Forces define loads and compliances on parts. Forces do not absolutely prohibit or prescribe motion. Therefore, they do not add or remove
degrees of freedom (DOF) from your model. Some forces can resist motion, such as spring dampers, and some can try to induce motion.
Adams View provides the following types of forces:
■Flexible connectors - Note that flexible connectors resist motion and are simpler and easier to use than applied forces because you only supply constant coefficients for the forces. The forces include
Beams,
Bushings, translational spring dampers, and torsion springs that provide compliant force relationships.
■Special forces - Special forces are forces that are commonly encountered, such as tire and gravity forces.
■Contacts - Specify how parts react when they come in contact with each other when the model is in motion.
See
Create Forces Palette and Tool Stack dialog box help for more information.
Defining Force Magnitude
When defining a force’s magnitude, you can either define it as one resultant magnitude along a direction, or you can resolve the resultant into as many as three components that are associated with the three mutually perpendicular axes of a particular coordinate system.
You can define force magnitudes in Adams View in the following ways:
■Enter values used to define stiffness and damping coefficients. In this case, Adams View automatically makes the force magnitude proportional to the distance and velocity between two points. The coefficients represent the proportionality constants. You specify coefficients for flexible connectors, such as spring-dampers and beams. You can also specify these values for applied forces.
■Enter a function expression using the Adams View library of built-in functions. You can enter expressions for all types of applied forces. Built-in functions include the types listed below. For more information on using expressions and available functions, see
Function Builder.
♦Displacement, velocity, and acceleration functions that allow the force to be related to the movement of points or bodies in the system. Examples include springs and viscous dampers.
♦Force functions that allow the force to depend on other forces in the system. An example would be a Coulomb friction force that is proportional to the normal force between two bodies.
♦Mathematical functions, such as sine and cosine, series, polynomials, and steps.
♦Spline functions that allow the force to depend on data stored in lookup tables. Examples of these include motors using torque-speed curves or nonlinear bushings whose stiffness is not entirely linear.
♦Impact functions that make the force act like a compression-only spring-damper that turns on and off as bodies intermittently contact one another.
■Enter parameters that are passed to
User-written subroutines that are linked to Adams View. You can enter parameters for all types of applied forces. You can also enter parameters to a subroutine for the field flexible connector to create a nonlinear force between two parts. For more information on how to use subroutines to define your force magnitudes, see the Subroutines section of the
Adams Solver online help.
Defining Force Directions
You can define force directions in one of two ways:
■Along one or more of the axes of a
marker.
■Along the line-of-sight between two points.
If your force direction remains fixed with respect to some part in your model, either a moving part or the ground part, then you can define the force using one vector component and specify only one magnitude and direction.
If you have two or more forces whose directions always remain perpendicular to one another (such as a normal force and a friction force), you can either define multiple
Single-component forces whose directions are perpendicular or you can use a
Multi-Component force element. You must define several expressions, one for each of the force magnitudes you need.
If the direction along which you want the force applied is defined by the line between two points in your model and is constantly changing throughout the
Simulation, you only need to define one component of force along this direction and one expression for the corresponding force magnitude.
As you define forces, Adams View gives you shortcuts for defining the force application. These shortcuts allow you to let Adams View automatically create the force definition using only a few clicks of the mouse. For example, as you create a bushing, you can simply specify one location. Adams View automatically determines the parts which should be included. You can also specify that the force be aligned to the coordinates of the
Working grid or screen or a feature of a part.