There are fundamental differences in the mechanical contact algorithms in ABAQUS/Standard and ABAQUS/Explicit. These differences are reflected in how contact conditions are defined. The main differences are the following:
ABAQUS/Standard uses a strict master-slave weighting when enforcing contact constraints (see Defining contact pairs in ABAQUS/Standard, Section 29.2.1 of the ABAQUS Analysis User's Manual); the nodes of the slave surface are constrained not to penetrate into the master surface. The nodes of the master surface can, in principle, penetrate into the slave surface. ABAQUS/Explicit includes this formulation but typically uses a balanced master-slave weighting by default (see Contact formulation for general contact, Section 29.3.4 of the ABAQUS Analysis User's Manual, and Contact formulation for ABAQUS/Explicit contact pairs, Section 29.4.4 of the ABAQUS Analysis User's Manual).
ABAQUS/Standard and ABAQUS/Explicit both provide a finite-sliding contact formulation (see Contact formulation for ABAQUS/Standard contact pairs, Section 29.2.2 of the ABAQUS Analysis User's Manual, and Contact formulation for ABAQUS/Explicit contact pairs, Section 29.4.4 of the ABAQUS Analysis User's Manual). However, the two-dimensional finite-sliding contact formulation in ABAQUS/Standard requires that the master surfaces be smooth; whereas in ABAQUS/Explicit the master surfaces are faceted, except for analytical rigid surfaces, which can be smoothed.
ABAQUS/Standard and ABAQUS/Explicit both provide a small-sliding contact formulation (see Contact formulation for ABAQUS/Standard contact pairs, Section 29.2.2 of the ABAQUS Analysis User's Manual, and Contact formulation for ABAQUS/Explicit contact pairs, Section 29.4.4 of the ABAQUS Analysis User's Manual). However, the small-sliding contact formulation in ABAQUS/Standard transfers the load to the master nodes according to the current position of the slave node. ABAQUS/Explicit always transfers the load through the anchor point.
ABAQUS/Explicit can account for the current thickness and midsurface offset of shells and membranes in the contact logic, whereas ABAQUS/Standard cannot.
Many benefits of the ABAQUS/Explicit general contact algorithm are not available in ABAQUS/Standard.