Use the Altair Bushing Model with MotionSolve

The information is also applicable for other solver packages including:

• MATLAB^TM
• ADAMS^TM
• SIMPACK^TM

Principles of Usage

The following principles are in play when using the Altair Bushing Model with MotionSolve. While the specific elements you add to your model for a bushing depend on the host simulation tool, the principles of usage remain the same.

• The bushing model acts between two bodies, for example, between a suspension control arm and sub-frame. These bodies are referred to as Body-I and Body-J at a point fixed in Body-I (on a marker on Body-I using MotionSolve).
• Inputs to the simulation model are the displacement and velocity, both translational and rotational, of Body-I relative to Body-J in a specified coordinate system fixed in Body-J (on a marker on Body-J using MotionSolve).
• Outputs from the simulation model are the forces and torques on Body-I in the specified coordinate system fixed in Body-J.
• The simulation model requires the host simulation tool to integrate the model’s internal states associated with bushing force formulation.

Altair Bushing Model in a MotionSolve Model

The Altair Bushing Model is complex and relies on a number of atomic solver elements to represent the individual effects described earlier in this guide. The figure below illustrates these elements and the data flow between them as they exist in a single Altair Bushing Model within a MotionSolve model.

Figure 1.

Components of a Bushing Model

The following sections describe the components shown above in more detail:

Data Blocks

The blocks in the simulation model include:

Block	Description
GSE-Friction (Control_StateEqn)	Computes the friction moment. The friction acts in response to rotational motions of the I-Body relative to the J-Body.
GSE-Bushing (Control_StateEqn)	Computes the bushing forces and moments and the time derivatives of states associated with the bushing forces and moments. This modeling entity also includes the forces and moments due to the bushing reaching the limits of its travel. This may include material contact between the I-Body and J-Body.
GSE-MountLimits (Control_StateEqn)	Computes the local structural deflection and rate of change of deflection given the sum of the friction, bushing, and limit forces and moments acting between the I-Body and J-Body.
GFO FORCE (Force_Vector_TwoBody)	Applies the net bushing forces and moments to the I-Body and J-Body.

For examples of blocks in the .gbs file, see: Bushing Property File. Bushing design data is passed in through a combination of files and solver REFERENCE_ARRAYs and String objects.

Inputs

Regardless of the bushing model used with it, the Altair Bushing Model requires twelve (12) inputs, which are listed for you in the following table. These inputs are the displacements and velocities between the two bodies measured at the location where the bushing acts.

[A] = angle dimension, [L] = length, [T] = time

Input	Units	Description	MotionSolve Function
U(1)	[L]	X-deflection	DX(i,rm,rm)
U(2)	[L][T-1]	X-deflection-rate	VX(i,rm,rm,rm)
U(3)	[L]	Y-deflection	DY(i,rm,rm)
U(4)	[L][T-1]	Y-deflection-rate	VY(i,rm,rm,rm)
U(5)	[L]	Z-deflection	DZ(i,rm,rm)
U(6)	[L][T-1]	Z-deflection-rate	VZ(i,rm,rm,rm)
U(7)	[A]	Angular-deflection-X	AX(i,rm,)
U(8)	[A][T-1]	Angular-deflection-rate-X	WX(i,rm,rm)
U(9)	[A]	Angular-deflection-Y	AY(i,rm,)
U(10)	[A]	Angular-deflection-rate-Y	WY(i,rm,rm)
U(11)	[A]	Angular-deflection-Z	AZ(i,rm,)
U(12)	[A]	Angular-deflection-rate-Z	WZ(i,rm,rm)

States

The Altair Bushing Model uses internal states for modeling the following: dynamics inside of the bushing; structural deflection of mount bodies (Mount Stiffness); and friction slip (bristle) states. For rubber bushings these states model the rubber’s hysteretic, frequency-dependent and amplitude-dependent behavior. For hydromounts, these states model the rubber’s behavior in addition to the mass and flow of the internal fluid. For more information about bushing models, see: Theory and Formulations.

