Investigation on True Stress-Strain Curves of Flat and Corner Regions of Cold-Formed Section Using 3D Digital Image Correlation Method

Table 4

Mechanical parameters of true stress-strain curves.

Types of coupons	Specimens	(MPa)		(MPa)		(MPa)
Flat coupons	TW-1	262.033	0.0013	554.07	0.332	—	—
	TW-2	255.463	0.0012	548.14	0.324	—	—
	TW-3	262.68	0.0012	542.26	0.323	—	—
	BW-1	255.13	0.0013	570.56	0.354	—	—
	BW-2	266.04	0.0013	576.83	0.331	—	—
	BW-3	262.63	0.0012	553.42	0.308	—	—
Corner coupons	TB-1	411.55	0.002	441.59	0.028	396.57	0.105
	TB-2	384.96	0.002	458.03	0.039	384.67	0.128
	TB-3	392.64	0.002	450.32	0.021	386.67	0.128
	BB-1	404.35	0.002	451.08	0.029	406.28	0.103
	BB-2	382.45	0.002	460.51	0.034	419.02	0.104
	BB-3	414.21	0.002	451.09	0.029	414.09	0.102
Average values of flat coupons		260.66	0.0013	557.55	0.329	—	—
Average values of corner coupons		398.36	0.002	452.10	0.030	401.22	0.112
Improvements of average values		52.83%	61.54%	−18.91%	−90.88%	—	—

Note. (1) is the true yielding strength; (2) is the true yielding strain; (3) is the true ultimate strength; (4) is the corresponding true ultimate strain; (5) is the true fracture stress; and (6) is the true fracture strain.