Answer:
yield strength before cold work = 370 MPa
yield strength after cold work = 437.87 MPa
ultimate strength before cold work = 440 MPa
ultimate strength after cold work = 550 MPa
Explanation:
given data
AISI 1018 steel
cold work factor W = 20% = 0.20
to find out
yield strength and ultimate strength before and after the cold-work operation
solution
we know the properties of AISI 1018 steel is
yield strength σy = 370 MPa
ultimate tensile strength σu = 440 MPa
strength coefficient K = 600 MPa
strain hardness n = 0.21
so true strain is here ∈ =
= 0.223
so
yield strength after cold is
yield strength = 
yield strength = 
yield strength after cold work = 437.87 MPa
and
ultimate strength after cold work is
ultimate strength = 
ultimate strength = 
ultimate strength after cold work = 550 MPa