A Mother-Daughter Mechanism of Mode I cracks: Supersonic Crack Motion Along Interfaces of Dissimilar Materials
- PDF / 175,148 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 46 Downloads / 234 Views
0904-BB03-05.1
A Mother-Daughter Mechanism of Mode I cracks: Supersonic Crack Motion Along Interfaces of Dissimilar Materials Markus J. Buehler1* and Huajian Gao2 1 2
Massachusetts Institute of Technology, Cambridge, MA, 02139, USA Max Planck Institute for Metals Research, 70569 Stuttgart, Germany
ABSTRACT In this paper we summarize recent progress in applying large-scale atomistic studies of crack dynamics along interfaces of dissimilar materials. We consider two linear-elastic material strips in which atoms interact with harmonic potentials, with a different spring constant in each layer leading to a soft and a stiff strip. The two strips are bound together with a weak potential whose bonds snap early upon a critical atomic separation. An initial crack serves as initiation point for the failure. We will focus on the maximum speed of mode I loaded cracks along such a biomaterial interface. Upon nucleation of the crack, it quickly approaches a velocity a few percent larger than the Rayleigh-wave speed of the soft material. After a critical time, we observe that a secondary crack is nucleated a few atomic spacings ahead of the crack. This secondary crack propagates at the Rayleigh-wave speed of the stiff material. If the elastic mismatch is sufficiently large, the secondary crack can be faster than the longitudinal wave speed of the soft material, thus propagating supersonically. Supersonic crack motion is clearly identified by two Mach cones in the soft material. This suggests that mother-daughter mechanisms, formerly only reported in mode II cracks in homogeneous materials, play an important role in interfacial mode I crack dynamics. The studies reported in this paper exemplify the usage of large-scale atomistic simulation to investigate the physics of fracture. INTRODUCTION Large-scale atomistic simulation is becoming an increasingly important tool to investigate fundamental aspects of dynamic crack propagation. Recent progress in this field include systematic atomistic-continuum studies of fracture [1, 2], investigations of the role of hyperelasticity in dynamic fracture [3] and studies on the instability dynamics [4]. Here we extend existing atomistic models of dynamic fracture in homogeneous materials to study cracking along interfaces of dissimilar materials. Such investigations are motivated by both the
Figure 1: Simulation geometry and lattice orientation for the studies of interfacial cracking. The figure shows the slab under far-field tensile mode I loading. The inlay shows the orientation of the atomic lattice.
*
Department of Civil and Environmental Engineering, Email: [email protected]
0904-BB03-05.2
Figure 2: Crack tip history and crack velocity history for a mode I crack propagating at an interface with Ξ = 10 . Subplot (a) shows the crack tip history, and subplot (b) shows the crack tip velocity over time. A secondary daughter crack is born propagating at a supersonic speed with respect to the soft material layer.
scientific and technological relevance of this problem. From perspective of fu
Data Loading...
