LOW CYCLE FATIGUE OF PRESSURE VESSEL MATERIALS. Final Technical Report

Technical Report · Fri Jun 01 04:00:00 EDT 1962

OSTI ID:4769774

Weiss, V; Sessler, J; Packman, P

The low-cycle controlled strain fatigue behavior of several steel and Al alloys was studied by means of axial tension-compression and bend cycling fatigue tests. The effects of a number of parameters including mean strain, stress biaxiality, superimposed stresses, test temperature, and type of loading were examined systematically. In addition, studies of accumulative and cumulative damage were undertaken in an attempt to gain a deeper understanding of the nature of strain-cycling fatigue and the damage mechanisms that are operatlve during the life of a strain-cycled specimen. It is shown that low-cycle fatigue phenomena are best analyzed from strain-controlled rather than stresscortrolled test data. It is shown that the relationship proposed independently by both Manson and Coffin predicts the failure life of strain-cycled specimens, but only for mean strains equal to zero. A modified equation is proposed which accounts for the effects of mean strain and indicates the equivalence of mean strain and prestrain. Total strain can be utillized instead of the plastic strain components up to approximately 10,000 cycles. Results obtained in tensioncompression and in bending are in general agreement if the testing conditions are similar. The effect of both stress biaxialtty and superimposed stress is to reduce specimen life at a given strain-cycling level. The latter effect appears to be dependert upon material characteristics. The effect of test temperature can be regarded as a reflection of the effect of temperature on uniaxial fracture ductility. Damage studies indicate that the accumulation of fatigue damage in a strain-cycled specimen is not predictable by the same equations that predict the failure life. Rather, it appears that accumulated damage'' is governed by the loss of available ductility owing to strain hardening and the formation and growth of cracks. Limited studles of cumulative damage'' indicate that subsequent cycling at a strain level higher than a prior precycle strain level results in failure at shorter lives than is predicted by a linear damage assumption. The cumulative damage problem appears to be quite complex. It is suggested that a better understanding of cumulative damage may be gained by the acquisition of additional basic information from accumulated damage studies. This information, obtained under a given set of cycling conditions, might then be translated to various cycling conditions. (auth)

• Research Organization: Syracuse Univ., N.Y. Research Inst.
• NSA Number: NSA-17-001944
• OSTI ID: 4769774
• Report Number(s): TID-16455
• Country of Publication: United States
• Language: English

Related Subjects

ALUMINUM ALLOYS
CONTROL
CRACKS
DEFORMATION
DUCTILITY
EQUATIONS
FAILURES
FATIGUE
MATERIALS TESTING
METALS, CERAMICS, AND OTHER MATERIALS
PRESSURE VESSELS
STEELS
STRESSES
TEMPERING
TENSILE PROPERTIES