Problem

Calculate the maximum internal crack length allowable for a 7075-T651 aluminum alloy (Tabl...

Calculate the maximum internal crack length allowable for a 7075-T651 aluminum alloy (Table 9.1) component that is loaded to a stress one-half its yield strength. Assume that the value of Y is 1.35.

Table 9.1 Room-Temperature Yield Strength and Plane Strain Fracture Toughness Data for Selected Engineering Materials

	Yield Strength		KIc
Material	MPa	Ksi	MPa	ksi
Metals
Aluminum alloya (7075-T651)	495	72	24	22
Aluminum alloya (2024-T3)	345	50	44	40
Titanium alloya (Ti-6Al-4V)	910	132	55	50
Alloy steela (4340 tempered @ 260°C)	1640	238	50.0	45.8
Alloy steela (4340 tempered @ 425°C)	1420	206	87.4	80.0
Ceramics
Concrete	—	—	0.2–1.4	0.18–1.27
Soda–lime glass	—	—	0.7–0.8	0.64–0.73
Aluminum oxide	—	—	2.7–5.0	2.5–4.6
Polymers
Polystyrene (PS)	25.0–69.0	3.63–10.0	0.7–1.1	0.64–1.0
Poly(methyl methacrylate) (PMMA)	53.8–73.1	7.8–10.6	0.7–1.6	0.64–1.5
Polycarbonate (PC)	62.1	9.0	2.2	2.0