Volume 65, Issue 11

This study investigates the influence of infill patterns and densities on crack propagation behavior in additive manufactured parts. Through three-point bending tests, force–displacement data were obtained for specimens with different infill patterns, densities, and crack sizes. The results demonstrate that infill density significantly affects the mechanical properties and fracture characteristics of the parts. Higher infill densities result in increased strength but reduced tolerance for deformation, leading to a more abrupt failure mode. The findings highlight the importance of carefully selecting the infill pattern and density to optimize the mechanical performance of 3D-printed parts. Understanding these relationships is crucial for designing robust and reliable structures for various applications in additive manufacturing.

To improve the ductility and toughness of refractory high entropy alloy (Ti, Zr, V), Mn and Cu were added to form TiZrVMnCu high entropy alloy with soft and hard phases. Carbon nanotubes (CNTs) and Er were introduced to fabricated composites with high strength and ductility. The relative density, microhardness, and compressive strength of TiZrVMnCu–Er–CNTs composites were in direct proportional to CNTs content from 0 to 0.5 wt%. The composite with 0.5 wt% CNTs has the highest hardness (634.4 HV) and strength (1720.7 MPa), and the strain variable is 14.3 %. The fracture toughness of the composites was improved by the crack bridging mechanism and crack deflection mechanism induced by adding CNTs. The fine grain, second phase strengthening mechanism, and the load transfer mechanism induced by CNTs improved the strength and hardness of the composites. Er can achieve solid solution strengthening or play a role in the second phase and fine grain strengthening.

The corrosion and bacterial behavior of AZ91 magnesium alloy coated with sol–gel-deposited amorphous tantalum oxide and hydroxyapatite have been investigated. The objective was to assess the potential suitability of AZ91 for permanent prosthesis applications. The coatings were applied in layered and hybrid configurations and characterized using various techniques including X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectrometry, and drop analyses. The antibacterial properties were evaluated through interactions with Staphylococcus aureus and Escherichia coli strains. Mechanical properties and adhesion were determined via linear scratch tests, and electrochemical corrosion tests were conducted in different media. The release of aluminum ions from the samples in Dulbecco’s Modified Eagle’s Medium was monitored over 28 days. The findings revealed that the amorphous tantalum oxide coating, particularly in combination with hydroxyapatite, improved antibacterial properties and positively influenced corrosion and scratch resistance. The layered and hybrid coatings demonstrated the highest corrosion resistance. The release of aluminum ions remained within acceptable levels in the tested medium. Overall, the study provides valuable insights into the potential of sol–gel coatings on AZ91 for prosthetic applications, considering antibacterial behavior, corrosion resistance, and aluminum release.

Since the development of laser systems technology led to a significantly decreased energy input by pulsing, laser cutting became a noteworthy method for cutting fiber-reinforced polymers. Despite the occurrence of heat introduction and heat-affected zones (HAZ), there are advantages regarding processing speed and maneuverability. Within this work, the influence of two cutting parameters (low (A) and high heat introduction (B)) on the fatigue properties of carbon fiber–reinforced epoxy and polyamide 6 were investigated. At the same time, micro waterjet cut specimens were added as a reference. In doing so, laminates were cut to different specimen widths and orientations. Multiple amplitude tests were performed with strain and temperature measurements. The results show an influence of specimen width on fatigue lifetime for the epoxy system, but not in polyamide 6. The 45° specimens for both CFR-EP and CFR-PA6 showed a decreased lifetime when cut with parameters B . However, these findings do not apply to 0° specimens, since parameters A lead to a smaller lifetime for CFR-EP, and no influence was found for CFR-PA6. Furthermore, no clear HAZ could be identified for A . Since there is a decrease in lifetime for CFR-EP, the necessity of applying further methods for HAZ detection is described.

