Evaluation of Trapezoidal Shaped Grooves
closing in on the groove. The edges or walls of the trapezoidal-shaped grooves also experienced some disfiguring but still maintained its basic shape. Figure 47 shows a picture of the standard groove with a 1/4-in. measurement ruler placed over the groove, and figure 48 shows a picture of a trapezoidal-shaped groove with the same ruler. Note how the standard groove has closed to less than a 1/4 in., while the trapezoidal-shaped groove has closed slightly but is still fairly close to its original 1/2 in. width. Figure 49 shows a comparison in the amount of damage in a transition area in which the type of groove switches from trapezoidal (on left) to standard (on right). These results validated the data collected earlier during the profiling activity conducted at the NAPTF that showed the trapezoidal-shaped grooves suffered some failure under extreme weight conditions but were still able to maintain a recognizable shape. The standard grooves, however, did not.
Figure 47. Standard Groove Damage
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