This paper is concerned with the prediction of deformation pattern, strains and strain-rates in sea ice indentation problems and their application to ice load prediction.
The paper discusses the applicability of the rigid plastic assumption in sea ice indentation and presents a procedure for estimating deformation, strains, and strain-rates from the velocity fields which are constructed for the purpose of estimating the maximum indentation pressure. Results are given for the case or plane, steady state indentation. A procedure roar estimating the stress field around the indenter room these results is outlined and its limitations discussed.
The paper also discusses the development of indentation pressure with deformation as well as the similarity between test results and cavity expansion solutions.
Indentation problems have several possible applications in arctic offshore engineering such as in the prediction of (1) the upper bound ice load on a fixed structure and (2) the local ice contact pressure. In addition, small scale indentation tests can potentially be developed into simple and convenient means for measuring ice strength and deformability. This type of procedure has long been used in metal working and soil exploration (2, 20).
In the past several years, indentation has been subjected to extensive theoretical and experimental research. Most of this effort has been directed at the prediction of the maximum indentation pressure and its relationship to the strength properties of sea ice to provide a basis for designing structures for ice infested waters.
This paper is concerned with the deformation pattern, strains and strain-rates, as well as the load displacement relationship during sea ice indentation. These are important for the following reasons:
The strength properties of sea ice and consequently the maximum indentation pressure have been found to vary with strain and strain rate (15).
The Upper Bound Method of plastic limit analysis has been relied upon to predict the maximum indentation pressure. This method assumes the likely modes of deformation in the ice around the indenter by constructing velocity fields. The prediction of the deformation implied by these velocity fields provides a means roar checking whether these velocity fields are realistic.
In some applications, the relative displacement between the indenter and the ice may not be sufficient to develop the maximum indentation pressure. In this case, the pressure or load versus displacement relationships will be required.
The interaction between a structure and the surrounding ice field often involves very large and complicated deformation in the ice. A rigorous analysis of such a problem, including realistic constitutive relationships for ice, will require the prediction of the accumulated strains and the strain-rate in the ice.
Indentation refers to contact between a solid indenter and another solid body. When the contact load is small, the problem belongs to the classical theory of elasticity. Solutions for different indenter shapes can be found in Sneddon (19) and Green and Zerna (5). When the contact load exceeds certain limits, large deformation will occur around the indenter.
