Quantitative Wear Analysis Research Articles

Accelerated Wear Test Design Based on Dissipation Wear Model Entropy Analysis under Mixed Lubrication

Theoretical life prediction of tribo-pairs such as seals, bearings and gears with the failure form of wear under mixed lubrication depends on quantitative analysis of wear. Correspondingly, the wear life test depends on an accelerated wear test method to save the time and financial costs. Therefore, the theoretical basis of accelerated test design is a wear model providing a quantitative relationship between equivalents and accelerated test duration. In this paper, an accelerated wear test design method based on dissipation wear model entropy analysis under mixed lubrication is proposed. Firstly, the dissipation wear model under mixed lubrication is verified by standard experiments as a theoretical basis. Then, an accelerated wear test design method is proposed, taking the entropy increase in the dissipation wear model as an equivalent. The verification test shows that 20 times acceleration could be reached by adjustment of the entropy increase rate. The effect of entropy increase rate gradient of duty parameters is also discussed, revealing the fastest acceleration direction. Finally, the advantages and disadvantages of the proposed method are discussed. The results in this paper are expected to contribute to long life predictions of tribo-pairs.

Effects of steel fibres on hammer drilling in concrete for the installation of post-installed anchors

Dispersed short steel fibres can be used as an addition to the concrete matrix as reinforcement to improve the material's macroscopic characteristics such as tensile strength, ductility and toughness. On the other hand, fibres may lead to negative effects in terms of constructability. For post-installed anchors, the tensile performance of the concrete plays a decisive role in certain failure mechanisms, and some fundamental investigations have already been performed in this respect. Studies on the influence of steel fibres on drilling and the respective installation have not been presented yet, although the installation quality is very significant for the fastener's load-bearing performance. This study aims to provide insight into the bearing interface characteristics of post-installed anchors and the boreholes in steel fibre-reinforced concrete generated by hammer drilling. This interface is of high importance for the performance of anchorages in special concrete composites such as steel fibre-reinforced concrete. To investigate this aspect, the research investigation is based on a combination of sophisticated but practical experimental methods ranging from drilling tool performance monitoring, qualitative and quantitative wear analysis of the borehole, optical and scanning electron microscopy of the inner borehole surface. The studies yield original findings on the interaction between drilling equipment and steel fibre-reinforced concrete in the context of the installation of post-installed anchors.

Wear and damage in retrieved humeral inlays of reverse total shoulder arthroplasty-where, how much, and why?

Polyethylene (PE) wear and material degradation have been reported as complications in reverse total shoulder replacements (rTSAs). In this regard, scapular notching is associated with more clinical complications. Therefore, the purposes of the study were to quantify the linear and volumetric wear, as a measure for the amount of removed material, and to qualitatively assess the PE damage modes to describe the material degradation in retrieved rTSA humeral PE inlays that contribute to failure of shoulder replacements. Furthermore, this study aimed to evaluate the effect of scapular notching on PE wear and rim damage of the humeral components. The total study population of 39 humeral inlays contains 2 cohorts that were used for the damage mode analysis and for the wear analysis, respectively. The extent and presence of wear damage modes in 5 defined zones were assessed by a grading system for all PE joint replacements. For quantitative wear analysis the most frequent design (n = 17) was chosen. Using a coordinate-measuring machine and postprocessing software, volumetric wear measurements for the retrieved humeral PE inlays were undertaken. Furthermore, prerevision radiographs were analyzed for scapular notching. Finally, retrieval findings were correlated with clinical and radiographic data to consider the effect of notching and to identify risk of failures for these prostheses. Damage on the rim of the humeral PE inlays was more frequent and severe than on the intended articulation surface. Irrespective of the damage mode, the inferior rim zone sustained the greatest amount of wear damage followed by the posterior zone. Burnishing, scratching, pitting, and embedded particles are most likely to occur in the articular surface area, whereas surface deformation, abrasion, delamination and gross material degradation are predominantly present in the inferior and posterior rim zones. The retrieved inlays exhibited a mean volumetric wear rate of 296.9 mm³/yr ± 87.0 mm³/yr. However, if the notched and non-notched components were compared, a significant higher volumetric wear rate (296.5 ± 106.1 mm³/yr) was found for the notched components compared to the non-notched group (65.7 ± 7.4 mm³/yr). Generally, there was a significantly greater incidence of damage and greater amount of wear if scapular notching occurred. The notched components showed a 5-fold increase in PE wear rate. Therefore, scapular notching has a strong effect on PE damage and wear. If scapular notching can be clinically avoided, the PE wear performance is in a similar magnitude as found for hip and knee replacements.

