Search Results (113)

Material wear significantly impacts the clinical success and longevity of dental ceramic restorations. This in vivo study aimed to assess the wear behavior of IPS Empress^® glass-ceramic inlays and onlays over 14 years, considering the influence of different antagonist materials. Fifty-four indirect restorations of 21 patients were available for comprehensive wear analysis, with complete follow-up data for up to 14 years. Three-dimensional measurements relied on digitized epoxy resin models produced immediately post-insertion (baseline) and subsequently at 2, 4, and 14 years. The occlusal region on the baseline model was delineated for comparative analysis. Three-dimensional superimpositions with models from subsequent time points were executed to assess wear in terms of average linear wear and volumetric loss. Statistical analyses were conducted in R (version 4.4.1), employing Mann–Whitney U tests (material comparisons) and Wilcoxon signed rank tests (time point comparisons), with a significance threshold of p ≤ 0.05. During the entire study period, an increase in wear was observed at each assessment interval, gradually stabilizing over time. Significant differences in substance loss were found between the follow-up time points, both for mean (−0.536 ± 0.249 mm after 14a) and integrated distance (−18,935 ± 11,711 mm³ after 14a). In addition, significantly higher wear was observed after 14 years with gold as antagonist compared to other materials (p ≤ 0.03). The wear behavior of IPS Empress^® ceramics demonstrates clinically acceptable long-term outcomes, with abrasion characteristics exhibiting stabilization over time. Full article

Background: Artificial tooth wear impacts prosthesis durability and function; understanding material–antagonist interactions guides clinical choices. Aim: This in-vitro study aimed to assess the wear behavior of isosit and nanohybrid composite resin artificial teeth when opposed to various antagonist materials using 3D volumetric wear analysis. Materials and Methods: Sixty specimens (n = 10 per group) were prepared from two artificial tooth materials and assigned to six antagonist combinations: isosit–isosit, isosit–nanohybrid composite, isosit–porcelain, nanohybrid composite–isosit, nanohybrid composite–nanohybrid composite, and nanohybrid composite–porcelain. Specimens were scanned before and after 600,000 chewing cycles using a structured-light 3D scanner. Volumetric wear was calculated by superimposing pre- and post-test scans. Data were analyzed using two-way ANOVA and Tukey’s HSD test (α = 0.05). Results: Porcelain antagonists produced the highest wear values (p < 0.05). No significant difference was found between isosit and nanohybrid antagonists (p > 0.05). Identical material pairings showed less wear, though differences were not statistically significant. Conclusions: Porcelain as an antagonist increased wear risk. Using identical materials bilaterally, such as isosit–isosit or nanohybrid–nanohybrid, may help reduce artificial tooth wear in removable prostheses. Full article

High-entropy alloys are known for their promising mechanical properties, wear and corrosion resistance, which are maintained across a wide range of temperatures. In this study, a CoCrFeNiCu-based high-entropy alloy, distinguished from conventional CoCrFeNi systems by the addition of Cu, which is known to enhance toughness and wear resistance, was investigated to better understand the effects of compositional modification on processability and performance. The influence of key process parameters, specifically laser power and scan speed, on the processability of CoCrFeNiCu-based high-entropy alloys produced by laser powder bed fusion additive manufacturing was investigated, with a focus of low laser power, which is critical for minimizing defects and improving the resulting microstructure and mechanical performance. The printed sample density gradually increases with higher volumetric energy density, achieving densities exceeding 99.0%. However, at higher energy densities, the samples exhibit susceptibility to hot cracking, an issue that cannot be mitigated by adjusting the process parameters. Mechanical properties under optimized parameters were further evaluated using Charpy impact and (in situ) tensile tests. These evaluations were supplemented by in situ tensile experiments conducted within a scanning electron microscope to gain insights into the behavior of defects, such as hot cracks, during tensile testing. Despite the sensitivity to hot cracking, the samples exhibited a respectable ultimate tensile strength of 662 MPa, comparable to fine-grained steels like S500MC (070XLK). These findings underscore the potential of CoCrFeNiCu-based high-entropy alloys for advanced applications. However, they also highlight the necessity for developing strategies to ensure stable and reliable processing methods that can mitigate the susceptibility to hot cracking. Full article

