The present study describes friction properties of sintered copper alloy journal bearing The sliding surface of the journal bearing of the copper alloy was finished with reaming and roller burnishing process to evaluate effect of the surface finish on the friction properties The experiment was carried out using a developed testing apparatus consisted from a spindle driven with an air cooled DC motor and a disc shape bearing holder in air atmosphere without lubricants and a hardened steel shaft having fine ground surface as the mating specimen As results, the friction property as a function of the sliding distance was different depending not only on the sulfide contents but also processing condition Seizure was frequently occurred on the journal specimen with lower content of the sulfide In addition, it was found that the morphology of transfer layer on the mated shaft surface observed with SEM/EDX analysis was different in connection with the friction properties

View full abstract

To investigate an applicability for reduction of the friction loss of tapered roller bearing, a surface modification technic using a roller burnishing and a micro shot peening was proposed Bronze containing micro sized sulfur phase acting as solid lubricant or molybdenum di-sulfide was penetrated into micro dimples fabricated to a chromium alloy steel surface The friction properties was evaluated with a ring on disc type testing apparatus mated with a chromium alloy steel surface in lubricated condition Results showed that the friction coefficient of sulfide alloy penetrated surface was relatively stable and lower, compared with those of molybdenum di-sulfide, bronze without sulfide and dimpled surfaces Therefore, it was estimated that the composed surface consisted from chromium alloy steel and bronze with micro sized sulfur fabricated with the roller burnishing and the micro shot peening is effective for reduction of friction loss of a tapered roller bearing

View full abstract

Laser peening (LP) is a material processing for surface of metal to improve its mechanical properties, sensitivity of stress corrosion crack The processing is expected to be effective for thin film metals, however conventional LP is performed under water Wet process cause significant restriction of micro-machining because of contamination, hydroscopic resist materials, or sticking In this paper, conventional wet LP is applied to thin film metal and LP under dry condition is demonstrated using bulk metal After LP under water on thin film metal, residual compression stress was generated Dry LP was conducted using borosilicate glass and it achieved hardness as much as conventional LP under LP and the result is much improved a result of LP under air The effect of the dry LP using glass was much influenced by inner crack of the glass induced by laser abrasion

View full abstract