Freeze-bond strength: Analysis of experiments and FE modeling of a shear test on freeze bonds

The objective of this study was to contribute to the knowledge on ice-ridges structures interactions. This work is a follow-up of previous research on simulations of ice-structure interaction using finite element method (Gürtner, 2009b; Konuk, et al., 2009a,b) and a preliminary study of freeze-bond (FB) shear strength (Repetto-Llamazares, et al., 2009b). The presented data should be regarded as illustrative rather than exhaustive. Many important aspects of ice-ridges structures interactions have not been addressed in this thesis. An analysis of experiments with FBs was performed, and a finite element model was built in order to simulate these experiments. Within the framework of the classical theory of elasticity, the numerical model incorporates a cohesive model in order to simulate ice fracture along the FB during shear test. The cohesive behavior of the FB was described by the bilinear traction-separation law. The approach of Camanho and Davila (2002) was applied in order to calculate stresses in the FB under mixed-mode loading conditions. A 6-node cohesive finite element was used for implementation of assumed behavior of the FB. Information obtained via detailed analysis of the FB shear strength experiments and via their numerical simulation can be used for a better understanding of FB failure processes and for a numerical modeling of ice-ridges. The results of numerical simulation confirmed that the finite element model could reproduce phenomena commonly observed in actual shear tests of FBs, including the shear strength hardening and partly softening behavior. The peak load in simulations was completely determined by the maximum traction strength and the initial part of a traction-separation law. This study also showed that from the conducted experiments intended to study FB strength in model ice, it is also possible to study ice fracture processes as well as post-failure behavior. By improving the experimental procedure as described in Repetto-Llamazares, et al. (2009b) it will be possible to study not only FB shear strength but also the frictional behavior of ice after the FB failure. By video monitoring of the crack initiation and growth it will be possible to study a fracture process inside the FB. This work is of appeal to different scientists actively participating in investigations in, and possibly also on the standardization of methods for, measuring strength of freeze-bonds in order to improve existing analytical and numerical models, which are used nowadays for calculation of loads for scenarios of ice-ridges interactions with structures.

Subject

freeze-bonds
ice ridges
finite element model
cohesive zone model
ice engineering

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master thesis

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