Quantitative wear analysis of H13 steel tool during friction stir welding of Cu-0.8%Cr-0.1%Zr alloy

Joining of high strength materials using friction stir welding (FSW) is difficult due to severe tool wear and change in the shape/size of the tool. However, quantitative understanding of tool wear during FSW of high melting point metallic materials is very limited. Here we present quantitative wear analysis of H13 steel tool during FSW of CuCrZr alloy. Higher amount of total tool wear is observed for faster tool rotational speeds, and slower traverse speeds. Progressive wear rate shows similar relationship with these process parameters during initial traverse stage. With further tool traverse the wear rate decreases significantly and is not much affected by the process parameters. The quantitative wear study provides insights about tool wear during FSW process and would be useful to better estimate and improve tool life. This would also be helpful to optimize the process parameters and tool shape to reduce tool wear during FSW of high strength materials.

Evaluation of mechanical and optical behavior of current esthetic dental restorative CAD/CAM composites

ObjectivesTo determine the mechanical and optical properties of CAD/CAM composites (LAVA Ultimate, Cerasmart, Shofu Block and two exp. CAD/CAM composites), a hybrid material (VITA Enamic), a leucite (IPS Empress CAD) and a lithium disilicate glass-ceramic (IPS e.max CAD). Materials and methodsThree-point flexural strength (FS) was investigated according ISO 6872:2008 (N=240/n=30). Two-body wear (TBW) was analyzed in a chewing simulator (1,200,000 cycles, 50N, 5°/55°C) using human teeth as antagonists (N=120/n=15). Quantitative analysis of wear was carried out with a 3D-scanner and associated matching software. Discoloration rate (DR) after 14 days of storage in cress, curry, red wine, and distilled water (N=384/n=12), and translucency (T) (N=384/n=48) of CAD/CAM materials were measured in a spectrophotometer (400–700nm wavelength). Data were analyzed using two-/one-way ANOVA with Scheffé post-hoc test, Kruskal–Wallis-H test, and linear mixed models (α=0.05). ResultsIPS e.max CAD showed the highest FS (p<0.001), followed by LAVA Ultimate; however, not different from the remaining CAD/CAM composites (exception: Shofu Block). The lowest FS showed VITA Enamic and IPS Empress CAD (p<0.001). IPS Empress CAD, VITA Enamic, exp. CAD/CAM composite 2, followed by IPS e.max presented lower material TBW than the remaining CAD/CAM materials (p<0.001). The highest antagonist wear was observed for the tested glass-ceramics and the hybrid material (p<0.001). Storage medium (red wine>curry>cress>distilled water) exerted the highest influence on DR (p<0.001), closely followed by CAD/CAM material. Glass-ceramics showed lower DR than CAD/CAM composites (p<0.001). ConclusionsCAD/CAM composites presented moderate FS, high T and antagonist friendly behavior. Glass-ceramic demonstrated the most favorable DR and lowest TBW on the material side.

WEAR BEHAVIOUR AND SURFACE ROUGHNESS OF POLYMER INFILTRATED CERAMIC MATERIAL COMPARED TO PRESSABLE GLASS CERAMIC

Abstract: Introduction: Multiple restorative materials with various chemical, mechanical and physical characteristics are used as permanent dental restorations. The appropriate selection of a restorative material is crucial for preserving the occlusal harmony and normal masticatory function. Several aspects during selection of restorative materials should be considered, among which are the wear behaviour and abrasive nature of the restorative materials and natural enamel. Objectives: The study determines the two-body wear and surface roughness measurement, of polymer infiltrated ceramic (Vita Enamic) and pressable lithium disilicate based ceramic (IPS e.max press). Materials and methods: Two-body wear was investigated in custom made tooth wear brushing machine (60,000 cycles, 20 N and 60 cycle/min). The test specimens were divided into two groups, each group consisted of 8 ceramic specimens and 8 enamel cusp antagonists. Quantitative analysis of wear was carried out with subtractive weight loss of all specimens before and after wear test. Surface roughness measurements were evaluated before and after the wear test using a white light interference microscope. The data was collected and statistically analyzed using Mann-Whitney (U) test. Results: Statically significant differences were found for two-body wear, with Vita Enamic samples show lower wear loss than IPS e.max press samples and cause less enamel wear loss. The Vita Enamic showed lower surface roughness and caused less surface roughness to enamel cusp antagonist than IPS e.max press samples. Conclusions: Vita Enamic revealed lower wear loss contributed by terms of weight loss and surface roughness change than IPS e.max press. IPS e.max press contributed to more surface roughness and wear loss of opposing enamel than Vita Enamic. Keywords: CAD/CAM - Two-body wear - Tooth brushing wear - Surface Roughness

