Fretting Behavior Research Articles

Experimental investigation on acoustic emission in fretting friction and wear of bolted joints

Fretting between bolted interfaces may change the dynamic characteristics of structures under vibration loading. The acoustic emission (AE) technique has been successfully used to investigate friction and wear mechanisms between different kinds of contact pairs. This paper experimentally investigates the AE signals of a bolted joint structure during friction and long-time fretting wear to explore the relationship between AE characteristics and interface fretting behaviors. A test apparatus dedicated to the study of fretting behaviors of bolted joints together with an AE acquisition system is used to carry out the experimental tests. Relative displacement, tangential friction force and the related AE waveform features are obtained simultaneously to better relate acoustic emission signals with hysteresis loops. The effects of external excitation amplitude and fretting wear cycles are investigated. The frequency signatures of the individual burst acoustic emission event under different excitation amplitudes and wear stages are analyzed. Results show that AE events mainly occur in the micro-slip and the gross-slip regime, and AE technique is more sensitive to the transition point from micro-slip to gross-slip regime. As the external excitation amplitude increases, the value of most AE parameters is gradually increased. As the fretting wear cycles increase, evolutions of bolt preload, frictional coefficients, and AE parameters first show a significant change and then become asymptotically stable. Furthermore, the frequency intensity and range will increase with the increase of excitation amplitude and decrease with the wear cycles.

Study on improving fretting wear properties of AISI 4135 steel via diverse surface modifications under grease lubrication

To alleviate the fretting damage of the locking pin in variable-gauge train, the substrate (AISI 4135 steel) was surface-treated with laser quenching (LQ), plasma nitriding (PN), and bonded MoS2 coating respectively. Their fretting behavior and wear mechanism under grease lubrication conditions were experimentally analyzed. The results indicated that the two surface strengthening measures (LQ and PN) significantly improved the wear resistance of the substrate. The lowest energy dissipation occurs on the bonded MoS2 coating, but its low surface hardness results in the largest abrasion loss. Furthermore, a high-hardness and rough Fe–N compound layer was generated on the PN-treated surface, which is conducive to the formation of synergistic lubrication at the contact interface with grease, and had the optimum effect of reducing fretting damage. This study provides solutions and application reference for the surface engineering protection of similar mechanical components in the engineering field.

Fretting Wear and Scratch Resistance of Cold-Sprayed Pure Cu and Ti

The paper analyses the fretting and wear behavior of pure copper and pure titanium coatings realized through cold spray. The coatings were designed and produced by employing processing conditions leading to minimum porosity and high hardness; these conditions were 700 °C and 40 bar for Ti powders and 400 °C and 30 bar for Cu ones. The low porosity and high strength materials led to high resistance to wear damaging through the optimal energy dissipation upon fretting. Due to the sprayed particles deformation mode, the sprayed materials show non-uniform hardening along the deposition distance. As a matter of fact, hardness varied in the range 3.7–4.2 GPa for Ti coatings and 1.5–2 GPa for the Cu ones depending on the distance from the substrate and on the coatings thickness. This influenced the materials properties and the response to the wear damaging. This was demonstrated by the scratch tests performed on coatings with different thicknesses. Those coatings sprayed in major thickness revealed the best wear resistance due to the deformation hardening. The harder coatings also revealed brittle fracture at the experienced highest loads.

Wear and Fretting Behavior of Cold Sprayed IN625 Superalloy

The wear and fretting behaviour of IN625 cold spray coatings was analysed and the results are presented. The cold spray conditions were selected in order to obtain coatings with minimum porosity and maximum particles splat. This leads to compact and hard deposited material able to resist wear damaging and to dissipate energy during fretting. The coating’s strength was evaluated through nanoindentation that revealed an increased hardness from the surface toward the substrate. This different hardening behaviour from the coating surface toward the substrate leads to increased resistance to fretting and wear as the maximum stresses increase. This was revealed by scratch tests performed at linearly increasing loads that allowed identifying of the damage mechanisms acting on the coating as the triaxial stresses increase. The hardening behaviour of the coating also influenced the fretting behaviour revealed by the weight loss experienced by varying the fretting maximum load.

Fretting cracking behavior of nub of last-stage blade for steam turbine

Nub-and-sleeve of last-stage blade for steam turbine is a part-span damper. The nub is vulnerable to fretting cracking since it is in contact with the sleeve under centrifugal force, and a small-amplitude oscillatory movement occurs at the nub-sleeve contact interface due to the blade vibration during operation of turbine. The present study developed a rig test that mimics fretting behavior at the nub-sleeve contact interface and reproduces fretting cracking of the nub. The rig tests reveal that fretting cracking occurs if the contact interface is in partial slip state and the tangential contact force amplitude is sufficiently large. The minimum tangential contact force amplitude for cracking increases with the normal contact force. Moreover, under the partial slip condition, the tangential contact force amplitude increases with the imposed displacement amplitude and its maximum value increases with the normal contact force.

