13
LINDBERG AND KULACHENKO
FIGURE 16
Close-up of critical points in the lower corner using the two different boards. In (A) Board A, and in (B) Board B
FIGURE 17 (B) for Board B
Histograms of the Monte Carlo simulations of the Tsai – Wu stress and fitted GEV PDF. (A) Plot of results for Board A, and in
TABLE 5 Figure17
the Tsai – Wu stress deviates depending on the stress state can be seen in, for instance, Mukherjee et al. 38 It should be emphasized that at σ TW ¼ 1 failure is initiated , and is not necessarily the same thing as visible failure. The number of trays with visible failure can be expected to be fewer than what has been calculated in this study. Further, the stochastic approach can be extended to include a variation of the stress state. This means having a variation of the load or the material parameters in the constitutive equations. The assumption of zero variation of the stress state is of course non-conservative. The pressing of the punch can be
GEV distribution parameters for the fitted PDF seen in
Paperboard
Scale η [ ]
Shape β [ ]
Mode μ [ ]
BoardA
0.154
0.067
1.71
BoardB
0.053
0.003
0.78
considered to be quite a controlled process, but friction possibly adds a small variation of the stress levels in the paperboard blank. The non- uniformities of paperboard result in a variation of constitutive material
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