Test

You can add any number of tests that stroke the spring to determine the spring’s force-deflection curve and stiffness, either with the shackle (slipper end) as if the spring was installed in the vehicle or without the shackle (SAE J510). The inputs that describe a test are described below.

Figure 1. Test Component in Leaf Builder

Inputs

Test Type

There are two test types: “Spring and Shackle” and “Spring only (SAE J510)”.

Spring and Shackle

Test Type: Spring and Shackle strokes the spring as mounted in the vehicle.

Figure 2.

The test has three phases:

1. Apply offset: either force or displacement depending on the actuator type.
2. Stroke in Jounce: The spring is stroked upward to the specified jounce displacement or force, again depending on the actuator type, and then downward back to the offset displacement or force value over time=0 to time = End Time/2.
3. Stroke in Rebound: The spring is stroked downward to the specified rebound displacement or force and then upward back to the offset displacement or force from time = End Time/2 to time = End Time.

Spring Only (SAE J510)

Test type “Spring Only” strokes the spring without the shackle following the SAE J510 guidelines to generate the spring’s characteristic Force vs Deflection curve. For this test the spring eyes contact a flat plate and a displacement is input via a loading block on the bottom of the spring. In an actual test the spring is inverted and pushed downward into a plate. In the Leaf Spring Builder, gravity is directed in the +Z direction effectively inverting the spring and the centers of the spring eyes or the spring tips for slipper ends are constrained by in-plane joints.

The test has four phases:

1. Relax the spring to its free position.
2. Move the spring from free position to curb position over time = 0 to time = End Time / 3.
3. Move from curb position to design position over time = End Time / 3 to time = End Time * 2/3.
4. Move from design position to metal-metal position from time = End Time * 2/3 to time = End Time.

Figure 3.

Spring and Shackle - Force/Motion Inputs

Actuator

Select Force or Motion to determine how the input applied to the spring.

Offset Force/Displacement

Enter the offset force or displacement from which the test begins. The offset is relative to initial load or position of spring as built.

Jounce Force/Displacement

Enter the increment of force or displacement relative to the initial force of displacement for jounce. The sum of the offset force and jounce force give the maximum force applied to the spring, if the actuator is force. Likewise, the sum of the offset displacement and jounce displacement give the maximum displacement applied to the spring, if the actuator is motion.

Rebound Force/Displacement

Enter the decrement (positive value) of force or displacement relative to the offset force or displacement for rebound. For a force actuator, the difference between the offset force and rebound force gives the minimum force applied to the spring. For example, if the initial force is 1000 N and the rebound force is 1000 N, then the minimum force in the test is zero (free position). For a motion actuator, the difference between the offset displacement and rebound displacements gives the minimum spring displacement.

Spring-only (SAE J510) - Motion Inputs

Curb

Enter the increment of spring displacement from the initial spring position to curb position.

Design

Enter the increment of spring displacement from curb position to design position.

Metal-Metal

Enter the increment of spring displacement from design position to metal-metal position.

The total spring displacement from the initial position is sum of the curb, design, and metal-metal values.

Simulation Settings

Print Interval

Enter the time between output steps. The end time divided by the print interval gives the number of outputs steps.

Step Size

Enter the time between solution steps. The step size must not be greater than the print interval.

Simulation Type

Select Quasi-static or Transient. Quasi-static simulation removes inertia and damping forces. Transient simulation includes damping and inertia forces. It is recommended that you select Quasi-static. If there are problems obtaining a solution, then switch to transient. When using transient simulations, consider using larger end times to slow the rate of change of spring deflection to reduce inertia and damping forces.

End Time

Enter the end time of the simulation. Simulations start at time=0, hence the end time is also the duration of the simulation.

Build Leaf

Check the build leaf box to build the leaf spring before running the test. You should check the box if you have changed the spring tag that defines if the leaf spring that is loaded in the Leaf Builder has to be built when the Run Test Rig button is clicked.

Run Test Rig

Click the Run button to run the simulated leaf spring test.

Test Block for Leaf Property File (*lpf)

$----------------------------TEST_RIG
[TEST_RIG]
(TEST_1)
BUILDLEAF = 'FALSE'
CURB = 0.0
DESIGN = 0.0
DIRECTORY = 'C:\USERS\DESKTOP'
ENDTIME = 10.0
FORCEJOUNCE = 0.0
FORCEOFFSET = 0.0
FORCEREBOUND = 0.0
METALTOMETAL = 0.0
MOTIONJOUNCE = 0.0
MOTIONOFFSET = 0.0
MOTIONREBOUND = 0.0
OPTION = 'MOTION'
OUTPUTFILELABEL = 'TEST_'
PRINTINTERVAL = 0.01
RUNNO = 1.0
SIMULATIONTYPE = 'QUASI-STATIC'
STEPSIZE = 0.001
TESTTYPE = 'SPRING AND SHACKLE'