Mechanical Properties Of Fabricated Samples Research Articles

A novel low-cost ultra-strong maraging steel by additive manufacturing

A novel Co/Mo free maraging steel, hardened by nano-sized β-NiAl precipitates, has been developed for additive manufacturing (AM). The composition was designed to achieve ultra-high strength with low cost, simultaneously maintaining the formability. The steel was successfully fabricated using laser powder bed fuse (L-PBF) additive manufacturing (AM) technology, and the effect of heat-treatment on the microstructure and mechanical properties of fabricated samples was investigated. Due to the refined microstructure and high-density dislocations, the as-built samples displayed in excess of 1400 MPa ultimate tensile strength with about 16% total elongation. This is the highest reported strength to date for any as-built AM materials. Upon direct aging treatment, nanoscale ordered β-NiAl precipitated in the martensite matrix, resulting in a remarkable combination of mechanical properties, i.e. the strength levels exceeding 2000 MPa and elongation up to ∼8% at room temperature. This work contributes to the development of advanced ultrahigh-strength steel for AM.

Mechanical Behaviour of Polymer Matrix Composite Reinforced by Silicon Carbide Particles

In various fields, Polymer-based composites are used extensively instead of traditional materials. The hand lay-up technology has been employed to prepare the composites of Silicon carbide particles-epoxy. Mechanical properties; shore D hardness, Flexural strength, tensile strength and impact strength were measured for all specimens. The present work has also studied the impact of different weight percentages (including 3, 6, 9, 12, 15 and 18) wt.% of SiC solid powder on the mechanical properties of fabricated samples with two average particle sizes of 75 and 105 µm. SiC particles were utilized as reinforcement with the epoxy with hardener according to the mixing of (3:1) ratio. The experimental results found that hardness, flexural strength and impact strength can be increased by increasing the weight percentage of Silicon carbide, while tensile strength is decreased with an increased weight fraction of silicon carbide. At the same time, these properties were enhanced when the particles of SiC have 75 µm more than at 105 µm.

A hybrid ANN/PSO optimization of material composition and process parameters for enhancement of mechanical characteristics of 3D-printed sample

PurposeThis paper aims to study the effects of inorganic CaCO3 nanoadditives in the polylactic acid (PLA) matrix and fused filament fabrication (FFF) process parameters on the mechanical characteristics of 3D-printed components.Design/methodology/approachThe PLA filaments containing different levels of CaCO3 nanoparticles have been produced by mix-blending/extrusion process and were used to fabricate tensile and three-point bending test samples in FFF process under various sets of printing speed (PS), layer thickness (LT), filling ratio (FR) and printing pattern (PP) under a Taguchi L27 orthogonal array design. The quantified values of mechanical characteristics of 3D-printed samples in the uniaxial and the three-point bending experiments were modeled and optimized using a hybrid neural network/particle swarm optimization algorithm. The results of this hybrid scheme were used to specify the FFF process parameters and the concentration of nanoadditive in the matrix that result in the maximum mechanical properties of fabricated samples, individually and also in an accumulative response scheme. Diffraction scanning calorimetry (DSC) tests were conducted on a number of samples and the results were used to interpret the variations observed in the response variables of fabricated components against the FFF parameters and concentration of CaCO3 nanoadditives.FindingsThe results of optimization in an accumulative scheme showed that the samples of linear PP, fabricated at high PS, low LT and at 100% FR, while containing 0.64% of CaCO3 nanoadditives in the matrix, would possess the highest mechanical characteristics of 3D-printed PLA components.Originality/valueFFF is a widely accepted additive manufacturing technique in production of different samples, from prototypes to the final products, in various sectors of industry. The incorporation of chopped fibers and nanoparticles has been introduced recently in a few articles to improve the mechanical characteristics of produced components in FFF technique. However, the effectiveness of such practice is strongly dependent on the extrusion parameters and composition of polymer matrix.

Gas Atomization of X6CrNiTi18-10 Stainless Steel Powder for Selective Laser Melting Technology