Wear characteristics of current aesthetic dental restorative CAD/CAM materials: Two-body wear, gloss retention, roughness and Martens hardness

ObjectivesThis study determined the two-body wear and toothbrushing wear parameters, including gloss and roughness measurements and additionally Martens hardness, of nine aesthetic CAD/CAM materials, one direct resin-based nanocomposite plus that of human enamel as a control group. Materials and methodsTwo-body wear was investigated in a computer-controlled chewing simulator (1.2 million loadings, 49N at 1.7Hz; 3000 thermocycles 5/50°C). Each of the 11 groups consisted of 12 specimens and 12 enamel antagonists. Quantitative analysis of wear was carried out with a 3D-surface analyser. Gloss and roughness measurements were evaluated using a glossmeter and an inductive surface profilometer before and after abrasive toothbrushing of machine-polished specimens. Additionally Martens hardness was measured. Statistically significant differences were calculated with one-way ANOVA (analysis of variance). ResultsStatistically significant differences were found for two-body wear, gloss, surface roughness and hardness. Zirconium dioxide ceramics showed no material wear and low wear of the enamel antagonist. Two-body wear of CAD/CAM-silicate and -lithium disilicate ceramics, -hybrid ceramics and -nanocomposite as well as direct nanocomposite did not differ significantly from that of human enamel. Temporary polymers showed significantly higher material wear than permanent materials. Abrasive toothbrushing significantly reduced gloss and increased roughness of all materials except zirconium dioxide ceramics. Gloss retention was highest with zirconium dioxide ceramics, silicate ceramics, hybrid ceramics and nanocomposites. Temporary polymers showed least gloss retention. Martens hardness differed significantly among ceramics, between ceramics and composites, and between resin composites and acrylic block materials as well. ConclusionsAll permanent aesthetic CAD/CAM block materials tested behave similarly or better with respect to two-body wear and toothbrushing wear than human enamel, which is not true for temporary polymer CAD/CAM block materials. Ceramics show the best gloss retention compared to hybrid ceramics, composites and acrylic polymers.

The development of quantitative methods using virtual models for the measurement of tooth wear

Tooth wear is an unavoidable process associated with aging. Currently, virtual three-dimensional dental models are widely used and provide an advantage for studying tooth wear. However, there are no wear assessment parameters using virtual tooth models for the quantitative analysis of wear. Therefore, the aim of this study is to develop and evaluate quantitative wear measurement parameters. Ninety maxillary and mandibular dental casts were prepared and rendered as virtual three-dimensional models. For qualitative wear scoring, Hooper's new tooth wear index (NTWI) was used. For quantitative wear measurement, virtual vectors and occlusal planes were generated with reference points. Angles, height, and distance parameters were measured from reference points, vectors or planes. Intra- and interobserver reproducibility was determined for NTWI scoring and quantitative measurements. Quantitatively measurements for all parameters were subgrouped according to age groups and NTWI score groups. The mean and standard deviation were calculated for each group. One-way analysis of variance (ANOVA) test and the coefficients test were performed on the groups. Overall, intra- and interobserver reproducibility was good for both qualitative and quantitative measurement. In the ANOVA test, angle and height parameters showed significant differences between groups, whereas distance parameters did not. Similar results were observed in the coefficients test. However, plane heights and lingual side measurement parameters of the mandible are not recommended. In conclusion, this study indicates that all angle or height parameters of the maxilla and angle or vector height parameters of the buccal side of the mandible can be used as meaningful parameters in a quantitative wear study.

