Modeling of shape memory alloys with plasticity

Shape memory alloys are a special class of metals that can undergo large deformation yet still be able to recover their original shape through the mechanism of phase transformations. However, when they experience plastic slip, their ability to recover their original shape is reduced. This is due to the presence of dislocations generated by plastic flow that interfere with shape recovery through the shape memory effect and the superelastic effect. A one-dimensional model that captures the coupling between shape memory effect, the superelastic effect and plastic deformation is introduced. The shape memory alloy is assumed to have only 3 phases: austenite, positive variant martensite and negative variant martensite. If the SMA flows plastically, each phase will exhibit a dislocation field that permanently prevents a portion of it from being transformed back to other phases. Hence, less of the phase is available for subsequent phase transformations. A constitutive model was developed to depict this phenomena and simulate the effect of plasticity on both the shape memory effect and the superelastic effect in shape memory alloys. In addition, experimental tests were conducted to characterize the phenomenon in shape memory wire and superelastic wire. ^ The constitutive model was then implemented in within a finite element context as UMAT (User MATerial Subroutine) for the commercial finite element package ABAQUS. The model is phenomenological in nature and is based on the construction of stress-temperature phase diagram. ^ The model has been shown to be capable of capturing the qualitative and quantitative aspects of the coupling between plasticity and the shape memory effect and plasticity and the super elastic effect within acceptable limits. As a verification case a simple truss structure was built and tested and then simulated using the FEA constitutive model. The results where found to be close the experimental data. ^

Numerical Investigation of the Effect of Magnetic Field on Natural Convection in a Curved-Shape Enclosure

This investigation reports the magnetic field effect on natural convection heat transfer in a curved-shape enclosure. The numerical investigation is carried out using the control volume-based-finite element method (CVFEM). The numerical investigations are performed for various values of Hartmann number and Rayleigh number. The obtained results are depicted in terms of streamlines and isotherms which show the significant effects of Hartmann number on the fluid flow and temperature distribution inside the enclosure. Also, it was found that the Nusselt number decreases with an increase in the Hartmann number.

How monuments shape urban identity

Monuments in our society commemorate historical events, acts or heroes, and educate people about them. Monuments are landmarks that stand out from other buildings to give the city identity and order. This thesis asks how a monument can be designed to project a clear image at a distance and articulate a spatial experience at close range. Two important monuments that form part of the life of America serve as examples: (1) The Statue of Liberty, in the New York Harbor, that has become the visual icon of New York if not the nation and (2) The Holocaust Memorial in Miami Beach, Florida, that leads the visitor through a poignant experience at close range. The second part of the thesis is the design of a monument and museum for The Port of Miami, as part of the Port Boulevard Enhancement Project, sponsored by the Florida Foreign Trade Association, to celebrate the trade pioneers who helped Miami-Dade County achieve its prominence. The site for the monument is located at Biscayne Boulevard and Fifth Street, between Bayside Market Place and The American Airlines Arena in downtown Miami, at the Biscayne Bay.