  Crystallographic slip system identification methods are widely employed to
characterize the fine scale deformation of metals. While powerful, they usually
rely on the occurrence of discrete slip bands with clear slip traces and can
struggle when complex mechanisms such as cross-slip, curved slip, diffuse slip
and/or intersecting slip occur. This paper proposes a novel slip system
identification framework, termed SSLIP (for Slip Systems based Local
Identification of Plasticity), in which the measured displacement gradient
fields (from Digital Image Correlation) are locally matched to the kinematics
of one or multiple combined theoretical slip systems, based on the measured
crystal orientations. To identify the amounts of slip that conforms to the
measured kinematics, an optimization problem is solved for every datapoint
individually, resulting in a slip activity field for every considered slip
system. The identification framework is demonstrated and validated on an HCP
virtual experiment, for discrete and diffuse slip, incorporating 24 slip
systems. Experimental case studies on FCC and BCC metals show how full-field
identification of discrete slip, diffuse slip and cross-slip becomes feasible,
even when considering 48 slip systems for BCC. Moreover, the methodology is
extended into a dedicated cross-slip identification method, which directly
yields the orientation of the local slip plane trace orientation, purely based
on the measured kinematics and on one or two chosen slip directions. For even
more challenging cases revealing a persistent uncertainty in the slip
identification, a two-step identification approach can be employed, as is
demonstrated on a highly challenging HCP virtual experiment.