Fretting Behavior of Thermoplastic Polyurethanes

Fretting tests were conducted with five different thermoplastic polyurethanes against a steel ball. Their fretting behaviors were investigated under various test parameters, such as normal load and displacement amplitude. In order to test the sliding performances, tribological tests were conducted using a ring-on-disc setup. The results show that their fretting behaviors can be related to the dynamic mechanical properties, which were characterized by dynamic mechanical analysis (DMA). The three fretting regimes were identified by means of hysteresis and wear scar analysis. In addition, investigations were carried out until the transition regimes occurred. Different wear processes were revealed for each of the three regimes. Differences were identified using dissipated energy. The profiles of wear scars and the counterparts were analyzed using a microscope. The coefficient of friction was calculated separately for the partial slip and gross slip regimes. In the mixed fretting regime, the coefficient of friction is almost at the same level among the five materials. In the partial slip regime, however, it can be distinguished. Temperature measurements were conducted on the counterparts during the tests. Overall, the material that showed the best tribological properties also performed the best in the fretting tests.

Probing fretting behavior of Mg–Sn–Y alloy under high-performance fluids lubrication

Abstract The attention is focused on high-performance Mg alloys due to their favorable biocompatibility, lightweight, physicochemical and mechanical properties. Here, the fretting performance of Mg–Sn–Y alloy was evaluated under fluids lubrication, and the fretting mechanism was explored in detail via analysis of wear track/debris using SEM and XPS depth profile. The results illustrate that the friction reduction is superior to wear resistance for lubricated Mg–Sn–Y/Steel contact under fretting conditions, mainly depending on the oil-film induced transformation of fretting running regime and transition of fretting wear (from adhesive/oxidation wear and delamination under dry friction to abrasive wear and delamination under fluids lubrication). Hence fretting performance of Mg–Sn–Y alloy under fluids lubrication depends on fretting running regime and synergy of oil-film/protective film.

Titanium Alloys 2017

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Effect of contact pressure on torsional fretting fatigue damage of 316L austenitic stainless steel

Fretting is the small amplitude relative oscillatory motion between two solid contact surfaces. Many factors would make impacts on the fretting process, the body stress and contact pressure can be regarded as two major independent factors resulting in the fretting fatigue. The effects of torque and contact pressure on torsional fretting behavior of 316L austenitic stainless steel are studied in a cylinder-on-cylinder contact configuration. The results indicate that torsional fatigue life drops rapidly due to fretting. The S-N curves of torsional fretting fatigue show a shape of “C”. Along with increasing the contact pressures, the fretting fatigue life decreases and enters to a platform area. The variety law of friction coefficient under different contact pressures is obtained. Both fatigue fracture and fretting scar are analyzed with SEM, EDX, XPS and three-dimensional white light interferometer (3D). The study shows that the torsional fretting fatigue is influenced by fretting running behavior. Meanwhile, the depth of crack initiation position would also be affected by contact pressure. In this paper, we proposed the failure mechanisms of the fretting zone, including plastic deformation, delamination, plow and oxidative wear.

Retrieval Analysis of Neck-Stem Coupling in Modular Hip Prostheses

BackgroundDual-taper modular stems have suffered from high revision rates caused by adverse local tissue reactions secondary to fretting and corrosion. We compared the fretting and corrosion behavior of a group of modular neck designs to that of a design that had been recalled for risks associated with fretting and corrosion at the modular neck junction. MethodsWe previously analyzed fretting and corrosion on 60 retrieved Rejuvenate modular neck-stem implants. Here we compare those results to results from 26 retrieved implants from 7 other modular neck designs. For the 26 additional cases, histology slides of tissue collected at revision were reviewed and graded for aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Multivariate analyses were performed to assess differences in fretting and corrosion, adjusting for confounding factors (eg, length of implantation). ResultsThe Rejuvenate design had higher damage and corrosion scores than the other 7 designs (P < .01). Histologic samples from the recalled design were 20 times more likely to show ALVAL than samples from the other designs (P < .01). Mixed metal couples had higher fretting (P < .01) and corrosion (P = .02) scores than non-mixed metal couples. ConclusionFretting and corrosion occurred on all modular neck-stem retrievals regardless of design. However, mixed metal couples suffered more corrosion than homogenous couples. This may be due to the lower modulus of the titanium alloy used for the stem, allowing for increased metal transfer and surface damage when loaded against a cobalt alloy modular neck, which in turn could account for the higher ALVAL and corrosion scores. Due to increased corrosion risk with mixed metals and increased neck fracture risk with non-mixed metal stem and necks, we suggest that clinicians avoid implantation of modular neck-stem systems.

