Similar Wear Research Articles

Effect of cryogenic treatment on tribological behavior of Ti6Al4V alloy fabricated by selective laser melting

Ti6Al4V fabricated by selective laser melting (SLM) is commonly used as an artificial hip joint. However, the inferior tribological properties fall far short of the requirements for biomedical engineering and is harmful to the patients. In this study, cryogenic treatment (CT) was proposed to solve this problem. CT at −196 °C with a soaking time of both 2 h and 72 h were conducted, and their tribological properties were investigated by microstructure observation, Vickers hardness, and wear tests. The results showed that the microstructure of the as-fabricated and cryogenic treated (CTed) for 2 h are mainly composed of acicular martensite (α′ phase). However, the microstructure is transformed into alpha and beta phases after CT for 72 h. Vickers hardness of the specimens as-fabricated, CTed for 2 h and 72 h are 390.79 HV, 388.03 HV, and 371.34 HV, respectively. CT induces a significant improvement in tribological properties, which is correlated with the microstructure evolution. A similar wear mechanism can be observed for the specimens as-fabricated and CTed for 2 h, which is the co-action of severe abrasive wear, adhesive wear, and fatigue wear. While the specimen CTed for 72 h is slight abrasive wear mechanism.

Sub-nano to nanometer wear and tribocorrosion of titanium oxide-metal surfaces by in situ atomic force microscopy

Wear and tribocorrosion of passive oxide film covered metals have been studied at the micro and macroscopic scales. Recent advances in nanotechnology have contributed to breakthroughs in understanding of fundamental friction and wear mechanisms of atomically thin 2D materials at the nanoscale. However, for metals and materials without ultra-flat surfaces, a gap in knowledge exists at or below a few nanometers, which is too small for continuum mechanics theories and experiments including conventional atomic force microscopy (AFM) methods, due to resolution limits arising from surface roughness. Here, we report the near-atomic-scale wear of titanium in air and physiological solution from a single atomic layer to beyond the full oxide thickness using an AFM-based tribology method. Sub-nano to nanometer wear of titanium was revealed with different stages of contact pressure dependent wear regions identified as wear depth increased, featured by a transition from atomic wear (below 2.4 GPa) to elasto-plastic driven wear (above 3.6 GPa) at its oxide thickness (3.8 nm) in air. Higher stress was required to generate a similar wear penetration process in PBS compared to air. Tribocorrosion at this scale was grain orientation and voltage-dependent. Our study opens up a new method to achieve reliable angstrom-level resolution wear quantification to advance the understanding of wear and tribocorrosion of metals at the nanoscale. Statement of significanceExperimental tests of wear for metallic biomaterials at the nanoscale are difficult because engineered metal surfacesare never perfectly atomically flat, limiting the resolution of precise wear measurements to a few nanometers scale or more. To systematically address this problem, we have introduced the AFM ‘image-wear-image’ tribology method and obtained quantitative stress dependent measurement of the near-atomic-scale wear of titanium surfaces in air and tribocorrosion in physiological solution from a single atomic layer to beyond the full oxide film thickness. This allowedto measure sub-nano scale wear by partial removal of oxide. Nanoscale wear has been found to be grain orientation-dependent above the ‘atomic scale’ wear region. The nano-tribocorrosion of CP-Ti across scales and voltage effects on oxides in physiological solution was studied. Our study opens up a new method for future studies to advance the understanding of sub-nanoscale and nanoscale wear and tribocorrosion phenomenon as well as oxide growth mechanism of metallic biomaterials.

Wear detection of WC-Cu based impregnated diamond bit matrix based on SEM image and deep learning