In this study, Inconel 625 alloy was initially aluminide coated by halide-activated pack cementation at 700 °C for 4 h using fine (40–45 µm) globular and coarse (10–75 µm) ligament aluminum particles. Microstructural features and hardness variation of the coatings along with their oxidation behavior at 1000 °C during 50 h were investigated to reveal the effect of pack characteristics on the properties. Investigations revealed that (i) a homogeneous and continuous coating layer was formed on the surface without internal oxidation, (ii) a thicker coating (∼60 µm) was formed due to the pack consisting of coarse particles, (iii) a higher hardness value (1369 HV0.5) was measured for the coated alloy using fine particles in the pack, and (iv) the coating with coarse powder exhibited higher oxidation resistance during the first 50 h of oxidation test period. Secondly, superalloy was coated at different temperatures (700 and 1000 °C) and times (2 and 4 h) using coarse particles. In this stage, the findings showed that by increasing process temperature and time, the accumulation of aluminum on the superalloy surface increased and the oxidation tendency remained at a lower level in coatings containing thicker layers.

Additive manufacturing (AM) using 3D printing techniques such as fused deposition modeling (FDM) has now found much attention, not only in prototyping but also in industrial production. Indeed, the 3D-printed components are now widely used as structural elements in many applications such as biomechanical engineering (dentistry, orthopedics, bio implants, etc.) and therefore, full understanding of their strength, load carrying capacity, improving the mechanical behaviors, and manufacturing process is an important issue. Charpy impact experiments offer information on the strength of a material to sudden failure where a sharp stress raiser or notch is present. In addition to providing information not available from any other simple mechanical experiments, the impact resistance tests are quick and inexpensive, so they are often used. In this research, impact strength experiments were conducted at room temperatures on rectangular samples containing three different notches including V-notch, U-notch, and Keyhole-notch to determine impact resistance of the 3D-printed polylactic acid (PLA) components. The capability of multiple comparison tests for analysis of variance like ANOVA, Tukey, and Fisher methods for prediction of impact resistance in the tested specimens were also investigated. The samples containing Keyhole notch showed highest Charpy impact resistance. In contrary, V-notched sample provided the lowest impact energy. All the employed statistical analyses reveal that the notch type has meaningful influence on the impact energy of 3D-printed parts.

Today, a variety of implant designs with different attachment types are widely used in dental implant systems to eliminate connection problems. However, there are still design issues that can significantly affect the long-term success of dental implants. One of these problems is the formation of a microgap in the abutment–implant interface, which can lead to abutment screw loosening, screw fracture, and abutment fracture under masticatory loading. In this in vitro study, the effects of gingival height, dental implant diameter, and abutment type (solid, digital, and ball) on microgap formation were observed after repetitive fatigue tests using an experimental design. After the tests, the optimal design factors were determined to minimize microgap formation. According to the results of the experimental design, the abutment type was found to be the most influential parameter on microgap formation. An implant diameter of 4.1 mm, the smallest gingival height of 0.5 mm, and a digital attachment combination were identified as the optimal design parameters based on the statistical approach ( R 2  = 85.3 %).

Adhesive bonding is used to join materials that are difficult to join with other joining methods. In this study, the effects of adhesive bonding curing conditions and different ambient conditions on the tensile shear loading process were investigated for dual-phase 600 steel materials that are widely preferred in the automotive industry. Steel sheets used in the automotive industry are exposed to environmental conditions at different temperatures. For this purpose, uniaxial tensile tests at different ambient temperatures were carried out to determine the mechanical properties of the adhesive bonded materials. The curing conditions affect adhesive mechanical properties. The lap shear strength decreased as the ambient temperature increased.

Arc erosion studies are carried out on electrical contact materials in the switching current experiment. A test rig is developed to capture the 2-D image and the 3-D profile of eroded silver tin oxide electrical contact material in situ . Image processing algorithms are specially presented to accurately recognize the features of erosion region. The initial small patch of erosion traces gradually evolves into the deep crater with the increment of switching cycle enabling a study of the arc erosion behavior. 2-D image, 3-D profile, and micro surface morphologies of the eroded contacts are analyzed and then related to the extent of erosion. The results show that the evolution process of central erosion region could be divided into the enlargement in breadth of contact surface and the extension in depth of contact profile. The end result of arc erosion is the net loss of contact material, which would lead to the substantial reduction of contact force and potential electrical contact instability.

