A METHOD FOR THE ASSESSMENT OF THE ROLLING CONTACT FATIGUE OF MODERN ENGINEERING MATERIALS IN LUBRICATED CONTACT

It is widely recognised that apart from scuffing, rolling contact fatigue (RCF) is one of the most predominant failure types in highly loaded non-conformal friction joints. The fatigue life of machine parts depends on many factors that can be divided into three groups: design, technology and operating conditions. The main factors influencing pitting are material properties, the geometry of the tribosystem, surface finish, dimensional precision, and working conditions as well as the physicochemical properties of the lubricant. The aim of this paper is to present the experimental method for determining fatigue life of modern engineering materials in lubricated rolling contact. The developed method allows an investigation into the effect of all these factors on rolling contact fatigue (pitting). The method is employed by using a modified four-ball testing machine denoted as T-03. The modification embraces the replacement of testing specimens. The upper ball is replaced with a cone that can be made of various materials. The method exhibits good resolution and is time and cost effective. It was successfully applied to the investigation into various types of surface coatings including single, multilayer and duplex coatings. This method can be employed by using a widespread four-ball apparatus

A METHOD FOR THE ASSESSMENT OF THE ROLLING CONTACT FATIGUE OF MODERN ENGINEERING MATERIALS IN LUBRICATED CONTACT

It is widely recognised that apart from scuffing, rolling contact fatigue (RCF) is one of the most predominant failure types in highly loaded non-conformal friction joints. The fatigue life of machine parts depends on many factors that can be divided into three groups: design, technology and operating conditions. The main factors influencing pitting are material properties, the geometry of the tribosystem, surface finish, dimensional precision, and working conditions as well as the physicochemical properties of the lubricant. The aim of this paper is to present the experimental method for determining fatigue life of modern engineering materials in lubricated rolling contact. The developed method allows an investigation into the effect of all these factors on rolling contact fatigue (pitting). The method is employed by using a modified four-ball testing machine denoted as T-03. The modification embraces the replacement of testing specimens. The upper ball is replaced with a cone that can be made of various materials. The method exhibits good resolution and is time and cost effective. It was successfully applied to the investigation into various types of surface coatings including single, multilayer and duplex coatings. This method can be employed by using a widespread four-ball apparatus

Testing of the Resistance to Scuffing of Spiral Bevel Gears: Test Rig, Method, and Results of Verification Testing

In spite of long-term development of the technology of bevel gear production, the automotive industry reports various operational demands such as the need of the size and mass reduction of gears without lowering their durability and reduction of friction leading to a decrease in the energy losses and a decrease of the tendency to scuffing. What is more expected, EU regulations may impose the use of new generation gear oils (ecological-friendly) providing the proper operational properties of the transmission. In view of these demands, a new, bevel gear test rig and scuffing test method have been developed at ITeE-PIB. The idea resulted from a necessity to improve reliability of tests—popular gear tests are run mostly on spur gears having the tooth geometry significantly different than bevel gears. The test rig, test method, and results of verification testing are presented. The effect of various gear oils and the deposition of a low-friction coating on the resistance to scuffing were investigated. It is shown that the new test rig fulfils the research requirements and that the new test method has a good resolution

A NEW APPROACH TO OPTIMIZATION OF THE METAL-POLYMER TRIBOLOGICAL CHARACTERISTICS

ABSTRACT The paper presents a new approach to optimization of the metal-polymer tribological characteristics based on correlation between the total sum of polar component values of surface free energy tribological characteristics (wear and friction) of rubbing materials. The authors predict that research of friction and wear mechanism of modified friction joints should make possible to generalize the principles of rational selection of manufacturing technology of polymer-metal friction joints. TRIBOLOGY OF METAL-POLYMER FRICTION JOINTS The common practice in reducing adhesive interactions in metal-polymer friction joints is addition of some modifiers to the polymer matrix The current efforts put in the improvement of the mechanical properties of polymers do not take into consideration the energy state of the surface layer of elaborated polymer composites. Furthermore, the aspects of presence of oxides on steel surfaces, which create bonds with hydrogen also is not usually take into consideration. It is well known, that this process promote the tendency to creation of adhesive bonds between metal and polymer. At present, in the most research works, the interaction between poromer polymer coating filled with graphite or molybdenum disulfide and ceramic coated steel is not taken into consideration. The authors propose the hypothesis that optimal correlation between polymer coating and coated steel may reduce the tendency to hydrogen bonds creation

