The chemical nature of the Transfer Film (T.F.) or Third-Body Layer (T.B.L.) formed at the friction interface of an automotive friction brake during off-brake motoring has been studied using Energy Dispersive X-ray (E.D.X.) analysis and Scanning Electron Microscopy (S.E.M.). Although these third-body layers are deposited on both mating surfaces of the friction couple, special attention has been paid to those formed on the disc brake rotor surface. Concurrently, detailed investigations have been undertaken examining the temperature-dependent, physico-chemical interactions of friction material constituents with each other, atmospheric oxygen and countermember materials using X-Ray Diffraction (X.R.D.).Evidence is presented relating the tribological performance of the friction pair to both the transfer film thermochemistry and the friction material composition. Among those characteristics describing the tribological performance of the friction couple, particular attention has been applied to the generation of Disc Thickness Variations (D.T.V.) induced by Off-Brake or Non-Braking Wear (O.B.W. or N.B.W.). The critical role of solid lubricants and abrasive friction modifiers and their effectiveness over a range of contact pressures / temperatures has received particular attention. Information obtained using various surface analytical techniques combined with detailed dimensional assessments of the affected triboelements has been used to show the considerable significance of abrasive particle size in determining the overall tribological behaviour of the friction pair, especially with respect to the wear regime and extent encountered at the surface of the countermember during O.B.W.Wear mechanisms are described for the generation of off-brake wear, these varying with friction material formulation. Dynamic and temperature-dependent influences on the level of in-service disc brake rotor runout are named as causes for particular forms of disc thickness variation generated by aggressive friction materials. Keywords: Third-body layer; Transfer film; Tribochemistry; Automotive Friction Braking; Cold Judder; Disc Thickness Variation; Disc Brake; Friction Material.

Yes / This paper reports on an experimental investigation into braking-related steering drift in motor vehicles, and follows on from a previous paper by the authors in which it was concluded that braking can cause changes in wheel alignment that in turn affect the toe-steer characteristics of each wheel and therefore the straight-line stability of the vehicle during braking. Changes in suspension geometry during braking, their magnitude and the relationships between the braking forces and the suspension geometry and compliance are further investigated in an experimental study of wheel movement arising from compliance in the front suspension and the steering system of a passenger car during braking. Using a kinematic and compliance (K&C) test rig, movement of the front wheels and the suspension subframe, together with corresponding changes in suspension and steering geometry under simulated braking conditions, have been measured and compared with dynamic measurements of the centre points of the front wheels. The results have enabled the causes and effects of steering drift during braking to be better understood in the design of front suspension systems for vehicle stability during braking.

Yes / In spite of the many signi cant improvements in car chassis design over the past two decades, steering drift during braking where the driver must apply a corrective steering torque in order to maintain course can still be experienced under certain conditions while driving. In the past, such drift, or `pull¿, would have been attributed to side-to-side braking torque variation [1], but modern automotive friction brakes and friction materials are now able to provide braking torque with such high levels of consistency that side-to-side braking torque variation is no longer regarded as a cause of steering drift during braking. Consequently, other in uences must be considered. This paper is the rst of two papers to report on an experimental investigation into braking-related steering drift in motor vehicles. Parameters that might in uence steering drift during braking include suspension compliance and steering o set, and these have been investigated to establish the sensitivity of steering drift to such parameters. The results indicate how wheel movement arising from compliance in the front suspension and steering system of a passenger car during braking can be responsible for steering drift during braking. Braking causes changes in wheel alignment which in turn a ect the toe steer characteristics of each wheel and therefore the straight-line stability during braking. It is concluded that a robust design of suspension is possible in which side-to-side variation in toe steer is not a ected by changes in suspension geometry during braking, and that the magnitude of these changes and the relationships between the braking forces and the suspension geometry and compliance require further investigation, which will be presented in the second paper of the two.

Yes / Results and analysis from investigations into the behaviour of the interfacial layer (Tribolayer) at the friction interface of a brake friction pair (resin bonded composite friction material and cast iron rotor) are presented in which the disc/pad interface temperature has been measured using thermocouple methods. Using a designed experiment approach, the interface temperature is shown to be affected by factors including the number of braking applications, the friction coefficient, sliding speed, braking load and friction material. The time-dependent nature of the Tribo-Iayer formation and the real contact area distribution are shown to be causes of variation in interface temperatures in friction braking. The work extends the scientific understanding of interface contact and temperature during friction braking.

