# Defining the local basis system The sequence of the nodes forming the slide line defines the tangent, . The plane formed by the slide line normal, , and is called the contact plane. Abaqus/Standard defines the slide line normal as $\mathbf { n } = \mathbf { s } \times \mathbf { t }$ (see Figure 40.4.1–3), where $\mathbf { s } = ( 0 , 0 , 1 )$ is the vector that is orthogonal to the contact plane. As shown in Figure 40.4.1–3, a slide line is created using nodes $i , j , k , . . . , p ,$ which are specified in that order, thereby identifying the slide line tangent. Nodes $I , J , K , . . . , N$ are the nodes of the slide line elements that are associated with this slide line. The slide line normal is defined by specifying , the normal to the contact plane. 

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contact plane ISL element s I J K L M N n t m o p i j k l slide line

Figure 40.4.1–3 Defining the local basis for a slide line. The tangent to the slide line coincides with the first local tangent direction, $\mathbf { t } _ { 1 }$ , of the local basis system. The second local tangent direction, $\mathbf { t } _ { 2 }$ , is in the opposite direction of . # The master-slave concept for slide lines and slide line elements When creating a model that contains slide line elements, it is useful to remember that Abaqus/Standard uses a strict “master-slave” concept to enforce the contact constraints. The slide line contact elements form the “slave” surface. The nodes that you specify to define the slide line define the “master” surface. The nodes of the slide line contact elements are constrained not to penetrate the master surface. The considerations for choosing the master and slave surfaces are the same regardless of whether surfaces or elements are used to define contact. The master surface should be chosen as the surface of the stiffer body if the materials are different or as the surface with the coarser mesh. If the materials and mesh density are the same on both surfaces, the choice is arbitrary. # Defining the slide line (master surface) You can specify the nodes that make up the slide line, or they can be generated as described below. If you choose to specify the nodes directly, you must specify them in a sequence that defines a continuous slide line. The nodal sequence defines a tangent vector, , for the slide line. The slide line can be made up of linear or parabolic segments, depending on whether the model is made up of first-order or second-order elements. In either case convergence may be improved by smoothing the slide line. # Defining a linear slide line When the surfaces of the bodies are meshed with first-order elements, define a slide line made up of linear element segments. As shown in Figure 40.4.1–4), nodes $i , j , k , . . . , p$ are specified in that order, thereby identifying a slide line progressing from i through p. Nodes I, J, K, …, N are the nodes of the ISL-type elements that are associated with this slide line. Input File Usage: \*SLIDE LINE, ELSET=element\_set\_name, TYPE=LINEAR first node number, second node number, etc. 

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I J K L M N i j k l m n o p

Figure 40.4.1–4 First-order (linear) slide line example. # Defining a parabolic slide line When the surfaces of the bodies are meshed with second-order elements, define a slide line made up of second-order element segments. In this case the slide line should consist of an odd number of nodes. As shown in Figure 40.4.1–5, nodes $i , j , k , . . . ,$ u are specified in that order, thereby identifying a slide line progressing from i through u. Nodes $I , J , K , . . . , O$ are the nodes of the ISL-type elements that are associated with this slide line. Input File Usage: \*SLIDE LINE, ELSET=element\_set\_name, TYPE=PARABOLIC first node number, second node number, etc. 

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I J K L M N O i j k l m n o p q r s t u

