Variations in the microstructure and the dominant fretting wear mechanisms of carbon steel alloy in oscillatory sliding contact against stainless steel in a dry atmosphere were evaluated by various mechanical testing and microanalytical methods. These included scanning electron microscopy and energy dispersive spectrometry with corresponding elemental maps of the wear tracks, in conjunction with cross-sectional transmission electron microscopy of samples prepared by focused ion beam machining to assess subsurface and through-thickness changes in microstructure, all as a function of applied load and sliding time. Heavily dislocated layered microstructures were observed below the wear tracks to vary with both the load and sliding time. During the accumulation of fretting cycles, the subsurface microstructure evolved into stable dislocation cells with cell walls aligned parallel to the surface and the sliding direction. The thickness of the damaged subsurface region increased with the load, consistent with the depth distribution of the maximum shear stress. The primary surface oxide evolved as Fe2O3 and Fe3O4 with increasing sliding time, leading to the formation of a uniform oxide scale at the sliding surface. It is possible that the development of the dislocation cell structure in the subsurface also enhanced oxidation by pipe diffusion along dislocation cores. The results of this study reveal complex phase changes affecting the wear resistance of steels undergoing fretting wear, which involve a synergy between oxidative wear, crack initiation, and crack growth along dislocation cell walls due to the high strains accumulating under high loads and/or prolonged surface sliding.

This data article describes the extensive experimental dataset of friction hysteresis measured during the round robin test of the original research article [1]. The round robin test was performed on the two different fretting rigs of Imperial College London and Politecnico di Torino, and consisted of recording comparable friction hysteresis loops on specimen pairs manufactured from the same batch of raw stainless steel. The reciprocating motion of the specimens was performed at room temperature under a wide range of test conditions, including different normal loads, displacement amplitudes, nominal areas of contact and excitation frequencies of 100 Hz and 175 Hz. Friction forces and tangential relative displacements for each specimen pair were recorded and stored as hysteresis raw data. Each hysteresis loop was post-processed to extract friction coefficient, tangential contact stiffness and energy dissipated, whose evolution with wear was thus obtained and stored as well. MATLABⓇ scripts for post-processing and plotting data are included too. The dataset can be used by researchers as a benchmark to validate theoretical models or numerical simulations of friction hysteresis models and wear mechanisms, and also to study the physics of friction hysteresis and its contact parameters. This friction data can also be used as input in models for nonlinear dynamics applications as well as to provide information on the contact measurement uncertainty under fretting motion. Other applications include using this data as a training set for machine learning applications or data-driven models, as well as supporting grant applications.

Additive manufacturing (AM) of orthopedic implants has increased in recent years, providing benefits to surgeons, patients, and implant companies. Both traditional and new titanium alloys are under consideration for AM-manufactured implants. However, concerns remain about their wear and corrosion (tribocorrosion) performance. In this study, the effects of fretting corrosion were investigated on AM Ti-29Nb-21Zr (pre-alloyed and admixed) and AM Ti-6Al-4V with 1% nano yttria-stabilized zirconia (nYSZ). Low cycle (100 cycles, 3 Hz, 100 mN) fretting and fretting corrosion (potentiostatic, 0 V vs. Ag/AgCl) methods were used to compare these AM alloys to traditionally manufactured AM Ti-6Al-4V. Alloy and admixture surfaces were subjected to (1) fretting in the air (i.e., small-scale reciprocal sliding) and (2) fretting corrosion in phosphate-buffered saline (PBS) using a single diamond asperity (17 µm radius). Wear track depth measurements, fretting currents and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis of oxide debris revealed that pre-alloyed AM Ti-29Nb-21Zr generally had greater wear depths after 100 cycles (4.67 +/- 0.55 µm dry and 5.78 +/- 0.83 µm in solution) and higher fretting currents (0.58 +/- 0.07 µA). A correlation (R2 = 0.67) was found between wear depth and the average fretting currents with different alloys located in different regions of the relationship. No statistically significant differences were observed in wear depth between in-air and in-PBS tests. However, significantly higher amounts of oxygen (measured by oxygen weight % by EDS analysis of the debris) were embedded within the wear track for tests performed in PBS compared to air for all samples except the ad-mixed Ti-29Nb-21Zr (p = 0.21). For traditional and AM Ti-6Al-4V, the wear track depths (dry fretting: 2.90 +/- 0.32 µm vs. 2.51 +/- 0.51 μm, respectively; fretting corrosion: 2.09 +/- 0.59 μm vs. 1.16 +/- 0.79 μm, respectively) and fretting current measurements (0.37 +/- 0.05 μA vs. 0.34 +/- 0.05 μA, respectively) showed no significant differences. The dominant wear deformation process was plastic deformation followed by cyclic extrusion of plate-like wear debris at the end of the stroke, resulting in ribbon-like extruded material for all alloys. While previous work documented improved corrosion resistance of Ti-29Nb-21Zr in simulated inflammatory solutions over Ti-6Al-4V, this work does not show similar improvements in the relative fretting corrosion resistance of these alloys compared to Ti-6Al-4V.

