How heat controls fracture: the thermodynamics of creeping and avalanching cracks

Abstract

Fast fractures and the brittleness of matter are explained by statistical physics and by thousands of degrees hot rupture fronts, the blackbody radiation of which elucidates fractoluminescence.

Thermal dissipation as both the strength and weakness of matter. A material failure prediction by monitoring creep

“…While qualitative statements, such as larger f in metals rather than, say, polymers, are tempting, we have here arbitrarily fixed this percentage to 50% in all materials, except for a couple of instances where we could estimate it. 9,13 For different materials, we however show how f affects the prediction of our model in the ESI. † Note that, while the velocity is often reported in relation to the stress intensity factor K rather than the energy release rate G, we have here converted from one to the other with the following relation: 1 G B K 2 /E to derive a and b, and then l and G c .…”

“…Such processes can however be included in the model. 9 We have also assumed no rate-limiting environmental factor, that is, no significant chemical interaction of the matrix with the fracture fluid (i.e., no stage I or II). We have hence restricted our comparison to experimental data to such a non-environmental creep case (stage III), although distinguishing it with certitude is not always straightforward.…”

“…All the introduced parameters can now be estimated, and we did so for twenty materials for which the creeping behaviour was studied in the literature. 9,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] The corresponding G to V curves and a table of all the inferred parameters values are shown in the ESI. † We can then solve numerically the two non linear eqn (1) and (2), now taking into account the temperature rise DT.…”

“…The detailed procedure is discussed and applied to two materials (PMMA and Pressure Sensitive Adhesive) in ref. 9. This comparison is summarised for all the media in Fig.…”

“…In a previous study, 8 we indeed proposed a unifying model of the slow creep and the fast regime, holding a precise quantification of the energy budget and the heating of the crack tip, which is coupled with an Arrhenius-type activation law. We have shown how it accounts, in some polymers, 9 for seven decades of propagation velocities and for the transition, at the avalanche load, from creep to sudden failure. Here, we present how well this thermodynamics based model can predict the threshold G a for a broad range of materials, by comparing its forecasts to actual experimental failure thresholds from twenty data sets from the literature.…”