Springs, also known as elastic connections, are a type of discrete stiffness feature. Springs can be used as connections between bodies, as well as between bodies and the ground. They can be axial springs or torsional springs. By default, springs are assumed to be in a free state (unloaded state), but their preload can be specified using either the free length or the load value. In addition, parallel dampers can be defined in the spring’s properties.
In the Mechanical component, springs need to be created under the Connections branch. If the model includes multiple bodies, the Connections branch will automatically appear. To create a spring, first, select the Connections branch and choose Insert > Spring from the right-click menu. This will add a spring object with a default name of “Longitudinal – No Selection To No Selection” under the Connections branch. The various properties of the spring can be set in its Details, as shown in the figure below.
The spring properties that are involved include:
(1) Spring Type
The Type option is used to define the type of the spring, which can be either longitudinal or torsional.
(2) Spring Behavior
In Rigid Dynamics and Explicit Dynamics systems, the Spring Behavior provides three options: Both, Compression Only, or Tension Only.
This option belongs to the Definition part of the spring properties, and it sets the longitudinal stiffness coefficient of the spring.
This option also belongs to the Definition part of the spring properties, and it sets the longitudinal damping coefficient of the spring.
The Preload option is used to define the preload of the spring and belongs to the Definition part of the spring properties. The default value is None, which means that no preload is considered. If preload needs to be defined, the Load or Free Length option can be selected from the dropdown list, and the corresponding value can be specified.
The Scope option can be set to Body-Body or Body-Ground. If the spring object is added through the Spring>Body-Ground or Spring>Body-Body options on the toolbar, this option does not need to be specified separately.
(7) Reference and Mobile
Reference and Mobile are used to define the two ends of the spring and can be set in two ways:
Two vertices or nodes can be selected, and the Reference and Mobile will be automatically set as the selected two endpoints, with the Applied By option defaulting to Direct Attachment.
In this more general case, Reference and Mobile need to be defined separately. They can be specified using a geometry selection method based on a Remote Point, such as selecting a face in the Reference’s Scope, which will set the Reference Location to the center of the face, with its coordinates listed in the Reference XYZ Coordinate section, as shown in the figure below. The Mobile is specified in a similar way. When using the Remote Attachment method, a Remote Point is actually established, so the Behavior and Pinball Region options for the Remote Point can also be specified.
For Body-Ground springs, the Reference is assumed to be at the ground position, as shown in the figure above. The Mobile part can be specified using the above methods, while the Reference part only needs to specify the coordinate position.
The body-ground spring specifies the Mobile part in the above way, while the Reference part only needs to specify the coordinate position, as shown in the following figure.