Front Internal Jounce Bumper

Introduction

The Internal Jounce Bumper system is used to simulate a jounce bumper that is internal to the shock absorber, or strut, on a front or rear suspension. The system creates forces, requests, and graphics of the bumper. The force acts between the strut or shock rod and the strut or shock tube. The bumper is oriented using lengths along the strut/shock instead of XYZ coordinates. The Force-Deflection characteristics of the Jounce bumper are defined by the Curve in the Jounce Bumper system. In models built via the Assembly Wizard, the Jounce Bumper system is a child of the suspension system.

front_internal_jounce_bumper_example

Front Internal Jounce Bumpers with Full Vehicle

front_internal_jounce_bumper_example2

Jounce Bumper Points and Distances

front_internal_jounce_bumper_curve_graph

Jounce Bumper Force - Deflection Curve

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Notes

•	The Force element in the system uses an expression to turn on and off the jounce bumper when the tip reaches the contact.

•	Linear extrapolate is on by default in the jounce bumper curve. For robust simulations, make sure the force deflection curve values exceed the forces and deflections seen in the simulation.

•	The system uses calculated point locations to define the graphics and force locations. Markers (based on the points) are used in the Force expression.

•	The Force deflection curve of the Jounce bumper is 0,0 when the bumper just touches the contact point, and is a positive pair of points after contact.

•	The graphics are defined so the Jounce bumper graphic (represented by the cone) begins to pass through the contact plane graphic (a flat round plate) at the same time the jounce bumper force initiates.

•	The jounce bumper force acts at the “contact point” and is an action/reaction force which acts along the axis of the strut, or shock, between the strut/shock rod and the strut/shock tube bodies.

•	Damping is ignored, however it is able to be added.

System Description

The entities in the analysis are displayed in the MotionView Project Browser as shown in the image below:

front_internal_jounce_bumper_browser

Project Browser View - Front Internal Jounce Bumper

Attachments determine how the system connects to the rest of the model. The Front Internal Jounce Bumper system includes four attachments (Rod Body, Tube Body, Upper Rod, and Lower Tube).

front_internal_jounce_bumper_attachments

Front Internal Jounce Bumpers - Attachments

Attachment	Description
Rod Body	By default, the Rod Body attaches to the Strut rod (upper strut) in struts and to the Shock rod (upr shk) in shock absorbers. This is the first of the action/reaction Force bodies.
Tube Body	By default, the Tube Body attaches to the Strut tube (lower strut) on struts and to the Shock Tube (lwr shk) on shock absorbers. This is the second of the action/reaction Force bodies.
Upper Rod	By default, the Upper Rod attaches to the Point pair, Strut rod upper on struts, and the Shock Upr bush on shock absorbers. The Jounce bumper distances are defined from this point.
Lower Tube	By default, the Lower Tube attaches to the Point pair, Strut tube lower on struts, and Shock lwr bush on shock absorbers. The Lower Tube attachment and Upper Rod attachment points define the axis of the jounce bumper. Forces, graphics, and markers use this axis to define the Jounce bumper system.

The Front Internal Jounce Bumper system contains one option: Compliant. Setting this option to No will have no affect on the internal jounce bumper system entities.

front_internal_jounce_bumper_compliant_option

Front Internal Jounce Bumpers - Options

A single curve is included in the system (Jounce Bumper 1). The curve defines the Force-displacement behavior of the jounce bumper. The 0,0 point on the curve is when the bumper initially contacts the contact surface. Data should always be in the positive quadrant and should always increase in both the X and Y directions.

front_internal_jounce_bumper_browser_curves

Project Browser View - Curves - Jounce Bumper 1

front_internal_jounce_bumper_curves

Curve Panel - Jounce Bumper 1

front_internal_jounce_bumper_curves_graph

Preview Window Dialog - Jounce Bumper 1

One dataset (Jounce Bumper Lengths) is used in the system and contains dimensions that define the Jounce Bumper system. Two lengths define the graphics and forces of the jounce bumper. The Shock length is a calculated value.

front_internal_jounce_bumper_browser_data_set

Project Browser View - Datasets - Jounce Bumpers Lengths

front_internal_jounce_bumper_data_set_property_dialog

Dataset Property Dialog - Datasets - Jounce Bumper Lengths

Label

Description

Rod upper to bumper tip (mm)

Determines the coordinates of the jounce bumper tip PointPair.

