Swelling strains from gamma-irradiated silica - Evaluation of results by Shelby

Water introduced in silica reacts with the silica network under hydroxyl generation that causes a volume swelling. This effect has been discussed quantitatively in much detail in [1] for the case of water entrance by a heat treatment procedure. In the present Report we include also data by Shelby [8] obtained by in-situ generation of hydroxyl in gamma-irradiated silica. This procedure resulted in stronger density changes compared with the heat-treated material. Independent of this fact, we can show that the same volume swelling results for both methods. As an application of the results an estimation of the molar volume of hydroxyl is made

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

Glass breaks like metals, but at the nanometer scale

We report in situ Atomic Force Microscopy experiments which reveal the presence of nanoscale damage cavities ahead of a stress-corrosion crack tip in glass. Their presence might explain the departure from linear elasticity observed in the vicinity of a crack tip in glass. Such a ductile fracture mechanism, widely observed in the case of metallic materials at the micrometer scale, might be also at the origin of the striking similarity of the morphologies of fracture surfaces of glass and metallic alloys at different length scales.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Lett, few minor corrections, Fig. 1b change

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)

Small-specimen double-cantilever-beam test applicable to monoliths and joints

A small-specimen double-cantilever-beam test has been used to measure the tughness of monolithic ceramics and joined ceramics. The specimen was tested on several monolithic ceramics to evaluate its quality before it was used for joints. Despite the small dimensions of the specimen, the test appears to be reliable and to yield reproducible data. Two bonding processes were used for joining single-crystal Mn-Zn ferrite tiles. After optimization, toughness values were comparable to those of single crystals