Three-dimensional finite-element models for the treatment of the nonlinear, transient response of a fast breeder reactor's above-core structures are described. For purposes of treating arbitrarily large rotations, node orientations are described by unit vectors and the deformable elements are treated by a corotational formulation in which the coordinate system is embedded in the elements. Deformable elements may be connected either to nodes d i rectly or through r i gid bodies. The ti1ne integration is carried out by the Newmark ~ method. These features have been incorporated to form the finit e-element program SAFE/RAS (§_afety Analysis by finite Elem:ents/ Reactor Analysis and §_afety Division). Computations are presented for semianalytical comparisons, simple s e eping studies, and Stanford Research Institute (SRI) test comparis o ns.. J. M. Kennedy (20) A. B. _Krisciunas ANL Contract File ANL Libraries (5)
A three-dimensional analytical model of the cervical spine is described. The cervical vertebrae and the head are modeled as rigid bodies which are interconnected by deformable elements representing the intervertebral disks, facet joints, ligaments and muscles. A special pentahedral continuum element for representing the articular facets is described which effectively maintains stability of the cervical spine in both lateral and frontal plane accelerations, which is very difficult with multi-spring models of the facets. A simplified representation is used for the spine and body below the level of T1. The neck musculature is modeled by over 100 muscle elements representing 22 major muscle groups in the neck. The model has been validated for frontal and sideways impact accelerations by simulating published experimental data. Results are also presented to show the effects of the stretch reflex response on the dynamics of the head and neck under moderate acceleration.
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