1. CHANGING MODEL TOPOLOGY II
SECTION 5
CHANGING MODEL TOPOLOGY II

2. CHANGING MODEL TOPOLOGY II
What does this section contain?
Standard Components (Part 2)
Jounce Bumper
Rebound Bumper
Construction Options

3. STANDARD COMPONENTS (PART 2)
The standard components covered here are:
Springs
Jounce bumper
Rebound bumper
Because different vehicles use different methods of springing each wheel, Adams/Chassis offers four of the most common spring models. All spring property files are stored in the spring.tbl directory of the vehicle database. The four spring models are:
Coil
Torsion
Air
Leaf

4. SPRINGS Coil Springs Coil springs can be linear or nonlinear.
Linear properties:
Constant rate (force/length unit)
Free length
Nonlinear spline:
Independent axis - Either distance between spring seats or deflection from initial configuration
Dependent axis - Force in spring at independent axis value
Preload is calculated by considering the following:
Initial distance between spring seats
Specified install length
Specified preload
You can also specify a second set of springs.

5. SPRINGS (CONT.) Torsion springs Air Springs
Torsion springs come with the following parameters:
Material properties (modulus, Poisson’s ratio, density)
Inner/outer radius
Active length
Finish angle – used to adjust ride height
Air Springs
Air springs have the following properties:
Trim length
Trim load
Force-Deflection 3D Spline
X Values – Deflection in air spring
Z Value – Trim load
Y Value – Force in air spring at X and Z value

6. SPRINGS (CONT.) Leaf springs
Two leaf spring models are outlined below:
SAE 3 link model
Beam-element model
The SAE 3 link model is an approximate model. The stiffness is defined by three torsional stiffness components for the front and rear section of the model.
KT(x) = Longitudinal twist stiffness of the (front or rear) section of the spring. This parameter is important for roll stiffness.
KT(y) = Lateral bending stiffness of the (front or rear) section of the spring. This value is important for the lateral stiffness of the suspension.
KT(z) = Vertical bending stiffness of the (front or rear) section of the spring. This value is important because it defines the spring rate of the spring.
Instructor: Comment on difference between g_loads and analytical g_loads.

7. SPRINGS (CONT.) SAE 3 link model (Cont.)
The second stage, or helper spring, can be defined as a linear or nonlinear force vs. displacement profile.

8. SPRINGS (CONT.) Beam element model
The beam element model is a more accurate model than the SAE 3 link model. The leaf spring free profile is entered and the leaf is modeled as a series of beams and parts. It contains the Makeleaf process:
Leaf exercised to design load
Leaf spring template created at design load

9. JOUNCE BUMPER The jounce bumper contains the following:
Metal-to-metal rate parameter
Optional damping (rate or spline)
Metal-to-metal contact that can be in separate location
Point 75 at mount location, not bottom of bumper
Polynomial or spline force method
The polynomial is defined by:
Where
a is the linear rate
b is the quadratic rate
c is the cubic rate defined in the jounce bumper editor.

10. REBOUND BUMPER The rebound bumper contains:
Metal-to-metal rate parameter
Optional damping
Free length, which determines when bumper is activated
Polynomial or spline force method

11. CONSTRUCTION OPTIONS
Construction options allow you to change how different components are modeled or how they are attached. This is another example of how Adams/Chassis offers modeling flexibility without extensive customization.
Constructions options offer:
Different modeling methods for subsystems and components
Variation without customization
Most construction options available in your subsystem files
Option to add other construction options
NOTE: The Adams/Chassis online help contains additional information that is helpful when using construction options.

12. CONSTRUCTION OPTIONS (CONT.)
Examples of construction options:
Lower control arm (1 piece, 2 piece (double ball joint), and so on.)
Panhard rod
Hub compliance
Steering column U-joint phasing
Double cardon joint
nonlinear rack and pinion gear

13. CONSTRUCTION OPTIONS (CONT.)
Hub Compliance
You use hub compliance in this workshop to model wheel bearing play in the MSC.Adams model. Physical systems will show compliance between the wheel and the hub parts in the suspension. Adams/Chassis has four ways to account for this compliance in your model:
Off - No compliance between wheel and hub
On - Additional compliance part added between wheel and hub
Carrot_on - See online documentation
Carrot_off - See online documentation

14. CONSTRUCTION OPTIONS (CONT.)
Hub Compliance (Cont.)
Below is a diagram of hub compliance on topology.

15. CONSTRUCTION OPTIONS (CONT.)
Hub Compliance (Cont.)
The parameters that affect the hub compliance model are:
Point 9 (wheel center) in hardpoint table
Optional point 9h (defined as offset along wheel spin axis in construction option editor)
Note that bushing properties are defined in the connector editor defining stiffness at ball joint
Point 9h has the effect of creating a moment arm between loads applied to the wheel center and the bushing location. The longer the offset, the more compliance there will be for a given load and bushing property.