Figure 40.4.1–5 Second-order (parabolic) slide line example. # Generating the slide line nodes Alternatively, you can indicate that the slide line nodes should be generated and specify only a first node number, a last node number, and an increment between node numbers. Input File Usage: \*SLIDE LINE, ELSET=element\_set\_name, GENERATE first node number, last node number, increment between node numbers # Smoothing the slide line Convergence is often improved by smoothing the discontinuities in surface tangents between slide line segments, thereby providing a smoothly varying tangent along the slide line. For details about smoothing slide lines, see “Contact formulations in Abaqus/Standard,” Section 38.1.1. # Defining slide line elements (slave surface) Many finite-sliding contact simulations can use the surface-based contact approach, described in Chapter 36, “Defining Contact Interactions,” to define the model. Axisymmetric stress/displacement and coupled temperature-displacement slide line elements are recommended only for specific applications, such as when a contact surface is the surface of a substructure or when CAXA or SAXA elements are involved in contact (see “Contact modeling if asymmetric-axisymmetric elements are present,” Section 36.3.10). The slide line contact elements define the slave surface. The contact area associated with each node on the slave surface is calculated using the current length of the slide line contact element and the constant “width” assigned to the element, which depends on the underlying finite elements. # Associating the slide line elements with a slide line You must associate the slide line with a set of slide line contact elements. Details on defining slide lines are discussed below. Input File Usage: \*SLIDE LINE, ELSET=element\_set\_name # Defining the slide line element’s section properties You must associate the section properties with a set of slide line elements. There are no section data for axisymmetric slide line elements. Input File Usage: \*INTERFACE, ELSET=element\_set\_name # Defining nondefault mechanical surface interactions with slide line elements By default, Abaqus/Standard uses “hard,” frictionless contact with slide line elements. You can assign optional mechanical surface interaction models. The following mechanical surface interaction models are available: • Friction. See “Frictional behavior,” Section 37.1.5, for details. • Modified “hard” contact, softened contact, and viscous damping. See “Contact pressure-overclosure relationships,” Section 37.1.2, and “Contact damping,” Section 37.1.3, for details. # Obtaining the “maximum torque” that can be transmitted across axisymmetric slide lines When modeling contact with slide lines with axisymmetric elements (type CAX and CGAX elements), Abaqus/Standard can calculate the maximum torque that can be transmitted across the axisymmetric slide lines. This capability is often of interest when modeling threaded connectors. The maximum torque, T, is defined as $$ T = \iint r ^ {2} p d s d \theta , $$ where p is the pressure transmitted across the interface, r is the radius to a point on the interface, and s is the current distance along the interface in the r–z plane. This definition of “torque” effectively assumes a friction coefficient of unity. You can request that this torque output be written to the data (.dat) file. The data are provided for every slide line in the model. You can specify the output frequency to limit how often Abaqus/Standard writes this output to the data file. The default output frequency is 1. For surface-based contact with axisymmetric elements, output variable CTRQ provides functionality similar to this torque output request (see “Defining contact pairs in Abaqus/Standard,” Section 36.3.1). Input File Usage: \*TORQUE PRINT, FREQUENCY=n # 40.4.2 AXISYMMETRIC SLIDE LINE ELEMENT LIBRARY # Product: Abaqus/Standard # References • “Slide line contact elements,” Section 40.4.1 • \*INTERFACE • \*SLIDE LINE # Overview This section provides a reference to the axisymmetric slide line elements available in Abaqus/Standard. # Element types ISL21A 2-node element for use with first-order axisymmetric elements ISL22A 3-node element for use with second-order axisymmetric elements Active degrees of freedom 1, 2 at the nodes Additional solution variables Two additional variables at each node relating to the contact stresses. # Nodal coordinates required r, z # Element property definition

Input File Usage:

Use the following option to identify the slide line (master surface) with which the slide line elements interact:*SLIDE LINEUse the following option to define the slide line element’s section properties:*INTERFACE

# Element-based loading None. # Element output Stress components

S11	Pressure between the node on the body and the slide line with which it interacts.
S12	Shear stress between the node on the body and the slide line with which it interacts.

Strain components

E11	Separation between the node on the body and the slide line.
E12	Accumulated relative tangential displacement between the node on the body and the slide line.

# Node ordering and integration point numbering 

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linear element 2 - node element n ×1 ×2 n master surface (defined as a slide line) integration points


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quadratic element 3 - node element 1 2 3 master surface (defined as a slide line) ×1 n ×2 n ×3 n integration points

# 40.5 Rigid surface contact elements • “Rigid surface contact elements,” Section 40.5.1 • “Axisymmetric rigid surface contact element library,” Section 40.5.2