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Based on the molecular mechanics approach, the purpose of this paper is to analytically investigate the torsional buckling behavior of single-walled silicon carbide nanotubes (SiCNTs) with different values of diameter and chiral angles.

To this end, the mechanical properties and atomic structure of a silicon carbide (SiC) sheet are evaluated based on the density functional theory (DFT) within the framework of the generalized gradient approximation. After that force constants of the total potential energy are theoretically obtained through establishing a linkage between the viewpoints of the quantum mechanics and molecular mechanics. Explicit expressions are presented to obtain the critical buckling shear strain corresponding to different types of chirality. The present model is capable to calculate the torsional buckling behavior of SiCNTs related to various chiral angles. The critical buckling shear strain is obtained for various types of chirality and compared with each other.

It is concluded that for all diameters, zigzag nanotubes are more stable than armchair ones. Besides it is found that the minimum critical buckling shear strain is for nanotubes with (n, n/2) chiral vector.

Investigating the torsional buckling behavior of single-walled SiCNTs with different values of diameter and chiral angle. Obtaining the mechanical properties and atomic structure of the SiC sheet based on the DFT calculations. Establishing a linkage between the molecular mechanics and quantum mechanics and obtaining the force constants of the molecular mechanics. Presenting the closed-form expression to calculate the critical buckling shear strain of single-walled SiCNTs corresponding to various types of chirality.

To investigate the influence of different process parameters of the laminated object manufacturing (LOM) process on the roughness of vertical surfaces along Z‐axis on ZX‐plane of parts produced by LOM.

The process parameters tested were layer thickness, heater temperature, platform retract, heater speed, laser speed, feeder speed and platform speed. A typical test part has been used, and matrix experiments were carried out based on Taguchi design. Optimal process parameter values were identified and finally, a regression model was applied onto the experimental results, and compared with bibliography models, using arbitrary experiments.

The statistical analysis of the experimental results showed that the surface roughness depends mainly on the heater temperature, layer thickness, and laser speed. Moreover, the regression model gave good predictions when heater temperature values were within the initial experimental area and inaccurate predictions when heater temperature takes the value 200°C.

Future work should involve extensive matrix experiments using parameters such as dimensions of test part (X_max, Y_max, Z_max), hatch spacing in X and Y directions, and delay time between sequential layers.

Using the extracted regression model, vertical surface roughness can be predicted and selected proprietary process parameter values. This means minimization of post processing time, easier disengagement between supporting frame and part, easier decubing, process optimization, and less finishing.

This methodology could be easily applied on different materials and initial conditions for optimisation of LOM processes.

This paper aims to overcome the corrosion in AA7075 by incorporating the dual-reinforcements like Al2O3 and SiC through friction stir processing (FSP). In recent days, an automotive monocoque structure undergoes corrosion because of changes in environmental conditions.

Surface hybrid composites (SHCs) of AA7075 with different weight ratios of Al₂O₃ and SiC were fabricated at a rotating speed of 1000 rpm, traveling speed of 56 mm/min and tool tilt angle of 2º with two passes. Surface regions were observed using optical microscopy, and the potentiodynamic corrosion test was performed under a 3.5 per cent NaCl environment at room temperature. Then, the surface morphology analysis of corroded samples and their structural properties were also investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron dispersive spectroscopy (EDS).

Through FSP, an improved interface between the reinforced particles and the AA7075 base matrix was observed because of the severe plastic deformation. Potentiodynamic polarization tests confirmed that the AA7075 matrix with a higher concentration of Al₂O₃ and a lower concentration of SiC (Al₂O₃ – 75 per cent and SiC – 25 per cent) possesses a lower corrosion rate than other specimens. This result is because of the combined effect of stable passive film formation and the resistance produced by hard SiC particles. In addition, the formation of a stronger interface between the reinforcements and the base matrix impedes the NaCl solution attack. The SEM micrograph depicts the film crystallinity variations with an increase in Al₂O₃ content. Debonding between the layers was observed on increasing the SiC content in the base matrix. XRD shows the peaks of reinforcing elements that influence the corrosion behavior. These observations suggest that the AA7075 reinforced with a higher concentration of Al₂O₃ and a lower concentration of SiC through FSP affords a suitable solution for automotive monocoque applications.

The corrosion rate has been identified for AA7075 SHCs with various concentrations of Al₂O₃ and SiC and has been compared with that of the base metal and the friction stir processed specimen without reinforcement.

The purpose of this study to investigate the organized porous network zinc (OPNZ) scaffolds. Their mechanical characteristics, surface roughness and fracture mechanism were assessed in relation to their structural properties. The prospects of fused deposition modeling (FDM) for printing metal scaffolds via rapid tooling have also been studied.

Zn scaffolds with different pore and strut sizes were manufactured via the rapid tooling method. This method is a multistep process that begins with the 3D printing of a polymer template. Later, a paraffin template was obtained from the prepared polymer template. Finally, this paraffin template was used to fabricate the Zn scaffold using microwave sintering. The characterization of prepared Zn samples involved structural characterization, microstructural study, surface roughness testing and compression testing. Moreover, based on the Gibson–Ashby model analysis, the model equations’ constant values were evaluated, which can help in predicting the mechanical properties of Zn scaffolds.