UNASSIGNED: Corrosion at the head-neck junction of femoral stems is a rare complication of total hip arthroplasty (THA) with manifestations ranging from subclinical wear to failure. Prior studies have identified a single femoral component design with an increased propensity for catastrophic trunnion failure. The purpose of the present study was to quantify trunnion damage of this femoral component retrieved from patients undergoing revision THA for non-trunnionosis indications.
UNASSIGNED: 24 femoral components from a single manufacturer were identified for study inclusion. Each prosthesis underwent stereomicroscopic inspection. Corrosion and fretting scores were assigned per the Goldberg criteria to quadrants of the trunnion. Material loss was calculated based on cone angles across trunnion quadrants. This was carried out using a coordinate measuring machine that digitised each trunnion surface. Stems were compared to a series of femoral stems with the same trunnion design.
UNASSIGNED: 20 of the 24 (83%) trunnions demonstrated corrosion, all 24 trunnions demonstrated fretting. Corrosion scores did not statistically differ with respect to trunnion zone (p = 0.53), while fretting scores were higher in the inferior compared to the superior zones (p < 0.001). There was no significant difference in cone angles assessing material loss between stems (p = 0.25).
UNASSIGNED: Evidence of trunnion damage was observed in each stem retrieved for non-trunnionosis revision. Fretting occurred more frequently about the inferior quadrants. However, digitised trunnion shapes were similar between compared stems exhibiting no material loss. Therefore, it is possible that previous reports of trunnion failures for this implant are not a systemic issue, and that further investigation is required.

In applications involving fretting wear damage, surfaces with high yield strength and wear resistance are required. In this study, the mechanical responses of materials with graded nanostructured surfaces during fretting sliding are investigated and compared to homogeneous materials through a systematic computational study. A three-dimensional finite element model is developed to characterize the fretting sliding characteristics and shakedown behavior with varying degrees of contact friction and gradient layer thicknesses. Results obtained using a representative model material (i.e., 304 stainless steel) demonstrate that metallic materials with a graded nanostructured surface could exhibit a more than 80% reduction in plastically deformed surface areas and volumes, resulting in superior fretting damage resistance in comparison to homogeneous coarse-grained metals. In particular, a graded nanostructured material can exhibit elastic or plastic shakedown, depending on the contact friction coefficient. Optimal fretting resistance can be achieved for the graded nanostructured material by decreasing the friction coefficient (e.g., from 0.6 to 0.4 in 304 stainless steel), resulting in an elastic shakedown behavior, where the plastically deformed volume and area exhibit zero increment in the accumulated plastic strain during further sliding. These findings in the graded nanostructured materials using 304 stainless steel as a model system can be further tailored for engineering optimal fretting damage resistance.

BACKGROUND: Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems.
METHODS: Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information.
RESULTS: In this series, 158 of explants were from female patients (male = 107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P < .001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P < .001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P < .001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P = .002).
CONCLUSIONS: In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings.

Artificial intelligence (AI) is used in the clinic to improve patient care. While the successes illustrate AI\'s impact, few studies have led to improved clinical outcomes. In this review, we focus on how AI models implemented in nonorthopedic fields of corrosion science may apply to the study of orthopedic alloys. We first define and introduce fundamental AI concepts and models, as well as physiologically relevant corrosion damage modes. We then systematically review the corrosion/AI literature. Finally, we identify several AI models that may be implemented to study fretting, crevice, and pitting corrosion of titanium and cobalt chrome alloys.

Within modular taper junctions of total hip implants (THA), nominally \"smooth\" metallic surfaces contain multiple micro-asperities that slide, are plastically deformed, have their oxide film surfaces disrupted and corrode during the fretting corrosion processes. In this work, a mass/volume balance approach is developed and used to assess the contribution of individual components of wear and corrosion to the entirety of the single-asperity tribocorrosion process for the popular THA alloy, Ti-6Al-4V. This analysis measures the total volume change (trough) in the surface due to low cycle single asperity fretting corrosion and compares it to the measured pileup volume which is comprised of plastic deformation, metal particles and oxide particles, plus the fretting current and the concentration of solution-bound species. A simple 17 μm spherical geometry diamond asperity was used and the trough volume, pileup volume, fretting currents and ion concentrations were measured to assess their contribution to the fretting corrosion process. The effects fretting in or out of solution (phosphate buffered saline), and the role of electrode potential, e.g., freely corroding or forced potential (-1.0 V, 0 V, and +1.0 V vs Ag/AgCl) were investigated. Under constant 30 mN loading, 100 cycles duration, 3 Hz cyclic frequency and 80 μm sliding amplitude, the volume abraded, fretting currents, ion release, and pileup volume were all recorded. Damage was analyzed and quantified using digital optical microscopy (DOM), atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and inductive coupled plasma mass spectrometry (ICP-MS). The results were analyzed with ANOVA statistics (α = 0.05). The extent of wear damage (asperity trough volume) is as follows: air = Ecorr, air > -1.0 V = 0 V = +1.0 V. As the amount of pileup volume decreased between conditions, visible oxide generation increased, with V > 0 V having more oxide debris generation and air fretting resulting in the least oxide (and most plastic deformation). Ions in solution were not significant, accounting for less than 1% of the damage. Volume analysis showed trough volumes and pileup volumes were very close to one another and were dominated by plastic deformation. Synergy between wear and corrosion were not observed in this work.

