where:
T = tear strength in force/unit thickness (per unit length torn),
l = extension ratio in legs of piece,
F = force applied to ends of piece,
w = total width of specimen,
T = thickness, and
E = strain energy density in legs of piece. For certain vulcanizates, if w is chosen large enough, the elongation of the legs is minimal (ʎ= 1) and E is essentially zero. Then: T