ABAQUS中定义弹簧单元 2011-12-16 17:57
Abaqus Analysis User's Manual
29.1.1 Springs
Products: Abaqus/Standard Abaqus/Explicit Abaqus/CAE
References
? ?
?
Overview
Spring elements:
? ? ? ? ? ?
can couple a force with a relative displacement;
in Abaqus/Standard can couple a moment with a relative rotation; can be linear or nonlinear;
if linear, can be dependent on frequency in direct-solution steady-state dynamic analysis;
can be dependent on temperature and field variables; and
can be used to assign a structural damping factor to form the imaginary part of spring stiffness.
The terms “force” and “displacement” are used throughout the description of spring elements. When the spring is associated with displacement degrees of freedom, these variables are the force and relative displacement in the spring. If the springs are associated with rotational degrees of freedom, they are torsional springs; these variables will then be the moment transmitted by the spring and the relative rotation across the spring.
Viscoelastic spring behavior can be modeled in Abaqus/Standard by combining frequency-dependent springs and frequency-dependent dashpots.
Typical applications
Spring elements are used to model actual physical springs as well as idealizations of axial or torsional components. They can also model restraints to prevent rigid body motion.
They are also used to represent structural dampers by specifying structural damping factors to form the imaginary part of the spring stiffness.
Choosing an appropriate element
SPRING1 and SPRING2 elements are available only in Abaqus/Standard. SPRING1 is between a node and ground, acting in a fixed direction. SPRING2 is between two nodes, acting in a fixed direction.
The SPRINGA element is available in both Abaqus/Standard and
Abaqus/Explicit. SPRINGA acts between two nodes, with its line of action being the line joining the two nodes, so that this line of action can rotate in large-displacement analysis.
The spring behavior can be linear or nonlinear in any of the spring elements in Abaqus.
Element types SPRING1 and SPRING2 can be associated with displacement or rotational degrees of freedom (in the latter case, as torsional springs). However, the use of torsional springs in large-displacement analysis requires careful consideration of the definition of total rotation at a node; therefore, connector elements () are usually a better approach to providing torsional springs for large-displacement cases. Input File Usage: U se the following option to
specify a spring element between a node and ground, acting in a fixed direction: , TYPE=SPRING1
Use the following option to specify a spring element between two nodes, acting in a fixed direction: , TYPE=SPRING2
Use the following option to specify a spring element between two nodes with its line of action being the line joining the two nodes: , TYPE=SPRINGA
Abaqus/CAE Usage: P roperty or Interaction module:
SpecialSprings/DashpotsCreate, then select one of the following:
Connect points to ground: select points: toggle on Spring stiffness (equivalent to SPRING1)
Connect two points: select points: Axis: Specify fixed direction: toggle on Spring stiffness
(equivalent to SPRING2)
Connect two points: select points: Axis: Follow line of action: toggle on Spring stiffness (equivalent to SPRINGA)
Stability considerations in Abaqus/Explicit
A SPRINGA element introduces a stiffness between two degrees of freedom without introducing an associated mass. In an explicit dynamic procedure this represents an unconditionally unstable element. The nodes to which the spring is attached must have some mass contribution from adjacent elements; if this condition is not satisfied, Abaqus/Explicit will issue an error message. If the spring is not too stiff (relative to the stiffness of the adjacent elements), the stable time increment determined by the explicit dynamics procedure () will suffice to ensure stability of the calculations.
Abaqus/Explicit does not use the springs in the determination of the stable time increment. During the data check phase of the analysis, Abaqus/Explicit computes the minimum of the stable time increment for all the elements in the mesh except the spring elements. The program then uses this minimum stable time increment and the stiffness of each of the