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In this study, the process parameters of fused filament fabrication are optimized to improve the tensile strength and impact energy of polylactic acid/carbon nanotube (PLA/CNT) composite. Hence, the utility function (UF) technique and response surface method (RSM) are applied to explore the optimal levels of the effective parameters of print speed, nozzle temperature, and CNT content. The differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and SEM analyses are employed to examine the thermal properties of the printed samples. The results of DSC and TGA analyses exhibited that the incorporation of CNT into PLA enhanced the thermal strength of PLA/CNT composite. The addition of CNTs in the composite improved the tensile strength by 37%, while the addition of CNTs up to 4 wt% improved the impact energy by 29%. Moreover, an increment of the print speed to 60 mm/s reduced the impact energy (12%) and tensile strength (22%), while an increment of the nozzle temperature to 200[degrees] C enhanced the impact energy (9%) and tensile strength (12%). The optimization results demonstrated that the strength and impact energy of PLA/CNT composite optimized at CNT content of 2.8 wt%, print speed of 20 mm/,s, and nozzle temperature of 209 C. Additionally, the impact energy and tensile strength of the PLA/CNT composite enhanced up to 62.5 MPa and 2.14 J at the optimum conditions. Highlights * Application of FFF process for producing the PLA/CNT composite * Investigating the impact of FFF parameters on the mechanical properties * Estimating the optimal conditions of the FFF process KEYWORDS impact energy, optimization, PLA/CNT composite, tensile strength, 1 | INTRODUCTION Polylactic acid (PLA) is a thermoplastic polymer that has excellent biocompatibility, good biodegradability, high mechanical strength, and suitable processability. (1) This polymer is widely used in the [...]

In this paper, the selective laser sintering process was used to fabricate the Ti[O.sub.2]/PA12 nano-composite parts by considering the parameters of laser power, scanning speed, and Ti[O.sub.2] content. The response surface methodology was used to improve the mechanical properties of Ti[O.sub.2]/PA12 nano-composite parts. The fracture surface characteristics of the specimens were examined using the scanning and transmission electron microscopy. The results indicated that the increase in laser power from 10 to 15 W improved the tensile strength, modulus, and impact strength of the nano-composite parts because of the fine dispersion of Ti[O.sub.2] nano-particles. An increase in the scanning speed from 2000 to 3000 mm/s resulted in the reduction of tensile strength and modulus due to lower heat input and consequently incomplete densification of polyamide-12. In addition, the increase of Ti[O.sub.2] content up to 5 wt% can improve the tensile strength, modulus, and impact strength, but requires increasing the laser power. However, the mechanical properties of the nano-composite parts were enhanced simultaneously at laser power of 12.4 W, scanning speed of 2000 mm/s and Ti[O.sub.2] content of 1.9 wt%. Moreover, the addition of Ti[O.sub.2] up to 5 wt% showed a slight influence on thermal stability and crystallinity of the sintered specimens. KEYWORDS 3D printing, additive manufacturing, mechanical properties, optimization, selective laser sintering, Ti[O.sub.2]/PA12 nano-composite, 1 | INTRODUCTION Selective laser sintering (SLS) is a powder-based additive manufacturing technology that can be used to produce complex 3D parts from metals, ceramics, and polymers. The material (powder) [...]

The objective of this research is to optimize the yield strength and hardness of AZ31/AA3105 joint during the single pass friction stir welding (FSW). For this purpose, Taguchi method was used to examine the influence of FSW parameters such as rotating speed, linear speed, advancing side and shoulder diameter on the hardness and yield strength of the welding. The microstructure of the joint has also been analyzed by optical and scanning electron microscopy (SEM) to evaluate the joint quality. The results of microstructure analysis indicated that a high quality joint with thin intermetallic layers obtained at rotating speed of 1100 rpm and linear speed of 30 mm/min. The optimization results indicated that the hardness (78.06 HV) and yield strength (129.2 MPa) can be improved simultaneously with the advancing side of Mg, rotating speed of 1100 rpm, linear speed of 30 mm/min, and shoulder diameter of 15 mm. The fracture surface of samples indicated that a combination of brittle and ductile fracture was occurred at rotating speed of 1100 rpm and linear speed of 30 mm/min, which improved the ductility and toughness. It was concluded from the obtained results that a high-quality joint with improved mechanical properties can be obtained between AZ31 and AA3105 alloys in the optimal conditions of FSW parameters. [ABSTRACT FROM AUTHOR]

