The fatigue behavior of an alpha + beta titanium alloy, Ti-6Al-2Sn-4Zr-6Mo, has been characterized in the very-high-cycle fatigue (VHCF) regime using ultrasonic-fatigue (20 kHz) techniques. Stress levels (r max ) of 40 to 60 pct of the yield strength of this alloy have been examined. Fatigue lifetimes in the range of 10 6 to 10 9 cycles are observed, and fatigue cracks initiate from both surface and subsurface sites. This study examines the mechanisms of fatiguecrack formation by quantifying critical microstructural features observed in the fatigue-crack initiation region. The fracture surface near the fatigue-crack-initiation site was crystallographic in nature. Facets, which result from the fracture of primary alpha (a p ) grains, are associated with the crack-initiation process. The a p grains that form facets are typically larger in size than average. The spatial distribution of a p grains relative to each other observed near the initiation site did not correlate with fatigue life. Furthermore, the spatial distribution of a p grains did not provide a suitable means for discerning crack-initiation sites from randomly selected nominal areas. Stereofractography measurements have shown that the facets observed at or near the initiation sites are oriented for high shear stress; i.e., they are oriented close to 45 deg with respect to the loading axis. Furthermore, a large majority of the grains and laths near the site of crack initiation are preferentially oriented for either basal or prism slip, suggesting that regions where a p grains and a laths have similar crystallographic orientations favor crack initiation. Microtextured regions with favorable and similar orientations of a p grains and the lath a are believed to promote cyclic-strain accumulation by basal and prism slip. Orientation imaging microscopy (OIM) indicates that these facets form on the basal plane of a p grains. The absence of a significant role of spatial clustering of a p grains, coupled with the observation of regions of microtexture on the order of 300 to 500 lm supports the idea that variability in fatigue life in the very-high-cycle fatigue regime results from the variability in the nature (intensity, coherence, and size) of these microtextured regions.

IMPORTANCE Previous trials have suggested that vasopressin and methylprednisolone administered during in-hospital cardiac arrest might improve outcomes.OBJECTIVE To determine whether the combination of vasopressin and methylprednisolone administered during in-hospital cardiac arrest improves return of spontaneous circulation. DESIGN, SETTING, AND PARTICIPANTS Multicenter, randomized, double-blind, placebo-controlled trial conducted at 10 hospitals in Denmark. A total of 512 adult patients with in-hospital cardiac arrest were included between October 15, 2018, and January 21, 2021. The last 90-day follow-up was on April 21, 2021.INTERVENTION Patients were randomized to receive a combination of vasopressin and methylprednisolone (n = 245) or placebo (n = 267). The first dose of vasopressin (20 IU) and methylprednisolone (40 mg), or corresponding placebo, was administered after the first dose of epinephrine. Additional doses of vasopressin or corresponding placebo were administered after each additional dose of epinephrine for a maximum of 4 doses. MAIN OUTCOMES AND MEASURESThe primary outcome was return of spontaneous circulation. Secondary outcomes included survival and favorable neurologic outcome at 30 days (Cerebral Performance Category score of 1 or 2). RESULTS Among 512 patients who were randomized, 501 met all inclusion and no exclusion criteria and were included in the analysis (mean [SD] age, 71 [13] years; 322 men [64%]). One hundred of 237 patients (42%) in the vasopressin and methylprednisolone group and 86 of 264 patients (33%) in the placebo group achieved return of spontaneous circulation (risk ratio, 1.30 [95% CI, 1.03-1.63]; risk difference, 9.6% [95% CI, 1.1%-18.0%]; P = .03). At 30 days, 23 patients (9.7%) in the intervention group and 31 patients (12%) in the placebo group were alive (risk ratio, 0.83 [95% CI, 0.50-1.37]; risk difference: −2.0% [95% CI, −7.5% to 3.5%]; P = .48). A favorable neurologic outcome was observed in 18 patients (7.6%) in the intervention group and 20 patients (7.6%) in the placebo group at 30 days (risk ratio, 1.00 [95% CI, 0.55-1.83]; risk difference, 0.0% [95% CI, −4.7% to 4.9%]; P > .99). In patients with return of spontaneous circulation, hyperglycemia occurred in 77 (77%) in the intervention group and 63 (73%) in the placebo group. Hypernatremia occurred in 28 (28%) and 27 (31%), in the intervention and placebo groups, respectively.CONCLUSIONS AND RELEVANCE Among patients with in-hospital cardiac arrest, administration of vasopressin and methylprednisolone, compared with placebo, significantly increased the likelihood of return of spontaneous circulation. However, there is uncertainty whether this treatment results in benefit or harm for long-term survival.

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A B S T R A C T Research on fatigue crack formation from a corroded 7075-T651 surface provides insight into the governing mechanical driving forces at microstructure-scale lengths that are intermediate between safe life and damage tolerant feature sizes. Crack surface marker-bands accurately quantify cycles (N i ) to form a 10-20 μm fatigue crack emanating from both an isolated pit perimeter and EXCO corroded surface. The N i decreases with increasingapplied stress. Fatigue crack formation involves a complex interaction of elastic stress concentration due to three-dimensional pit macro-topography coupled with local microtopographic plastic strain concentration, further enhanced by microstructure (particularly sub-surface constituents). These driving force interactions lead to high variability in cycles to form a fatigue crack, but from an engineering perspective, a broadly corroded surface should contain an extreme group of features that are likely to drive the portion of life to form a crack to near 0. At low-applied stresses, crack formation can constitute a significant portion of life, which is predicted by coupling macro-pit and micro-feature elastic-plastic stress/strain concentrations from finite element analysis with empirical low-cycle fatigue life models. The presented experimental results provide a foundation to validate next-generation crack formation models and prognosis methods.Keywords AFGROW; aluminium; corrosion fatigue; finite element analysis; fatigue at notches; fatigue crack initiation; hydrogen embrittlement; life prediction. N O M E N C L A T U R Eb = fatigue strength exponent c = fatigue ductility exponent E = Young's modulus f = loading frequency K = stress intensity factor K IC = plane strain fracture toughness K max = maximum stress intensity k t−e = elastic stress concentration factor k t−ep = elastic-plastic stress concentration factor k ε = strain concentration factor K = stress intensity range L = longitudinal (rolling) grain orientation direction L p = pit height along the L-direction N i = crack formation cycles to ≈ 20 μm N f = total cycles to failure (N i + N p ) N p = crack propagation cycles to failureCorrespondence: James T. Burns.