## 13.185. SOLID185 - 3-D 8-Node Structural Solid

SOLID185 is available in two forms:

### 13.185.1. SOLID185 - 3-D 8-Node Structural Solid

Matrix or VectorShape Functions Integration Points
Stiffness and Stress Stiffness Matrices; and Thermal Load Vector Equation 11–214, Equation 11–215, and Equation 11–216

2 x 2 x 2 if KEYOPT(2) = 0, 2, or 3
1 if KEYOPT(2) = 1

Mass MatrixSame as stiffness matrix2 x 2 x 2
Pressure Load Vector Quad Equation 11–69 and Equation 11–70 2 x 2
Triangle Equation 11–49 and Equation 11–50 3
Element TemperatureTrilinear thru element
Nodal TemperatureTrilinear thru element
PressureBilinear across each face

### 13.185.2. SOLID185 - 3-D 8-Node Layered Solid

Matrix or VectorShape Functions Integration Points
Stiffness and Stress Stiffness Matrices; and Thermal Load Vector Equation 11–214, Equation 11–215, and Equation 11–216

In-plane:
2 x 2
Thru-the-thickness:
2 if no shell section defined.
1, 3, 5, 7, or 9 per layer if a
shell section is defined

Mass MatrixSame as stiffness matrix Same as stiffness matrix
Pressure Load Vector Quad Equation 11–69 and Equation 11–70 2 x 2
Triangle Equation 11–49 and Equation 11–50 3
Element TemperatureBilinear in plane of element, linear thru each layer
Nodal TemperatureTrilinear thru element
PressureBilinear across each face

### 13.185.3. Other Applicable Sections

Structures describes the derivation of structural element matrices and load vectors as well as stress evaluations. General Element Formulations gives the general element formulations used by this element.

### 13.185.4. Theory

If KEYOPT(2) = 0 (not applicable to layered SOLID185), this element uses method (selective reduced integration technique for volumetric terms) (Hughes([220]), Nagtegaal et al.([221])).

If KEYOPT(2) = 1 (not applicable to layered SOLID185), the uniform reduced integration technique (Flanagan and Belytschko([233])) is used.

If KEYOPT(2) = 2 or 3, the enhanced strain formulations from the work of Simo and Rifai([319]), Simo and Armero([320]), Simo et al.([321]), Andelfinger and Ramm([322]), and Nagtegaal and Fox([323]) are used. It introduces 13 internal degrees of freedom to prevent shear and volumetric locking for KEYOPT(2) = 2, and 9 degrees of freedom to prevent shear locking only for KEYOPT(2) = 3. If mixed u-P formulation is employed with the enhanced strain formulations, only 9 degrees of freedom for overcoming shear locking are activated.

### 13.185.5. Shear Correction

The element does not perform interlaminar shear correction. Stresses are calculated from strains as is.