STP1546: Fatigue Crack Growth Rate Behavior of A36 Steel using ASTM Load-Reduction and Compression Precracking Test Methods

    Newman, J. C.
    Dept. of Aerospace Engineering, Mississippi State Univ., Mississippi State, MS

    Ziegler, B. M.
    Dept. of Aerospace Engineering, Mississippi State Univ., Mississippi State, MS

    Shaw, J. W.
    Dept. of Aerospace Engineering, Mississippi State Univ., Mississippi State, MS

    Cordes, T. S.
    HBM n-Code Federal, LLC, Advanced Applications Center, Mississippi State Univ., Mississippi State, MS

    Lingenfelser, D. J.
    HBM n-Code Federal, LLC, Advanced Applications Center, Mississippi State Univ., Mississippi State, MS

    Pages: 22    Published: Jul 2012


    Abstract

    Eccentrically-loaded single-edge crack tension, ESE(T), specimens made of A36 structural steel were tested over a wide range in stress ratios (R = 0.1 and 0.7) in laboratory air. Two test methods were used: (1) ASTM Standard E647 load-reduction method and (2) compression precracking. After compression precracking (CP), three different loading sequences were used: (1) constant amplitude (CPCA), (2) load reduction (CPLR), and (3) constant stress-intensity factor (CPCK). The crack-compliance method was used to determine that the specimens had no residual stresses; and that the effects of tensile residual stresses from compression precracking dissipated in about 2 compressive plastic-zone sizes. Agreement was found between the A36 and TC-128B steel ΔK-rate data tested at both low and high stress ratio (R) conditions. At R = 0.1 loading, the CPCA and CPLR tests generated lower thresholds and faster rates than using the standard ASTM load-reduction method. All load-reduction tests exhibited an accumulation of debris at the crack front near threshold conditions. A crack-closure analysis was preformed to calculate the effective stress-intensity factor range (ΔKeff) against rate using measured 1 % offset (OP1) values for all R = 0.1 tests. The ΔKeff-rate data correlated well with the high-R results.

    Keywords:

    cracks, fatigue crack growth, crack closure, stress intensity factor, plasticity, steel


    Paper ID: STP154620120004

    Committee/Subcommittee: E08.07

    DOI: 10.1520/STP154620120004


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