Tip to contact dist. (mm) - clearance to be set manually in the curve x offset

Determines the coordinates of the jounce bumper contact PointPair.

Shock length (mm)

Parametric value that determines the PointPair co-ordinates for “jounce bumper tip” and “jounce bumper contact”.

It is of the form:

sqrt((p_rod.l.x-p_tube.l.x)^2+(p_rod.l.y-p_tube.l.y)^2+(p_rod.l.z-p_tube.l.z)^2)

front_internal_jounce_bumper_data_set_example

Datasets - Jounce Bumpers Lengths

The Front Internal Jounce Bumper contains one force (Jounce Bumper). This is an action-reaction force that acts in the translational direction, between the Strut Tube and Strut Rod along the axis of the strut or shock absorber. The translational force properties are non-linear and are defined using a curve.

front_internal_jounce_bumper_browser_forces

Project Browser View - Forces - Jounce Bumper

front_internal_jounce_bumper_forces_panel

Jounce Bumper Panel

front_internal_jounce_bumper_forces_example

Principal Forces - Front Internal Jounce Bumper

One Form is used in the Front Internal Jounce Bumper system (Jounce Bumper Lengths). The Form is the only place where changes should be made to the Jounce Bumper length data. The two parameters that can be changed are: Rod upper to Bumper tip and Tip to contact distance.

front_internal_jounce_bumper_browser_forms

Project Browser View - Forms - Jounce Bumpers Lengths

front_internal_jounce_bumper_lengths_dialog

Jounce Bumper Lengths Dialog

front_internal_jounce_bumper_forms_example

Forms - Jounce Bumpers Lengths

Two Graphics are used in Front Internal Jounce Bumper (Jounce Bumper and Jounce Bumper Contact). The Jounce Bumper attaches to the Strut Rod (upper strut) and the Jounce Bumper Contact attaches to the Strut Tube (lower strut).

front_internal_jounce_bumper_browser_graphics

Project Browser View - Graphics - Front Internal Jounce Bumper

front_internal_jounce_bumper_graphics_example

Jounce Bumper and Jounce Bumper Contact Graphics

Two Markers that are symmetrical about XZ plane are used in the Front Internal Jounce Bumper system (Force Direction Reference and Displacement Reference).

front_internal_jounce_bumper_browser_markers

Project Browser View - Markers - Front Internal Jounce Bumpers

The force direction reference marker is located on the strut tube and the displacement reference marker is located on the strut rod. These markers are used define the location and direction for the Forces and Requests in the Jounce Bumper system.

Marker

Location Description

Use

Force Direction Reference

Origin is at the strut rod upper or shock upper bush.

Z axis points at the Jounce bumper contact

Attached to the Strut tube (lwr strut) or shock tube (lwr shk).

The jounce bumper force acts along the z axis of this marker.

The jounce bumper force request reports forces in this reference frame.

Displacement Reference

Origin is at the jounce bumper tip.

Z axis points at the Strut rod upr or shock upper bush.

Attached to the Strut rod (upr strut) or shock rod (upr shk).

The jounce bumper displacement request is measured in this coordinate frame.

The jounce bumper Force expression uses this marker in the equation to calculate force.

front_internal_jounce_bumper_markers_example

Markers - Front Internal Jounce Bumper

Four output requests are used in Front Internal Jounce Bumper system (Left Jounce Bumper Displacement, Right Jounce Bumper Displacement, Left Jounce Bumper Force, and Right Jounce Bumper Force). These four requests will generate eight sets of results.

front_internal_jounce_bumper_browser_outputs

Project Browser View - Outputs - Front Internal Jounce Bumpers

Output	Description
Left Jounce Bumper Displacement	Displacement of the jounce bumper on the left side of the vehicle. Displacement of the bumper contact relative to the bumper tip, and the displacement of the contact tip relative to the bumper contact are reported. Both requests are in the Displacement Marker reference frame.
Right Jounce Bumper Displacement	Displacement of the jounce bumper on the right side of the suspension. The contact tip relative to the bumper contact are reported. Both requests are in the Displacement Marker reference frame.
Left Jounce Bumper Force	The Jounce bumper force on the left side suspension. The force pushes the bodies apart when the bumper is engaged. The force is reported on both parts of the force element, and the forces will be equal and opposite.
Right Jounce Bumper Force	The Jounce bumper force on the right side of the suspension. The force pushes the bodies apart when the bumper is engaged. The force is reported on both parts of the force element, and the forces will be equal and opposite.

