( ( ( The region ) ( of ( ( the ( stress-strain curve ) ) ( ( in which ) ( ( the material ) ( ( returns ( to ( the ( undeformed stress ) ) ) ) ( when ( ( applied forces ) ( are removed ) ) ) ) ) ) ) ) ) ( ( is ( called ( the ( elastic region ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN region)) (PP (IN of) (NP (NP (DT the) (JJ stress-strain) (NN curve)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (DT the) (NN material)) (VP (VBZ returns) (PP (TO to) (NP (DT the) (JJ undeformed) (NN stress))) (SBAR (WHADVP (WRB when)) (S (NP (JJ applied) (NNS forces)) (VP (VBP are) (VP (VBN removed))))))))))) (VP (VBZ is) (VP (VBN called) (NP (DT the) (JJ elastic) (NN region)))) (. .)))
The region of the stress-strain curve in which the material returns to the undeformed stress when applied forces are removed is called the elastic region.
(ROOT (S (NP (NP (DT The) (NN force)) (VP (VBN applied) (PP (TO to) (NP (DT an) (NN object))))) (VP (VBZ is) (VP (VBN called) (NP (NN stress)))) (. .)))