Search Results (21,671)

Rolling resistance is a critical factor that influences vehicle energy consumption, emissions, and overall performance. It directly impacts fuel efficiency, tire longevity, and driving dynamics. Traditional rolling resistance tests are conducted on smooth steel drums, which fail to replicate real-world road surface textures, potentially skewing results. This article presents the process of designing surface replicas using 3D printing technology, which consisted of selecting the internal structure, material, and print parameters of the surface sample. In order to verify the designed structures, an original mechanical strength test was performed. The test was based on pressing the tire onto the test sample with an appropriate force that corresponded to typical conditions during rolling resistance measurements. The test results included surface texture profiles before and after the application of load, which were then superimposed to detect any possible sample deformation. The obtained strength test results confirmed the validity of using 3D printing technology in the process of obtaining road surface replicas. Full article

Models used to study the fracture process of concrete are often considered 2D, ignoring the influence of specimen width. However, during the fracture process in pre-cracked concrete beams, the crack length varies along the thickness direction, especially in reinforced concrete. To study the influence of specimen width on reinforced concrete fracture behavior, a 3D numerical method was used to simulate the crack propagation processes of lightly reinforced concrete beams based on Fracture Mechanics. Nonlinear spring elements with different stress-displacement constitutive laws were employed to characterize the softening behavior of concrete and the bond-slip behavior between the steel bars and concrete, respectively. It is assumed that the crack begins to propagate when the maximum stress intensity factor at the crack tip along the beam width reaches the initial fracture toughness of concrete. To verify the validity of the proposed method, the completed crack propagation processes of lightly reinforced concrete three-point bending notched beams were simulated, and the calculated load-crack mouth opening displacement curves showed a reasonable agreement with the experimental data. Moreover, the impact of the 2D reinforced concrete beam model on the crack propagation process was analyzed. The results indicate that at the initial loading stage, the external load P obtained from the 2D model is significantly larger than the result from the presented 3D model. Full article

In response to the issue of reduced horizontal bearing capacity due to inadequate compaction of backfill soil in traditional grillage foundations, a novel grillage root foundation is proposed in this study. That is, the root is introduced into undisturbed soil at a traditional grillage foundation base plate. To assess the applicability of this innovative foundation under horizontal loading conditions, on-site experimental research was conducted. It was employed to comparatively analyze the load–displacement curves, changes in internal forces of steel components, and the development patterns of soil cracks around the foundation between traditional grillage foundations and various sizes of grillage root foundations subjected to horizontal loading. The results indicate that the horizontal bearing capacity of the grillage root foundation increased by 1.3 times compared to traditional grillage foundations, with economic benefits surpassing those of the traditional counterparts. The determination of the “m” value serves as the proportional coefficient of the horizontal resistance coefficient of the foundation soil, and the synthesis of the reactive force provided by the soil to the roots contribute to enhancements in soil resistance and the horizontal bearing capacity of the foundation. The horizontal load at which cracks appear in the grillage root foundation exceeds that of the traditional metal grillage foundation, with a slower rate of development. Finite element analysis was conducted to optimize the arrangement of roots, maximizing the foundation’s bearing capacity. This research provides certain references in terms of enhancing foundation bearing capacity, reducing ground treatment costs, and promoting sustainable development. Full article

Corrosion of steel reinforcement in concrete slabs undermines structural durability and shortens the lifespan of concrete structures. Carbon Fiber-Reinforced Polymer (CFRP) is a promising material offering benefits such as high strength, corrosion resistance, and light weight. This study aims to investigate the punching shear performance of concrete slabs reinforced with CFRP grids, focusing on the effects of different reinforcement ratios. A series of experiments were conducted on two-way concrete slabs reinforced solely with CFRP grids to assess their punching shear resistance. Experimental results show that the CFRP grid achieves an ultimate tensile strength of 2181 MPa, with the cracking load of CFRP grid-reinforced slabs reaching approximately 20% of the ultimate load, highlighting a strong correlation between the ultimate load and grid reinforcement ratio. The observed punching failure exhibited clear brittle characteristics, characterized by the formation of radial and circumferential cracks on the tensile surface of the slab. The reinforcement ratio significantly influences the failure mode of the slabs; as the reinforcement ratio increases, the ultimate punching loads also increase. Additionally, a mathematical formula is proposed to predict the punching bearing capacity, achieving calculation errors below 20%. These findings contribute valuable insights into using CFRP grids as primary reinforcement, enhancing the design and application of durable concrete slab structures. Full article