The working efficiency and lifetime of impregnated diamond tools are closely related to their wear conditions, among which different wear modes of the metal matrix play an essential role. Since traditional qualitative description cannot meet the requirement of mathematical relationship establishment, a deep learning method, Mask R-CNN, was applied for the quantitative determination of the matrix wear based on scanning electron microscope (SEM) images. A series of WC-Cu based metal matrix composite (MMC) samples had been prepared by hot-pressed sintering, followed by a pin-on-disc wear test to obtain the wear surface images, and the datasets were established based on a normal wear classification principle where classification is of four basic types: abrasive wear, adhesive wear, fatigue wear and corrosion wear (corrosion wear is not involved in this study). After training, validation, and test based on the SEM wear image datasets, the wear segmentation results from the trained model indicated that Mask R-CNN could automatically identify the wear of metal matrices efficiently and accurately, which was in good agreement with the results obtained by manual labelling. By modifying the algorithm codes, the masks of abrasive, adhesive, and fatigue wear were extracted and counted for model effectiveness evaluation. Moreover, the wear condition values (i.e., wear region areas) obtained from extracted masks would be easily applied for correlation analysis between cutting tool qualities and drilling efficiencies in future research as well. In comparison with statistic results by artificial cognition, the three types of wear showed an average wear region mask IoU over 70%, and an average wear region area loss of less than 3%. In the process of wear detection on similar wear images in published work, the Mask R-CNN model also presented good performances. All related codes and SEM image datasets are available at https://github.com/sunwucheng/IDB_matrix_wear.

High temperature tribological behaviour of additively manufactured tool material for applications in press hardening

In hot sheet metal forming, minimising material transfer and ensuring homogenous cooling of the workpiece are important for quality and productivity reasons. The development of additive manufacturing (AM) opens up possibilities for novel tooling concepts by tailoring the tool material (new chemistries, microstructure, and size/distribution of hard phases) and producing conformal cooling channels. Implementing surface functionality for improved tribological performance is another advantage of AM. Research pertaining to high temperature tribological behaviour of AM tool materials is, however, very limited.The aim of this work is to study the high temperature friction and wear behaviour of AM produced maraging steel and compare this to a conventional hot-work tool steel. The AM maraging steel was post-machined to different surface conditions (milled, ground and shot blasted).The tribological behaviour was evaluated using a hot-strip drawing tribometer and the counter surface was an Al–Si coated 22MnB5 steel. The temperatures of the Al–Si coated steel strips were 600 and 700 °C during the tribological tests.The results have shown that the friction behaviour of the maraging steel and the hot-work tool steel at 600 °C was stable and very similar. At 700 °C, the maraging steel showed more unstable friction and early failure of the tests due to high friction compared to the hot forming tool steel. This was associated with increased material transfer and embedment of FeAlSi intermetallics from the workpiece surface.The maraging steel experienced material removal and development of transfer layers composed of debris from both surfaces in contact. Comparable wear behaviour was observed at both temperatures, but its severity increased with temperature. The milled and ground surfaces showed similar wear mechanisms including ploughing and delamination of material, as well as embedment of FeAlSi particles. The shot blasted surface showed less build-up of transferred material but instead more deformation and folding of asperities leading to entrapment of FeAlSi particles in the near surface region.

Heat treatment effect on the microstructure, mechanical properties, and wear behaviors of stainless steel 316L prepared via selective laser melting

Abstract The influence of heat treatment on the microstructure, mechanical properties, and wear behaviors of stainless steel 316L (SS316L) produced via selective laser melting (SLM) was investigated. The fabricated SLM samples were subjected to two different heat treatments: a typical furnace-type heat treatment conducted at 1100 °C for 0.5 h and hot isostatic pressing performed at 1100 °C and 100 MPa for 1.5 h. High-density SLM samples with low porosities were obtained by increasing the laser power and decreasing the scan speed. The heat treatments of the fabricated SLM samples induced the removal of porosity, cellular microstructure, and dense dislocation structures with a slight increase in grain size. In terms of mechanical properties, the fabricated SLM samples exhibited similar hardness and tensile strength properties to those of the conventional SS316L, while a significantly lower elongation was evident. The heat treatments of the fabricated SLM samples improved elongation, while the surface hardness and tensile strength decreased owing to microstructural evolution. During the pin-on-disk test, the conventional SS316L and fabricated SLM sample exhibited similar wear resistance values, which decreased after the heat treatments of the fabricated SLM samples owing to the heat treatment-induced surface softening.

