Date: 
12.06.16

Deformation 3

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Weight Sensing:

We used an arduino and a weight sensor to obtain different strains across a surface with the same point load moving across it. We did so by using a clamp attached to the surface at different points.The arduino sensor reading was in grams. We then obtained the strain across the surface by plotting the results for different points on the grid. Since the mounting of the sensor was in the center of the surface, and the surface was constrained on one side only, the plot is symmetrical across one axis.

Temperature change during plastic deformation:

We use live thermal photography to sense the temperature change in the surface during its deformation (See figure). Because temperature increase occurs in the area undergoing plastic flow, thermal photographs can clearly indicate the area of highest strain and the pattern of plastic flow through the surface.

Through the deviation from thermal equilibrium induced by the internal friction associated with plastic deformation, a region of plastic deformation can be isolated. The system must be allowed to equilibrate once more before subsequent images can be analyzed since the range of the coloration must be within small tolerance threshold dictated by the average temperature of the material.

Simultaneously, a 3D scanner (Kinect) directed at the surface is used to compare the geometry of the incrementally twisted surface to a goal geometry constructed digitally. Because aluminum does have an elastic range, when bent it will unroll back into a flat surface unless it is plastically deformed.

Form transformation:

When twisting the aluminium surface, its two opposite edges are constrained as straight lines but the rest of the surface is free to change its shape. Because aluminum has an elastic range, a reversible slow twist will fully unroll back into a flat position once the surface is unloaded unless the force is large enough to cause plastic flow in the material . We track the transformation and check for the reversibility of the twist motion. We could measure the elastic reaction during unloading until the goal geometry has been achieved.