On the mechanical interaction of a boa constrictor and its prey

The rather gruesome title provides the inspiration for an example involving the interaction between two different nonlinear viscoelastic material models. The boa constrictor is modeled as a circular band of muscle that can contract while exhibiting nonlinear viscoelastic tensile properties. It is wrapped around a prey whose chest and lungs are modeled as a cylinder of a compressible nonlinear viscoelastic material. Contraction results in tension in the muscle and a radial compressive load on the cylinder. It is assumed that the boa constrictor, as would a human, feels discomfort when its muscle tension becomes too large. The initial muscle contraction thus raises the boa constrictor’s muscle tension to the level of incipient discomfort, which then relaxes due to muscle viscoelasticity combined with compressive creep of the prey’s volume. Further muscle contraction raises the tension back to the maximum comfort level and the process is repeated until the volume of the prey has reduced to an extent that its viability is no longer possible. This behavior is illustrated with a numerical example.