In comparison to conventional cruise control, adaptive cruise control (ACC) vehicles are capable of sensing forward traffic and slowing to accommodate as necessary. When no forward vehicles are present, ACC function is the same as conventional cruise control. However, with ACC, when a slower vehicle is detected, the ACC system will decelerate and follow at a selected time-based distance. While slowing to follow, the driver will experience a system-controlled deceleration of the ACC vehicle. An experiment was conducted to evaluate driver preferences for the distance at which the primary deceleration occurs and the level of deceleration that is obtained. Driver intervention was required in one trial and driver response behavior was measured. Ten men and ten women in two age groups evaluated the decelerations from a cruise speed of 70mph to a following speed of 55mph behind a confederate lead vehicle on the highway. Evaluations can be made using four scales: Good vs. Bad, Comfortable vs. Uncomfortable, Jerky vs. Smooth, and Early vs. Late. Decelerations of approximately 0.06g which occur approximately 200ft to 250ft behind the lead vehicle were most preferred. Prior to intervention, foot position ranged from a point directly below the brake pedal to 16.4in from the brake pedal. Foot motion began between 21.12s time-to-collision (TTC) and 3.97s TTC. Eighty percent of the participants paused to "cover" the brake before final motion to activate the brake. The older age group intervened (braked) later than the younger age group. Driver braking after intervention ranged from 0.16g to 0.32g. / Master of Science

The thesis deals with the possibilities of identifying the relevant tire traces at the place of a traffic accident based on their physical characteristics. Braking traces on the road are one of the most important objective elements for accident analysis, their easy and accurate detection is very important for accurate accident assessment. With the increasing technical equipment of vehicles, especially with the introduction of newer generations of braking assistance systems, traces left by the tires become almost invisible to the human eye. It is therefore highly desirable that their detection should be not only as accurate as possible but also as easy and fast as possible, not only for forensic experts, but especially for members of the traffic police departments. In line with the development and introduction of new safety and assistance systems for vehicles should also be the development of means and methods of providing the basis for technical analysis of traffic accidents. Reality shows that the procedures, even if still functional, are practically identical for several decades, are dependent on the subjective capabilities of the documenting person. An essential element of the work, compared to the previously described measurement procedures, is the use of modern methods and devices at the highest known level of knowledge. The aim is to find and verify a simple, accurate, subjectively least influenced detecting method for tire traces on the road. A series of measurements confirmed the possibility of using the thermal camera at the technical level usually available at the place of the accident, under limited atmospheric and time conditions. In addition, laser-induced plasma spectroscopy and rLIBS were used. This method of detecting spotless tire treads can be marked as a minimally feasible documentary and at the same time as fast enough, based on the measurements made and the intended removal of defects of the instrument in the development phase of the prototype.

Volvo Group Truck Technology has the ambition to automate parts of their routine service. Therefore a project was launched to investigate which parts of the routine that could be automated. The idea of this project is to lower the time spent on the service and also improve the working environment for the personnel. The purpose of this thesis is to develop and build a conceptional prototype for a low-cost crack detecting sensor. This thesis is a part of a larger proof of concept project which Volvo GTT runs in cooperation with Robotdalen and Robot Application Center (RAC). The work done in this thesis has been based on literature studies, interviews and company visits. The gathered knowledge and observations was translated into what would be required to fit the needs. This thesis covers different techniques that could be used to detect flaws in braking discs. However, this thesis is mostly focused on one non-destructive method technique based on induced eddy currents. Several non-destructive techniques and conceptual designs has been tested and evaluated with varying results during this project. The result of this thesis was a design that reacts to discontinuities in conductive materials, such as the grey cast iron material used in the Volvo trucks braking discs. The results are represented as a voltage drop change and can be visualized by an oscilloscope. This study shows that the method of choice has the potential to be used as a crack detecting system and that the system can be built reliable with rather cheap components. Further development should aim towards making the design even cheaper and the components should be assembled on a PCB instead of a breadboard in order to make the system less sensitive to noise and easier to assemble alongside the trucks braking discs.

