Explicit 3-D Structural Mass

Compatible Products: – | – | – | – | – | – | DYNA

MASS166 Element Description

MASS166 is a point element having up to nine degrees of freedom: translations, velocities, and accelerations in the nodal x, y, and z directions.

Figure 166.1:  MASS166 Geometry

MASS166 Geometry

MASS166 Input Data

The mass element is defined by a single node with concentrated mass components (Force*Time2/Length) in the element coordinate directions about the element coordinate axes. The element also has an option for rotary inertia (without mass) which allows the definition of lumped rotary inertia at a defined nodal point. For the inertia option (KEYOPT(1) = 1), six polar moment of inertia values must be input instead of mass. To include both mass and rotary inertia, you must define two MASS166 elements at the same node.

A summary of the element input is given in "MASS166 Input Summary". A general description of element input is given in Element Input.

MASS166 Input Summary



Degrees of Freedom


Note:  For explicit dynamic analyses, V(X, Y, Z) refers to nodal velocity, and A(X, Y, Z) refers to nodal acceleration. Although V(X, Y, Z) and A(X, Y, Z) appear as DOFs, they are not actually physical DOFs. However, these quantities are computed as DOF solutions and stored for postprocessing.

Real Constants
If KEYOPT(1) = 0:
MASS - Concentrated mass (Force*Time2/Length) (must be > 0)
If KEYOPT(1) = 1:
IXX - Moment of inertia (must be > 0),
IXY - Moment of inertia,
IXZ - Moment of inertia,
IYY - Moment of inertia (must be > 0),
IYZ - Moment of inertia,
IZZ - Moment of inertia (must be > 0)
Material Properties

None, but you must define realistic dummy material properties to make this element behave correctly. The dummy properties will not be used in any solution.

Surface Loads


Body Loads


Special Features

All nonlinear features allowed for an explicit dynamic analysis.


Rotary inertia option:

0 -- 

3-D mass without rotary inertia (default)

1 -- 

3-D rotary inertia (no mass)

MASS166 Output Data

Nodal displacements are included in the overall displacement solution. There is no printed or post element data output for the mass element.

MASS166 Assumptions and Restrictions


MASS166 Product Restrictions

There are no product-specific restrictions for this element.

Release 18.2 - © ANSYS, Inc. All rights reserved.