Session: CT-04-01 Assembly of Bolted Joints - 1

Paper Number: 106237

106237 - Tribological Behaviour in the Underhead for High Strength Socket-Head Screws Coupled With Cast Iron and Tightened in Dry and Lubricated Condition 

The present paper investigates the influence of several design parameters on the frictional response at the underhead in a bolted joint, involving high strength socket-head screws: M8 class 14.9 with black oxidization coating. The experimentation deals with underhead materials (Cast iron), lubrication conditions (dry, lubricated) and repeated tightening operations. The awareness of the actual friction coefficients, depending on the current operating parameters, is a useful tool, to support the most proper design of a bolted joint. The experimental campaign has been run by a testing rig for friction coefficient estimation, complying with the recommendations by International Standard ISO 16047 and the automotive Standard VW01131-1 in order to consider the effect of the tightening speed normally adopted in the automotive field. The axial preload generated upon tightening induces a high pressure on the remarkably small underhead surface of the utilized high strength socket-head screws and is therefore likely to affect the tribological response. Consequently, some differences may be expected with respect to the tribological behaviour of screws belonging to lower strength grades. This is particularly true, when tightening is done without bearing lubrication, and through several repeated assembly-disassembly operations. The collected data have been processed by the tools of ANOVA and F-Test, in order to assess the significance of each factor, as well as related interactions.

Presenting Author: Stefano Fini University of Bologna

Presenting Author Biography: Born in Bologna in 1981.
Master Degree in Mechanical Engineering at the University of Bologna in 2007.
PhD in Mechatronics and Product Innovation Engineering at the University of Padua in 2017.
Currently Assistant Professor at the University of Bologna.

Authors:

Dario Croccolo University of Bologna
Massimiliano De Agostinis University of Bologna
Stefano Fini University of Bologna
Giorgio Olmi University of Bologna
Chiara Scapecchi University of Bologna
Nicolò Vincenzi Bucci automations S.p.A.