This thesis is concerned with the development of a new measurement device for the realistic assessment of braking capability of landing airplanes for winter runways. Landing represents one of the most safety-critical phases of aircraft operation. Aircraft runway excursion incidents occur due to the unpredictability of the runway pavement condition. This is especially true during winter time when the runway is often covered by deformable contaminants. Several accidents are discussed that list the deteriorated condition of the runway pavement and the inability to accurately report this condition as the main causes for the excursions. The accuracy of the approaches currently adopted by the airport authorities around the world to monitor the condition of the runway pavement are evaluated. The conventional and current practice of runway condition monitoring is focused on identifying the maximum tire-pavement frictional drag mu value and often neglects the characteristics of actual aircraft brake control system as well as the comprehensive effects coming from various factors such as deformable contaminants on the winter runway. The braking availability tester discussed here is designed to take a different approach for the realistic assessment of braking availability of landing aircrafts. The main idea of this device is to mimic the braking operation of actual aircrafts as closely as possible by incorporating the same brake mechanism and the brake control system used in existing aircrafts. The architecture of the device from the ground-up including the suite of sensors, the structure of the wheel, important actuators, and the real-time brake control system are discussed in detail. More importantly, the operational principles of the braking availability tester (BAT) are outlined which help one understand how the system works together. A new method to quantify the braking availability on the runway using the BAT is explained. The testing and data collection strategy for implementing this technique is also outlined. Additionally, the results from preliminary tests are presented to verify the functionality of the BAT. The results are used to verify that the BAT operates with the brake control system of an aircraft. Finally, experimental data sets from dry and contaminated pavement testing are presented to show the effect of different weather conditions on the operation of the BAT.

This thesis is concerned with the development of a new measurement device for the realistic assessment of braking capability of landing airplanes for winter runways. Landing represents one of the most safety-critical phases of aircraft operation. Aircraft runway excursion incidents occur due to the unpredictability of the runway pavement condition. This is especially true during winter time when the runway is often covered by deformable contaminants. Several accidents are discussed that list the deteriorated condition of the runway pavement and the inability to accurately report this condition as the main causes for the excursions. The accuracy of the approaches currently adopted by the airport authorities around the world to monitor the condition of the runway pavement are evaluated. The conventional and current practice of runway condition monitoring is focused on identifying the maximum tire-pavement frictional drag mu value and often neglects the characteristics of actual aircraft brake control system as well as the comprehensive effects coming from various factors such as deformable contaminants on the winter runway. The braking availability tester discussed here is designed to take a different approach for the realistic assessment of braking availability of landing aircrafts. The main idea of this device is to mimic the braking operation of actual aircrafts as closely as possible by incorporating the same brake mechanism and the brake control system used in existing aircrafts. The architecture of the device from the ground-up including the suite of sensors, the structure of the wheel, important actuators, and the real-time brake control system are discussed in detail. More importantly, the operational principles of the braking availability tester (BAT) are outlined which help one understand how the system works together. A new method to quantify the braking availability on the runway using the BAT is explained. The testing and data collection strategy for implementing this technique is also outlined. Additionally, the results from preliminary tests are presented to verify the functionality of the BAT. The results are used to verify that the BAT operates with the brake control system of an aircraft. Finally, experimental data sets from dry and contaminated pavement testing are presented to show the effect of different weather conditions on the operation of the BAT.

High mobility has been a standard in the modern world for decades. This has resulted in high energy consumption, diminishing fossil energy reserves and rising levels of greenhouse gases. By recovering the energy lost in deceleration of vehicles the total energy consumption can be decreased and exhaust emissions reduced. This can be done with a kinetic energy recovery system (KERS) that converts kinetic energy to electric energy during deceleration, which then can be used for acceleration. KERS requires an electrical storage device with high power density, due to the high power levels generated at heavy braking. Batteries does not generally meet these requirements, especially in the cost-effective point of view, but different types of capacitors can be used to obtain a cheap and effective system. To get such an energy storage device small, lightweight and inexpensive while the technology is sustainable requires avoidance of rare metals and hazardous materials. In this master thesis energy and power levels for KERS has been modelled, based on standardized measurements techniques and small paper-based supercapacitors have been built and tested in order to model size, weight and price for a full-scale energy storage device to a KERS-application. The models showed that energy consumption in urban traffic could be reduced with 18% and with an electrode material for the energy storage device with a capacitance of about 1500 F/m2 a reasonable size and weight is obtained. To reach these values of capacitance in paper-based supercapacitors further testing is required on area and layer dependence and for different electrodes.