Baixe connector - element - connection - library e outras Notas de estudo em PDF para Planejamento e Controle de Produção, somente na Docsity! Copyright 2006 ABAQUS, Inc. Connection Elements and Connection Library Lecture 2 Flexible Multibody Systems with ABAQUS L2.2 Copyright 2006 ABAQUS, Inc. Overview • Introduction • Defining Connector Elements • Understanding Connector Sections • Understanding Connection Types • Understanding Connector Local Directions • Rotational Degrees of Freedom at Nodes • Components of Relative Motion • Connector Local Kinematics • Summary of Orientations and Local Directions Copyright 2006 ABAQUS, Inc. Introduction Flexible Multibody Systems with ABAQUS L2.4 Copyright 2006 ABAQUS, Inc. Introduction • General characteristics of connector elements • Connector elements model discrete (point-to-point) physical connections between deformable or rigid bodies or can be connected to ground. • Example: typical connections in automotive suspension systems Typical connections in automotive suspension Rack and pinion Control arm Tie rod Knuckle Strut JOIN CYLINDRICAL AXIAL CYLINDRICAL LINK Flexible Multibody Systems with ABAQUS L2.9 Copyright 2006 ABAQUS, Inc. Defining Connector Elements • Defining a connector element – Keywords interface • To connect two points: *ELEMENT, TYPE=[CONN2D2 or CONN3D2] element number, first node number, second node number • Example: Shock absorber *ELEMENT, TYPE=CONN3D2 101, 11, 12 Simplified connector model of a shock absorber a b 1 Flexible Multibody Systems with ABAQUS L2.10 Copyright 2006 ABAQUS, Inc. Defining Connector Elements • To connect a point to ground: • The ground “node” can be the first or second node on the connector element. *ELEMENT, TYPE=name element number, , node number on the body or *ELEMENT, TYPE=name element number, node number on the body • The ground node is fixed. 2 Flexible Multibody Systems with ABAQUS L2.11 Copyright 2006 ABAQUS, Inc. Defining Connector Elements • Defining connector geometry – ABAQUS/CAE interface • Create assembly-level wire features to define connector geometry in the Interaction module. • disjoint wires • chained wires • wires to ground. • Click Add to add points • Tip: two coincident points can be selected simultaneously by double-clicking on the location of the points • Click Delete to delete the selected point pair. • Click Swap to swap the points of the selected point pair. • Tip: the point pair needs to be selected by click its index number. Flexible Multibody Systems with ABAQUS L2.12 Copyright 2006 ABAQUS, Inc. Defining Connector Elements • A geometry set including all of the wires can be created when creating the wire feature. • The set can be used during the subsequent selection procedures. • For example, you can use sets to assign connector sections, request output, or prescribe motions. • Note: Multiple sets can be merged into a new set using the set merge feature. • Assembly-level wire features cannot be modified directly once created. • Wires can be removed by selecting Remove Wires From Feature. Flexible Multibody Systems with ABAQUS L2.13 Copyright 2006 ABAQUS, Inc. Defining Connector Elements • Example: Truck door hinges • In this example, hinge connectors connect a truck door to the truck body. ABAQUS/CAE interface Create wire geometry Keywords interface Define a connector element *ELEMENT, TYPE=CONN3D2, ELSET=CONN_DOOR_HINGE 620601, 9000009, 9000010 620602, 9000011, 9000012 ... 2 nodes per element RP-2 node 9000010 HINGE connectors at door hinges Copyright 2006 ABAQUS, Inc. Understanding Connector Sections Flexible Multibody Systems with ABAQUS L2.19 Copyright 2006 ABAQUS, Inc. Understanding Connector Sections • Assign a connector section • Connector section assignment is used to assign a connector section to a region (wires) of the model. Assign the connection section DOOR_HINGES to the wire Wire-1-DOOR_HINGES. 2 Copyright 2006 ABAQUS, Inc. Understanding Connection Types Flexible Multibody Systems with ABAQUS L2.21 Copyright 2006 ABAQUS, Inc. Understanding Connection Types • Connection types • The connection-type library contains: • Translational basic connection components, which affect translational DOFs at both nodes and may affect rotational DOFs at the first node of the connector element. • Rotational basic connection components, which affect only rotational DOFs at both nodes of the connector element • Assembled connections, which are a predefined combination of translational and rotational basic connection components. • The above choices determine which element local DOFs exist. • Given the number of connection types available, it is clear that connector elements can easily be customized to suit an application. Flexible Multibody Systems with ABAQUS L2.22 Copyright 2006 ABAQUS, Inc. • Examples of translational basic connections: • AXIAL – Provide a connection between two nodes that acts along the line connecting the nodes. • CARTESIAN – Provide a connection between two nodes that allows independent behavior in three local Cartesian directions. • JOIN – Join the position of two nodes. • ACCELEROMETER – Provide a connection between two nodes to measure the relative acceleration, velocity, and position of a body in a local coordinate system. • Available only in 3D analysis in ABAQUS/Explicit. • Will be converted internally to a CARTESIAN connector type in ABAQUS/Standard. b a u1 b a b a AXIAL JOIN CARTESIAN