BACKGROUND: Morse taper junction tribocorrosion is recognized as an important failure mode in total hip arthroplasty. Although taper junctions are used in almost all shoulder arthroplasty systems currently available in the United States, with large variation in design, limited literature has described comparable analyses of taper damage in these implants. In this study, taper junction damage in retrieved reverse total shoulder arthroplasty (RTSA) implants was assessed and analyzed.
METHODS: Fifty-seven retrieved RTSAs with paired baseplate and glenosphere components with Morse taper junctions were identified via database query; 19 of these also included paired humeral stems and trays or spacers with taper junctions. Components were graded for standard damage modes and for fretting and corrosion with a modified Goldberg-Cusick classification system. Medical records and preoperative radiographs were reviewed. Comparative analyses were performed assessing the impact of various implant, radiographic, and patient factors on taper damage.
RESULTS: Standard damage modes were commonly found at the evaluated trunnion junctions, with scratching and edge deformation damage on 76% and 46% of all components, respectively. Fretting and corrosion damage was also common, observed on 86% and 72% of baseplates, respectively, and 23% and 40% of glenospheres, respectively. Baseplates showed greater moderate to severe (grade ≥ 3) fretting (43%) and corrosion (27%) damage than matched glenospheres (fretting, 9%; corrosion, 13%). Humeral stems showed moderate to severe fretting and corrosion on 28% and 30% of implants, respectively; matched humeral trays or spacers showed both less fretting (14%) and less corrosion (17%). On subgroup analysis, large-tapered implants had significantly lower summed fretting and corrosion grades than small-tapered implants (P < .001 for both) on glenospheres; paired baseplate corrosion grades were also significantly lower (P = .031) on large-tapered implants. Factorial analysis showed that bolt reinforcement of the taper junction was also associated with less fretting and corrosion damage on both baseplates and glenospheres. Summed fretting and corrosion grades on glenospheres with trunnions (male) were significantly greater than on glenospheres with bores (female) (P < .001 for both).
CONCLUSIONS: Damage to the taper junction is commonly found in retrieved RTSAs and can occur after only months of being implanted. In this study, tribocorrosion predominantly occurred on the taper surface of the baseplate (vs. glenosphere) and on the humeral stem (vs. tray or spacer), which may relate to the flexural rigidity difference between the titanium and cobalt-chrome components. Bolt reinforcement and the use of large-diameter trunnions led to less tribocorrosion of the taper junction. The findings of this study provide evidence for the improved design of RTSA prostheses to decrease tribocorrosion.

Material wear caused by relative micromotion of multi-part orthopaedic implants can impact physiology near the implant site and ultimately lead to revision surgery. Cryogenic Thermal Cycling (CTC) is a process that refines and stabilizes the crystal lattice structure of materials by introducing them to temperature modulation cycles that include extremely low temperatures. This method has been proven to significantly improve the performance and wear life capabilities of mechanical components in an efficient, sterile and non-polluting process. This technical note is aimed to evaluate the impact of CTC on wear resistance at head-neck taper connections used in total hip arthroplasty (THA).
Mock up components (heads and trunnions) using the same materials representative of THA implants were manufactured for this study. Components were placed into a custom-designed cooling chamber in which they underwent CTC. Short-term Incremental Cyclic Fretting Corrosion (ICFC) testing was conducted on thermally cycled and control (untreated) components, subjected to a full simulated gait with periodically increasing incremental peak loads (modified BioPuls Dual Station ASTM Hip Simulator). Corrosion-related electrical activity was measured for samples with and without CTC. A long-term wear test was also conducted to evaluate corrosion and fretting under double peak compression loading (no rotation).
From the short-term tests, samples that underwent CTC showed a significantly reduced corrosion current at the maximum testing compression load of 3,300 N (p = 0.048). The elevated corrosion onset load seen in the treated components did not reach significance (p = 0.152) and no significant difference in the mean change in open circuit potential (OCP) was observed (p = 0.471). Longer-term wear testing found variable differences in CTC and control components with respect to damaged surface areas.
CTC was shown to be a viable method to reduce short-term corrosion-related electrical activity in THA head-neck taper connections. While consistent differences were not seen in longer-term measures of corrosion, further study is warranted to evaluate the potential of CTC in the context of reducing wear in modular THA implants.