Powders of X6CrNiTi18-10 stainless steel were fabricated from original workpieces of different grade by gas atomization method. It was found that it is necessary to use argon as a gas for gas atomization of X6CrNiTi18-10 steel, since the use of nitrogen leads to the formation of its compounds, namely, titanium nitride. It is shown that all used workpieces – electric arc, electric slag and vacuum arc refinement – allow one to obtain powders suitable for further utilization in selective laser melting technology of 3D printing. The main physicochemical and technological properties of the obtained powders have been investigated. Changes in the chemical composition and quality of the powders are not significant within the X6CrNiTi18-10 grade. The 0...20 μm fraction of powders does not have fluidity, and thus cannot be used for additive technologies. The fraction 20...63 μm have suitable rheological properties for additive technologies and may be used in selective laser melting (SLM) process. The yield of target fraction 20 ... 63 microns was ≈45%. The fraction 63...120 μm may be used for the direct metal deposition (DMD) additive technology. Considering the economic aspect of the technology, it is preferable to use original workpieces of X6CrNiTi18-10 steel produced by electric arc or electroslag process, since the market price of vacuum arc steel is significantly higher. The fraction of ferrite phase in the powder increases with a decrease of particle size of the resulting powder and is lower comparing to the original workpiece. In the future, for a detailed study of the technological properties, it is planned to grow samples from each type of the obtained powders on installation for selective laser melting and direct laser deposition to determine the physical and mechanical properties of fabricated samples (tensile and impact bending tests) and carry out metallographic studies.

Effect of filler loading on mechanical properties of natural carbon black reinforced polymer composites

In this article, the study of mechanical and morphological properties of orange peel and carbon black material from orange peel/ polypropylene composites was carried out taking various filler loadings (0, 10, 20, 30 and 40 wt%). The new carbon black materials were developed from bio-waste (orange peel) material using the pyrolysis method at different carbonization temperature (400 °C and 600 °C). All the mechanical properties such as tensile strength, modulus of elasticity, flexural strength, flexural modulus, impact strength and hardness properties were investigated as per ASTM standard. The experimental results demonstrate that the mechanical properties of fabricated samples are enhanced by increasing the carbonization temperature and filler weight percentage. In addition, the scanning electron microscope results reveal that the void percentage and pull out of reinforcing material increases with increase of filler loading.

Surface characterization of nanostructured commercially pure titanium modified by sandblasting and acid-etching for implant applications

This study investigated the surface characteristics of ultrafine-grain commercially pure titanium (UFG CP-Ti) substrates produced by equal channel angular pressing (ECAP), compared with those of coarse-grain commercially pure titanium (CG CP-Ti) and Ti–6Al–4V (Ti-64) substrates. All Ti surfaces were sandblasted and acid-etched (SLA-treated) to produce micro-rough surfaces. Tensile and microhardness tests were carried out to measure the mechanical properties of fabricated samples. Then the surface characteristics of samples including contact angle measurements, surface morphology and in vitro cell response were evaluated after polishing, sandblasting and acid etching procedures. The results showed that after applying four passes of ECAP, the average grain size of microstructure decreased from 25 µm to 170 nm, while the ultimate tensile strength increased from 545 ± 24 MPa to 971 ± 38 MPa. Investigation of surface morphologies carried out by scanning electron microscopy indicated that ECAP-processed substrate exhibits nano-topography compared with CG CP-Ti and Ti-64 substrates after applying SLA process. In addition, the contact angle of SLA-treated CG CP-Ti and UFG CP-Ti substrates decreased from 68.3° to 9.5° and 51.9° to 7.4°, respectively, indicating a significant improvement of surface wettability. The morphologies of MG63 cells cultured on the developed surfaces proved the potential superior osteoblast cell compatibility of the micro-roughened surface made of UFG CP-Ti substrates over CG CP-Ti and Ti-64 substrates.

Rapid manufacturing of copper components using 3D printing and ultrasonic assisted pressureless sintering: Experimental investigations and process optimization

The present work deals with the comprehensive study of ultrasonic and sintering parameters effect on the rapid manufacturing of pure copper components by ultrasonic assisted pressureless sintering and 3D printing. The customized sintering setup with the stepped horn was designed and fabricated for the experiments. First, the ultrasonic assisted sintering process was compared to conventional pressureless sintering process in regards of physical and mechanical properties of fabricated samples. The study revealed that the ultrasonic vibrations increased the contact area between the particles and raised the local heating for large sintering necks. Thus, the ultrasonic assistance enhanced the properties of the fabricated parts. Further, response surface methodology was used to design the set of experiments with sintering temperature, heating rate, soaking time and ultrasonic power percentage intensity to study the parameters effect. The analysis of variance was performed to analyze the significant contribution of parameters on relative density, compressive yield strength, and volumetric shrinkage. The sintering temperature and ultrasonic power percentage intensity dominated the other parameters with respect to responses. The less effect of low ultrasonic power intensity and short soaking time at high sintering temperatures was revealed by the significant interactions. Furthermore, the genetic algorithm based multi-objective optimization was used for the parameters optimization on maximizing relative density, compressive yield strength and minimizing the volumetric shrinkage. The efficacy of the developed method was tested by the fabrication of a customized heat sink on the optimized parameters.