In this work, electrostatic minimum quantity lubrication (EMQL) has been applied in grinding. When the droplets were charged, it could promote penetrability in the processing area. The electric field formed between the charged droplets and the surface of Cr12 die steel could affect the hardness of the workpiece surface. The grinding mechanism of EMQL has been revealed under different charging voltage by analyzing the wetting angle of droplets and the hardness of Cr12 surface. The reduction of grinding force (11.5% to 49%), surface roughness (10% to 22.1%), and the increase in grinding ratio (1.9% to 27.3%) and surface quality of EMQL under various charging voltages were studied. The results showed that the wetting angle decreased when the droplets were charged. Compared to MQL, the charged lubricant droplets with better penetrability are easier to penetrate and spread on the contact surface between the grinding wheel and the workpiece, thereby improving the lubrication of the friction interface and obtaining better grinding performance. Moreover, we also found that the positively charged EMQL not only effectively improves the penetrability of droplets but reduces the hardness of the Cr12 surface. Thus, the grinding performances under positively charged EMQL are always better than these under negatively charged when grinding Cr12. Full article

The steel ball, as a key rolling element in mechanical equipment, directly affects the performance and service life of the bearing through its surface quality. Traditional methods for detecting surface defects on steel balls often face challenges in efficiency and stability. They struggle with three-dimensional surfaces and are easily affected by noise interference. This paper proposes a defect detection method for the steel ball surface based on Axial Cone mirror expansion and Improved Image Difference (ACID). The axial cone mirror unfolds the entire surface of the steel ball, allowing complete surface images to be obtained with just two captures. This simplifies the acquisition process and increases efficiency. The improved image difference method, combined with adaptive thresholding and adjacent frame difference techniques, effectively reduces noise interference. It enhances both the accuracy and robustness of defect detection. Frequent threshold adjustments and unstable detection, common in traditional methods, are avoided. Experimental results demonstrate that the ACID-based detection method surpasses traditional methods in terms of efficiency and accuracy. The improved method significantly reduces the missed detection rate. For example, the detection rates for cluster, scratch, and stain have increased from 86%, 80%, and 84% to 98%, 96%, and 98%, respectively. Moreover, the improved method reduces noise interference, avoids frequent threshold adjustments, simplifies the operation process, and shows higher stability and robustness in complex background conditions. Full article

This study aims to examine the effects of local corrosion on the axial compression performance of concrete-filled steel tubular (CFST) members. Nineteen CFST short columns with local corrosion were designed and fabricated to undergo axial compression mechanical property tests, with the radial corrosion depth of the local corrosion area as the key test parameter. The failure mechanism and mechanical property change laws of CFST axial compression short columns with circumferential full corrosion at the ends and middle were studied. Combined with finite element modeling, the influence laws of the three-dimensional geometrical characteristics of the local corrosion zone, i.e., the axial length, the annular width and the radial depth, on the structural bearing performance were thoroughly explored and discussed. The results revealed that the main reason for the reduction in load-carrying capacity of circular CFST axial columns due to local corrosion is attributed to the reduction of the effective cross-sectional area of the steel tube in the corrosion area. When local corrosion occurs at different axial positions, the variation range of the bearing capacity of CFST columns is within 10%. Regarding the impact of the three dimensions of local corrosion on the axial load-carrying capacity of CFST, the radial corrosion depth was identified as the most influential factor, followed by the annular corrosion width, and finally by the axial corrosion length. When the axial corrosion length exceeds 20% of the specimen length, its further influence on the load-carrying capacity is considered limited. Finally, a practical calculation formula for the bearing capacity of locally corroded CFST columns is proposed. The predicted results of this formula fit well with the test results and can quickly estimate the remaining bearing capacity of the structure by measuring the geometric parameters of the local corrosion area, providing a reference for the assessment and maintenance of CFST structures. Full article

