Wheel and Brake Assembly Testing

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Brake systems and wheel/hub assemblies are critical safety-relevant components of the vehicle chassis exposed to severe loads. Their reliability can only be safeguarded by performing tests in the laboratory under conditions which resemble actual loading conditions as closely as possible.

The wheel and brake assembly testing rig enables the simulation of all loads acting on the wheel/brake assembly which have a bearing on its service strength. All relevant parameters and service loads acting on the overall system are derived from loads occurring during actual driving conditions. These are:

• driving speed equivalent to vehicle speeds up to approx. 160 km/h, depending on the size of drum
• side loads resulting from the centrifugal forces acting on the wheel/brake assembly during cornering maneuvers
• wheel contact force resulting from vehicle weight and impacts resulting from the road surface
• braking pressure
• drive torque

Features

The wheel and brake assembly testing rig meets all above requirements by providing the following capabilities:

• Simulation of all external forces acting on the wheel, with dynamic simulation possible, including:
  • Vertical loads resulting from vertical acceleration of the wheel and static wheel load
  • Side loads due to lateral acceleration during cornering maneuvers or impacts resulting from road unevenness
  • Longitudinal and/or circumferential forces resulting from braking and acceleration maneuvers
• Simulation of braking power, with due consideration to appropriate cooling in the vehicle, with the following parameters:
  • Braking events and/or speed profile to simulate vehicle deceleration
  • Dynamic braking pressure generation by the vehicle's own braking system
  • Appropriate flow of cooling air for brake cooling and dust removal (optional)
  • Consideration of the friction between the tire and the road surface
  • Simulation of drive torque
  • Input of drive torque by means of universal-joint shaft and wheel hub, as in the actual vehicle

Operational Safety

Outstanding features of the second generation testing systems are a combination of sturdy mechanics with digital controller offering unparalleled operational safety. Extensive safety systems adapted to the specific requirements of the testing system contribute essentially to the active and passive safety of the system.

Sturdy Actuator Design

The actuators used in IST road simulators are equipped with oversized hydrostatic bearings. This results in minimum wear, low maintenance requirements and provides a significant cost saving potential for the user.

Applications

• Fatigue testing of wheels as part of a design validation process for release into production
• Rim roll accelerated durability testing: vertical input of high dynamic loads caused by road roughness and vehicle maneuvering, superimposed on the car weight component acting on a wheel
• Grist mill fatigue tests simulating severe cornering conditions, i.e. series of high lateral inbound and outbound loads superimposed on the corresponding vertical loads
• Specific service strength tests of wheel fastening and braking elements (bolts, discs etc.), hub units and truck twin wheel designs using supplementary rig equipment