Dale L. Hartsock

Effect of Pad/Caliper Stiffness, Pad Thickness, and Pad Length on Thermoelastic Instability in Disk Brakes

Thermoelastic instability (TEI) results in uneven heating of the rotor and the development of hot spots in automotive disk brake systems. The hot spots cause rotor distortion and thickness variation which can cause torque variation resulting in brake roughness or low frequency noise. Lee and Barber (1993, ASME J. Tribol., 115, pp. 607-614) developed an analytical model to predict the critical speed above which TEI would occur. This paper describes enhancements to the model to include the effects of caliper/pad stiffness, the pad friction material thickness, and the pad length. The effects of these changes on the predicted speed are calculated and compared to the original model.

PARAMETRIC ANALYSES OF THERMOELASTIC INSTABILITY IN DISC BRAKES

Thermoelastic instability (TEI) results in uneven heating of the rotor and the development of hot spots in automotive disk brake systems. The hot spots cause rotor distortion and thickness variation which can cause torque variation resulting in brake roughness and low frequency noise. An analytic study has been performed using the basic equations developed by Lee and Barber (1993) extended to include the pad thickness (Hartsock and Fash, 1999) and partial rotor surface contact with the pad (Lee and Barber, 1995; Ayala et al., 1996). Relevant pad and rotor material properties as well as the pad thickness, rotor thickness and coefficient of friction were varied by a fixed percentage to determine the effect on the critical speed for TEI. The relative importance of each parameter was established and the predicted direction of change to increase the critical speed was identified.

Development of a Brake Dynamometer-Vehicle Model Hardware-in-the-Loop System

This paper presents the development of a hardware in the loop (HIL) simulation system for evaluating and optimizing the interactions of the brake system with the vehicle. This unique HIL set-up consists of an inertial brake dynamometer with a brake corner module, an electronic control unit, a real time 3D total vehicle model and a computer system with a high-speed operating platform. The HIL system simultaneously confers advantages of both computer modeling and hardware testing. It offers the capability to do upfront design and assess performance of the foundation brake hardware and the chassis controls, as well as their interactions, in advance of testing and tuning a vehicle. This powerful tool enables reduction in development time and cost. A simple example of applying the brake dynamometer HIL system will be presented. The FMVSS135 test was simulated using the HIL approach, demonstrating the effect of various front brake corner modules on vehicle stopping distance in the inoperative power condition.

Development of a high speed system for temperature mapping of a rotating target

This paper covers the development and comparison of two systems to measure the temperature variation on rotating components. Measurement of hot spots on a rotating brake disk is used for demonstration purposes. The two systems utilized are a high-speed infrared camera and an array of fiber optics connected to multiple high-speed single-point two-color infrared detectors coupled to a high-speed data acquisition system. The advantages and disadvantages of the two systems are discussed relative to real time data and post processing analyses. Results from both systems are presented for comparison.

A Simplified Structural Ceramic Design Technique

This paper reviews the basic theory of the ceramic design methodology, and discusses the relative importance of the various parameters. A simplified technique is presented for estimation of the component reliability from the component stresses or for determining an acceptable design stress. These techniques can be used with or without a finite element stress analysis. A comparison of predicted probabilities of failure for actual components is made between the traditional computerized Weibull analysis and this simplified technique which shows reasonable agreement. An example of how to use this method is presented and an error analysis is included. This technique can be used to aid in material selections and design modifications, rank alternate designs and help the individual develop a “feel” for successful ceramic design.Copyright