In this research, we evaluated the relationship of early splitting with the growth of Aspergillus section Flavi and aflatoxin production in Iranian pistachio cultivars. From each cultivar, six trees and from each tree, six fruit clusters were randomly harvested at maturity time and their fruits mixed. Finally, healthy fruits, and earlysplitted fruits with irregular cracks of each cultivar were separated. The population density of Aspergillus section Flavi fungi in the nut kernel was measured using AFPA and DRBC culture media suspension preparation and serial dilution methods. The amount of aflatoxin in different pistachio samples was measured by high-performance liquid chromatography (HPLC). The results showed a significant difference in Aspergillus section Flavi contamination among different pistachio cultivars. The population density of Aspergillus section Flavi colonies in pistachio cultivars of Shahpasand (74.6667 CFU g-1) and Kal-Khandan (73.6667 CFU g-1) was much higher than other cultivars. The percentage of early-splitting was higher in the Shahpasand cultivar (13.66%) than in other cultivars, followed by the Kal-Khandan cultivar (5.66%). There was a positive and significant relationship between the growth rate of Aspergillus section Flavi and the fruit's early splitting percentage (r = 81%). In other words, with an increase in the early splitting percentage of pistachio fruit, the growth rate of Aspergillus section Flavi increased. It can be said that early-splitting is an unfavorable trait and causes an increase in aflatoxin contamination, and early-splitted fruits of Shahpasand and Kal-Khandan cultivars showed more contamination. Therefore, cultivars with less early-splitted nuts should be considered more in export. [ABSTRACT FROM AUTHOR]

Additive manufacturing encompasses technologies that produce three-dimensional computer-aided design (CAD) models through a layer-by-layer production process. Compared to traditional manufacturing methods, additive manufacturing technologies offer significant advantages in producing intricate components with minimal energy consumption, reduced raw material waste, and shortened production timelines. AM methods based on shielded gas welding have recently piqued the interest of researchers due to their high efficiency and cost-effectiveness in manufacturing critical components. However, one of the most formidable challenges in additive manufacturing methods based on shielded gas welding lies in the irregularity of weld bead height at different points, compromising the precision of components produced using these techniques. In this current research, we aimed to achieve uniform weld heights along the welding path by considering the most influential parameters on weld bead geometry and conducting experimental tests. Input parameters of the process, including nozzle angle, welding speed, wire speed, and voltage, were considered. Simultaneously, image processing and wavelet transform were employed to assess the uniformity of weld bead height. These parameters were applied to produce intricate parts after identifying optimal parameters that yielded the smoothest weld lines. According to the results, the appropriate bead for manufacturing the part was extracted. The results show that the smoothest bead line is achieved in 27 V as the highest level of voltage, at a 90° nozzle position and the maximum wire feed rate. Parts manufactured using this method across different layers exhibited no distortions, and the repeatability of production substantiated the high reliability of this approach for component manufacturing. [ABSTRACT FROM AUTHOR]

The friction stir welding of A365 and AZ91C alloys was conducted in this study to assess the effect of tilt angle, linear velocity and rotating speed on the elongation, hardness and tensile strength using the response surface method. Then, the weld microstructure was investigated by SEM, TEM and EDS analysis to deeply investigate the structure of A365–AZ91C weld. It was realized that the grain size of weld joint has grown and the crack and tunnel were formed when the rotating speed improved from 1000 to 2000 rpm, which produced a decline in the hardness and strength and a rise in the elongation. Moreover, an increment of linear velocity up to 60 mm/min led to the refinement of the weld microstructure, which was followed by an enhancement in the strength and hardness of the weld, whereas the elongation deteriorated. In the case of tilt angle, the highest elongation and strength were detected at a tilt angle of 2∘, but the highest hardness was observed at a tilt angle of 4∘ because of the nucleation of Al3Mg2 and Al 1 2 Mg 1 7 intermetallics. Results of optimization exhibited that the concurrent improvement of the strength, hardness and elongation can be acquired with the tilt angle of 3∘, rotating speed of 1600 rpm and linear velocity of 53 mm/min. [ABSTRACT FROM AUTHOR]

