Search Results

During the automotive brake system design and development process, a large number of performance characteristics must be comprehended, assessed, and balanced against each other and, at times, competing performance objectives for the vehicle under development. One area in brake development that is critical to customer acceptance due to its impact on a vehicle's perceived quality is brake pedal feel. While a number of papers have focused on the specification, quantification and modeling of brake pedal feel and the various subsystem characteristics that affect it, few papers have focused specifically on brake corner hoses and their effect on pedal feel, in particular, during race-track conditions. Specifically, the effects of brake hose fluid consumption pedal travel and brake system response is not well comprehended during the brake development process.

Misfire diagnostics are required to detect missed combustion events which may cause an increase in emissions and a reduction in performance and fuel economy. If the misfire detection system is based on crankshaft speed measurement, driveline torque variations due to rough road can hinder the diagnosis of misfire. A common method of rough road detection uses the ABS (Anti-Lock Braking System) module to process wheel speed sensor data. This leads to multiple integration issues including complexities in interacting with multiple suppliers, inapplicability in certain markets and lower reliability of wheel speed sensors. This paper describes novel rough road detection concepts based on signal processing and statistical analysis without using wheel speed sensors. These include engine crankshaft and Transmission Output Speed (TOS) sensing information. Algorithms that combine adaptive signal processing and specific statistical analysis of this information are presented.

There is an increasing interest in transient thermal simulations of automotive brake systems. This paper presents a high-fidelity CFD tool for modeling complete braking cycles including both the deceleration and acceleration phases. During braking, this model applies the frictional heat at the interface on the contacting rotor and pad surfaces. Based on the conductive heat fluxes within the surrounding parts, the solver divides the frictional heat into energy fluxes entering the solid volumes of the rotor and the pad. The convective heat transfer between the surfaces of solid parts and the cooling airflow is simulated through conjugate heat transfer, and the discrete ordinates model captures the radiative heat exchange between solid surfaces. It is found that modeling the rotor rotation using the sliding mesh approach provides more realistic results than those obtained with the Multiple Reference Frames method.

This paper discusses an analytical technique for computing the failure rate of steel springs used in automotive part applications. Preliminary computations may be performed and used to predict spring failure rates quickly at a very early stage of a product development cycle and to establish program reliability impact before commitment. The analytical method is essentially a combination of various existing procedures that are logically sequenced to compute a spring probability of failure under various operational conditions. Fatigue life of a mechanical component can be computed from its S-N curve. For steels, the S-N curve can be approximated by formulae which describe the fatigue life as a function of its endurance limit and its alternating stress. Most springs in service are preloaded and the actual stress fluctuates about a mean level. In order to compute an equivalent alternating stress with zero mean, an analytical method based on the Goodman Diagram is used.

A methodology involving Design for Six Sigma (DFSS) and Multi-body dynamic simulation is employed to tune a body-on-frame vehicle, for improved ride (shake) performance. The design space is limited to four sets of symmetric body mounts for a vehicle. The stiffness and damping characteristics of the mounts are the control factors in the virtual experiment. Variation of these design parameters from the nominal settings, as well as axle size, tire and wheel combinations, tire pressure, shock damping, and vehicle speed constitute the noise factors. This approach proves to be an excellent predictor of the vehicle behavior, by which much insight as to influence of each parameter on vehicle performance is gained. Ultimately, specific recommendations for the control factor settings are provided. Subsequent hardware builds show excellent agreement with the analytical model and suggested tuning.

Since 1997, General Motors Body Manufacturing Engineering - Die Engineering Services (BME-DES) has been working jointly with our software vendor to develop and implement a parallel version of stamping simulation software for mass production analysis applications. The evolution of this technology and the insight gained through the implementation of DMP/MPP technology as well as performance benchmarks are discussed in this publication.

