4.11 LINK11 Linear Actuator

4.11 LINK11 Linear Actuator (UP19980821 ) LINK11 may be used to model hydraulic cylinders and other applications undergoing large rotations. The element is a uniaxial tension-compression element with three degrees of freedom at each node: translations in the nodal x, y, and z directions. No bending or twist loads are considered. See Section 14.11 in the ANSYS Theory Reference for more details about this element.

Figure 4.11-1 LINK11 Linear Actuator



4.11.1 Input Data

The geometry and node locations for the element are shown in Figure 4.11-1. The element is defined by two nodes, a stiffness K (force/length), viscous damping C (force*time/length), and mass M (force*time2/length). The element initial length Lo and orientation are determined from the node locations.

Element loads are described in Section 2.7. The stroke (length) is defined through the surface load input using the PRES label. The stroke is relative to the zero force position of the element. A force may be defined in the same manner as an alternate to the stroke.

A summary of the element input is given in Table 4.11-1. A general description of element input is given in Section 2.1.

Table 4.11-1 LINK11 Input Summary

Element Name

LINK11

Nodes

I, J

Degrees of Freedom

UX, UY, UZ

Real Constants

K, C, M

Material Properties

None

Surface Loads

Pressures: face 1 - Stroke, face 2 - Axial Force

Body Loads

None

Special Features

Stress stiffening, Large deflection, Birth and death

4.11.2 Output Data

The solution output associated with the element is in two forms:

A general description of solution output is given in Section 2.2. See the ANSYS Basic Analysis Procedures Guide for ways to view results.

The following notation is used in Table 4.11-2:

A colon (:) in the Name column indicates the item can be accessed by the Component Name method [ETABLE, ESOL] (see Section 2.2.2). The O and R columns indicate the availability of the items in the file Jobname.OUT (O) or in the results file (R), a Y indicates that the item is always available, a number refers to a table footnote which describes when the item is conditionally available, and a - indicates that the item is not available.

Table 4.11-2 LINK11 Element Output Definitions

Name

Definition

O

R

EL

Element number

Y Y
NODES

Nodes - I, J

Y Y
ILEN

Initial element length

Y Y
CLEN

Current element length (this time step)

Y Y
FORCE

Axial force (spring force)

Y Y
DFORCE

Damping force

Y Y
STROKE

Applied stroke (element load)

Y Y
MSTROKE

Measured stroke

Y Y
Table 4.11-3 lists output available through the ETABLE command using the Sequence Number method. The following notation is used in Table 4.11-3:

Table 4.11-3 LINK11 Item and Sequence Numbers for the ETABLE and ESOL Commands

Name

Item

E

FORCE

SMISC

1
ILEN

NMISC

1
CLEN

NMISC

2
STROKE

NMISC

3
MSTROKE

NMISC

4
DFORCE

NMISC

5

4.11.3 Assumptions and Restrictions

The element must not have a zero length. The element assumes a straight line, axially loaded at the ends. A twist (torsion) about the element x-axis (defined from node I to node J) has no effect. No bending of the element is considered, as in a pin-jointed structure. The mass is equally divided between the nodes. Only the lumped mass matrix is available.

4.11.4 Product Restrictions

There are no product-specific restrictions for this element.