Digital photogrammetry for quantitative wear analysis of retrieved TKA components

The use of new materials in knee arthroplasty demands a way in which to accurately quantify wear in retrieved components. Methods such as damage scoring, coordinate measurement, and in vivo wear analysis have been used in the past. The limitations in these methods illustrate a need for a different methodology that can accurately quantify wear, which is relatively easy to perform and uses a minimal amount of expensive equipment. Off-the-shelf digital photogrammetry represents a potentially quick and easy alternative to what is readily available. Eighty tibial inserts were visually examined for front and backside wear and digitally photographed in the presence of two calibrated reference fields. All images were segmented (via manual and automated algorithms) using Adobe Photoshop and National Institute of Health ImageJ. Finally, wear was determined using ImageJ and Rhinoceros software. The absolute accuracy of the method and repeatability/reproducibility by different observers were measured in order to determine the uncertainty of wear measurements. To determine if variation in wear measurements was due to implant design, 35 implants of the three most prevalent designs were subjected to retrieval analysis. The overall accuracy of area measurements was 97.8%. The error in automated segmentation was found to be significantly lower than that of manual segmentation. The photogrammetry method was found to be reasonably accurate and repeatable in measuring 2-D areas and applicable to determining wear. There was no significant variation in uncertainty detected among different implant designs. Photogrammetry has a broad range of applicability since it is size- and design-independent. A minimal amount of off-the-shelf equipment is needed for the procedure and no proprietary knowledge of the implant is needed.

Wear and fatigue in rolling contact

Researches on wear and fatigue in rolling contact from a tribological viewpoint are introduced. Transmission of traction and accompanying microslip in the contact region play critical roles in these phenomena. First, a quantitative analysis of wear in rolling contact with microslip is introduced, and it is shown that a simplified microslip theory can explain its behavior. Second, a marked change in contact fatigue life with traction is demonstrated, and a theory is introduced which relates the fatigue life with cumulative shear strain in the subsurface.

Tibial post wear in posterior stabilized total knee arthroplasty. An unrecognized source of polyethylene debris.

With extensive use of posterior stabilized total knee arthroplasty implants, it is increasingly important to assess the mechanical performance of this design alternative. The purpose of this study was to examine the wear patterns at the femoral cam-tibial post interface in a series of posterior stabilized prostheses retrieved at revision arthroplasty. Qualitative and quantitative wear analysis was performed over the surface of the stabilizing posts from twenty-three retrieved total knee components that had been implanted for a mean of 35.6 months (range, 2.3 to 107.2 months). The implants were designs from four different manufacturers. Digital images of the anterior, posterior, medial, and lateral surfaces of the tibial post were made for quantitative analysis and determination of a post wear score. Wear was characterized with a grading system that isolates adhesive, abrasive, and fatigue wear, inferring a weighted score from an estimation of generated polyethylene debris. Evidence of wear or damage was observed on all twenty-three of the stabilizing posts, including those revised because of infection. On the average, 39.9% (range, 18.5% to 60%) of the post surface demonstrated some form of deformation, with adhesive wear, or burnishing, being the predominant wear mechanism. Seven posts (30%) exhibited severe damage with gross loss of polyethylene. The wear caused premature failure and early revision of two components: one of these failures was related to isolated post wear and the other, to severe post wear and subsequent fracture. Overall, wear was primarily posterior, but wear over the anterior, medial, and lateral surfaces was also notable. The cam-post articulation in posterior stabilized implants can be an additional source of polyethylene wear debris. The variability in wear patterns observed among designs may be due to differences in cam-post mechanics, post location, and post geometry. The surgeon should be aware that the cam-post interface is not an innocuous articulation, and manufacturers should be motivated to produce implants that maintain the function of the post while limiting wear and surface damage.

Quantitative wear analysis using atomic force microscopy

A new method is presented to measure the volume of locally restricted topographical changes on surfaces due to wear with ultra-high precision. For this purpose a so-called stand-alone atomic force microscope (AFM) is used in combination with a special sample holder that allows to observe the same section of the sample surface before and after tribological stressing in a conventional tribometer. Exceeding the resolution limits of standard profilometry by far, the AFM can be used for quantifying smallest wear events and gives new insights in the details of the tribological process. As examples, measurements of hardness indentations on a Si wafer, as well as wear events due to sliding motion on an AuNi coating and filled polymers for electrical contact systems are shown. In addition, some practical aspects such as avoiding measurement errors and possible applications are discussed in detail.