Effects of friction and high torque on fatigue crack propagation in mode III. [AISI 4140 and 4340]

Journal Article · Wed Dec 01 00:00:00 EST 1982 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02648390· OSTI ID:5785323

Nayeb-Hashemi, H; McClintock, F A; Ritchie, R O

Turbo-generator and automotive shafts are often subjected to complex histories of high torques. To provide a basis for fatigue life estimation in such components, a study of fatigue crack propagation in Mode III (anti-plane shear) for a mill-annealed AISI 4140 steel (R /SUB B/ 88, 590 MN/m/sup 2/ tensile strength) has been undertaken, using torsionally-loaded, circumferentially-notched cylindrical specimens. As demonstrated previously for higher strength AISI 4340 steel, Mode III cyclic crack growth rates (dc/dN) /SUB III/ can be related to the alternating stress intensity factor ..delta..K /SUB III/ for conditions of small-scale yielding. However, to describe crack propagation behavior over an extended range of crack growth rates (about 10/sup -6/ to 10/sup -2/ mm per cycle), where crack growth proceeds under elastic-plastic and full plastic conditions, no correlation between (dc/dN) /SUB III/ and ..delta..K /SUB III/ is possible. Accordingly, a new parameter for torsional crack growth, termed the plastic strain intensity GAMMA /SUB III/, is introduced and is shown to provide a unique description of Mode III crack growth behavior for a wide range of testing conditions, provided a mean load reduces friction, abrasion, and interlocking between mating fracture surfaces A micro-mechanical model for the main radial Mode III growth is extended to high nominal stress levels, and predicts that Mode III fatigue crack propagation rates should be proportional to the range of plastic strain intensity (..delta..GAMMA /SUB III/) if local Mode II growth rates are proportional to the displacements. Such predictions are shown to be in agreement with measured growth rates in AISI 4140 steel from 10/sup -6/ to 10/sup -2/ mm per cycle.

• Research Organization: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5785323
• Journal Information: Metall. Trans., A; (United States), Vol. 13A
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STEELS
CRACK PROPAGATION
FATIGUE
ABRASION
ANNEALING
COALESCENCE
ELASTICITY
FRICTION
INCLUSIONS
LOADING
PLASTICITY
SHAFTS
SHEAR
STRESS INTENSITY FACTORS
SURFACES
TENSILE PROPERTIES
TESTING
TORQUE
TURBOGENERATORS
ALLOYS
ELECTRIC GENERATORS
HEAT TREATMENTS
IRON ALLOYS
IRON BASE ALLOYS
MACHINE PARTS
MATERIALS HANDLING
MECHANICAL PROPERTIES
360103* - Metals & Alloys- Mechanical Properties