v-K-data for silica from interrupted lifetime measurements

Different methods were applied so far in order to determine subcritical crack growth for silica. Mostly, fracture mechanics standard tests with macro cracks were used for this purpose. In this report, we evaluated the subcritical crack growth curves from interrupted lifetime tests on silica bending specimens containing small natural flaws. The resulting v-K-curve showed crack growth rates down to 10$^{-14}$ m/s indicating a threshold for subcritical crack growth at K$_{th}$$\approxeq$0.31 MPa$\sqrt{m}$ In the plot of v=f(K/K$_{Ic}$) slight material differences could be eliminated and suitable agreement with macro-crack results by Wiederhorn and Bolz [1] on DCB-specimens and Michalske et al. [2] on DCDC-specimens could be stated

Cavitation Damage During Flexural Creep of SiAlON–YAG Ceramics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65505/1/j.1151-2916.1991.tb07156.x.pd

Swelling strains from density measurements

Water in contact with silica glass surfaces diffuses into the glass, and reacts with the silica network under hydroxyl generation. Clear evidence has been reported in the literature for a volume swelling due to the water uptake and reaction in silica. In the past, the authors showed in a couple of papers the principle effects of volume swelling by hydroxyl generation on mechanics and fracture mechanics properties. From literature data on density as a function of water content a linear dependence of the volume swelling strain with water concentration was established. This dependency will be discussed in the present report including data scatter

Strength measurement on silica soaked in hot water. Open Access am KIT

The effect of water soaking on the strength of silica glass is studied. When silica glass is immersed in warm water and held there for an extended period of time, the strength increases over that of freshly damaged glass. The increase in strength is a consequence of water diffusion into exposed surfaces of the test specimen, which results in swelling of the glass and shielding of cracks present in the surface of the glass. In our first paper on this subject (Report 19 of this series), we considered swelling effects on the inert strength. In the present report, the strength under subcritical crack growth conditions is studied. For tests carried out in humid environment at various loading rates, so-called dynamic strength tests, we could show theoretically that the swelling effect cuased by the reaction of water with silica must result in apparently increased crack-growth exponents. This prediction is in good agreement with results from literature. In our experiments we could show via an evaluation of the crack extension that even in silicone oil environment local subcritical crack growth accurs

Inert strength measurement on hot water soaked silica

The effect of water soaking on the strength of silica glass is studied. When silica glass is immersed in warm water and held there for an extended period of time, the strength increases over that of freshly damaged glass. The increase in strength is interpreted as the consequence of water diffusion into exposed surfaces of the test specimen, which results in swelling of the glass and shielding of cracks present in the surface of the glass. Experimental results are compared with theoretical predictions

Fabrication of Mullite Body Using Superplastic Transient Phase

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65799/1/j.1151-2916.1992.tb05542.x.pd

J-Integral Calculation by Finite Element Processing of Measured Full-Field Surface Displacements

© 2017 The Author(s)A novel method has been developed based on the conjoint use of digital image correlation to measure full field displacements and finite element simulations to extract the strain energy release rate of surface cracks. In this approach, a finite element model with imported full-field displacements measured by DIC is solved and the J-integral is calculated, without knowledge of the specimen geometry and applied loads. This can be done even in a specimen that develops crack tip plasticity, if the elastic and yield behaviour of the material are known. The application of the method is demonstrated in an analysis of a fatigue crack, introduced to an aluminium alloy compact tension specimen (Al 2024, T351 heat condition)