ACCELEROMETER Understanding Connection Types Flexible Multibody Systems with ABAQUS L2.23 Copyright 2006 ABAQUS, Inc. • Examples of rotational basic connections: • REVOLUTE – Provides a revolute connection between two nodes. • CARDAN – Provides a rotational connection between two nodes parameterized by Cardan angles. • EULER – Provides a rotational connection between two nodes parameterized by Euler angles REVOLUTE CARDAN EULER Understanding Connection Types Flexible Multibody Systems with ABAQUS L2.24 Copyright 2006 ABAQUS, Inc. Understanding Connection Types Basic rotationalBasic translational ROTATION-ACCELEROMETERSLOT ROTATIONSLIDE-PLANE UNIVERSAL REVOLUTERADIAL-THRUST PROJECTION FLEXION-TORSIONPROJECTION CARTESIAN FLEXION-TORSIONLINK EULERJOIN CONSTANT VELOCITYCARTESIAN CARDANAXIAL ALIGNACCELEROMETER a b 1 2 3 φ a 2 3 b 1 Summary of basic connection types Flexible Multibody Systems with ABAQUS L2.29 Copyright 2006 ABAQUS, Inc. • Understanding connector local directions • Orientations are used to define local directions for connection types that use local directions (local directions may be required or optional) • The local directions are defined by reference to a local orientation or coordinate system. • Example: HINGE connector requires an orientation to be associated with the first node a. • The hinge axis is aligned with the orientation X-direction. (local orientation) X Understanding Connector Local Directions Flexible Multibody Systems with ABAQUS L2.30 Copyright 2006 ABAQUS, Inc. • Not all connection type require the local directions (e.g. LINK). • In some cases default local directions are chosen (e.g. CARTESIAN) • Local directions at the second node are not used by all connection types. • Example: SLOT connection • The line of the slot is defined by the first local direction at node a and the initial position of node b. (fig. a) • The SLOT connection constrains the position of node b (xb) to remain on the line of the slot. • Note: different results would be obtained if different orientations are used for the local directions. (figs. b, c) 2 1 u1 u1 12 b. Orientation pointing from node a to node b c. 45o counterclockwise rotation of the slot a. SLOT connection a Understanding Connector Local Directions Flexible Multibody Systems with ABAQUS L2.31 Copyright 2006 ABAQUS, Inc. Understanding Connector Local Directions • The default directions at the second node are the local directions at the first node. • It may be necessary to define local directions at the second node to model the mechanism correctly, e.g. UJOINT. • In geometrically nonlinear analyses, the element local directions associated with the nodes rotate with the rotational degrees of freedom at the nodes. • A summary of connector local directions will be in the section “Summary of Orientations and Local Directions” in this lecture. Flexible Multibody Systems with ABAQUS L2.32 Copyright 2006 ABAQUS, Inc. • Defining connector orientation • Example: Truck door hinges Z Y X ORI_CONN_DOOR ABAQUS/CAE interface Define orientation using a datum coordinate system Keywords interface Define orientation using local CSYS *ORIENTATION, NAME=ORI_CONN_DOOR 0.,0.,1., 1.,0.,0. 3,0 Understanding Connector Local Directions Flexible Multibody Systems with ABAQUS L2.33 Copyright 2006 ABAQUS, Inc. • Example: Truck door hinges *ORIENTATION, NAME=ORI_CONN_DOOR 0.,0.,1.,1.,0.,0. 3,0 *ELEMENT, TYPE=CONN3D2, ELSET=CONN_DOOR_HINGE 620601,9000009,9000010 620602,9000011,9000012 *CONNECTOR SECTION, ELSET=CONN_DOOR_HINGE HINGE ORI_CONN_DOOR Connector elements CONN_DOOR_HINGEKeywords interface Z Y X ORI_CONN_DOOR Understanding Connector Local Directions Flexible Multibody Systems with ABAQUS L2.34 Copyright 2006 ABAQUS, Inc. • Specify local orientations for the endpoints of the wires – ABAQUS/CAE interface. • Connector section assignment is used to specify local orientations for the endpoints of the wires. • Example: Truck door hinges Z Y X ORI_CONN_DOOR Understanding Connector Local Directions Flexible Multibody Systems with ABAQUS L2.39 Copyright 2006 ABAQUS, Inc. Rotational Degrees of Freedom at the Nodes • JOIN connection does NOT activate rotational degrees of freedom • This allows the user to define a join constraint between two solids expressed only in terms of translations. • Example 1: Two deformable solids connected by the JOIN connection type rotate under certain loading and boundary conditions. • Orientation at node a does not rotate with the rotation of the deformable body since the solid element does not have rotational DOFs actived. Deformable 1 2 X Y Z JOINDeformable C3D8R C3D8R Deformable CLOAD CLOAD Deformable 1 2 JOINa b Note: The examples discussed here and the next two slides consider geometric nonlinearity. Flexible Multibody Systems with ABAQUS L2.40 Copyright 2006 ABAQUS, Inc. Rotational Degrees of Freedom at the Nodes • Example 2: Make one solid in Example 1 rigid. • Orientation at node a rotates with the rotation of the rigid body since the rigid body has rotational DOFs. • Node b will move accordingly with node a. 1 2 X Y Z JOINRigid C3D8R C3D8R Deformable CLOAD CLOAD 1 2 JOI N Rigid Deformable RP a b Flexible Multibody Systems with ABAQUS L2.41 Copyright 2006 ABAQUS, Inc. Rotational Degrees of Freedom at the Nodes X Y Z JOIN b 2 13 a Surface-based coupling constraintDeformable C3D8R Deformable C3D8R 1 2 JOI N Deformable Deformable CLOAD CLOAD • Example 3: Define