CHANGING MODEL TOPOLOGY II SECTION 5 CHANGING MODEL TOPOLOGY II

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

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

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.

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

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.

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.

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

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.

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

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.

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

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

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

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.