The current pre-clinical testing standards for total hip replacements (THRs), ISO standards, use simplified loading waveforms that do not fully replicate real-world biomechanics. These standards provide a benchmark of data that may not accurately predict in vivo wear, necessitating the evaluation of physiologically relevant loading conditions. Previous studies have incorporated activities of daily living (ADLs) such as walking, jogging and stair negotiation into wear simulations. However, these studies primarily used simplified adaptations that increased axial forces and applied accelerated sinusoidal waveforms, rather than fully replicating the complex kinematics experienced by THR patients. To address this gap, this study applied patient-derived ADL profiles—jogging and stair negotiation—using a three-station hip simulator, obtained through 3D motion analysis of total hip arthroplasty patients, processed via a musculoskeletal multibody modelling approach to derive realistic hip contact forces (HCFs). The results indicate that jogging significantly increased wear rates compared to the ISO walking gait waveform, with wear increasing from 15.24 ± 0.55 to 28.68 ± 0.87 mm³/Mc. Additionally, wear was highly sensitive to changes in lubricant protein concentration, with an increase from 17 g/L to 30 g/L reducing wear by over 60%. Contrary to predictive models, stair descent resulted in higher volumetric wear (8.62 ± 0.43 mm³/0.5 Mc) compared to stair ascent (4.15 ± 0.31 mm³/0.5 Mc), despite both profiles having similar peak torques. These findings underscore the limitations of current ISO standards in replicating physiologically relevant wear patterns. The application of patient-specific loading profiles highlights the need to integrate ADLs into pre-clinical testing protocols, ensuring a more accurate assessment of implant performance and longevity. Full article

In recent days, aluminum-based hybrid composites have garnered more interest than monolithic alloys owing to their remarkable properties, encompassing a high strength-to-weight ratio, excellent corrosion resistance, and impressive wear durability. The present study attempts to optimize the multiple wear attribute characteristics of Al6061/SiC/Al₂O₃ hybrid composites using grey and entropy-based VIKOR techniques. The composites were produced by adding equal proportions of SiC/Al₂O₃ (0–12 wt.%) ceramics through the stir-casting process, using an ultrasonication setup. Dry sliding wear experiments were executed with tribometer variants, namely reinforcement content (wt.%), load (N), sliding velocity (v), and sliding distance (SD), following L₂₇ OA. The optimal combination of process variables for achieving high GRG values from grey analysis was found to be A₃-B₃-C₃-D₃. The S/N ratios and ANOVA results for GRG indicated that RF content (wt.%) is the predominant component determining multiple outcomes, followed by sliding distance, load, and sliding velocity. The multi-order regression model formulated for the VIKOR index (Q_i) displayed high significance and more accuracy, with a variance of 0.0216 and a coefficient of determination (R²), and adjusted R² values of 99.60% and 99.14%. Subsequent morphological studies indicated that plowing, abrasion, and adhesion mechanisms are the dominant modes of wear. Full article

