# CONM2

Bulk Data Entry Defines a concentrated mass at a grid point of the structural model.

Attention: Valid for Implicit and Explicit Analysis

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONM2 EID G CID M X1 X2 X3
I11 I21 I22 I31 I32 I33
RAYL ALPHA

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CONM2 2 15   49.7
16.2   16.2     7.8

## Definitions

Field Contents SI Unit Example
EID Unique element identification number.

No default (Integer > 0)

G Grid point identification number.

No default (Integer > 0)

CID Coordinate system identification number.

Default = 0 (Integer ≥ -1)

M Mass value.

No default (Real)

X1, X2, X3 Offset distance from the grid point to the center of gravity of the mass in the coordinate system defined by CID, unless CID = -1, in which case X1, X2, and X3 are the coordinates (not offsets) of the center of gravity of the mass in the basic coordinate system.

Default = 0.0 (Real)

Iij Mass moments of inertia measured at the mass center of gravity.
• If CID is zero, then Iij is defined in the basic coordinate system.
• If CID > 1, then Iij refers to the local coordinate system.
• If CID is -1, then Iij refers to the basic coordinate system.

Default = 0.0 (Real)

RAYL Continuation line flag for material-dependent Rayleigh damping 5
ALPHA Rayleigh damping coefficient for the mass matrix 5

Default = 0.0 (Real ≥ 0.0)

## Comments

1. If the continuation is omitted, all rotary inertia is assigned zero values.
2. The form of the inertia matrix about its center of gravity is:(1)
$M=\left[\begin{array}{cccccc}M& & & 0.0& \left(X3\cdot M\right)& -\left(X2\cdot M\right)\\ & M& & -\left(X3\cdot M\right)& 0.0& \left(X1\cdot M\right)\\ & & M& \left(X2\cdot M\right)& -\left(X1\cdot M\right)& 0.0\\ & & & I11+\left(X{2}^{2}+X{3}^{2}\right)M& -I12-X1\cdot X2\cdot M& -I13-X1\cdot X3\cdot M\\ & \mathit{Symmetric}& & & I22+\left(X{1}^{2}+X{3}^{2}\right)M& -I32-X2\cdot X3\cdot M\\ & & & & & I33+\left(X{1}^{2}+X{2}^{2}\right)M\end{array}\right]$
Where,
M
Input mass value
Iij
Input inertia values
X1, X2, and X3
Offsets
3. If CID = -1, the offsets are computed internally as the difference between the grid point location and X1, X2, and X3. The grid points may be defined in a local coordinate system, in which case the values of ${\text{I}}_{\text{ij}}$ must be in a coordinate system that parallels the basic coordinate system.
4. If CID > 0, then X1, X2, and X3 are defined by a local Cartesian system, even if CID references a spherical or cylindrical coordinate system.
5. For material-dependent Rayleigh damping, the equivalent viscous damping, $C$ , is defined as:(2)
$C=\text{ALPHA}*M$
Where,
$\text{ALPHA}$
Defined on the RAYL continuation line on the material entry
$M$
Mass matrix
Supported solutions for material-dependent Rayleigh damping on CONM2:
• Nonlinear Transient Analysis
6. This card is represented as a mass element in HyperMesh.