No abstract

Abstract-The parameters are considered that control the threshold stress intensity in fatigue and relationships existing between these parameters are examined. A new relation is derived which is shown to be consistent with experimental data for a O.l5%C, 1,5%Mn steel.

A B S T R A C TThe phenomena of branching and blunting of stress corrosion cracks are reviewed and their effects demonstrated for a martensitic steel. The stress intensity that a crack can sustain is proportional to the square root of its tip radius, so that blunt cracks require a higher apparent stress intensity. A simple procedure is outlined for converting apparent stress intensities to effective stress intensities, so eliminating anomalous effects due to crack branching and blunting.

Duplicate tests have been performed to determine the effect of cathodic protection potential on corrosion fatigue crack growth rate of a modern offshore structural steel, produced by thermomechanically controlled processes. The experiments were carried out using compact tension specimens exposed to artificial seawater at 10°C and subjected to constant amplitude loading at 0.35 Hz. Reproducible results showed that the merits of cathodic protection potentials are strongly dependent on stress intensity ratio R and stress intensity range AK. It appears that a spcci6c value of cathodic potential may not give comprehensive protection against corrosion fatigue within the spectrum of variable amplitude loading experienced in service. Fractography showed the initiation of secondary cracks on the fracture surface to be associated with the dissolution of calcium sulphide inclusions, regardless of imposed cathodic potential. NOMENCLATURE u = crack length B = specimen thickness CEV = carbon equivalent value du/dN = crack growth rate K, = mean s t m intensity factor AK = stress intensity range AP = load range K-, K,,,,,, = maximum, and minimum, strcss intensity factor R = stress intensity ratio (K,,,,,,/K,) w = tpecimen width Y = compliance function uuu = tensile strength uy = yield strength

We propose to use stopping cosmic-ray muons in the energy calibration of planned and deployed large underwater detectors. The method is based on the proportionality between the incident muon energy and the length of the muon path before it stops. Simultaneous measurements of the muon path and the amplitude of the signal from the photomultiplier tubes allow a relation between the energy deposited in the sensitive volume of the detector and the observed signal to be derived, and also provide a test of detector simulations. We describe the proposed method and present the results of simulations.