A novel tester to examine micro-abrasion of materials in oscillating sliding contact – The case study of a total knee replacement biomaterial

Wear of metallic biomaterials is critical in controlling and determining the long-term clinical performance of total joint replacements. Apart of reduced biomaterial's life span by wear, debris can cause hazardous inflammation and damage to the bone supporting the implant. The micro-abrasion tester is broadly used to evaluate wear resistance of biomaterials by the effect of hard debris interacting at the sliding interface. However, this tester is only capable to reproduce micro-abrasion in unidirectional sliding, contrary to that occurring in actual knee joints where sliding is oscillatory. So, micro-abrasion testing under oscillating sliding would be more realistic for this kind of biomedical applications since different sliding motion can promote dissimilar micro-abrasion mechanisms and wear rates. Hence, this paper presents a novel micro-abrasion tester able to reproduce both unidirectional and oscillating sliding modes. To illustrate the methodology using the tester, an ASTM-F1537 CoCrMo alloy against an AISI 52100 steel countersurface was tested under unidirectional and oscillating sliding modes under rolling and grooving abrasion at different loads and sliding distances. The results obtained suggest similar wear rates and patterns for rolling abrasion but different for grooving for both sliding modes. Acceptable reproducibility, accuracy and versatility for micro-abrasion testing under different sliding modes were accomplished with this novel tester.

Influence of Adhesive Layer Thickness on Wear Damage of the Bonded Interface Between Enamel and Composite Inlays

The objective of this study was to evaluate the influence of adhesive layer thickness on wear damage of the bonded interface between enamel and composite inlays using self-adhesive resin cement. Sixty bonded interface samples consisting of four different adhesive layer thicknesses (10 ± 10, 50 ± 10, 100 ± 10 and 150 ± 10 μm) were prepared from resin composite (Tetric N Ceram Bulk Fill; Ivoclar Vivadent AG), self-adhesive resin cement (RelyX U200; 3M ESPE) and tooth enamel. Ball-on-flat sliding wear tests (20 N, 1 Hz, 5 × 104 cycles) were performed on four groups of samples (n = 15). The wear depth and wear track morphology of each sample after 5 × 102, 5 × 103, and 5 × 104 cycles were recorded by white light interferometry and scanning electron microscopy, respectively. Optical microscopy was also used to evaluate cracks and their propagation in the samples. Stress distribution of the interface with four different adhesive layer thickness was analyzed by Finite Element Analysis. All the four groups had similar wear evolution on the bonded interface and the adjacent enamel showed characteristic brittle fracture and microcracks. But the extent of wear damage varied among different groups. The 50 ± 10 μm group owned the slightest damage after 5 × 102, 5 × 103, and 5 × 104 cycles. Stress concentration always happened on the enamel near the interface and thinner adhesive layer owned more stress concentration. In conclusion, for self-adhesive resin cement, 50 ± 10 μm was the best thickness of adhesive layer for the enamel–composite inlay interface from the aspect of tribology.

Tool wear progression of SiAlON ceramic end mills in five-axis high-feed rough machining of an Inconel 718 BLISK

The machining of heat-resistant super alloys such as Inconel 718 is still challenging. Processes are characterized by low productivity and high tool costs compared to the machining of steel or titanium materials. SiAlON ceramics offer potential for productivity increases, but are rarely used in industrial application due to uncertainties regarding the correct machining parameters or applicable tool life criteria. In this study, a complex miniaturized high-pressure compressor blisk component was machined using ceramic end mills for the roughing operation. Based on these experiments, the productivity increase of SiAlON ceramic roughing tools was compared to conventional cemented carbide tools. Additionally, a detailed tool wear analysis was conducted. Thereby, a wear-related tool radius decrease could be observed over the machined volume and a linear approximation could be made. Multiple tools exhibited similar tool wear progression.

Evaluation of contact-wear behavior of lithium disilicate glass ceramic materials; In vitro study

Background: The purpose of this work is to evaluation of contact-wear behavior of lithium disilicate glass ceramic materials under in vitro chewing tests. Methods: Eight specimens of each ceramic materials were exposed contact-wear tests using a computer-controlled chewing simulator (1.2 Hz 50 N bite force loads, 120.000 mechanical cycles, constantly 37 °C temperature immersed in distill water. Al2O3 balls of 6 mm in diameter were used for each chewing test. The mean volume loss of all ceramic specimens after the contact-wear tests was determined with use 3D profilometer. In addition to a random specimen was selected from each test group and scanning electron microscopy (SEM) images were taken for analysis of wear tracks. Results: As a result, the ceramic materials tested in this study showed similar wear behaviors after 120.000 chewing tests. Conclusions: However, it was observed that more particles were carried on the wear surface and occurred micro cracks of the IPS e.max ceramic material. These micro cracks can be the continuation of cracks that occur subsurface of ceramic material.

