On the quantification of bridging tractions during subcritical crack growth under monotonic and cyclic fatigue loading in a grain-bridging silicon carbide ceramic
✍ Scribed by C.J. Gilbert; R.O. Ritchie
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 457 KB
- Volume
- 46
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
AbstractÐThe mechanisms of cyclic fatigue-crack propagation in a grain-bridging ceramic, namely an in situ toughened, monolithic silicon carbide, is examined. The primary goal is to directly quantify the bridging stresses as a function of cyclic loading. To investigate the eect of the number of loading cycles on the strength of the wake bridging zone, crack-opening pro®les of cracks grown at high velocity near the K c instability (to simulate behavior on the R-curve) and at low velocity near the fatigue threshold (to simulate the cyclically-loaded crack) were measured in situ in the scanning electron microscope at a ®xed applied stress intensity. Dierences between the measured pro®les and those computed for elastic traction-free cracks permit the estimation of the traction distributions. These are then used to simulate resistance curve and fatigue-crack growth rate date. Predictions are found to be in close agreement with experimental measurements on disc-shaped compact-tension specimens. The results provide direct, quantitative evidence that bridging tractions are indeed progressively diminished due to cyclic loading during fatigue-crack propagation in a grain-bridging ceramic.