In response to the TREAD act of 2002, ASTM F09.30 Aged Tire Durability Task Group was formed with the objective of developing a scientifically valid, short duration aged durability test which correlates to field behavior. The target end-of-test condition was belt edge separation (or related damage). One strategy, driven by that objective, has been a steady state design of experiment investigating aging temperature and duration as well as roadwheel speed, pressure and deflection. The rationale behind investigating a steady state test and selecting these parameters and methodology for setting their initial values is reviewed.

In response to the TREAD act of 2002, ASTM F09.30 Aged Tire Durability Task Group was formed with the objective of developing a scientifically valid, short duration, laboratory aged tire durability test which correlates to field behavior. The target end-of-test condition was belt edge separation (or related damage). Two strategies have been investigated, aged stepped-up load and steady state DOE. Results of the two strategies are compared and contrasted and a test condition from the steady state DOE has been identified as the preferred direction for further validation.

In the work leading to the TREAD Act, some members of Congress expressed the need for some type of aging test on light vehicle tires. Since no industry-wide recommended practice existed, the ASTM F09.30 Aged Tire Durability task group was established in 2002 to develop a scientifically valid, short duration, laboratory aged tire durability test which correlates to in-service aging. The target end-of-test condition was belt edge separation (or related tire conditions). One strategy, driven by that objective, has been a Steady State DOE investigating aging temperature and duration, as well as, roadwheel speed, pressure and deflection. Testing was performed on three tire types, including two where relevant field aging data was publicly available from NHTSA studies. A region of interest, within the design space, was identified where target end-of-test conditions were possible and undesirable (non-target or non-representative of those seen in consumer use) were avoided.

Magnesium alloys are the lightest structural metal and recently attention has been focused on using them for structural automotive components. Fatigue and durability studies are essential in the design of these load-bearing components. In 2006, a large multinational research effort, Magnesium Front End Research & Development (MFERD), was launched involving researchers from Canada, China and the US. The MFERD project is intended to investigate the applicability of Mg alloys as lightweight materials for automotive body structures. The participating institutions in fatigue and durability studies were the University of Waterloo and Ryerson University from Canada, Institute of Metal Research (IMR) from China, and Mississippi State University, Westmorland, General Motors Corporation, Ford Motor Company and Chrysler Group LLC from the United States.

Over the last five years, the automotive industry has experienced a trend towards niche performance vehicles equipped with high-output powertrains. These high performance vehicles also demand higher output braking systems. One method used to provide enhanced pedal feel and fade performance is to equip vehicles with higher apparent friction linings. The challenge then becomes how to design and manufacture these brake systems without high-frequency disc brake squeal and without paying a significant mass penalty. One alternative is to design disc brake rotors with increased damping. There are several options for increasing rotor damping. The classical approach is to increase the rotor's cast iron carbon content, thus increasing the internal material damping of the rotor. However, this methodology provides only a small increase in rotor damping. Alternatively, the rotor damping can be increased by introducing friction, sometimes referred to as Coulomb damping.

Brake caliper and corner behavior in the off-brake condition can lead, at times, to brake system performance issues such as residual drag (and related issues such as pulsation, judder, and loss of fuel economy), and caliper pryback during aggressive driving maneuvers. The dynamics in the brake corner can be strikingly complex, with numerous friction interfaces, rubber component and grease dynamics, deflections of multiple components, and significant dependence on usage conditions. Displacements of moving parts are usually small, and the residual forces in the caliper interfaces involved are also small in comparison with other forces acting on the same components, making direct observation very difficult. The present work attempts to illuminate off-brake behavior in two different conditions - residual drag and pryback - through the use of low-range pressure distribution sensors placed in between the caliper (pistons and fingers) and the brake pad pressure plates.

