The rupture process of Wenchuan earthquake is complicated including an obvious change in slip direction
, which suggests that several faults participated in the rupture.
The dislocation pileup direction was the same as the single-crystal slip direction
, which was beneficial to the slip and motion of crystal, resulting in the enhanced plastic ability of material.
One was marked as A-A' (Figures 2 and 3), which was consistent with the main slip direction
of the landslide, arranged in the axial position of the landslide; the other was perpendicular to the slip direction
and approximately paralleled to the road which crossed the landslide at about 200 m above sea level (Figure 3).
For a material with [alpha] = 1, ..., N slip systems defined by orthonormal vector pairs ([m.sup.[alpha].sub.0], [n.sup.[alpha].sub.0]) denoting the slip direction
and slip plane normal, respectively, at time t = 0, the constitutive equations relate the following basic fields (all quantities expressed in crystal lattice coordinate frame): the deformation gradient F defined with respect to the initial undeformed crystal which can be decomposed into elastic and plastic parts as F = [F.sup.e][F.sup.p] (with det([F.sup.p]) = 1), the Cauchy stress a, and the slip resistances [s.sup.[alpha]] > 0.
With the increase in cold-rolled thickness reduction degree, the grains in the specimens are gradually elongated and flattened, and the slip direction
of the grains turned to the rolling direction.
where [n.sup.([alpha])] and [m.sup.([alpha])] are the unit vectors normal to the slip plane and along the slip direction
of the slip system [alpha], respectively.
Each crystal possesses only four possible slip planes, each one with a chain and a transverse slip direction
, as shown in Fig.
He also demonstrated that the slip direction
may be parallel to the direction of maximum shear stress resolved along the preexisting fracture surface.
Like for orthorhombic polyethylene and PEEK (11, 13) eight slip systems are taken into consideration, either with the slip direction
along the chain axis ("chain slip") or perpendicular to the chain axis ("transverse slip").
We clustered known source mechanisms according their slip directions
; two general types of slip directions
are considered: lying in the main fault plane and significantly deviating ones.
Possible slip directions
[01 1] and  on (111) are also indicated in Figure 7(a).
Each of the 4 slip planes has 3 slip directions
, along which the stress, necessary for a deformation, is the lowest.