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.

Influence of wet contact conditions on the multidirectional fretting behavior of Polyetheretherketone and composites

Polyetheretherketone (PEEK) polymers are increasingly used in tribological applications where fretting damage occurs. Fretting wear results from the repeated sticking and slipping of mutually loaded contacts. In this study, a custom built multi-axis tribometer is used to replicate fretting of filled and unfilled PEEK in a pin-on-flat configuration in both dry and wet conditions. The performance of the PEEK based polymers is shown to depend on the shear stresses generated when adhesive contacts are broken during slip. Unfilled PEEK experiences frictional heating that leads to softening of the wear surface. The softened material can be easily sheared from the bulk and leads to cratering and fracture of the samples. The extent of damage depended strongly on MW. The buildup of heat is prevented when water lubrication is used and wear is also reduced. Lubricating fillers such as PTFE and graphite lower the frictional forces and reduce the tractive shear stresses. Filled samples however were susceptible to softening from water that exacerbated fretting damage. The fretting performance appears strongly tied to the static friction response on the material. Static friction measurement along with FEA analysis was conducted to better understand the observed phenomena. A stop-go experiment was used to capture the friction response due to the shearing of adhesive contacts.

Contact Properties and Wear Behaviour of Nickel Based Superalloy René 80

A superalloy traditionally offers excellent mechanical strength, resistance to thermal creep deformation, good surface stability and resistance to corrosion or oxidation. However, a superalloy often also needs performance in terms of fretting resistance. Experimental results regarding fretting wear and contact properties of the superalloy René 80 are illustrated and discussed. The widespread applications of superalloys in jointing with friction as in the jointing of a turbine blade, is the main motivation for characterizing their fretting behaviour. The fretting experiments were performed at 100 Hz for two temperatures (600, 800 °C), and two sliding amplitudes (30, 60 µm). These temperatures and strokes are typical at the medium stage of a low-pressure gas turbine. Wear volume and the contact properties such as friction coefficient and tangential contact stiffness were measured and analysed. Results show that the lowest friction coefficient was measured at the temperature of 800 °C. This temperature hence appears to be an optimum working condition for the fretting wear of René 80. With regard to wear mechanism, a fundamental role of the sliding amplitude was found. In particular, the ratio between the sliding amplitude and the characteristic contact length has a significant influence upon the oxide growth on contact surfaces.

Simulation of shot peening: From process parameters to residual stress fields in a structure

Manufacturing industries perform mechanical surface treatments like shot peening at the end of the manufacturing chain to protect important working parts. This treatment modifies the near surface of the treated part with the introduction of compressive residual stresses due to the repeated impacts of the shot. Then, the treated part exhibits, not only a longer life, but also a better fretting behavior, an improved resistance to corrosion… The objective of the present paper is first to study the relation between the process parameters and the material state (residual stress and plastic variables…) for a complex geometry. Next, a numerical tool is proposed, able to predict this material state in a time frame that is consistent with industrial constraints. The originality of the proposed approach thus consists in the chaining of the different steps. The first step is to choose the process parameters for the shot peening process considering conventional or ultrasonic shot peening and model the shot dynamics for a complex geometry. Once the impact velocity field is known, the objective is to compute the local incompatible plastic deformation field due to the repeated impacts using analytical methods. Then, a finite element model is used to compute the residual and deformation fields in the considered mechanical part. The complete method has been performed on the model of a gear, a mechanical part that is most often shot peened and exhibits a complex geometry.

Comparison of the torsional fretting behavior of three porous titanium coatings for biomedical applications

This research evaluated the torsional fretting wear proprieties of three porous bio-coatings modified with anodic oxidation, acid–base treatment, and alkali–heat treatment. Torsional fretting wear tests were carried out under a ball-on-flat contact configuration. Torsional fretting wear mechanisms were investigated by a combination of scanning electron microscope observations, energy dispersive X-ray analysis and X-ray diffraction analysis. Results showed that the torsional fretting wear resistance of anodic oxidation coating was better than that of acid–base coating and alkali–heat coating. Adhesive wear was the main damage mechanism of the three porous titanium coatings in partial slip regime. The combination of abrasive wear, delamination, and material transfer was the main wear mechanism of mixed and gross slip regimes.