A comparative study on wear behaviors of hot work and cold work tool steel with same hardness under dry sliding tribological test

Abstract In the present study, two different commercial tool steels SKD-61 and SKD-11 were hardened to attain the similar hardness of 50 HRC (5.51 GPa) and nanoindentaion test was performed to obtain the nanomechanical properties of the hardened steels. Furthermore, wear behavior of these steels were investigated using tribo test with different combination of load and sliding velocity. FE-SEM along with EDS was used to examine the surface morphology of the hardened steels before and after the tribo test. Results showed similar wear behavior at low sliding velocity and low applied load for both the steels but with the increase in sliding velocity beyond 0.20 m/s, the specific wear rate of SKD-11 steel also increases. Whereas, wear of SKD-61 tool steel exhibited no sever changes. Microgroove with plastic deformation, micro cracks, adhesion and oxidation was observed as primary wear mechanism. It can be said that at high load and high sliding velocity, SKD-61exhibits better wear performance than SKD-11 tool steel.

Optimization of abrasive wear behaviour of halloysite nanotubes filled carbon fabric reinforced epoxy hybrid composites

This research article presents the role of halloysite nanotubes (HNTs) incorporated carbon fabric/epoxy under a dry sand three-body abrasive wear (D3BW) condition. HNTs filled carbon fabric/epoxy nanocomposites are structured by hand layup assisted by the vacuum bagging process. The experiments were planned using L16 Taguchi array. The load, abrading distance, and filler loading were considered as a controlling factor. Wear volume loss associated in D3BW with two different sand particles size (212 μm and 425 μm) were investigated. Post-wear surface morphology was observed under the scanning electron microscope, and micro-cutting, and micro-ploughing were predominant. Both 212 μm and 425 μm sand particles had a similar wear volume loss, but, the composites were wear-resistant towards the 425 μm sand particles. Based on the experimental results, analysis of variance and multi-linear regression models, the load, abrading distance, load + abrading and load + filler loading had considerable impact on the abrasive wear on the composites. However, the filler loading had no definite impact on the abrasive wear behaviour.

Tribological investigations of wear resistant layers developed through EDA and WEDA techniques on Ti6Al4V surfaces: Part II – High temperature

This work investigates the potential of electrical discharge machining assisted alloying (EDA) and wire-electrical discharge machining assisted alloying (WEDA) techniques in developing tribo-adaptive layers on Ti6Al4V (Ti64) surfaces. The bare Ti64 (BTi64), electrical discharge machined and alloyed Ti64 (ETi64), and wire-electrical discharge machined and alloyed Ti64 (WETi64) specimens are subject to in-situ wear testing at high-temperature conditions (200 °C, 400 °C, and 600 °C). The SWR and CoF curves of the ETi64 follow reverse trends, with the former demonstrating a decrement with the rise in temperature. The WETi64 specimens develop phenomenal wear resistance at 200 °C and 400 °C (due to excessive formation of protective oxides) but possess similar wear response to that of BTi64 during dry sliding at 600 °C (assisted by layer spalling and delamination). The material removal mechanism of BTi64, ETi64, and WETi64 specimens shift from abrasive wear to delamination, composite wear (abrasive + oxidative) to oxidative wear, and oxidative wear to delamination, respectively, with increment in temperature during dry sliding at low load conditions (50 N). For ETi64, the recast layer (RL) over the substrate aided in achieving improved tribological characteristics by imparting stability to the developed oxides (TiO, TiO2, Ti8O15, and Fe2O3) at elevated temperatures. In the EDA process, the high carbon diffusion into the RL and low cooling rates led to the formation of hard phases in the form of carbides (TiC and Ti24C15) and microstructural transitions to ∝p and α′-phases, respectively, improving the wear-resistant characteristics of the substrate.

A randomised clinical trial of multifocal contact lenses and contact lens discomfort.