Casting, machining and structural simulations were completed on a V8 engine block made in Compacted Graphite Iron (CGI) for use in a racing application. The casting and machining simulations generated maps of predicted tensile strength and residual stress in the block. These strength and stress maps were exported to a finite element structural model of the machined part. Assembly and operating loads were applied, and stresses due to these loads were determined. High cycle fatigue analysis was completed, and three sets of safety factors were calculated using the following conditions: uniform properties and no residual stress, predicted properties and no residual stress, and predicted properties plus residual stress.

This report summarizes the methodology used in automotive industry for virtual evaluation of vehicle structural integrity under abusive load cases. In particular, the development of a nonlinear finite element (FE) centric approach is covered that is based on the functions implemented in ABAQUS (by ABAQUS Inc.). An overview is also given for comparative study of the ABAQUS capability with the existing ADAMS (MSC Software) based methods.

The development and application of a traction control Kodiak and GMC TopKick are explained. Most traction systems use engine management to enable traction control, while the adaptive braking system can provide traction assist for either gas or Diesel powered vehicles from 14,000 lbs. to 33,000 lbs. GVW. The performance driven criteria that established the design requirements and the development of a new product to meet these objectives are discussed. Both the vehicle manufacturer and the traction controller supplier provided these criteria. The basic ABS and traction control hydraulic schematics will be described as they apply to the vehicles. The results of the development program will be compared to the criteria used to establish the goals, and the benefits of the traction control system will be discussed.

Fundamental differences exist between sheet metal forming and hydroforming processes. Sheet metal forming is basically a one step metal fabrication process. Almost all plastic deformation of an originally flat blank is introduced when the punch is moved normal to a clamped sheet metal. Hydroforming, however, consists of multiple steps of tube making, pre-bending, crushing, pressurization, etc. Each of the above mentioned steps can introduce permanent plastic deformations. The forming limit diagram obtained for sheet metal forming may or may not be used in hydroforming evaluations. A failure criterion is proposed for predicting bursting failures in tube hydroforming. The tube material's stress-strain curve, obtainable from uniaxial tensile test and subjected to some postulations under large stress/strain states, is used in judging the failure.

Several factors have influenced the size and design of domestic passenger cars over the past 30 years. Of most significance has been the influx of imported cars, initially from Europe, later from Japan. Interspersed within the fabric of this influx have been two energy crises and several recessions, and the onset of safety, emission, and energy regulations. These factors have led to various responses by domestic manufacturers as indicated by the types of products and vehicle systems that they have introduced during this period. This paper chronicles both the events as well as the responses.

General Motors has developed a portfolio of advanced propulsion vehicles that has set the standard for optimal fuel economy in full-size utility vehicles. An overview of power electronics used in this portfolio, already available in the market, is presented. These components are key enablers for the strategic products in portfolio. Block diagrams for various configurations are also described to show common power electronics components used in traction and auxiliary systems. Briefly real wheel drive (RWD) and front wheel drive (FWD) vehicle applications are described. Specific analysis and test results are presented from development of Traction Power Inverter used in RWD vehicles. Vehicle-based durability profiles are used in analysis to predict IGBT power modules thermal performance. Using key metrics for volume and mass, benchmarking data is also presented.

Typically, “Reliability and Maintainability (R&M)” is perceived as a tool for products alone. Putting emphasis on reliability only at the cost of maintainability is another archetype. Inclusion of both reliability and maintainability (R&M) in all the phases of the machinery and equipment (M&E) life cycle is required in order to be world competitive in manufacturing. R&M is mainly a design function and it should be a part of any design review. Inclusion of the R&M concept early in the life cycle of M&E is key to cost effective and competitive manufacturing. Neither responsive manufacturing nor preventive maintenance can raise it above the level of inherent R&M.

Engineers have used birefringent coating as a full field surface strain measuring tool for many years. The technique provides visual inspection of the structure on highly stressed areas that may lead to a potential structural failure. The usage of this technique for analysis of automotive brake components is very common. The recent development of the strain freezing technique extends further the capability of birefringent coating analysis. Hidden areas with high stresses can now be revealed for analysis.