Crack-Like Processes Governing the Onset of Frictional Slip.pdfVIP

CRACK-LIKE PROCESSES GOVERNING THE ONSET OF FRICTIONAL SLIP Shmuel M. Rubinstein, Meni Shay, Gil Cohen, and Jay Fineberg The Racah Institute of Physics, The Hebrew University of Jerusalem, Givat Ram, Jerusalem Israel Author for correspondence (E-mail: jay@vms.huji.ac.il) 1. INTRODUCTION Although relevant to many aspects of our everyday lives, scientists have yet to fully decipher the fundamental mechanisms of friction – that is, what occurs when two surfaces begin to slide against one another? Frictional slip is central to fields as diverse as physics (Baumberger et al., 1999; Ciliberto and Laroche, 1999; Filippov et al., 2004; Muser et al., 2001; Urbakh et al., 2004) tribology (Bowden and Tabor, 2001; Persson, 2000), the mechanics of earthquakes (Andrews and BenZion, 1997; Ben-Zion, 2001; Bouchon et al., 2001; Cochard and Rice, 2000; Dieterich and Kilgore, 1994; Heaton, 1990; Ohnaka and Shen, 1999; Rice et al., 2001; Scholz, 1998; Xia et al., 2004) and shear-driven fracture (Freund, 1979; Gao et al., 2001; Ravi-Chandar et al., 2000; Rosakis, 2002). Beyond their fundamental scientific interest, questions in the field of friction have relevance to the issue of earthquake measurement and predictions, as well as for numerous industrial applications. In 1699 Guillaume Amontons gave the modern formulation of the static friction laws. In 1785 Charles-Augustin de Coulomb added the first formulation of dynamic friction laws and suggested a model that partially accounts for them. The explanation as to why a friction coefficient exists and is independent of the (apparent) contact area was introduced in the Micro Contact Interface model (MCI) of Bowden and Tabor (Bowden and Tabor, 2001) in the 1940s. These authors were the first to note that, due to surface roughness, the real (net) area of contact actually consists of a myriad of micro-contacts. The net contact area formed by these micro-contacts is only a fraction of the apparent contact area