where b, h, tl and tz are the design variables; W is the weight of the panel; P"=10-4 is the

limit on the probability of failure, P. The four design variables are b, h, tl and tz.

 Geometric imperfections such as global, local, inter-ring, and general ovalization

of cylindrical panels are taken into account in PANDA2 software directly by specifying

the geometric imperfection amplitudes as shown in Table 8-1.

Table 8-1. Amplitudes of geometric imperfection handled by PANDA2 software
 .Buckling modal general
 Out of roundness (in) Initial local amplitude (in)
 amplitude (in)
 0.8 0.8 0.008

Uncertainties

 The material used in the study is Al 2219-T87, which has a density of 0.1 lb/in3

Two for elastic properties (Young's modulus E and Poisson's Ratio pu) and the strength

allowable o are assumed to be normally distributed and uncorrelated random variables

with mean values and coefficients of variation shown in Table 8-2.

Table 8-2. Uncertainties in material properties (Al 2219-T87) modeled as normal random
 variables

 Young's Modulus (E) Poisson Ratio (pu) Stress Allowable (4,)

 Mean value 0.107x10s psi 0.34 0.58x105 psi
 Coefficient of
 0.03 0.03 0.05
 variation

Table 8-3. Uncertainties in manufacturing process modeled as uniformly distributed
 random design variables around design (mean) value
 b h tl tz
 Percentage
 il % +2% +4% +4%
 variation


 The four design variables (b, h, tl and tt) are also random around design (mean)

value due to manufacturing uncertainties. They are assumed to be uniformly distributed

with percent variation shown in Table 8-3. These data are intended only for illustration.