A study of cyclic plastic stresses at a notch root
An experimental study is presented for cyclic plastic stresses at notch roots in specimens under constant-amplitude repeated tension and reversed loading. Edge-notched,KT=2, 2024-T3 aluminum-alloy sheet specimens were cycled until local stress conditions stabilized. Local stress histories were determined by recording local strain histories during cycling and reproducting these histories in simple, unnotched specimens. The fatigue lives for these notched specimens were estimated using stabilized local stresses and an alternating vs. mean stress diagram for unnotched specimens of the same material. These predictions compared favorably with lives from S-N data for the notch configuration tested.
In addition, an expression is presented for calculating local first-cycle plastic stresses. An acceptable correlation is shown between predicted stresses and experimental data within the scope of the investigation.
KeywordsFatigue Stress Condition Mechanical Engineer Fluid Dynamics Local Strain
List of Symbols
secant modulus corresponding to the local stress at the notch root for monotonically increasing tensile loads, psi
secant modulus corresponding to the local stress at the notch root for negative loading from tension. psi
secant modulus corresponding to the local stress at the notch root for positive loading from compression, psi
secant modulus corresponding to the average stress on the net section, psi
plastic stress-concentration factor for monotonically increasing tensile loads
plastic stress-concentration factor for negative loading from tension
plastic stress-concentration factor for positive loading from compression
elastic stress-concentration factor
number of cycles
ratio of Smin/Smax
nominal net-section stress, ksi
maximum nominal net-section stress, ksi
minimum nominal net-section stress, ksi
nominal stress range, ksi
specimen thickness, in.
local strain at the notch root
notch-root radius, in.
local stress at the notch root, ksi
local residual stress at the notch root, ksi
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