An example of the jounce bumper displacement output is shown below:

front_internal_jounce_bumper_outputs_graph_example

An example plot of the jounce bumper Force output plot is shown below:

front_internal_jounce_bumper_outputs_graph_example2

Two point pairs are used in the Front Internal Jounce Bumper system. These points are used to create the Jounce Bumper Tip and the Jounce Bumper Contact. The points contain parametric logic to define their X, Y, and Z locations. No user modification of any points should be necessary.

front_internal_jounce_bumper_browser_points

Project Browser View - Points - Front Internal Jounce Bumpers

front_internal_jounce_bumper_points_example

Jounce Bumper Points and Dimensions

The table below shows the coordinate values for the Jounce Bumper Tip point when located internally:

Coordinate	Expression (Front-Left)
X	p_rod.l.x+(p_tube.l.x-p_rod.l.x)/ds_jnc_bmp.shock_len.value*ds_jnc_bmp.end_to_tip.value
Y	p_rod.l.y+(p_tube.l.y-p_rod.l.y)/ds_jnc_bmp.shock_len.value*ds_jnc_bmp.end_to_tip.value
Z	p_rod.l.z+(p_tube.l.z-p_rod.l.z)/ds_jnc_bmp.shock_len.value*ds_jnc_bmp.end_to_tip.value

The variables used in the above expression are described below:

Expression	Model Equivalent
p_rod.l.x	X coordinate of the Upper Rod Attachment Point – Left
p_tube.l.x	X coordinate of the Lower Tube Attachment Point – Left
p_rod.l.y	Y coordinate of the Upper Rod Attachment Point – Left
p_tube.l.y	Y coordinate of the Lower Tube Attachment Point – Left
p_rod.l.z	Z coordinate of the Upper Rod Attachment Point – Left
p_tube.l.z	Z coordinate of the Lower Tube Attachment Point – Left
ds_jnc_bmp.shock_len.value	Total shock length value defined in the dataset
ds_jnc_bmp.end_to_tip.value	Distance from the shock rod upper to bumper tip defined in the dataset

The table below shows the co-ordinate values for the Jounce Bumper Contact point when located internally:

Coordinate	Expression (Front-Left)
X	p_rod.l.x+(p_tube.l.x-p_rod.l.x)/ds_jnc_bmp.shock_len.value*(ds_jnc_bmp.end_to_tip.value+ds_jnc_bmp.tip_to_cont.value)
Y	p_rod.l.y+(p_tube.l.y-p_rod.l.y)/ds_jnc_bmp.shock_len.value*(ds_jnc_bmp.end_to_tip.value+ds_jnc_bmp.tip_to_cont.value)
Z	p_rod.l.z+(p_tube.l.z-p_rod.l.z)/ds_jnc_bmp.shock_len.value*(ds_jnc_bmp.end_to_tip.value+ds_jnc_bmp.tip_to_cont.value)

The variables used in the above expression are described below:

Expression	Model Equivalent
p_rod.l.x	X coordinate of the Upper Rod Attachment Point – Left
p_tube.l.x	X coordinate of the Lower Tube Attachment Point – Left
p_rod.l.y	Y coordinate of the Upper Rod Attachment Point – Left
p_tube.l.y	Y coordinate of the Lower Tube Attachment Point – Left
p_rod.l.z	Z coordinate of the Upper Rod Attachment Point – Left
p_tube.l.z	Z coordinate of the Lower Tube Attachment Point – Left
ds_jnc_bmp.shock_len.value	Total shock length value defined in the dataset
ds_jnc_bmp.end_to_tip.value	Distance from the shock rod upper to bumper tip defined in the dataset
ds_jnc_bmp.tip_to_cont.value	Distance from the bumper tip to bumper contact defined in the dataset

Similar Systems:

•	Rear Internal Jounce Bumpers

•	Front Internal Rebound Bumpers

•	Rear Internal Rebound Bumpers