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FRINATEK-Fri mat.,naturv.,tek

Local dynamic and heat dissipation in randomly pinned crack front

Awarded: NOK 6.6 mill.

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Project Period:

2011 - 2016


In this project we have studied both experimentally and numerically fracturing of materials. We have a particular focus on the energy dissipation of fracturing and how temperature effects will influence the fracture dynamics. We have used an infrared camera where we directly can measure the heat dissipation of the fracture process and estimate how big part of the total energy that goes into heat . In other experiments and simulation we have studied how micro fractures in front of the fracture front develop. By using an ultra fast camera, we can measure the locale velocity fluctuations of the fracture front in a transparent material. The local velocities were found to follow a distribution which is not Gaussian, but a stable Levi distribution. We have further studied the shape of the locale velocity bursts (published recently in Nature communication) We have also in this project studied fracturing of porous and granular materials under gas or liquid injection

This project concerns the study of the dynamics and heat dissipation of an in-plane fracture front propagating in a transparent PMMA sample. The main goal of the project is to study in a systematic way, both experimentally and theoretically, mode 1 fractu re propagation along the weak interface between two sintered Plexiglas plates. We will study forced propagation with a constant deflection velocity of one of the plates and thermal creep with zero deflection velocity of the plate. We will use a waiting time matrix method, and an ultra fast image recording technique, to study the detailed velocity fluctuations of the front. The front propagation will be characterized by fast moving de-pinning regimes with corresponding velocity avalanches, and of low velocity pinning lines. The project will consist of three subprojects. In the first project we will study the heat dissipation measured by an infrared camera. In these experiments, the non deflected Plexiglas plate will be exchanged by a NaCl plate whic h is transparent to infrared light. The heat dissipation will be compared with the pinning and de-pinning dynamics of the contact line. In the second subproject we will study the local and global dynamics in the thermal creep regime. Our hypothesis is t hat the creep is activated thermally and following Arrhenius law. Preliminary results are consistent with this hypothesis, but more experiments are needed to be conclusive. In the third project we will study fracture propagation in a soft laponite gel. In this system we can measure both the inplane and the out of plane roughness of the fracture.

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FRINATEK-Fri mat.,naturv.,tek