Właściwości fizykochemiczne i tribologiczne wodnych roztworów hydrolizatu jako potencjalnych baz substancji smarowych

The study aimed to confirm the hypothesis that aqueous solutions of polymers with surfactants meet the criteria of ecological lubricant bases. An oat hydrolysate was used as the macromolecular substance, and the surfactants were successively: sodium dodecyl sulphate (SDS), Sodium Lauryl Ether Sulfate (SLES), Sodium Lauroyl Sarcosinate (SLS). The research was carried out for two-component solutions (water, hydrolysate) and three-component solutions (water, hydrolysate, surfactant). In order to document this thesis, tribological tests were performed with a constant and increasing load as a function of time. Stationary tests with loads of 2, 3, and 4 kN confirmed the predictions that active substances in two- and three-component solutions create a lubricating film that transfers high loads with relatively low motion and wear resistance. The stability and durability of the lubricating film were confirmed under the conditions of increasing load at a speed of 409 N/s. An approximately 12-fold increase in the seizing load for the hydrolysate solutions in relation to water was found, and the maximum load value for the T02 tester (7200 N) was achieved. The durability of the lubricating film was mainly determined by the adsorption of the hydrolysate, which was confirmed by physicochemical tests.Celem pracy było potwierdzenie hipotezy, że wodne roztwory polimerów z surfaktantami spełniają kryteria ekologicznych baz substancji smarowych. Jako substancję wielkocząsteczkową zastosowano hydrolizat owsa, a surfaktantami były kolejno: sodium dodecyl sulfate (SDS), Sodium Lauryl Ether Sulfate (SLES), Sodium Lauroyl Sarcosinate (SLS). Badania przeprowadzono dla roztworów dwuskładnikowych (woda, hydrolizat) oraz trójskładnikowych (woda, hydrolizat, surfaktant). Aby udokumentować tę tezę wykonano badania tribologiczne przy stałym i wzrastającym w funkcji czasu obciążeniu. Testy stacjonarne przy obciążeniach 2, 3, 4 kN potwierdziły przewidywania, że substancje ak tywne w roztworach dwu- i trójskładnikowych tworzą film smarowy, który przenosi wysokie obciążenia przy relatywnie niskich oporach ruchu i zużycia. Stabilność i trwałość filmu smarowego została potwierdzona w warunkach wzrostu obciążenia z szybkością 409 N/s. Stwierdzono około 12-krotny wzrost obciążenia zacierającego dla roztworów hydrolizatu względem wody oraz osiągniętą maksymalną dla testera T02 wartości obciążenia (7200 N). O trwałości filmu smarowego zdecydowała głównie adsorpcja hydrolizatu, co zostało potwierdzone badaniami fizykochemicznymi

Tribologiczne aspekty bezpieczeństwa użytkowania obuwia

The key factor, from the consumer's point of view, during the use of footwear is the safety of use, characterized, among others, by the friction coefficient. A low coefficient of friction can cause skidding, which is very dangerous for the elderly, people with motor apparatus injuries, those with impaired motor skills, and those with a high body BMI index. Fall injuries result in hospitalization, generating high costs of treatment and compensation. The article presents the results of tribological tests of typical footwear sole materials in combination with selected base materials depending on the load on the friction junction, the initial temperature, and the presence of water. The combination of the friction coefficient with the safety of footwear use for typical operating conditions is a new approach to the requirements of ergonomics and increasing comfort while walking.Kluczowym czynnikiem, z punktu widzenia konsumenta, podczas eksploatacji obuwia jest bezpieczeństwo użytkowania, charakteryzowane między innymi współczynnikiem tarcia. Mały współczynnik tarcia może powodować poślizg, który jest bardzo niebezpieczny dla osób starszych, osoby z urazami aparatu ruch, z upośledzoną motoryką oraz z wysokim indeksem BMI ciała. Urazy powstałe podczas upadku są powodem hospitalizacji generującej wysokie koszty leczenia oraz odszkodowania. W artykule przedstawiono wyniki badań tribologicznych typowych obuwniczych materiałów spodowych w skojarzeniu z wybranymi materiałami podłożowymi w zależności od obciążenia węzła tarcia, temperatury początkowej oraz obecności wody. Powiązanie współczynnika tarcia z bezpieczeństwem użytkowania obuwia dla typowych warunków eksploatacji stanowi nowe podejście do wymogów ergonomii i zwiększenia komfortu podczas chodzenia