To determine how multifocal contact lenses affect contact lens discomfort. This randomised, participant-masked, crossover clinical trial fitted 84 uncomfortable soft contact lens wearers (30-40years old) with single vision and multifocal contact lenses. Contact lens discomfort was assessed using the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8). There was no difference between multifocal and single vision survey scores (p=0.08). There was an interaction between lens type and age group (p=0.05). CLDEQ-8 scores with the single vision lens were less symptomatic than multifocal scores in participants <35years old (p=0.01). Single vision and multifocal scores for the older age group were not different. Subjectively, those in the <35year-old age group preferred the single vision lens for intermediate (p=0.02), distance (p=0.003), and overall vision (p=0.002). In the ≥35year-old age group, no lens was significantly preferred for vision. Participants in the younger age group had more favourable wearing experiences with the single vision lens compared to the multifocal lens. The older age group, however, had similar wearing experiences with both lens types. While younger contact lens wearers may prefer the wearing experience with single vision lenses, some uncomfortable contact lens wearers approaching 40years old may benefit from wearing a multifocal contact lens sooner in life than is typically practised.

Effect of Laser Heat-Treatment and Laser Nitriding on the Microstructural Evolutions and Wear Behaviors of AISI P21 Mold Steel

Laser heat-treatment and laser nitriding were conducted on an AISI P21 mold steel using a high-power diode laser with laser energy densities of 90 and 1125 J/mm2, respectively. No change in surface hardness was observed after laser heat-treatment. In contrast, a relatively larger surface hardness was measured after laser nitriding (i.e., 536 HV) compared with that of the base metal (i.e., 409 HV). The TEM and electron energy loss spectroscopy (EELS) analyses revealed that laser nitriding induced to develop AlN precipitates up to a depth of 15 μm from the surface, resulting in surface hardening. The laser-nitrided P21 exhibited a superior wear resistance compared with that of the base metal and laser heat-treated P21 in the pin-on-disk tribotests. After 100 m of a sliding distance of the pin-on-disk test, the total wear loss of the base metal was measured to be 0.74 mm3, and it decreased to 0.60 mm3 for the laser-nitrided P21. The base metal and laser heat-treated P21 showed similar wear behaviors. The larger wear resistance of the laser-nitrided P21 was attributed to the AlN precipitate-induced surface hardening.

The polyethylene on bone articulation, as occurs with scapular notching, is associated with osteolytic potential

IntroductionScapular notching is a common finding following reverse total shoulder arthroplasty. Severe notching can extend beyond the inferior baseplate screw or post and is therefore unlikely to be the result of isolated mechanical impingement. It is highly likely that the cause of this bone loss is biologically mediated osteolysis, but the driver of this osteolysis is unknown. We completed in vitro polyethylene on bone wear testing, as occurs with scapular notching, to characterize the osteolytic potential of this articulation. MethodsPhysiologically relevant wear testing was performed with 18 polyethylene pins articulating against cortical bone, cancellous bone, and cobalt-chrome pucks. Pins were cycled up to 1,000,000 times, or until failure, and incremental material loss was determined to calculate polyethylene and bone wear rates. Polyethylene particles were extracted from the associated lubricant and evaluated using scanning electron microscopy. To validate the model, wear patterns on polyethylene pins were compared to those on 24 explanted reverse prostheses. ResultsPolyethylene wear rates were significantly higher on cortical bone (3.5-times, P = .040) and cancellous bone (10,700-times, P = .015) than on cobalt-chrome. Cortical bone wear rates decreased over time (P = .003). Electron microscopy demonstrated that polyethylene on cortical and cancellous bone both produced submicron polyethylene particles, the size necessary to induce biologically mediated osteolysis. Analysis of explanted reverse polyethylene components with impingement demonstrated similar wear patterns to what was seen in vitro. ConclusionThe polyethylene on bone articulation, as occurs with scapula notching, has potential to be an osteolytic driver as it is marked by high polyethylene wear rates and produces particles small enough to cause macrophage-mediated osteolysis, as has been demonstrated following total hip arthroplasty. Level of evidenceBasic Science Study

The occlusal wear of ceramic fixed dental prostheses: 3-Year results in a randomized controlled clinical trial with split-mouth design