a surface-based coupling constraint on the surface of one of the deformable solids in Example 1; choose the reference point of the surface-based coupling constraint as node a. • Orientation at node a rotates with the rotation of the deformable body since the coupling constraint actives rotational DOFs. • Node b will move accordingly with node a. Copyright 2006 ABAQUS, Inc. Components of Relative Motion Flexible Multibody Systems with ABAQUS L2.43 Copyright 2006 ABAQUS, Inc. Components of Relative Motion • Components of relative motion • Connector elements have internal DOFs that do not exist at any node, but are a part of the connector element itself. • The connector local degrees of freedom, that is, the three translations and three rotations relative to the connector element local coordinate system (in three dimensions), are called the components of relative motion (CORM). • The three translations are in the element local coordinate directions. • The three rotations are angular quantities that depend on the specific connection definition and may or may not be rotations about orthogonal directions. • All components of relative motion are either constrained or available. • The definitions of constrained and available components of relative motion will be discussed in next two slides, respectively. Flexible Multibody Systems with ABAQUS L2.44 Copyright 2006 ABAQUS, Inc. Components of Relative Motion • Constrained components of relative motion • Constrained components of relative motion are displacements and rotations that are fixed by the connector element. • ABAQUS/Standard uses Lagrange multipliers to enforce the kinematic constraints. • The constraint forces and moments carried by the element appear as additional solution variables. • ABAQUS/Explicit uses an augmented Lagrange technique to enforce the kinematic constraints. • Constrained components of relative motion are measured by reaction forces and moments. • The kinematic constraint is equivalent to forcing one or more of the components of relative motion to behave according to some predefined relationship. Flexible Multibody Systems with ABAQUS L2.49 Copyright 2006 ABAQUS, Inc. Connector Local Kinematics • In three dimensions each of the above kinematic quantities requires six components to completely define it. • Three components in two dimensions. • For example, in three dimensions, a position requires • Three generalized coordinates to identify the location of the second node relative to the first. • Three angles to identify the orientation of the second node relative to the first. • In two dimensions, a position requires • Two generalized coordinates to identify the location of the second node relative to the first. • One angle to identify the orientation of the second node relative to the first. Flexible Multibody Systems with ABAQUS L2.50 Copyright 2006 ABAQUS, Inc. Connector Local Kinematics • Displacement, velocity, acceleration • These quantities are derived from position: • Displacement = change in position • Velocity = rate of change of position • Acceleration = rate of change of velocity • The reference position for constitutive response and constitutive displacements is relevant only for material behavior and will be discussed in Lecture 4. Flexible Multibody Systems with ABAQUS L2.51 Copyright 2006 ABAQUS, Inc. Connector Local Kinematics • Translations: • With the exception of RADIAL-THRUST, BUSHING, PROJECTION CARTESIAN and AXIAL, all the connections use Cartesian coordinates to locate the second node relative to the first. • For translations the second node’s position, displacement, velocity, etc. are identified by three Cartesian components relative to local directions at the connector element’s first node. • RADIAL-THRUST uses a cylindrical coordinate system with origin at the first node. • BUSHING and PROJECTION CARTESIAN use an orthonormal system that follows the systems at both nodes in the connection. • AXIAL does not use a coordinate system. The CORM is measured along the line separating the two nodes in the connection. Flexible Multibody Systems with ABAQUS L2.52 Copyright 2006 ABAQUS, Inc. Connector Local Kinematics • Rotations: • Describing directions at the second node relative to directions at the first node is much more complicated. • Example: REVOLUTE • Several different rotation parameterizations are used. • Cardan angles and Euler angles are successive rotation parameterizations. Examples: • Spinning top = EULER angles (precession, nutation, and spin). • Airplane attitude = CARDAN angles (roll, pitch, and yaw). Flexible Multibody Systems with ABAQUS L2.53 Copyright 2006 ABAQUS, Inc. Connector Local Kinematics • The rotation vector is a parameterization similar to the nodal rotational degrees of freedom in ABAQUS. • Example: Instantaneous angular velocity • FLEXION-TORSION has rotation parameterization angles consisting of total flexion, torsion, and sweep. • PROJECTION FLEXION-TORSION connection has rotation parameterization angles consisting of two component flexion angles and a torsion angle. • Example: Head position on the shoulders in a crash test dummy model. • Different rotation parameterizations are analogous to different coordinate systems (Cartesian versus cylindrical versus polar, etc.). • Use the one that makes the most sense for a particular application. Copyright 2006 ABAQUS, Inc. Summary of Orientation and Local Directions