Table 1.

Relationship between the extent of applied compression, contact circle radius, crack spacing, and induced circumferential normalized tensile stress in the equatorial plane. In addition, the crack spacing obtained in earlier work by directly applying tensile strains are compared to the spacing obtained in the present work. Microspheres were chosen to have a radius equal to approximately 400 µm.

Compression	79%	58%	33%
Microsphere radius, µm ± 2 µm	400	412	395
Contact circle radius, µm ± 15 µm	435	330	140
Crack spacing, µm	1.9 ± 0.3	3.8 ± 0.7	7.3 ± 0.6
Approximate equatorial circumferential normalized tensile stress (σθθ/E)	60%	25%	7%
Crack spacing of Zhu, et al. 2005, µm	2.7 ± 0.6	6.4 ± 0.8	12.3 ± 5
Crack spacing of Mills, et al. 2007, µm	--	1.9 ± 0.6	7.5 ± 3