The results are summarized in Figure 7 in which the undisturbed 

 and remolded strengths averaged over the core lengths are plotted 

 versus vane rotation rate. The general conclusions reached above are 

 clearly illustrated here. 



DATA REDUCTION AND RESULTS 



The first step in the data reduction process involved the 

 photographic enlargement of the accelerometer record for increased 

 clarity. For some tests the free-fall penetration region was interrupted 

 by the seam of the paper. Data analysis was simplified by cutting and 

 repiecing the plot paper so that the photo showed the free-fall and 

 penetration as a continuous line. 



The next phase of data reduction involved digitizing the plot. 

 The purpose was to have a series of coordinated points which represent 

 the plot. The discrete values could then be used in a digital computer 

 program for further analysis. The digitizing device was essentially 

 a measuring device which gave the coordinates of a selected point 

 from a reference point. The operator looked through an aiming device 

 at the photographically enlarged record and arbitrarily selected 

 points on the plot by depressing a button. The reference point was 

 established at the end of the penetration. The operator followed the 

 plot from the reference point in the aimer and selected various points 

 by depressing the button. This sampling scheme of various coordinated 

 points described that particular plot. The coordinate values for each 

 point were recorded as five-place integers on computer punch cards 

 and typed out on paper tape by the digitizer. These integers were 

 related to acceleration and time values by a computer program. 



The computer program had two salient functions. One was to read 

 the digitized data and make the conversion of coordinate values to 

 acceleration and time values. Also, the program had to compensate 

 for the helical nature of the output. This compensation was necessary 

 because a simple helix transforms into an inclined straight line when 

 the plot paper is unfolded from the drum. A correction factor was 

 incorporated in the program to account for this inclination in the 

 reference line, in effect, converting the output from "helical coordinates" 

 to rectilinear coordinates. The second function involved the 

 numerical integration of the acceleration to obtain velocity and displace- 

 ment. The plots were approximated by fitting linear segments between 

 each digitized point and integrated by summing the various areas under 

 these straight lines. Some inaccuracy was introduced since the actual 

 plot between any two points was not a straight line. However, close 

 digital sampling over the entire curve had a tendency to "average out" 

 any differences and thus mitigate the error. The typical digital output 

 included time increments (dictated by the digital sampling increments) , 

 acceleration increments, velocity increments (integration of acceleration), 

 displacement increments (integration of velocity) , and force increments 

 (the mass of the entire object times the acceleration). Plotting 

 subroutines were then used to transform the digital results back into 

 continuous plots. 



