Design and analysis of a high-performance shipping container for large payloads Page: 4 of 11
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only the membrane response of the drum wall, equivalent thickness shell elements are
meshed directly to the foam. This reduces the model cost, but may not accurately capture
the buckling or bending behavior of the outer drum.
To study the effect of the assumptions used in modelling the outer drum on the overall
system response, simulations were performed with test models utilizing two different
modelling approaches. In one model, both walls of the outer drum were modelled, and
contact relations were defined between the outer walls and the foam. In the other model,
the double-walled outer drum was modelled as a single, equivalent-thickness shell
meshed directly onto the foam. The mass, dimensions, and impact velocity of the test
models were similar to that of the H1636A.
To compare the effect of the outer drum on the system response, the maximum container
crush, the mock-up G levels, and the overall system kinetic energy were compared for the
two models for both axial and lateral impact. The test simulations showed that for the
quantities of interest in the H1636A impact simulations, detailed modelling of both walls
of the outer drum is not necessary; a single, equivalent thickness shell meshed directly
onto the foam is sufficient. Because this modelling approach greatly reduces the
computational cost of the model, it was employed.
To allow the major components of the H1636A to move relative to one another, contact
relations were defined. The resulting model allows the lid and containment vessel to
move relative to the drum overpack, and relative to one another. Within the
containment vessel, the foam support closest to the lid can move relative to the vessel
wall, and the mock-up can move relative to both foam supports. The foam in the drum
overpack was defined as a contact material to provide the self-contact capability required
to allow it to fold up on itself during the extensive crushing experienced in the CG-over-
The complete model included approximately 17,500 elements, with 13,200 8-noded
hexagonal elements, and 4,300 four-noded quadrilateral shell elements. The model had a
simulated weight of approximately 5000 lb, and required approximately 6 minutes of cpu
time per millisecond of simulation. The finite element mesh is shown in Figure 2(b).
The stainless steel (containment vessel and drum) and the aluminum (load spreaders and
mock-up) were modelled as elastic/power law hardening materials using the EP POWER
HARD constitutive model implemented in PRONTO. The nonlinear behavior of the
rigid polyurethane foam was modelled with the Orthotropic Crush Model. Since the
rigid polyurethane foam accounts for approximately 40 percent of the system mass, and
for the majority of the energy-absorbing capacity of the system, it was essential to validate
the foam model.
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York, A.R. II & Slavin, A.M. Design and analysis of a high-performance shipping container for large payloads, article, May 1, 1995; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc736215/m1/4/: accessed November 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.