Outputs

As listed in the table below, the Altair Bushing Model has six (6) outputs, three orthogonal forces, and three orthogonal moments acting on the I-body. Equal and opposite forces and moments that obey Newton’s Third Law are automatically applied on the J-body.

[F] = force, [L] = length

Output	Units	Description	Function
Y(1)	[F]	X direction Force on the I-Body	FX (i, rm, rm)
Y(2)	[F]	Y direction Force on the I-Body	FY (i, rm, rm)
Y(3)	[F]	Z direction Force on the I-Body	FZ (i, rm, rm)
Y(4)	[F][L]	Moment on the I-Body about the X axis	TX (i, rm, rm)
Y(5)	[F][L]	Moment on the I-Body about the Y axis	TY (i, rm, rm)
Y(6)	[F][L]	Moment on the I-Body about the Z axis	TZ (i, rm, rm)

Parameters

Prior to running an analysis, you have to define the parameters governing the behavior of the bushing, and you have to select a bushing property file. During the analysis the parameters do not vary. All of the parameters that you can define are listed in the table below.

Note: All of these are optional except PROPERTY_FILE.

[A] = angle dimension, [F] = force, [L] = length, [T] = time

Parameter	Type	Units	Entity	Description
PROPERTY_FILE	String	NA	GSE-Bushing	The name and path of the .gbs that specifies the stiffness and damping data for the bushing.
OFFSET_TRA	Array: 3 real values	[L]	GSE-Bushing	Translational displacement offsets for the bushing.
OFFSET_ROT	Array: 3 real values	[A]	GSE-Bushing	Rotational displacement offsets for the bushing.
PRELOAD_TRA	Array: 3 real values	[F]	GSE-Bushing	Force offsets for the bushing.
PRELOAD_ROT	Array: 3 real values	[F][L]	GSE-Bushing	Torque offsets for the bushing.
SCALE_DISP	Array: 3 real values > 0	None	GSE-Bushing	Scales the {x, y, z} translational displacement inputs to the bushing.
SCALE_RDISP	Array: 3 real values > 0	None	GSE-Bushing	Scales the {rx, ry, rz} rotational displacement inputs to the bushing.
SCALE_FORCE	Array: 3 real values > 0	None	GSE-Bushing	Scales the bushing force {fx, fy, fz} outputs.
SCALE_TORQUE	Array: 3 real values > 0	None	GSE-Bushing	Scales the bushing torque {tx, ty, tz} outputs.
LOCAL_STIFFNESS_ACT	Array: 6 int values	None	Mount	Switches the local stiffness: ON=1, OFF=0 for the X, Y, Z, RX, RY, RZ directions. For example {1,0,0,0,0,0} turns local stiffness on in the X direction, while all other directions are off (rigid).
LOCAL_STIFFNESS_TRA	Array: 3 real values ≥ 0	[F][L]	Mount	Combined local translational stiffness of I-Body and J-Body in the X, Y, Z directions.
LOCAL_STIFFNESS_ROT	Array: 3 real values ≥ 0	[F][L]	Mount	Combined rotational stiffness of I-Body and J-Body in the X, Y, Z directions.
LOCAL_DAMPING_TRA	Array: 3 real values ≥ 0	[F][T][L-1]	Mount	Combined local translational damping of the I-Body and J-Body in the X, Y, Z directions.
LOCAL_DAMPING_ROT	Array: 3 real values ≥ 0	[F][L][T][A]-1	Mount	Combined local rotational damping of the I-Body and J-Body about the X,Y,Z directions.
LOCAL_STIFNESS_FLAG	Enumeration: always_on always_off rigidbody_only	No Units	Mount	Switches local stiffness on and off: always_on = stiffness is active. always_off = stiffness is inactive. rigidbody_only=stiffness is active when the I-Body and J-Body are both rigid-bodies.