Wire Grid

%% aseering -- oops; Dan actually already wrote this.  Don't bother finishing it.
%Procedure:

%For this experiment, our goal was to capture video of glass deforming on impact with a BB.  Our setup was as in Figure \ref{fig:GridSetup1}, using the equipment shown in Table \ref{table:GridMaterials}.  The glass was taped to the Apple Boxes with black Gaffer's Tape.

%\begin{figure}[h!]
%\centering
%\includegraphics[width=6.5in]{grid_setup}
%\caption{This is the setup that we used to take video of glass deforming and being broken by impact with a BB.}
%\label{fig:GridSetup1}
%\end{figure}

%\begin{table}

%\label{table:GridMaterials}
%\end{table}

%For each run of the experiment, we first installed a new sheet of glass as shown in the setup diagram, removing any old glass as necessary.  We then loaded the BB gun and fired it at the glass, manually post-triggering the HSV camera so as to effectively capture the moment of impact.  


Results:

We ran several trial runs of this experiment.  A number of trials were run with mirrors.  However, in many of these trials the mirrors did not shatter.  It was found that the silver reflective mirror surface was 


In one trial with the $\frac{3}{32}''$ glass, we obtained the two images shown in Figure \ref{fig:grid_test1_frames}.  The two consecutive frames shown in this figure illustrate the glass deforming substantially on impact with the BB.  This deformation can be seen more clearly in the charts shown in Figure \ref{fig:grid_test1_graphs}.  These charts show plots of the positions of the vertices of the wire mesh that are visible in the image.

The glass deforms in a circular region surrounding the impact point of the BB.  The amount of deformation decreases with distance from the BB, up to a certain radius at which the magnitude of the deformation rapidly drops to zero.

In a subsequent trial with the $\frac{3}{32}''$ glass, we obtained the series of images shown in Figure \ref{fig:grid_test2_frames}.  The images show a similar deformation.  The third image in the series exhibits a number of irregular deformations; it appears that, in this frame, the glass has begun to crack.  Interestingly, these odd deformations don't show up effectively in the vertex graphs in Figure \ref{fig:grid_test2_graphs}.  The cracks manifest themselves as disjoint lines, which are very visible to the naked eye but which don't necessarily have a large or consistent effect on the positions of grid vertices.



\begin{figure}[h!]
\centering
\includegraphics[width=2.25in]{grid_test1_frame1}
\includegraphics[width=2.25in]{grid_test1_frame2} \\
\includegraphics[width=4.5in]{grid_test1_videodata}
\caption{Two consecutive frames from Trial 1.  The first frame is immediately prior to the BB's impact; the subsequent frame is immediately after the BB's impact.}
\label{fig:grid_test1_frames}
\end{figure}


\begin{figure}[h!]
\centering
\includegraphics[width=2.25in]{grid_test1_graph1}
\includegraphics[width=2.25in]{grid_test1_graph2}
\caption{Graphs of the grid vertices from Trial 1, as shown in Figure \ref{fig:grid_test1_frames}.  Units are in ``image pixels''.  The image that we worked with was scaled up to a resolution of 512x256 prior to gathering the data for these charts.}
\label{fig:grid_test1_graphs}
\end{figure}


\begin{figure}[h!]
\centering
\includegraphics[width=2.25in]{grid_test2_frame1}
\includegraphics[width=2.25in]{grid_test2_frame2}
\includegraphics[width=2.25in]{grid_test2_frame3} \\
\includegraphics[width=4.5in]{grid_test2_videodata}
\caption{Three consecutive frames from Trial 2.  The first frame is immediately prior to the BB's impact; the second frame is immediately after the BB's impact, and the third frame shows the glass beginning to crack.}
\label{fig:grid_test2_frames}
\end{figure}


\begin{figure}[h!]
\centering
\includegraphics[width=2.25in]{grid_test2_graph1}
\includegraphics[width=2.25in]{grid_test2_graph2}
\includegraphics[width=2.25in]{grid_test2_graph3}
\caption{Graphs of the grid vertices from Trial 1, as shown in Figure \ref{fig:grid_test2_frames}.  The image that we worked with was scaled up to a resolution of 512x256 prior to gathering the data for these charts.}
\label{fig:grid_test2_graphs}
\end{figure}