A significant number of alloyed metals applied for different purposes are currently available in industry. The hardness of a piece is an important parameter to consider. The tempering process is widely used to change a metal’s hardness, which is obtained using a hardness test. Once the response is obtained, a way to evaluate the system is by performing an analysis of variance to verify the significance of terms and obtain a regression equation to improve the response. The aim of this work is to illustrate the implementation of an experimental approach based on the steepest ascent method and stopping rules for optimization purposes by considering the hardening process of the steel alloy 4140. The regression coefficients obtained from an experimental design were used to build the steepest path of improvement. The Myers and Khuri stopping rule and the enhanced parabolic stopping rule were applied to determine the best value while individual experimentation is developed. The obtained results, discussion, and a conclusive analysis are disclosed in this document. Full article

Salmonella Infantis poses a significant challenge in poultry production due to its persistence and resistance to disinfectants. This study investigated the survival of the S. Infantis strain on different surfaces and evaluated the efficacy of disinfectants in both preventing and treating biofilms. The survival of the tested S. Infantis strain was assessed on plastic and stainless steel surfaces after 24 and 48 h. The minimum inhibitory concentrations (MICs) of five disinfectants were determined, and their antiadhesion effectiveness was evaluated using crystal violet. The efficacy of biofilm treatment was evaluated by cell culturability. The results showed that the adhesion of S. Infantis was significantly higher on the plastic surface. The disinfectants were effective at reducing biofilm formation only within the first 24 h. Fresh solutions of disinfectants based on quaternary ammonium compounds exhibited the highest antimicrobial efficacy, while chlorocresol was the most effective for both the prevention and treatment of biofilms. The study results suggest that the presence of plastic surfaces may contribute to the dissemination of Salmonella. Additionally, the effectiveness of disinfectants varied based on storage conditions and contact time, while biofilms demonstrated reduced susceptibility compared to planktonic cells. However, given the laboratory scale of this study, further validation on a commercial scale is necessary to confirm these findings. Full article

Obtaining metallic parts via Additive Manufacturing can yield several advantages over using other traditional manufacturing methods such as machining. Material extrusion (MEX) can handle complex shapes with porous structures and, at the present time, much low-end and desktop equipment is available. In the present work, different industrial and medical applications of metallic Fused Filament Fabrication (FFF) parts are presented. First, an overview of the process, equipment, and of the metal-filled filaments currently available is provided. Then, the properties of parts and different applications are shown. For example, metal-filled filaments with a low metal content that can be used to obtain plastic parts with metallic appearance (with either steel, copper, or bronze), and filaments with a high metallic content allow obtaining metallic parts with high mechanical strength after a sintering operation. The present contribution aims to be an up-to-date panorama for current industrial and medical results and lessons learnt from the application of FFF to obtain metallic parts. Full article

In this study, the effects of applied pressure (0, 90, 120, and 150 MPa) during solidification on the microstructure, mechanical properties, and impact–abrasive wear resistance of Cr-Mn-Mo steel prepared by squeeze casting were systematically investigated. The results demonstrated that the materials produced under pressure showed smaller grains compared to those of the samples fabricated without pressure. Compared to the unpressurized sample, the grain diameter of the sample prepared at 120 MPa decreased by 37.7%, the length of the primary arm shortened by 40.7%, and the spacing of the secondary arm contracted by 14.1%. Furthermore, the impact toughness results indicated that the samples prepared without pressure exhibited brittle fracture characteristics, whereas quasi-destructive fractures predominated in the samples prepared at 120 MPa. Simultaneously, three-point bending strength exhibited a gradual increase with increasing pressure, reaching a maximum value of 855.5 MPa when prepared under 150 MPa. Additionally, the impact–abrasive wear resistance of Cr-Mn-Mo alloyed steel produced by squeeze casting was significantly enhanced compared to the samples produced without pressure. The samples without external pressure exhibited a combination of abrasive and adhesive wear, whereas the wear characteristics of the samples prepared under pressure includes grooves, cutting marks, flaking pits, and accumulating ridges. Full article

This paper examines the challenges of machining structural alloy steels for carburizing, with a particular focus on gear manufacturing. TiN_0.85-Ti coatings were applied to cutting tool blades to improve machining quality and tool life. The research, supported by mathematical modeling, demonstrated that these coatings significantly reduce adhesive wear and improve blade life. The Kolmogorov–Arnold Network (KAN) was identified as the most effective model comprehensively describing tool life as a function of cutting speed, coating thickness, and feed rate. The results indicate that gear production efficiency can be significantly increased using TiN_0.85-Ti coatings. Full article