Wear resistance is of paramount importance for the long-term success of dental materials, especially when they are used for extensive indirect restorations in full-mouth rehabilitations. The present in vitro study aimed to evaluate the two-body wear resistance of a new and recently introduced CAD/CAM resin composite disc (Ena Cad, Micerium S.pA.), to compare it to the wear resistance of other two well-known and already marketed CAD/CAM composites (Brilliant Crios, Coltene/Whaledent AG; Grandio disc, Voco Gmbh) and to a conventional type 3 gold alloy (Aurocast 8, Nobil-Metal). Ten cylindrical specimens (diameter 8 mm, height 6 mm) were manufactured with each material and subjected to a two-body wear test in a dual-axis chewing simulator, performing 120,000 chewing cycles opposing antagonists (2-mm-diameter round tip) made out of the same corresponding materials. The total vertical wear (mm) and the total volumetric loss (mm³) for each sample/antagonist pair were calculated. Representative scanning electron microscope images were also taken. Data were statistically analyzed using one-way analysis of variance tests. No statistically significant differences were recorded among the wear properties of the restorative materials under investigation. The Ena Cad disc showed a wear resistance comparable to the type 3 gold alloy and to the already marketed Brilliant Crios and Grandio disc. Full article

This study investigates the properties of diamond-like carbon (DLC) coatings deposited onto a Ti6Al4V titanium alloy using plasma-assisted chemical vapor deposition (PACVD). The research encompasses adhesion tests, hardness, surface characterization, as well as corrosion and tribological evaluations. Artificial saliva was employed as both the lubricating and corrosive medium. Microscopic examination revealed a uniform coating with a thickness of about 3.2 µm. Scratch test results indicated that the deposited DLC coating exhibited superior adhesion, lower frictional resistance, and reduced wear compared to the titanium alloy. The coating deposition increased the hardness of the Ti6Al4V alloy by about 75%. Friction coefficients, measured under dry and lubricated conditions, were approximately 80% lower for the DLC-coated samples. Corrosion studies revealed that both the coated and uncoated surfaces demonstrated typical passive behavior and high corrosion resistance in artificial saliva. For DLC coatings, the corrosion current density and the corrosion rate were reduced by 85%. Microscopic observations of wear tracks following tribological and scratch tests confirmed the inferior wear and scratch resistance of the titanium alloy relative to the DLC coating. Under both dry and lubricated conditions (with artificial saliva), the volumetric wear rate of the titanium alloy was over 90% higher than for the DLC coating. Full article

The use of additives in asphalt concrete has improved the performance of road pavements. Some additives include silica powder, fly ash, and crumb rubber. This study analyzed additive levels’ effect on the volumetric characteristics of asphalt mixtures using a statistical approach. This research uses aggregate gradation for asphalt concrete wearing a coarse layer to determine the effect of additive content on the volumetric of hot asphalt mixtures. Asphalt modification is used with silica powder at compositions of 0%, 2%, and 6%; fly ash with 0%, 2%, and 4%; and crumb rubber with 0%, 1%, and 1.25%. Samples were made and tested according to the Marshall test procedure. The volumetric characteristics of the asphalt mixture were subjected to correlation analysis with the Pearson and Spearman rank approaches and the ANOVA test. The Pearson and Spearman rank correlation analyses showed that fly ash and silica additives were suspected of having no correlation and influence on volumetric characteristics except for crumb rubber. The ANOVA test results show that the largest volumetric characteristics are significantly influenced by the crumb rubber additive on voids in mineral aggregates. In contrast, the silica and fly ash additives affect voids in mineral aggregates and Marshall stability. The difference in silica and fly ash additive content has shown different ANOVA test results even though they have the same size and composition of the forming elements. Full article

Steel and aluminum alloys are used to manufacture the bodies of bulk material handling machines. The aluminum body enables a higher load mass and thus reduces transport costs. However, the greater abrasion of aluminum alloys leads to more frequent repairs to the underside of the body, as the abrasion parameters of aluminum are lower. This study, which used three different methods to evaluate abrasive wear (erosive/impact wear, abrasive wear in the mass of the free abrasive and abrasion test according to ASTM G65), showed that the most significant influence on the wear of 3004 series aluminum is the grain size of the abrasive. Only under erosive/impact wear conditions with abrasive particles of 2.0–5.0 and 5.0–8.0 mm is aluminum competitive with Hardox 450 in terms of volumetric wear, with aluminum exhibiting 1.3–1.4 times the wear rate of steel. Tests on the abrasive mass of the grinding fraction in question have shown that the volumetric wear of aluminum is 0.2–2.3 times higher at very low contact loads. In contrast, aluminum wears 7.5 and 4 times more than steel in the ASTM G65 test (0.1–0.4 mm fraction) at low and medium contact loads. Only in exceptional cases is the aluminum floor of bulk material handling equipment competitive with hardened steel in terms of wear intensity. Full article

