In a compression test, a steel test specimen (modulus of elasticity = 30 x 106lb/in2) has a starting height= 2.0 in and diameter = 1.5 in. the metal yields (0.2% offset) at a load = 140,000 lb. at a load of 260,000 lb, the height has been reduced to 1.6 in. determine (a)yield strength and (b) flow curve parameters (strength coefficient and strain-hardening exponent). assume that the cross-sectional area increases uniformly during the test.

Explanation:

A) we know that volume is given as V

where D = 1.5 in , h = 2.0 in

so

yield strenth is given as

b)

elastic strain

strain offsets  = 0.00264 + 0.002 = 0.00464     [where 0.002 is offset given]

area

True strain

At P= 260,000 lb ,

true stress

true strain

flow curve is given as \sigma = k\epsilon^n

so flow curve is

.........1

  .........2

Solving 1 and 2

we get

n = 0.103

and K =137,389 psi

Strength coffecient = K = 137.389ksi

strain hardening exponent = n = 0.103

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