This study investigates the effects of hot stamping on boron steel surface properties, comparing uncoated steel to Al–Si-coated steel, with a focus on developing atmosphere-controlled hot stamping technology. Experiments using a hat-shaped specimen revealed that uncoated steel formed a thick oxide layer due to exposure to atmospheric oxygen at high temperatures, negatively impacting surface quality and weldability. In contrast, the Al–Si-coated steel showed no oxide formation. Although uncoated steel exhibited higher average Vickers hardness, the detrimental effects of the oxide layer on weld quality necessitate advancements in process technology. A lab-scale hot stamping simulator was developed to control atmospheric oxygen levels, utilizing a donut-shaped induction heating coil to heat the material above 1000 °C, followed by rapid cooling in a forming die. Results demonstrated that maintaining oxygen concentrations below 6% significantly reduced oxide layer thickness, with near-vacuum conditions eliminating oxide formation altogether. These findings emphasize the critical role of oxygen control in enhancing the surface quality and weldability of uncoated boron steel for ultra-high-strength automotive applications, potentially reducing manufacturing costs while ensuring part performance. Full article

Background: The shaping of root canal space was completed using manual stainless steel files in earlier decades and with the advent of mechanical nickel–titanium (NiTi) instruments, there is potential for more efficient root canal preparation. Despite the advantages of NiTi instruments, their adoption in undergraduate dental education remains limited. The aim of this study was to evaluate three root canal instrumentation techniques, manual instrumentation using stainless steel hand files, continuous rotation employing ProTaper Gold (PTG) files, and reciprocation with WaveOne Gold (WOG) files, on endodontic resin blocks to assess the quality of preparation and the time required for instrumentation. Methods: A total of 36 third-year dental students, all lacking prior experience in root canal procedures, were divided into six groups to prepare 108 resin endodontic blocks with each student preparing 3 blocks. Images were captured at the preoperative, intraoperative, and postoperative stages to facilitate comparisons and measurements of the prepared blocks to assess the degree of resin removal, apical deviation, and mid-cervical wear. Furthermore, questionnaires were distributed to assess the students’ experiences and satisfaction with the techniques. The Friedman test, Wilcoxon test with Bonferroni correction, and Kruskal–Wallis test with Mann–Whitney U test were used to analyse and compare techniques, with the level of significance set at p < 0.05. Results: Instrumentation with PTG exhibited significantly reduced apical deviation (0.073 ± 0.003) compared to both the WOG and manual instrumentations (p < 0.001). Significant differences in mid-cervical wear were observed only between PTG and the manual instrumentation. In terms of resin removal, the manual instrumentation displayed greater variability and was five times slower to complete the instrumentation. In total, 90% of students favoured mechanical instrumentation, with substantial preferences for them over manual techniques. Conclusions: Mechanical instrumentation techniques, notably with the PTG system, were significantly faster and more effective in preparation quality. This highlights the potential for the inclusion of mechanical instrumentation in undergraduate dental curricula. Full article

Hydrogenated amorphous carbon (a-C:H) has been considered a promising biocompatible coating to protect metallic alloys against corrosion for medical applications, namely orthodontics. However, there is still no optimal solution for this biomedical field; hence, the investigation remains open. In this work, the effect of a nonmetallic doping element (N) on sputter-deposited a-C:H coatings was studied concerning both salivary corrosion and cytotoxicity behavior. After a 30-day corrosion test in an acidic modified Fusayama-Meyer artificial saliva, metal release from both coated and uncoated 316L stainless steel (SS) substrates was quantified. Tests on the corrosion extracts were then performed by using monocultures of macrophages and fibroblasts, and their coculture; and cell viability was evaluated via the MTT test. Results show an overall inhibition of the SS corrosion, which enhanced the in vitro biocompatibility with a minimal effect on the coatings’ microstructure. Among all the coatings tested, the undoped a-C:H coating performed the best, whereas an increase in N doping led to poorer protection against metal dissolution and a subsequent slightly lower biocompatibility. The findings corroborate that selecting the nonmetallic element N for doping C-based coatings is not a good choice for this biomedical field, even at low contents up to 10 at.%. Full article