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Volume Load

In the Volume Load boundary condition, a distributed load per unit volume is applied on a body (or set of bodies). It is useful to model body loads, such as weight, inertial effects, centrifugal force, electromagnetic loads, and any load that is proportional to the volume (or mass) of the body.

volume load boundary condition parameters panel
Figure 1: Volume load boundary condition panel. Enter the value in each direction with appropriate units and pick volumes to assign.

The parameters of the boundary condition are:

  1. Load: The components of the applied load, expressed in the global coordinate system directions of the model \( (t_x, t_y, t_z) \).
  2. Assignment: Set of volumes where the load will be applied.

Supported Analysis Types

The following analysis types support the usage of this boundary condition:

Resultant Force Magnitude and Direction

The traction vector is defined by the components of the load:

$$ \vec{t} = (t_x, t_y, t_z) $$

Each component has units of force (\(N\), \(lb.\), etc) per unit of body volume (\(m^3\), \(cubic in.\), etc). The total applied force vector over the assignment set depends on the total volume:

$$ \vec{F} = \int \vec{t} dV $$

Variable Load

Variable volume load values can be specified with the use of the formula or table inputs. The allowed functions are:

  • Time-dependent: The body force varies with respect to time (variable t) in a nonlinear static or dynamic simulation. This is useful, for instance, to ramp up the load from zero in nonlinear simulations, where a sudden application of load leads to numerical divergence, or for naturally time-varying loads in dynamic simulations.
  • Coordinate-dependent: The surface load varies with respect to the position in space (variables X, Y, Z). An example where this is useful is the case of hydrodynamic pressure, where the load varies with respect to the coordinates.

Maximum Number of Table Parameters

Due to numerical difficulties, the underlying structural solver (Code_Aster) only supports table function definitions of one or two variables. If you need to define a function of the three spatial coordinates (X, Y, Z), or even combine it with time, you must create an analytical formula for it.

volume load application example
Figure 2: Stress contour plot of a ring subject to a centrifugal force, modeled with a volume load (see validation case below).

Last updated: November 10th, 2020

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