Fretting and wear behaviors of Ni/nano-WC composite coatings in dry and wet conditions

The fretting and wear behaviors of Ni/nano-WC composite coatings were studied by considering the effect of fretting frequency of 1Hz during 10,000cycles, at different applied loads in dry or wet conditions. The studies were performed on a ball-on-disk tribometer and the results were compared with pure Ni coating. The nanohardness of pure Ni and Ni/nano-WC composite coatings was tested by nanoindentation technique. To evaluate the wet wear (tribocorrosion) behavior the open circuit potential (OCP) was measured before, during and after the fretting tests at room temperature in the solution that simulates the primary water circuit of Pressurized Water Reactors (PWRs). The results show that Ni/nano-WC composite coatings exhibited a low friction coefficient, high nanohardness and wear resistance compared with pure Ni coatings under similar experimental conditions. Ni/nano-WC composite coatings were obtained on stainless steel support by electrochemical codeposition of nano-sized WC particles (diameter size of ∼60nm) with nickel, from a standard nickel Watts plating bath. The surface morphology and the composition of the coatings were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) respectively.

Influence of the composition of titanium oxynitride layers on the fretting behavior of functionalized titanium substrates: PVD films versus surface laser treatments

In this work we compared the fretting behavior of pure titanium plates functionalized with titanium oxynitride surface layers, obtained by two methods: a Physical Vapor Deposition (PVD) method, reactive magnetron sputtering, and Surface Laser Treatments (SLT), under different mixtures of oxygen and nitrogen. The composition of the layers was determined by nuclear reaction analysis (NRA) and their structure was analyzed by Raman spectroscopy. PVD layers were TiN-like fcc layers, with an oxygen concentration going from 36 to 50at.%. Three SLT layers were studied. The first one was a TiN-like layer containing ~28at.% of oxygen. The second one was formed of different titanium oxide phases containing ~5at.% of nitrogen. The third one was a titanium dioxide layer with a negligible concentration of nitrogen.It was found that the steady friction coefficient was similar for all the layers and quite lower than that measured for uncoated Ti. The study of the fretting scars revealed a higher resistance of SLT layers to fretting wear, which can be due to the smooth layer-substrate interface. The detachment of coating particles was observed in some PVD layers.Finally, the transfer of matter between the first bodies was studied by micro-Raman spectroscopy and nuclear reaction techniques: NRA and Particle Induced X-ray Emission.

Measurement of Local Deformations in Steel Monostrands Using Digital Image Correlation

The local deformation mechanisms in steel monostrands have a significant influence on their fatigue life and failure mode. However, the observation and quantification of deformations in monostrands experiencing axial and transverse deformations is challenging because of their complex geometry, difficulties with the placement of strain gauges in the vicinity of the anchorage, and, most importantly, the relatively small magnitude of deformation occurring in the monostrand. This paper focuses on the measurement of localized deformations in high-strength steel monostrands using the digital image correlation (DIC) technique. The presented technique enables the measurement of individual wire strains along the length of the monostrand and also provides quantitative information on the relative movement between individual wires, leading to a more in-depth understanding of the underlying fatigue mechanisms. To validate the proposed image-based measurement method, two different tests were performed, with the one correlation method showing good agreement. Data collected from the DIC technique creates a basis for the analysis of the fretting and localized bending behavior of the monostrand and provides relevant information on the internal state of displacement of the monostrand under bending load.

Research on the torsional fretting behavior of the head–neck interface of artificial hip joint

The torsional fretting behavior of the head–neck interface of artificial hip joint composed of Ti6Al4V and CoCrMo was investigated. The torsional fretting mechanisms were evaluated by experiments at various angular displacement amplitudes. The friction coefficient for the head–neck interface was calculated using contact mechanics. The head–neck interface model was established in accordance with the artificial hip joint head–neck size. The conical angle and diameter of the artificial hip joint head were optimized using data derived from the finite element method (FEM). The results indicate that torsional fretting changes from partial slip regime to slip regime with increasing angular displacement amplitude. Friction torque, friction dissipated energy, and the friction coefficient increase with increasing angular displacement amplitude and wear intensifies. Finite element simulation results demonstrate that self-locking occurs in the head–neck interface of artificial hip joint more readily at small conical angles. The head–neck interface is least susceptible to fretting when the conical angle is 5°42′30″. Relative displacement and contact stress can be reduced by appropriately increasing the conical angle within a small angle range and increasing the artificial hip joint head diameter, which can decrease fretting wear.

The Influence of Head Size on Corrosion and Fretting Behaviour at the Head-Neck Interface of Artificial Hip Joints

The primary goal of this study was to determine if head size affects corrosion and fretting behaviour at the head-neck taper interface of modular hip prostheses. Seventy-four implants were retrieved that featured either a 28mm or a 36mm head with a metal-on-polyethylene articulation. The bore of the heads and the neck of the stems were divided into eight regions each and graded by three observers for corrosion and fretting damage separately using modified criteria as reported in the literature. The 36mm head size featured a significant difference in the corrosion head scores (p=0.022) in comparison to the 28mm heads. This may be attributed to a greater torque acting along the taper interface due to activities of daily living.