Part -1:

Question 1

The aluminum (7075 - T7351) panel has on edge crack of 1 inch and is subjected to constant amplitude cycle loading of σ_max = 10 sec and. σ_min = 0.

(a) use the walker growth vote equation and ΔN = 500 to determine the crack length after zoo cycles.

(b) Do the same thing but use the IHT growth rate equation or curve

K_max = 10√(Πa) [1.12 -.23(a/4) + 10.6(a/4)² - 21.x(a/4)³ + 30.3(a/4)⁴]

Question 2

For example +a, use the walker equation to determine the number of cycle required for the crack to become critical use aluminum 2024 T3

Question 3

How many cycles will it take to become critical?

Question 4

How many cycles will it take to reduce the residual strength by 20% ? by 40% ? use the Kmax vs d2a/dx curve given.

Question 5

Refer to the figure below to provide specific values of residual strength for the skin-stiffener structure for each of the following two cases:
a) Stiffener a is used
b) Stiffener b is used

Question 6

Set up a table to determine the crack growth of a panel subjected to the cyclic loading shown in the figure below.

Use the following growth data:

ΔN = 1,000 cycles
a_o = 2.0 in

Use the Walker growth rate equation:

da/dN = 10^-4 [zK_max/m_T]^P

z = (1 - R )^q

where p = 3.7 , q = 0.6 , m_T = 25

As an approximation, consider that the stress intensity of the cracked structure can be calculated at every stage of growth as

K₁ = (1.2) σ√(Πa)

Question 7

If the remote stress applied is σ = 20 (ksi) , determine the stress intensity factor for the edge cracked panel of the figure in the following cases:

A) No plastic zone adjustment
B) With plastic zone adjustment for both √Πa and β for plane stress
C) With plastic zone adjustment for both √Πa and β for plane strain

Note: assume the following values

σ_ys = 63 (ksi)

W = 8(in)

a = 2(in)