  Simplified model for current-voltage characteristics of weak links is
suggested. It is based on approach which considers Andreev reflections as
responsible for the dissipative current through the metallic Josephson
junction. The model allows to calculate current-voltage characteristics of weak
links (superconductor - normal metal - superconductor junctions, microbridges,
superconducting nanowires) for different thicknesses of the normal layer at
different temperatures. The current-voltage characteristics of tin microbridges
at different temperatures were computed.
