Official Answer
Answer
"Strongest" has to be defined as force per unit of installed height, and on that measure the Belleville disc washer wins — but it deflects almost nothing. Among springs that give a usable stroke, the nested wave spring is the highest-force option: its turns are stacked in phase so the loads add in parallel, and a nested design will deliver several times the load of a single-layer wave spring of the same height. Load is extremely sensitive to geometry. For a given deflection it varies with the cube of the flat wire thickness and with the fourth power of the number of waves per turn, and it falls as turns are added in series. Small changes on paper are large changes in force.
