Spider Diagram for Tubular Expansion with Restraints

 The aim of this study is to explain the mechanics of tubular expansion in irregularly shaped boreholes such as those frequently observed in the upper Natih reservoirs. Statistical analysis of borehole data does not indicate a strong correlation between the non-circularity and expanded tubular’s in such boreholes. A two-dimensional (2-D) finite element model was developed using commercial software to determine the non-circularity of an expanded tubular and those data were compared with the measured values. A parametric study was also conducted and spider plots were generated to determine the amount of irregularity in the expanded tubulars so that optimum operational parameters could be identified to limit cross-section irregularities during the expansion process.

Micromechanics of Transformation-Induced Plasticity and Variant Coalescence

Quantitative micromechanics descriptions of both transformation-induced plasticity (TRIP) associated with the martensitic transformation in an Fe-Ni alloy and of variant coalescence in a Cu-Al-Ni shape memory alloy are presented. The macroscopic deformation behavior of a polycrystalline aggregate as a result of the rearrangements within the crystallites is modelled with the help of a finite element based periodic microfield approach. In the case of TRIP the parent → martensite transformation is described by microscale thermodynamic and kinetic equations taking into account internal stress states. The simulation of a classical experiment on TRIP allows to quantify the Magee-effect and the Greenwood-Johnson effect. Furthermore, the development of the martensitic microstructure is studied with respect to the stress-assisted transformation of preferred variants. In the case of variant coalescence the strain energy due to internal stress states has an important influence on the mechanical behavior. Formulating the reorientation process on the size scale of self-accommodating plate groups in terms of the mobility of the boundaries between martensitic variants the macroscopic behavior in uniaxial tension is predicted by an incremental modelling procedure. Furthermore, influence of energy dissipation on the overall behavior is quantified