ObjectivesThis study’s hypothesis was to evaluate differences of the occlusal wear rate for monolithically fabricated lithium disilicate and hand-veneered zirconia crowns in-vivo. Furthermore, a comparison of the materials’ clinical performance according to CDA criteria was investigated. MethodsA total number of 15 patients in the need of full-coverage ceramic fixed dental prosthesis on molars were treated with two crowns each (n = 30), randomly assigned on the contralateral sides made of monolithic IPS e.max CAD (n = 15) and IPS e.max Ceram hand-veneered zirconia (n = 15). Clinical examination was conducted, silicone impressions were taken and plaster models fabricated at the day of crown insertion (baseline) and after 1, 2 and 3 years. The abrasion rate was digitally investigated: after model digitization with the industrial scanner Atos II, each follow-up model was superimposed with the baseline model. The wear was evaluated as the difference between two scans in terms of maximum vertical loss [mm], average decrease [mm] and volume loss [mm³]. For statistical analysis, the Mann–Whitney U test was performed and significance was set to less than 0.05. ResultsIPS e.max CAD crowns showed a volume loss of −0.68 mm³ after three years, while IPS e.max Ceram hand-veneered zirconia crowns showed a volumetric wear of −0.75 mm³ at the same point of time. However, no significant differences were found between both materials regarding the 3 evaluated wear parameters. The survival rate for both materials was 100 % and the clinical performance outcome was good to excellent. ConclusionThe two investigated materials for ceramic fixed dental prostheses showed similar wear rates and clinical performance over an in-vivo use of 3 years. Clinical SignificanceCeramic restorations are subject to occlusal wear over time due to the natural masticatory process. Both monolithic lithium disilicate and glass-ceramic veneered zirconia copings showed clinically satisfactory results over 3 years in-situ. In terms of abrasion, they are equally well suited for clinical use.

A comparison of the dry sliding wear of single-phase f.c.c. carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6 and CoCrFeMnNi high entropy alloys with 316 stainless steel

The dry sliding wear behaviors of the face-centred cubic (f.c.c.) high entropy alloys carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6 and equiatomic CoCrFeMnNi were determined under ambient conditions and compared with that of 316 stainless steel at two sliding velocities and in argon at a slow sliding velocity. Scanning electron microscopy, energy dispersive X-ray spectrometry, electron backscattered diffraction, X-ray photoelectron spectroscopy, and atom probe tomography analyses were employed to characterize the worn microstructures. It was found that in air at the slow sliding velocity of 0.1 m/s C-doped FeNiMnAlCr exhibited a much lower wear rate of 3.0 × 10−5 mm3/N/m compared to either 316 stainless steel (2.9 × 10−4 mm3/N/m) or CoCrFeMnNi (3.4 × 10−4 mm3/N/m). In contrast, both in argon at this slow sliding velocity and in air at the high sliding velocity of 1.0 m/s, all three material showed similar wear rates of ~ (2.4 ± 0.6) × 10−5 mm3/N/m and ~ (1.2 ± 0.3) × 10−5 mm3/N/m, respectively, indicating the strong effect of the environment and pin tip temperature on the wear rates. The oxide that formed on the C-doped FeNiMnAlCr alloy was found to be more stable and durable than that on either the CoCrFeMnNi or on the 316 stainless steel, and the wear debris from C-doped FeNiMnAlCr had the smallest diameter (3 μm) and the lowest oxygen content of 39 at. %. Greater Al2O3 and less Fe2O3, MnOx or Cr2O3 on the worn surface of C-doped FeNiMnAlCr contributed to a peeled-off or delaminated morphology with a higher oxygen content of 46 at. % compared to the worn surfaces of the 316 stainless steel and the CoCrFeMnNi, which both exhibited grooved worn surfaces with lateral cracks and lower oxygen contents of 7.5 at. % and 31 at. %, respectively. The harder Al2O3 oxide film was stable and adherent during wear testing and helped protect the worn pin's tip, which was the reason for the increased wear resistance of the C-doped FeNiMnAlCr. The wear protection mechanism of 316 stainless steel was attributed to a hard mechanically deformed layer, while the CoCrFeMnNi lacked protection from either the oxide film or a hard deformed layer.

