Papers by Keyword: Fretting

Abstract: Titanium and its alloys have a wide range of applications in various industries, including medicine. However, the low strength and high friction coefficient hinder their development in contact friction due to fretting fatigue. Among many factors, structure refinement, temperature and amplitude are the most responsible for fretting wear of structural materials. The purpose of the article is to investigate the effect of displacement amplitude, size of grain and test temperature on the fretting wear of the pure titanium in coarse-grained and ultrafine-grained states. It is shown that an increase in the test temperature for both structural states leads to a multiple increase in wear. Structural refinement of titanium to hundreds of nanometers helps to reduce wear at room and elevated temperatures.

Abstract: Metallic biomaterial are the most suitable for replacing failed hard tissue up to now and for that is important to know the tribocorrosion resistance of these materials before use in biomedical applications. Surface engineering can play a significant role in extending the performance of medical implants made of titanium and its alloys. In this work was chosen electrodeposition of hydroxyapatite (HA) coatings into nanoporous titania layer formed by anodic oxidation as modified Ti-6Al-4V alloy surface. The comparative tribocorrosion behavior of untreated Ti-6Al-4V alloy surface, anodic nanoporous TiO₂ surface and electrodeposited hydroxyapatite (HA) coatings into nanoporous TiO₂ layers has been investigated in a bio-simulated fluid solution. The results of these investigations have shown that both surface treatments applied have improved the tribocorrosion resistance and friction coefficients as compared to the untreated Ti–6Al–4V alloy surface.

Abstract: Fretting wear of components of kinematic pairs used in prosthetics and dental surgery is a significant problem limiting their operating lifetime. This article presents the results of in vitro studies of fretting processes in metal-metal systems. Special attention has been devoted to the degradation of titanium alloys (Ti6Al4V) under simulated conditions of the human oral cavity. Sample surfaces were observed under a microscope, and wear was assessed. Special attention has been devoted to products permanently adsorbed on friction surfaces, which were analyzed by means of spectroscopic methods. Obtained results of studies indicate that two primary mechanisms: abrasive (secondary) wear and adhesive wear, make up fretting wear.The products that mainly form as a result of friction are oxides. To limit fretting wear, it is beneficial to apply lubricants containing friction modifiers and isolating the area of contact from oxygen. Observations made over the course of studies have brought knowledge and will contribute to better identification of fretting wear mechanisms in biomaterials.

Abstract: A finite element procedure is implemented for the elastic-plastic analysis of carbon steels subjected to reciprocating fretting contacts. The nonlinear kinematic hardening rule based on Chaboche model is used to model the cyclic plastic behavior in fretting contacts. The results show that accumulation of plastic strains, i.e. ratchetting, may occur near the contact edge while elastic shakedown is likely to take place in substrate.

Abstract: Fretting and fretting-corrosion processes in elements of kinematic pairs used for medical applications are observed in metallic orthopedic implants, dental prosthetics elements, and orthodontic appliances. In most cases, the degradation of biomaterials significantly limits their useful life and the comfort of patients. The products formed as a result of wear may lead to poisoning of the body and the occurrence of inflammatory states, which often results in the failure of medical therapy. Fretting-corrosion processes are being paid more and more attention, although there is not much data concerning the stomatognathic system. This article presents the results of fretting-corrosion studies of one of the most frequently used metallic biomaterials, CoCrMo cobalt alloy, in the presence of human saliva and its substitutes. The results of studies indicate that friction has a large influence on corrosion processes (fretting-corrosion). Artificial saliva compositions with favorable tribological and anti-corrosion properties were successfully developed and may find applications in the stomatognathic system, e.g. for the purpose of reducing the unfavorable effects of bruxism. Fretting-corrosion studies were performed using a self-designed original device. The obtained results of studies are of great significance in scientific and applicatory terms.

Abstract: The article deals with the problem of transition quasi-static contact in global slip under cyclic tangential load. The state of stress in partial contact, the laws of friction and scenarios of transition to slip of metal surface was determined. Partial slip is defined by the existence of stick and slip zones within the contact area. Currently, there are two basic concepts concerning surface damage processes: one connected with surface activation, which involves an increase in free energy in a tribological system, and the other connected with surface passivity, when free energy decreases. Experimental and theoretical studies were conducted to determine the contact between a sphere and a plane, which is the most suitable system for simulating small-amplitude fretting (~ 0–3 microns).

Abstract: Wear is present in all mechanical interface interaction problems –contact, fretting, orrolling-contact–, and it is one of the main reasons for inoperability in mechanical components. Thepresented work is a review of recent research carried out by the authors [1, 2, 3]. A boundary-element-based methodology to compute anisotropic wear on 3D contact, fretting, or rolling-contact conditionsis presented. Damage on the geometries of the solids and the contact pressures evolution under or-thotropic tribological properties can be predicted using this contact framework, where the formulationuses the Boundary Element Method to compute the elastic inuence coefcients. Contact problem isbased on an Augmented Lagrangian formulation, and restrictions fullment is established by a set ofprojection functions. The boundary element anisotropic wear formulation presented is illustrated withsome examples, in which some studies about the inuence of anisotropic wear on contact variablesevolution are shown.

Abstract: Fretting is one of the main reasons for electric contact failure. Metal contact pairs have long been used, generally with the structure of copper alloy base, Ni interlayer and surface noble metal (such as gold) plating. The influences of plating material and plating thickness on fretting property have been researched deeply, meanwhile, new materials have been tried. In this paper, a new conductive material, silver conducting adhesive is used as the surface coating of contact pair, and a series of tests have been done to study the performance of fretting wear by compare with the coupons without silver conducting adhesive. The results show that the use of silver conductive adhesive improves the fretting property of electrical contacts, especially with small normal force.

Abstract: In this paper an experimental investigation has been carried on, in order to determinate the different damage patterns and the corresponding entity on the surface of splined couplings with straight and crowned teeth, subjected to variable working loadings. In particular, experimental tests have performed by means of a dedicated test rig, allowing to realize different working conditions, as the angle between the axis of shaft and hub and also the presence of lubrication. Teeth surfaces after tests have been analyzed by considering as damage parameters both surface roughness and gap between teeth. Results show that the wear pattern on crowned teeth is completely different with respect to the straight ones; in both cases, the value of the misalignment angle and the presence of lubrication may substantially influence the entity of the surface damage.

Abstract: The technologically important elliptical contact undergoing fretting is simulated using previously advanced state-of-the-art numerical tools. The influence of contact ellipse eccentricity on various contact parameters is assessed. An analogy with the circular contact is found when tractions equations are written in dimensionless coordinates in case of similarly elastic materials. However, when an elastic mismatch is introduced, the stick area no longer follows proportionally the established contact area.