The aim of this study was to evaluate the performance of two endodontic rotary files with different off-center geometries in bending and torsional tests using finite element analysis (FEA). Trunatomy Prime (TRN-P) and WaveOne Gold Primary (WOG-P) files were used in the study. Geometric models for finite element analysis were obtained by micro-computed tomography scanning. FEA analyses were performed according to ISO 3630-1 specifications to evaluate the bending and torsional tests of the files. Trunatomy Prime showed higher flexibility than WOG-P when subjected to bending. In terms of torsional strength, WOG-P showed higher torsional strength than TRN-P. The geometry of a rotary instrument file influences the mechanical behavior (bending and torsion) of rotary files. The clinician should be aware of the behavioral differences in rotary files and use the appropriate file according to the clinical situation in addition to the manufacturer’s instructions.

In this study, the effects of nitrocarburizing, QPQ, and Cr coating on the surface properties of 32CrMoV12-10 gun barrels are discussed. Hardness measurements, pin-on-disc tests, and anodic polarization tests were performed to examine the hardness values, wear resistance, friction coefficient, and corrosion resistance. The hardness of the specimen treated with QPQ was found to be the highest. Comparing the hardness profiles, it was observed that the casing depth of the nitrocarburized sample was shallower than that of the QPQ-treated sample. The pin-on-disc test revealed that the nitrocarburized sample exhibited a high coefficient of friction, while the Cr-coated sample showed the lowest coefficient of friction. Analyzing the Tafel polarization curve, it was determined that the nitrocarburized and QPQ-treated specimens demonstrated similar levels of corrosion resistance. However, it can be noted that the QPQ-treated specimen had a slightly lower corrosion rate.

This paper presents an experimental study aimed at providing new insights into passenger vehicle driver seat vibration. The study investigates the effects of various driver seat components on the damping coefficient. By employing a design for six sigma method, an optimized seating solution is proposed to enhance seat comfort levels. The control factors used in this study include seat cushion upholstery, topper foam, cushion foam, pulmaflex, torsion bar and seat structure. Seat position, foam thickness and body mass are considered as potential noise factors. Subjective evaluation of seat comfort is conducted using the SAE J 1441-2016, comparing three different passenger car driver seats. The seats are disassembled from the vehicles and mounted on a six-degree-of-freedom shaker test bench. Vertical vibration data are filtered, and transmissibility curves are experimentally obtained from the seat rail to the seat cushion via a pad. Uncomfortable seat prototypes are then manufactured, and alternative configurations are tested on the shaker. The objective and subjective evaluations of the seat prototypes reveal that lower foam hardness, higher foam density, and flexible upholstery contribute to improved comfort levels. Moreover, the prototype seat with optimum parameters receives a subjective evaluation SAE score of +0.75, indicating an enhancement in comfort.

The increased growth of Candida albicans ( C. albicans ) with allergy reaction of MMA remains an issue of concern among denture wearers. C. albicans growth inhibition, mechanical and water absorption potentials of extracted A19-saponin–commingled PMMA denture base composites were investigated. Soxhlet extraction technique for defatting of Dialium guineense (D. guineense) stem powder was used with ethanol to extract A19-saponin. Fungicidal inhibition concentration of A19-saponin extract of D. guineense was determined. PMMA denture base was prepared with incorporation of A19-saponin at different concentrations of obtained 23.2 % yield. The mechanical and water absorption properties were determined. The minimum and maximum fungicidal inhibition concentrations and susceptibility of 25 and 100 % for extracted A19-saponin were obtained, respectively. PMMA, MMA and extracted A19-saponin of ratio of 30 g: 5 ml: 5 ml denture was optimally fabricated. A19-saponin increased the impact strength and hardness by 352.94 and 11.54 % with reduced water absorption by 82.85 %. Thus, A19-saponin as an additive improved quality of denture.

Pure (CP2) and alloyed titanium (Ti-6Al-4V) have an important place in biomedical and aerospace applications due to their low density and high strength properties. In this study, the effect of the formability of CP2 and Ti-6Al-4V titanium alloy at different temperatures on mechanical properties and microstructure was investigated. The hot forming process was carried out by pressing 1 mm sheet titanium plates at different temperatures on the U profile mold. Specimens along the rolling direction and perpendicular to the rolling direction were taken from the bottom the formed U-plates. Afterward, tensile tests, microhardness measurements, and changes in microstructure were examined, respectively. As a result, at high temperatures and in different rolling directions, significant changes in microstructure and mechanical properties were observed. It was determined that the best forming temperature of CP2 and Ti-6Al-4V materials along the rolling direction was 500 °C, white it is 400° for perpendicular to the rolling direction was 400 °C.