasion resistance of artificial stones produced with granite cut waste. A total of four artificial specimens were produced under different compositions and methods. Their physicomechanical properties, such as density, porosity, water absorption, hardness, compressive strength, and abrasion resistance, were evaluated. Finally, the artificial stones were compared to natural granite and marble in abrasion resistance. It was found that an increase in the porosity and water absorption reduced hardness, compressive strength, and abrasion resistance. Furthermore, hardness, compressive strength, and abrasion resistance declined as the porosity and water absorption increased. The increased rotational speed and load in the Taber abrasion test diminished abrasion resistance. The epoxy resin-based artificial stone exhibited the highest performance among the artificial specimens. It had almost the same porosity and water absorption as natural granite and marble. However, the epoxy resin-based stone with lower Mohs hardness and compressive strength showed less abrasion resistance compared to the natural granite and marble. As a result, all four artificial stones showed satisfactory performance for the flooring of congested areas. پرونده مقاله

In the machining process, the friction between the tool and the surface being machined, in addition to the destructive effects on tool wear and surface quality, increases the cutting force. By applying lubricant, it is possible to reduce the friction force in the machining process, and as a result, the cutting force is reduced. Due to the harmful environmental effects of excessive use of lubricants, the method of minimum quantity lubricant (MQL) can be helpful. In this method, fluid is applied with controlled flow and pressure. In this research, the effect of machining conditions on the cutting force for the machining process of AISI 304 stainless steel, using the method of minimum quantity lubricant has been investigated. The results show that with the increase in the cutting speed, the cutting force has decreased. Also, with the increase of injection pressure when applying the lubricating fluid using the method of the minimum quantity lubricant, a significant increase in the cutting force has been observed. پرونده مقاله