An Improved Model to Calculate Pullback Force of Trenchless Horizontal Directional Drilling Pipeline

Table 3

Stress-strain data of pipeline in plastic stage.

True stress (MPa)	Plastic strain	True stress (MPa)	Plastic strain
418	0	882	0.25
500	0.01	908	0.35
605	0.02	921	0.45
695	0.056	932	0.55
780	0.095	955	0.65
829	0.15	\	\