The aim of this work is to enhance the impact strength and tensile modulus of the PP/EPDM/TiO2 nanocomposite fabricated by fused filament fabrication. Hence, the response surface methodology and desirability function procedure were applied to find the optimum values of TiO2 content, nozzle temperature and printing speed. Then, the microstructural features of the printed samples were investigated by SEM, TGA and DSC analyses. The results indicated that the greatest impact strength of samples (73 J/m) was attained at a TiO2 content of 4 wt%, while the tensile modulus of samples was maximized (1130 MPa) at a TiO2 content of 2 wt% due to good distribution of the nanoparticles. The increase of the nozzle temperature from 200 to 225 ºC resulted in an improvement in the impact strength (16.2%) and tensile modulus (11.1%) because of suitable viscosity of the filament, whereas the impact strength (11.2%) and tensile modulus (6.7%) were reduced with the increase of nozzle temperature from 225 to 250 ºC because of the thermal degradation of filament. Moreover, as the printing speed increased from 20 to 40 mm/s, the tensile modulus initially enhanced by 2.4% and then decreased by 1.2%, but the impact strength continuously decreased by 6.5%. Finally, the simultaneous enhancement of the impact strength and tensile modulus has been attained at a TiO2 content of 2.4 wt%, nozzle temperature of 226 ºC and printing speed of 28 mm/s. [ABSTRACT FROM AUTHOR]

In this paper, the selective laser sintering process was used to fabricate the TiO2/PA12 nano‐composite parts by considering the parameters of laser power, scanning speed, and TiO2 content. The response surface methodology was used to improve the mechanical properties of TiO2/PA12 nano‐composite parts. The fracture surface characteristics of the specimens were examined using the scanning and transmission electron microscopy. The results indicated that the increase in laser power from 10 to 15 W improved the tensile strength, modulus, and impact strength of the nano‐composite parts because of the fine dispersion of TiO2 nano‐particles. An increase in the scanning speed from 2000 to 3000 mm/s resulted in the reduction of tensile strength and modulus due to lower heat input and consequently incomplete densification of polyamide‐12. In addition, the increase of TiO2 content up to 5 wt% can improve the tensile strength, modulus, and impact strength, but requires increasing the laser power. However, the mechanical properties of the nano‐composite parts were enhanced simultaneously at laser power of 12.4 W, scanning speed of 2000 mm/s and TiO2 content of 1.9 wt%. Moreover, the addition of TiO2 up to 5 wt% showed a slight influence on thermal stability and crystallinity of the sintered specimens. [ABSTRACT FROM AUTHOR]

Internal conditions and external display of grafted fruit trees are the results of rootstock effects on nutrient uptake, type and amount of rootstock inductive effects on the scion, and scion consumption. Effect of grafting combination on nutrient content, phenyl propanoid pathway enzymes and their effect on secondary metabolites production of apple leaves was investigated in two consecutive years. Two Iranian red flesh apple cultivars and 'Red delicious' cultivar grafted on M9, B9 and one red flesh apple colony rootstock of Bekran were tested in a factorial randomized complete block design. To make a noticeable difference in the amount of nutrients in samples, the treatments in the second year were fertilized. Nitrogen, phosphorus, potassium and calcium were measured in leaves for two years. Also PAL (Phenylalanine ammonialyase) and UFGT (UDP-glucose: flavonoid 3-O-glucosyltransferase) enzymes activity, phenolic compounds and flavonoids were determined by high-performance liquid chromatography (HPLC) in vegetative tissues. According to results of this study, among studied rootstocks, M9 was able to accumulate and maintain high concentration of minerals in leaves. Red flesh apples are capable of production of secondary metabolites if they grafted on rootstocks with higher absorption rate. In this way, they can meet the goal of secondary metabolites production. Also, our results showed that calcium was effective in production of all phenolic and flavonoid compounds and induction of UFGT enzyme activity. [ABSTRACT FROM AUTHOR]