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Simulia Community Conference 2012

Bushing Connector Application in Suspension Modeling

John Deere Turf and UtilityCary, North Carolina-USA

Mukund RaoMay 15~17, 2012

Simulia Community Conference, Providence RI

Presentation Outline

1. Suspension assembly in utility vehicles – Overview

2. Coupled bushing-bolt joint construction

3. Ideal Modeling vs. Bushing Connector

4. ABAQUS documentation of bushing connector

5. Coupled bushing-bolt joint modeling

6. Bushing connector stiffness

7. Simplified suspension assembly analysis

8. TEST vs. Simulation correlation

9. Conclusions


Suspension assembly – Utility Vehicles

* Off the highway Utility vehicles, speed ranging from 27~40mph


Coupled Bushing-Bolt joint construction

•Bushing Construction has thin metal cylindrical structure with rubber sandwiched in-between•The rubber is already compressed and in a state of severe hyper-elastic strain•The Bushing is further hyper-elastically strained when clamped between the brackets


Ideal Modeling vs. Bushing Connector

Solid geometry of the Bushing Joint

•Modeling to include rubber bushing with solid hyper elastic elements•All contacts defined with bolt joint modeled and pretension


Suspension Modeling challenges

Bushing at severallocations in a simple rear suspension assembly


* Extensive modeling and computationally challenging, if all bushings are modeled as solids along with details of bolt joint

ABAQUS documentation of Bushing Connector

•The front and rear bushings as shown are represented with Bushing connector elements.•The Bushing connector model shows similar Force vs. Deflection response as fully meshed model or substructure model


Coupled Bushing-Bolt Joint Modeling


The contact surfaces represented for the hyper-elastic material bonded location and tied together with each node of bushing connector element

Bolt Joint modeled as Beam element or with solid element along with pretension

Bushing Connector Stiffness

Bushing stiffness measured along the tube axis

Bushing axial stiffness input as connector elasticity with nonlinear data



Bushing stiffness measured along the radial axis

Bushing radial stiffness along 2 and 3 rd axis input as connector elasticity with nonlinear data



Torsion stiffness, along the tube axis

Bushing torsion rigidity along axis input as connector elasticity with nonlinear data



Conical, normal to tube axis

Bushing conical rigidity input as connector elasticity with nonlinear data along other than axial direction


Simplified Suspension Assembly

The Bushing clamped at one of the upper arm fixed end

The shock replaced with rigid solid bar

FE Model with Bushing connector element and Bolt pretension


Vertical Load TEST vs. FE

•The correlation with beam bolt or solid bolt element with gap element shows Force vs. Deflection is quite sensitive to the gap in the bolt and hole. Higher the gap, the deflection is higher and vice-versa specifically load beyond bolt slip.•With 1mm gap (nominal of clearance), the force-deflection is correlating well with linear and as well non-linear range of load



•The correlation with solid bolt element using linear or nonlinear run shows that the infection points are well correlated with peak load <3% variation between FE and TEST results.•The solid bolt element nonlinear run modeled with assumed gap, shows some deviation for load beyond 10kN, as oppose to linear run likely due to varied plasticity in the bolt contact area•Also some deviation are seen in the unloading region likely due to stress relaxation in bushing.




Bushing Connector model with varied stiffness(Steel Bushing vs. Rubber Bushing) shows significantlydifferent response, both in elastic and plastic regions

Lateral Load Stiffness


Lateral Load TEST vs. FE

•The correlation with solid bolt element using linear or nonlinear run shows again a very close response between FE and TEST results


Fore-aft Load Stiffness


Fore-aft Load TEST vs. FE

•The correlation with beam model element shows good correlation, while the setup may not be suited with rigid shock as parallel load path.


Summary

1. The Bushing connector element available in ABAQUS standard/explicit has

shown excellent response of Force-Deflection, when correlated between

Simulation and TEST results.

2. The modeling of Bushing connector element with measured stiffness is simple

and complete with nonlinear range.

3. The Bushing connector application in suspension modeling is very useful and

makes solving computationally less intensive.

4. The Bushing connector application also helps to understand the influence of

numerous variables on coupled bushing-bolt joint connections. This is very

significant to understand the suspension assembly parts under peak loads.

5. The measured bushing stiffness is more appropriate, while estimated/simulated

is applicable for new designs in bushing for varied stiffness. However if

bushings are used with bolt pretension, than the bushing stiffness

measurement to include the bolt pretension. The axial stiffness in bushing

seems to see impact from bolt pretension load.


bushing connector application in suspension modeling john ... · bushing connector application in...

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