For two heats of ASTM A533 Grade B Class 1 pressure vessel steel and an ASTM A508 Class 2 forged steel, an extensive study of fatigue crack growth rate characteristics was conducted within the framework of linear elastic fracture mechanics. Experimental data obtained covered a wide variation in cyclic growth rates ranging from those associated with fatigue threshold (order of 10-9 in./cycle) up to rapid fracture. The bulk of experimental information obtained was at very low cracking rates, usually 10-6 in./cycle and below. Considered in the investigation were: (1) an evaluation of the effect of stress ratio, R = σmin/σmax, on verv slow rates of fatigue crack extension; (2) an evaluation of temperature (75 to 650 F) on very slow rates of fatigue cracking; (3) an examination of the combined effects of temperature and stress ratio and their influence on fatigue crack extension; (4) an evaluation of the effect of a distilled water environment on fatigue crack propagation rates; (5) an examination of the effects of specimen thickness; and (6) a comparison of results for two separate heats of the same alloy.

No abstract

Fracture toughness data are presented for two ASTM A533 Grade B Class 1, 12-in-thick plate submerged arc process weldments. These data were generated in accordance with current ASTM recommended toughness testing procedures using compact tension specimens up to 8 in. thick. The toughness (KIc) properties show a strong temperature dependence resulting in rapidly increasing toughness with increasing temperature. Each of the weld deposit materials and also some limited heat-affected-zone data revealed toughness properties comparable or superior to ASTM A533 Grade B Class 1 plate material. Pertinent data relating to the weld parameters and composition, as well as the conventional tensile and Charpy V notch data are also given. For these weldment materials, the high toughness (KIc) properties found provide excellent reliability against brittle fracture in heavy section pressure vessel applications.

No abstract

A review of fracture toughness and fatigue crack growth rate data currently available for medium-strength steels is presented. Data are included for three commonly used structural steels (AISI 1045, 1144, and 4140); two pressure vessel steels (ASTM A533 Grade B, Class 1 and A216 WCC grade); and three grades of rotor forging steels (ASTM A469, Class 4; A470, Class 8; and A471, Class 4). These data clearly illustrate that under conditions of sufficient restraint to ensure plane strain loading, existing linear elastic fracture mechanics technology is applicable to medium-strength steels. The advantages and overall potential of fracture mechanics technology as a quantitative tool for the prevention of failure is demonstrated by means of an example problem.