Fabrication and characteristic evaluation of direct metal laser sintered SiC particulate reinforced Ti6Al4V metal matrix composites

The present work deals with the fabrication of silicon carbide (SiC) reinforced Ti6Al4V metal matrix composites (MMC’s) by a direct metal laser sintering process, followed by characterization of microstructures and evaluation of mechanical properties. Variable process parameters like laser power density [3.528–5.172 W/cm2 (×104)], SiC reinforcements (5%–15% by volume), and beam scanning speed (3500–4500 mm/min) and constant process parameters such as spot diameter (0.4 mm), hatching gap (0.2 mm), and layer thickness (0.4 mm) were considered to perform the experiments. The influence of addition of reinforcements on mechanical and physical properties of fabricated samples as compared to Ti6Al4V was examined. Field emission scanning electron microscope images show good metallurgical bonding between reinforcement and matrix. The presence of intermetallic compounds formed during the sintering process was detected by x-ray diffraction, which enhances the mechanical properties of the fabricated samples. Density of sintered samples increased on the increment in laser power density but decreased with an increase in the percentage of SiC in the mixture. Mean value of coefficient of friction was found in the range of 0.157–0.115 in a testing duration of 10 min, showing improvement in the wear resistance property as compared to Ti6Al4V. The improved mechanical properties and surface characteristics result in the formation of effective MMC's for various engineering applications.

Optimization of SLM process parameters for Ti6Al4V medical implants

PurposeTi6Al4V alloy has received a great deal of attention in medical applications due to its biomechanical compatibility. However, the human bone stiffness is between 10 and 30 GPa while solid Ti6Al4V is several times stiffer, which would cause stress shielding with the surrounding bone, which can lead to implant and/or the surrounding bone’s failure.Design/methodology/approachIn this work, the effect of selective laser melting (SLM) process parameters on the characteristics of Ti6Al4V samples, such as porosity level, surface roughness, elastic modulus and compressive strength (UCS), has been investigated using response surface method. The examined ranges of process parameters were 35-50 W for laser power, 100-400 mm/s for scan speed and 35-120 µm for hatch spacing. The process parameters have been optimized to obtain structures with properties very close to that in human bones.FindingsThe results showed that the porosity percentage of a SLM component could be increased by reducing the laser power and/or increasing the scan speed and hatch spacing. It was also shown that there was a reverse relationship between the porosity level and both the modulus of elasticity and UCS of the SLM part. In addition, the increased laser power was resulted into a substantial decrease of the surface roughness of SLM parts. Results from the optimization study revealed that the interaction between laser process parameters (i.e. laser power, laser speed, and the laser spacing) have the most significant influence on the mechanical properties of fabricated samples. The optimized values for the manufacturing of medical implants were 49 W, 400 mm/s and 99 µm for the laser power, laser speed and laser spacing, respectively. The corresponding porosity, surface roughness, modulus of elasticity and UCS were 23.62 per cent, 8.68 µm, 30 GPa and 522 MPa, respectively.Originality/valuePrevious investigations related to additive manufacturing of Ti alloys have focused on producing fully dense and high-integrity structures. There is a clear gap in literature regarding the simultaneous enhancement and adjustment of pore fraction, surface and mechanical properties of Ti6Al4V SLM components toward biomedical implants. This was the objective of the current study.

3D Printing of PDMS Improves Its Mechanical and Cell Adhesion Properties

Despite extensive use of polydimethylsiloxane (PDMS) in medical applications, such as lab-on-a-chip or tissue/organ-on-a-chip devices, point-of-care devices, and biological machines, the manufacturing of PDMS devices is limited to soft-lithography and its derivatives, which prohibits the fabrication of geometrically complex shapes. With the recent advances in three-dimensional (3D) printing, use of PDMS for fabrication of such complex shapes has gained considerable interest. This research presents a detailed investigation on printability of PDMS elastomers over three concentrations for mechanical and cell adhesion studies. The results demonstrate that 3D printing of PDMS improved the mechanical properties of fabricated samples up to three fold compared to that of cast ones because of the decreased porosity of bubble entrapment. Most importantly, 3D printing facilitates the adhesion of breast cancer cells, whereas cast samples do not allow cellular adhesion without the use of additional coatings such as extracellular matrix proteins. Cells are able to adhere and grow in the grooves along the printed filaments demonstrating that 3D printed devices can be engineered with superior cell adhesion qualities compared to traditionally manufactured PDMS devices.