SEDL / STP / STP467-EB / STP26843S

Optimum Fatigue Crack Resistance

Throop, JF
Research mechanical engineerPersonal member ASTM, Maggs Research Center, Watervliet Arsenal, Watervliet, N. Y.

Miller, GA
Research engineerPersonal member ASTM, Homer Research Laboratories, Bethlehem Steel Corp., Bethlehem, Pa.

Pages: 15    Published: Jan 1970

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Abstract

An evaluation is made of the influence of mechanical properties on fatigue crack growth rate. Data representing SAE 4340 and modified 4330 steels show that for levels of the stress intensity factor, K, below about 40 ksi√in. mechanical properties have little influence on growth rate. However, at higher K levels both the product of Young's modulus, yield strength, and fracture toughness and the product of Young's modulus, tensile strength, and true strain at fracture seem to be reasonable indexes of crack growth resistance. For K levels above 40 ksi√in. the fatigue crack growth rate is minimized by tempering 4340 and modified 4330 steel at temperatures of about 1000 and 1100 F, respectively.