Wear behavior and microstructural characterization of translucent multilayer zirconia

ObjectiveTo characterize the composition, microstructure and wear properties of a multilayer translucent zirconia relative to the conventional 3Y-TZP. MethodsTwo types of ceramics were evaluated: a multilayer zirconia (MULTI, IPS e.max ZirCAD Multi, Ivoclar Vivadent) and a control 3Y-TZP (IPS e.max ZirCAD LT, Ivoclar Vivadent). Pre-sintered CAD-CAM blocks were cut, ground, sintered and polished to 1 μm finish. The phase fraction and grain size were measured using XRD and FE-SEM. For wear testing (n = 12), square-shaped specimens (16 × 16 × 1 mm) were adhesively bonded to a dentin analog. Sliding wear tests were performed using a spherical zirconia antagonist (r = 3.15 mm), with 30 N load at 1.5 Hz for 500,000 cycles in water. Optical and scanning electron microscopes and 3D laser scanner were used for quantitative wear analyses. Data were analyzed using Student’s t-test (α = 0.05). ResultsFor MULTI, the enamel layer had the highest cubic content and the largest grain size, followed by the two transition layers, and the dentin layer. 3Y-TZP showed the smallest grain size and cubic content. A significant amount of wear was observed in both materials up to 50,000 cycles until it reached a plateau. MULTI showed higher volume loss and greater wear depth than 3Y-TZP (p < 0.01). The higher volume loss was associated with extensive lateral fracture, leading to material spalling from the surface of cubic-containing zirconias. SignificanceThe wear pattern in multi-layered zirconia was more severe than 3Y-TZP. Additionally, the different layers of the multi-layered zirconia had similar wear behavior.

Flexor Pollicis Longus Tendon Wear Associated With Volar Plating: A Cadaveric Study

This study examined the effect of low-profile volar rim plates (VR), proximally placed standard variable-angle locking plates (pVA-LCP), and distally placed standard variable-angle locking plates (dVA-LCP) on the flexor pollicis longus (FPL) tendon in a cadaver model. We hypothesized that tendons from the VR and pVA-LCP groups would exhibit similar contact pressures, wear patterns, and post-fatigue testing mechanical properties, whereas dVA-LCP tendons would exhibit higher contact pressures, increased tendon wear patterns, and decreased mechanical properties. Nine matched pairs of cadaveric specimens were used in this study. Thin-film pressure sensors were used to measure the initial contact loads between plates and FPL tendons. Specimens were cyclically loaded for 10,000 cycles by actuating the FPL tendon. Cycled tendons were harvested, photographed with a stereomicroscope, and graded for wear on a Likert scale by 5 observers who were blinded to the study protocol. Uniaxial tensile testing measured mechanical properties of the tendon: ultimate failure load, ultimate stress, percent stress relaxation, elastic modulus, and stiffness. With regard to the cadaveric FPL tendon, VR and dVA-LCP had increased contact pressure and tendon wear compared with pVA-LCP. There were no significant differences in contact pressure or tendon wear between dVA-LCP and VR. There was no major difference in the tested mechanical properties of the FPL tendon among any of the groups. Plates placed directly on or beyond the volar rim demonstrate increased contact pressures and increased tendon wear in a cadaveric model. Although low-profile plates allow for fixation of smaller volar fragments in the distal radius, they cause substantial contact with the FPL tendon, which may rupture if the plate is not removed.

Optimized CNN model for identifying similar 3D wear particles in few samples

Typical wear particles can be considered as distinctive indicators of on-going wear faults in machines. However, the small number of samples has limited the identification accuracy for similar fault particles. Besides, the three-dimensional (3D) characterization of wear particles may face huge challenges due to excessive surface parameters. Focusing on the problems of high similarity particles and few samples, a CNN-based particle classification method is developed with an example set of fatigue and severe sliding particles, which are the product of severe wear of machines. For data reduction, imaged 3D particle surfaces are firstly converted into 2D depth maps without losing surface information. Virtual fault particle images are then synthesized using a Conditional Generative Adversarial Networks (CGAN), according to the particle generation mechanism and distinctive particle features. Furthermore, a non-parametric particle identification model is established with the optimization of the CNN structures and training method, and the network is further optimized with the particle image standardization and the network visualization. Validation experiments reveal that the proposed method can accurately identify all tested fatigue and severe sliding particles with their typical characteristics.