The durability problem caused by the high-water absorption of foamed concrete restricts its further development and application. This study aimed to improve the durability of foamed concrete by transforming its performance from hydrophilic to superhydrophobic. Firstly, polydimethylsiloxane-modified superhydrophobic bulk foamed concrete was produced through physical foaming. Then, multiple durability tests, like mechanical wear, acid–alkali–saline resistance, ultraviolet aging, and extreme temperatures resistance tests, were carried out to assess its performance. Finally, the mechanism of superhydrophobicity also was studied. The results indicated that the volumetric and capillary water absorption of the superhydrophobic foamed concrete decreased by 72.4% and 92.6%, respectively, compared to ordinary foamed concrete. The dry densities of ordinary foamed concrete and superhydrophobic foamed concrete were 720 kg/m³ and 850 kg/m³, respectively. Superhydrophobic foamed concrete exhibited excellent wear resistance and resistance to ultraviolet aging. The contact angles after 10 m polishing and 168 h of ultraviolet irradiation were 152.1° and 152.2°, respectively. High temperature increased its hydrophobicity, and the contact angle increased to 157.1° at 200 °C. Additionally, electrochemical tests proved its better chloride ion corrosion resistance, and the corrosion potential and corrosion current of the superhydrophobic foamed concrete after 7 days were −0.190 V and 3.177 × 10⁻⁶ A, respectively. Therefore, the superhydrophobic bulk modification technique shows considerable potential for enhancing the durability of foamed concrete applied in various scenarios. Full article

To address the issue of high wear of polymer composites during friction, WSe₂ nanofillers were incorporated into the polymer matrix as a reinforcing phase to enhance heat transfer and improve the composites’ wear resistance. Tannic acid (TA) was grafted onto the surface of WSe₂ through high-energy ball milling, which facilitated the exfoliation of the nanofillers and improved their interfacial compatibility with the matrix material. Tribological experiments revealed that adding 5 wt% TA-WSe₂ reduced the friction coefficient and volumetric wear rate to 0.0065 and 8.7 × 10⁻⁴ μm³/N·m, respectively, representing reductions of 98% and 94% compared to pure PEI. The TA-WSe₂ not only served as a reinforcing phase to enhance heat transfer but also facilitated the timely dissipation of heat generated during friction. Additionally, it formed strong interfacial bonds with both PEI and PTFE, allowing the applied load to be efficiently distributed throughout the composite material. This study offers a practical approach for the functionalization of WSe₂ and the development of ternary composite materials for tribological applications. Full article

The paper presents a numerical and experimental study of the radial gap influence on the external gear pump performance. The numerical study is performed with a two-dimensional (2D) computational fluid dynamics (CFD) model developed and advanced in previous authors’ works. The experimental study is carried out on a laboratory test bench. The presented numerical results are accurate in the entire operating range (500–3500 RPM) of the pump, which is confirmed by comparisons between the CFD results, experimental data, and manufacturer’s technical documentation. The comparative analysis shows that the differences obtained during the verifications are in the range of −6.44% to 2.48%. An original methodology has been developed that allows us to obtain the volumetric efficiency and overall efficiency characteristics as a function of the rotation frequency of the pump at different values of the radial gap, using the manufacturer’s data for the same characteristics at a nominal radial gap and the results of CFD simulations. The analysis of the numerical and experimental results shows that a gap size of 0.04 mm is close to the limit value for the investigated pump, if it is not operated at a rotational frequency above the nominal. The presented methodology can also be applied to other types of hydraulic displacement pumps in order to evaluate their performance in the wear process and to predict the maximum allowable value of a specific design parameter under different operating modes. Full article