The scanning electron microscopy study confirmed that the fabricated sample pores were open and interconnected. The X-ray diffraction analysis revealed that the Zn scaffold contained hexagonal closed-packed Zn peaks related to the a-Zn phase, validating that scaffolds were free from contamination and impurity. The range for ultimate compressive strength, compressive modulus and plateau stresses for Zn samples were found to be 6.75–39 MPa, 0.14–3.51 GPa and 1.85–12.6 MPa by adjusting their porosity, which are comparable with the cancellous bones. The average roughness value for the Zn scaffolds was found to be 1.86 µm.

This research work can widen the scope for extrusion-based FDM printers for fabricating biocompatible and biodegradable metal Zn scaffolds. This study also revealed the effects of scaffold structural properties like porosity, pore and strut size effect on their mechanical characteristics in view of tissue engineering applications.

The purpose of this paper was to investigate the lubricity of palm biodiesel (PB)–diesel fuel with plastic pyrolysis oil (PPO) and waste cooking biodiesel (WCB).

Three quaternary fuels were prepared by mechanical stirring. B10 (10% PB in diesel) fuel was blended with 5%, 10% and 15% of both PPO and WCB. The results were compared to B30 (30% PB in diesel) and B10. The lubricity of fuel samples was determined using high-frequency reciprocating rig in accordance with ASTM D6079. The tribological behavior of all fuels was assessed by using scanning electron microscopy on worn steel plates to determine wear scar diameter (WSD) and surface morphology. The reported WSD is the average of the major and minor axis of the wear scar.

The addition of PPO and WCB to B10 had improved its lubricity while lowering wear and friction coefficients. Among the quaternary fuels, B40 showed the greatest reduction in coefficient of friction and WSD, with 7.63% and 44.5%, respectively, when compared to B10. When compared to B30a, the quaternary fuel mixes (B40, B30b and B20) exhibited significant reduction in WSD by 49.66%, 42.84% and 40.24%, respectively. Among the quaternary fuels, B40 exhibited the best overall lubricating performance, which was supported by surface morphology analysis. The evaluation of B40 indicated a reduced adhesive wear and tribo-oxidation, as well as a smoother metal surface, as compared to B20 and B30b.

Incorporation of PPO and WCB in PB–diesel blend as a quaternary fuel blend in diesel engines has not been reported. Only a few researchers looked into the impact of PPO and WCB on the lubricity of the fuel.

The purpose of this paper is to study the effect of blending time, SiC content and fill ratio on the homogeneity of iron‐silicon carbide powder mixture, blended in double‐cone blender; to evaluate density, microstructure and micro hardness of laser sintered iron and iron‐SiC specimens; and study the feasibility of building a complex iron‐SiC metal matrix composite (MMC) part by direct metal laser sintering (DMLS) process.

The morphology and particle size of iron and silicon carbide powders were evaluated. Nickel coating was carried out on silicon carbide particles. Blending of iron‐SiC powders were carried out in two phases in a double‐cone blending equipment. In the first phase, three tests were conducted with fill ratios (ratio of volume of conical blender to volume of powder mixture) of 1.68, 3.39, and 6.8 percent while iron‐SiC weight ratio was kept constant at 97:3. In the second phase, four tests were conducted with iron‐SiC weight ratios of 99:1, 98:2, 97:3, and 95:5 while keeping a constant fill ratio of 1.68 percent. In both the phases, blending was carried out for duration of 43 minutes. Homogeneity of the powder mixture was evaluated at different intervals of time by adopting sampling process. Sintering was carried out on iron and iron‐SiC powder mixture using DMLS machine at laser speed of 50, 75, 100, and 125 mm/s. Microstructure, density and micro hardness studies were carried out on the sintered specimens. A 3D model of a part with complex geometry was modeled using Unigraphics CAD/CAM software and prototype part was built by DMLS technology using the blended iron‐2 weight percent SiC powder.

A reduction in blending time was observed with increase in SiC content and decrease in fill ratio. Microstructure and micro hardness tests conducted on laser sintered iron‐silicon carbide specimens, reveal the homogeneity of blended powder. The density of the iron‐SiC composites sintered at a laser speed of 50 and 75 mm/s, decreased with increase in SiC content. Further, an increase in the micro hardness of iron‐SiC composites was observed with increase in SiC content and decrease in laser speed. Complex functional part was built by DMLS technology with out any supports.

The experiments were conducted with standard blending equipment in which the speed is limited to 48 revolutions per minute only.

Meager information is available on blending of powders for producing MMCs by laser sintering process. The work presented in this paper will be a guideline for researchers to carry out further work in blending of powders for producing MMCs by rapid prototyping process.

This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.

Details the development of composites, in particular carbon fibre reinforced plastics, for use in aerospace structures. Describes a wide range of products manufactured by various companies. Looks at the integrity of these materials and the testing methods used to ensure this. In particular, discusses metal matrix composites, aluminium/silicon carbide particulate MMCs and fibre‐metal laminates. Finally looks at advanced composites’ promise of being able to meet the needs of high specific properties and enhanced temperature capability required for future engines.

AEROSPACE applications demand the ultimate performance out of every material used and at this year's Paris Show, Du Pont highlighted the significance of new developments in high‐grade low and elevated temperature composites and their potential for the future. Latest among the advances introduced were thermoplastic engineered preforms which represent a completely new product system developed in Europe. It constitutes a breakthrough in low cost and high performance aircraft primary and secondary structures.