Dear Alison,
If the topology of springs is within a ” topology container” like EdgeSetTopologyContainer for example, in order to break springs when their stress/strain exceed a threshold, you can simply use the removeEdges from EdgeSetTopologyModifier. Just after removal of the edge from your topology, you should propagate the change of the topology (by calling propagateTopologicalChanges() ) so that this change is taken into account in your force fields.
Hope these help.
Cheers,
Phuoc