Figure 1. LS-DYNA simulations of southern yellow pine showing brittle behavior in tension and shear, and ductile behavior in compression. Graphs, A, B, and C.

1. Tension. This graph shows a blue line rising diagonally across the graph before sloping back down. The vertical axis of this graph ranges from 0 to 25,000 and represents Tensile Stress Parallel to Grain (psi) while the horizontal axis of this graph ranges from 0.0 to 1.5 and represents Tensile Strain Parallel to grain (percent). The blue line rises from the zero points on both axes diagonally across the graph peaking at the points of 26,000 on the vertical axis and just before 1.0 on the horizontal axis. From there, is begins to slope back down until it meets the horizontal axis at the points of zero on the vertical axis and 1.2 on the horizontal axis. This slope depicts Brittle Post-Peak Softening.

2. Shear. This graph shows a blue line rising diagonally across half the graph before sloping back down toward the horizontal axis. The vertical axis of this graph ranges from 0 to 3,000 and represents Shear Stress Parallel to Grain (psi) while the horizontal axis ranges from 0 to 6 and represents Shear Strain Parallel to Grain (percent). The blue line rises from the points of zero on both axes diagonally, peaking at the points of 2,400 on the vertical axis and 2 on the horizontal axis. From there, it begins to gradually slope back down into the horizontal axis, where it leaves the graph at zero point on the vertical axis and 6 on the horizontal axis. This gradual slope depicts Moderate Post-Peak Softening.

3. Compression. This graph shows a blue line rising across a quarter of the graph where it plateaus and from there, runs straight off the graph. The vertical axis of this graph ranges from 0 to 8,000 and represents Compressive Stress Parallel to grain (psi) while the horizontal axis of this graph ranges from 0.0 to 1.5 and represents Compressive Strain Parallel to Grain (percent). The blue line rises at a slight angle up the length of the graph where it peaks at the points of 7,400 on the vertical axis and 0.5 on the horizontal axis. The curve just before the blue line peaks, at the points of 6,400 on the vertical axis and 0.3 on the horizontal axis depicts Pre-Peak Hardening. From the peak, the blue line plateaus and runs straight off the graph at the points of 7,600 on the vertical axis and 1.5 on the horizontal axis. This plateau depicts No Post-Peak Softening.

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FHWA-HRT-05-096