EXPERIMENTAL INVESTIGATIONS AND COMPUTATIONAL FRACTURE MECHANICS MODELLING OF BRITTLE ICE FRAGMENTATION

The ice loads on marine structures are affected by the failure process of ice. Brittle failure is one of the important failure modes. Ice fails in a brittle manner when the loading rate is high or the temperature is low. In this paper the brittle fragmentation of ice is studies experimentally and computationally. In laboratory experiments, a block of ice was crushed in a continuous manner against a structure, and a sequential flaking process was observed. After a test the top of an ice block was wedge shaped indicating a narrow contact area. It is suggested that flakes were formed through the growth of macro cracks. The growth of these cracks is analyzed by using linear elastic fracture mechanics. A boundary element method capable of analysing the growth of cracks under normal and frictional forces is developed. As such a contact problem is nonlinear due to both the friction phenomena and the boundary conditions, it is formulated in an incremental and iterative fashion. A model for brittle flaking is formulated using the developed computational method. In the model a population of surface cracks on a flat wedge top loaded with a rigid indentor is considered. It is shown that through edge flaking a solid can maintain a wedge shape and even evolve into it. Characteristic of the process is that the flakes form in cascades and that for a nonsymmetric wedge, the flakes form from the less steep side. Therefore, the process can sustain itself. The model predicts that the load-displacement record of the process comprises of triangular ramps. The slope of the rising part of a ramp is set by the elastic response of the ice-structure system and the peak load is defined by the instantaneous values of the stress intensity factors and the fracture toughness of the material. The drop of the load after the peak is due to a cascade of flakes. Comparisons with laboratory and field experiments support the proposed flaking model both qualitatively and quantitatively.

• Supplemental Notes:
  • Acta Polytechnica Scandinavica, Mechanical Engng Series n 120, 1996 [105 p, 102 ref, 15 tab, 56 fig]
• Authors:
  • Tuhkuri, J
• Publication Date: 1996

Language

• English

Subject/Index Terms

• TRT Terms: Boundary element method; Fracture mechanics; Ice; Ice phenomena; Loads; Mechanics
• Old TRIS Terms: Ice loads; Ice mechanics
• Subject Areas: Hydraulics and Hydrology; Marine Transportation;

Filing Info

• Accession Number: 00734475
• Record Type: Publication
• Source Agency: British Maritime Technology
• Files: TRIS
• Created Date: Mar 27 1997 12:00AM