▁table ▁below : ▁▁ ▁Typ ical ▁stress – stra in ▁properties ▁▁ ▁A ▁main ▁property ▁of ▁steel , ▁which ▁is ▁used ▁to ▁describe ▁its ▁behavior , ▁is ▁the ▁stress – stra in ▁graph . ▁The ▁stress – stra in ▁graphs ▁of ▁cold - formed ▁steel ▁sheet ▁mainly ▁fall ▁into ▁two ▁categories . ▁They ▁are ▁sharp ▁yield ing ▁and ▁grad ual ▁yield ing ▁type ▁illustrated ▁below ▁in ▁Fig . 1 ▁and ▁Fig . 2 , ▁respectively . ▁ ▁These ▁two ▁stress – stra in ▁curves ▁are ▁typical ▁for ▁cold - formed ▁steel ▁sheet ▁during ▁t ension ▁test . ▁The ▁second ▁graph ▁is ▁the ▁representation ▁of ▁the ▁steel ▁sheet ▁that ▁has ▁under g one ▁the ▁cold - redu cing ▁( hard ▁rolling ) ▁during ▁manufact uring ▁process , ▁therefore ▁it ▁does ▁not ▁exhib it ▁a ▁yield ▁point ▁with ▁a ▁yield ▁plate au . ▁The ▁initial ▁slope ▁of ▁the ▁curve ▁may ▁be ▁lower ed ▁as ▁a ▁result ▁of ▁the ▁pre work . ▁Un like ▁Fig . 1 , ▁the ▁stress – stra in ▁relationship ▁in ▁Fig . 2 ▁represents ▁the ▁behavior ▁of ▁an ne aled ▁steel ▁sheet . ▁For ▁this ▁type ▁of ▁steel , ▁the ▁yield ▁point ▁is ▁defined ▁by ▁the ▁level ▁at ▁which ▁the ▁stress – stra in ▁curve ▁becomes ▁horizontal . ▁ ▁Cold ▁forming ▁has ▁the ▁effect ▁of ▁increasing ▁the ▁yield ▁strength ▁of ▁steel , ▁the ▁increase ▁being ▁the ▁consequence ▁of ▁cold ▁working ▁well ▁into ▁the ▁stra in - hard ening ▁range . ▁ ▁This ▁increase ▁is ▁in ▁the ▁zones ▁where ▁the ▁material ▁is