This paper provides a detailed analysis of the operation of representative forging tools (in the context of using various surface engineering techniques) used in the process of the hot forging of nickel–chromium steel elements. The influence of the microstructure and hardness of the material on the durability of the tools is also discussed, which is important for understanding the mechanisms of their wear. The research showed that the standard tools used in the process (only after nitriding) as a reference point worked for the shortest period, making an average of about 1400 forgings. In turn, the tools coated with the CrAlSiN coating allowed for the production of the largest number of forgings, reaching 2400 pieces, with uniform wear. In comparison, the tools with the CrAlBN coating made 1900 forgings. Three-dimensional scanning analysis showed that CrAlSiN- and CrAlBN-coated tools have lower volumetric wear, around 41–43 mm³, compared to 59 mm³ for nitrided tools. For a better comparison of tool life, the authors proposed the Z-factor, as the material loss to the number of forgings. The CrAlSiN coating showed the lowest material loss, despite a slightly higher Z-factor value compared to the CrAlBN coating. The use of hybrid coatings such as CrAlSiN and CrAlBN significantly reduces tool wear while increasing service life compared to tools that are nitrided only. Full article

Due to the need to form a surface layer with specific operating properties, recent years have seen an increased interest in surface strengthening treatment, which aims to create a surface layer that improves the durability of parts. With a view to the economics of the machining process, it is common to combine shaping milling, characterised by high volumetric efficiency, with finishing burnishing, during which significant forces are applied. In the literature, one of the important limitations of such technological operations is the value of residual stresses, excessive values of which can lead to the flaking and falling off of surface fragments. In the present study, the authors put forward the research hypothesis that, in addition to stresses, the geometry of the machining roughness is also important and may contribute to faster tribological wear than stresses. It has been shown that what is important in hybrid machining is not so much the height of the resulting irregularities and the effectiveness of their levelling by burnishing, but the geometry of the irregularities. After milling, surfaces with small, regular irregularities with smooth peaks and shallow valleys were found to be the best in tribological tests. Such roughness can be plastically levelled out during burnishing. On the basis of the experimental studies carried out, it was shown that a higher burnishing force does not always lead to higher wear resistance. Full article

This study aimed to evaluate the retrievability and potential damage to implant–abutment connections caused by fractured abutment screw removal using conventional and drilling techniques. A total of forty abutment screws were randomly inserted into forty dental implants, and then they were fractured and extracted using different removal methods: Group A employed a conventional approach utilizing an exploration probe and an ultrasonic device without irrigation (n = 10) (conventional); Group B used the Phibo drilling removal system without irrigation (n = 10) (Phibo); Group C utilized the Rhein83^® drilling removal system without irrigation (n = 10) (Rhein83); and Group D implemented the Sanhigia^® drilling removal system without irrigation (n = 10) (Sanhigia). Pre- and postoperative micro-computed tomography (micro-CT) scans were performed on the dental implants, and Standard Tessellation Language (STL) digital files were generated for morphometric analysis to measure the wear volume. ANOVA was used to assess the volumetric differences (mm³) and percentage ratios of the internal thread volumes of the implant–abutment connections before and after the procedures. Results: This study found no statistically significant differences in the volumetric and percentage ratios of internal threads among the implant groups (Phibo, Rhein83, Sanhigia, and conventional). However, the success rate for retrieving fractured abutment screws was higher (90%) with the drilling systems compared to the conventional technique (50%). These results suggest that drilling systems are more effective for the retrieval of damaged screws. Although drilling techniques without irrigation demonstrated higher removal efficiency compared to the conventional method, both approaches resulted in similar wear volumes at the implant–abutment connections when used to extract fractured screws. Full article