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Daiyan H.,Sintef | Daiyan H.,Northern Research Institute NORUT Narvik | Andreassen E.,Sintef | Andreassen E.,Buskerud and Vestfold University College | And 3 more authors.
Experimental Mechanics | Year: 2012

Distributions of shear strains and strain states (triaxiality) were analysed for two in-plane shear test fixtures (Iosipescu and V-notched rail), using digital image correlation and numerical simulations. Three different polypropylene-based materials (two talc-filled compounds and one unfilled homopolymer) were tested. The three materials behaved differently in the shear tests. Most notably, cracks developed in tension near the notches for the particle-filled materials, while the unfilled homopolymer did not fracture. There were also differences between the materials regarding strain localisation between the notches, strain rates vs. strain level (for a given cross-head speed), thickness change in the sheared section, and triaxiality. The yield stresses in shear, uniaxial tension and uniaxial compression showed pressure sensitivity. At least for equivalent strain rates below 1 s -1, the strain rate sensitivity of the yield stress was approximately the same in these three stress states. The stress-strain curves obtained with the two methods were quite similar for these materials. There were some differences between the methods regarding the ease of mounting and aligning specimens, the complexity of specimen deformation patterns, and the uniformity of the shear strain distribution between the notches. © 2012 Society for Experimental Mechanics.

Petrich C.,Northern Research Institute NORUT Narvik | Saether I.,Northern Research Institute NORUT Narvik | Fransson L.,Lulea University of Technology | Sand B.,Northern Research Institute NORUT Narvik | Arntsen B.,Northern Research Institute NORUT Narvik
Cold Regions Science and Technology | Year: 2015

Static ice loads (ice actions) are a key design parameter for dams in cold climates. However, their theoretical description is still elusive, introducing uncertainty in design and hindering development of remediation measures. We present and analyze measurements of stresses due to thermal loads in a small reservoir in northern Norway. Several weeks of observations, including both cold and warm spells, were well-described by a simple equation that accounts for thermal expansion and temperature-dependent creep. One model parameter was found to depend systematically on the location of measurements within the reservoir. Biaxial stress measurements showed that the stress field was not homogeneous. Results suggest that the stress field in reservoirs should be predictable from first principles with numerical methods and point toward a promising, simple parameterization. © 2015 The Authors.

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