polito.it
Politecnico di Torino (logo)

ANALYSIS OF TRIBOLOGICAL PROPERTIES OF POLYOXYMETHYLENE BALL SLIDING AGAINST STEEL EN 52100 DISC AND POLYDIMETHYLSILOXANE BALL AGAINST POLYAMIDE DISCS = ANALYSIS OF TRIBOLOGICAL PROPERTIES OF POLYOXYMETHYLENE BALL SLIDING AGAINST STEEL EN 52100 DISC AND POLYDIMETHYLSILOXANE BALL AGAINST POLYAMIDE DISCS

Beatrice Piantoni

ANALYSIS OF TRIBOLOGICAL PROPERTIES OF POLYOXYMETHYLENE BALL SLIDING AGAINST STEEL EN 52100 DISC AND POLYDIMETHYLSILOXANE BALL AGAINST POLYAMIDE DISCS = ANALYSIS OF TRIBOLOGICAL PROPERTIES OF POLYOXYMETHYLENE BALL SLIDING AGAINST STEEL EN 52100 DISC AND POLYDIMETHYLSILOXANE BALL AGAINST POLYAMIDE DISCS.

Rel. Cristina Bignardi. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Biomedica, 2018

Abstract:

Why do human joints wear out during aging or better how do joints resist wear over a lifetime? Synovial joints of the human body are complex living biological and mechanical system consisting of articular cartilage, bone, menisci, ligaments and synovium that allow movement so that friction and wear are minimal.The success of many implant or medical instruments depends on the biomaterial used. Synthetic materials like metals, polymers, ceramics and composite have had an important role to several medical devices. Nowadays the life of an implant is about 15 years and consequently, a reduction in wear and friction of medical devices and the development of the design is becoming the core of several studies. The following thesis is divided in two parts.The main purpose of the first section is to investigate the effect of temperature on the tribological properties of polyoxymethylene (POM), used basically in hip, knee and shoulder joint replacements. Friction and wear tests of POM ball versus steel EN52100 disc were carried out at dry condition, steady pressure (2 N) and constant frequency (30Hz) at different temperatures (37°C, 45°C, 70°C) on High Frequency Reciprocating Rig (HFRR) tester. The results show that friction can increase in the course of time because of the formation of a transfer film of POM onto the metal counter-surface or in wear debris in the contact area. The Scanning Electron Microscopy (SEM) showed that polymer transfer is thin and highly oriented and it is promoted by an improved adhesion of polymer to the metal surface and by mechanical interlocking of metal asperities into the polymer. The second section is briefer than the first one and it focuses on the influence of the humidity on friction coefficient of a polydimethylsiloxane (PDMS) sphere against three discs of polyamide with different composition. Tribological tests were conducted on HFRR at room temperature, at the same pressure (2 N) and constant frequency (30 Hz) for 30 minutes, changing the relative humidity conditions (35%RH, 60%RH, 80%RH). The results show that the friction coefficient starts with a running-in period followed by a steady state period but the level remains low after 30 minutes of sliding, around 0.35 because of the chemical structure of PDMS.

Relatori: Cristina Bignardi
Anno accademico: 2017/18
Tipo di pubblicazione: Elettronica
Numero di pagine: 92
Informazioni aggiuntive: Tesi secretata. Full text non presente
Soggetti:
Corso di laurea: Corso di laurea magistrale in Ingegneria Biomedica
Classe di laurea: Nuovo ordinamento > Laurea magistrale > LM-21 - INGEGNERIA BIOMEDICA
Ente in cotutela: Ducom Instruments (Europe) B.V. & Scientific Staff Center for Innovation (PAESI BASSI)
Aziende collaboratrici: Ducom Instruments Europe B.V.
URI: http://webthesis.biblio.polito.it/id/eprint/7983
Modifica (riservato agli operatori) Modifica (riservato agli operatori)