Search Results

The FE analysis is one of approach to develop the reduction method for brake squeal. This study shows the results of applying the FE analysis method, developed for disc brake with opposed piston type caliper shown in reference [1] and [2], to the analysis of low frequency disc brake squeal of floating type caliper. The FE analysis results are confirmed with the vibration mode during squeal generation measured by experiment. And some effective factors to the brake squeal are clear on floating type caliper by FE analysis.

The chemical composition of the transfer film formed on brake rotor surfaces during a 208 second low, pressure drag was investigated by Sputtered Neutral Mass Spectrometry (SNMS)/Depth Profiling. A stiff non-commercial pad was employed and the applied pressure and cooling air flow were adjusted to induce judder. In addition to the usual dynamometer data, capacitive displacement transducers were used to monitor dynamic rotor thickness variations and an eight-channel dual- wavelength pyrometer was employed to measure dynamic surface temperatures. The time-dependent torque, rotor thickness and rotor surface temperature measurements were transformed to polar coordinates (rotor radius and angle) and provided the rationale for the locus of points on the rotor surfaces to be analyzed.

This paper will discuss the trends which are emerging in electronically controlled braking control systems and the challenges which are faced in the design of cost-effective solutions. General trends relating to conventional hydraulic systems will first be discussed, leading onto issues and challenges facing future implementations, such as brake-by-wire systems.

Hayes Lemmerz has patented a straight 42 fin rotor design which has air entry from the inboard and outboard side of the brake rotor. In a previous brake colloquium, we reported that a 5% increase airflow occurs in this design compared to the conventional 100% inboard entry rotor. We have now studied the thermal cooling rate and distortion due to temperature on the dynamometer. The current Hayes Airflow Rotor Design has exhibited 100 degrees F lower peak temperature and 50% less coning when compared to current production rotor design. More work is being done to analytically understand the airflow and thermal distortion of the rotor compared to instrumented vehicle tests like DST (Detroit Suburban Traffic), and LACT (Los Angeles City Traffic).

This paper summarizes a case study involving the characterization and reduction of the brake noise on the 1998 Mercedes-Benz M-Class Sport Utility Vehicle. Noise was identified on both the front and rear brake systems. The front disc brake noise was described as a low frequency squeal, while the rear disc brakes exhibited a high frequency squeal. Investigation into this problem incorporated vehicle and dynamometer testing as well as experimental modal analysis (EMA) for component characterization. The use of EMA and dynamometer testing resulted in the identification of several possible countermeasures including: pad chamfers, pad compressibility control, pad scorching, and rotor modifications. Various noise insulators were also examined as a potential solution to this problem without making any additional changes to the existing components. Dynamometer and vehicle testing were used in the evaluation and selection of a noise countermeasure for each the front and rear braking systems.

The mechanical properties of a gray cast iron disc brake rotor are directly influenced by the amount and morphology of the graphite present throughout the rotor. Two of these properties, the modulus of elasticity and the damping capacity, can have a significant effect on the propensity for the disc brake rotor to produce noise. The noise propensity of a disc brake is in a large part determined by the relationship between the rotor resonances and the resonances of the other brake components such as the pads. In this paper, we are concerned only with the effect that modulus of elasticity has on disc brake noise through its influence on rotor resonances. The amount and morphology of the graphite in gray cast iron is determined by the carbon content and silicon content of the iron. The carbon and silicon content are measured by one parameter called the carbon equivalent.

Friction materials with three different formulations containing different solid lubricants were investigated to study the role of lubricants on the friction performance. The three friction materials contained 10 vol.% graphite, 7 vol.% graphite + 3 vol.% Sb2S3, and 7 vol.% graphite + 3 vol.% MoS2, respectively, with the same amount of other ingredients. Results of this work showed that each formulation had advantages and disadvantages. The friction materials containing two lubricants (graphite + MoS2 or Sb2S3) showed better resistance to fading and improved friction stability than the friction material containing only graphite. However, the friction materials with two lubricants showed disadvantages on anti-fading, wear resistance, and DTV generation.

Noise, Vibration and Harshness problems in rotors and drums show up in different forms in automotive brakes. The NVH problems may reside either in foundation brakes, apply systems, anti-lock systems or having nothing to do with brake systems but are related to other automotive components such as suspensions, wheel bearings, tire and wheel, drive axle or body structure. The NVH issue is a major warranty cost issue that the car manufacturers and suppliers have to face. Hayes Lemmerz has patented a new rotor design where lowering noise and vibration were the main design criteria. We have used a design concept unique to the brake industry but commonly used to dampen noise. The rotor introduces a sound deadening layer under the brake cheeks. The brake cheeks are attached to brake ribs or fins by a safe and reliable joining method, with the noise damping layer molded on the rear of brake cheeks. We have achieved noise reduction of 50% compared to current production design rotors.

The complexity of brake NVH work is analyzed, demonstrating that current approaches and problem solving strategies are inadequate. A survey is given of existing NVH test procedures. State of the art, respectively advanced NVH tools are described. The idea of an “Integrated Development & Test Concept” is presented as a vision for future development and test work. Part of it is the new concept of an “Integrated NVH Diagnostic and Problem Solving System”

The correlation results between tests made with identical materials on a full size brake dynamometer and a compact vehicle dynamometer, have permitted to predict, since the beginning of the product development, the classification of GAWR according to the FMVSS 121 procedure and the RP-628 parameters.

Coldworking short edge margin applications, using nominal applied expansion levels, may result in the buckling of the short ligament. This paper describes a new coldworking procedure, Multiple Initial Coldworking, utilizing the split mandrel process. This coldworks the hole three times, instead of the usual one time. Static tests conducted on aluminum and titanium sheets analyzed the effect of the new process on low edge margin applications and other hole quality issues. Fatigue tests determined fatigue life increase on the basic process. Three passes at a lower applied expansion produce fatigue results similar to nominal single pass coldworking.

Today's Aerospace market has transitioned to an assembly system that requires its suppliers to provide high quality sub components at a very competitive price. Also, to remain competitive in the market, the Aerospace designers must be creative in designing structures that are less costly, both in materials and in the assembly methods required. In many cases these methods for fabricating such structures require unique automation to achieve the required results. In the forgoing article a demanding fabrication situation required versatility, many unique conditions to be met, and a great deal of creative thinking, to develop the final automation system.

A high level directive is in place at the St. Louis facility to increase the use of automation in our assembly processes. Likewise, the C-17 program has implemented a series of cost reduction initiatives. In line with these initiatives we have been implementing automatic fastening equipment into a variety of non-traditional applications. The C-17 Cargo Door Intercostals can easily be described as “non-traditional” and represent unique challenges for automatic fastening. The concept for The Intercostal Riveter uses proven drill and riveting techniques. However, it has miniaturized components and will be utilized like a portable power tool. Manipulated by a single operator, it will be maneuvered around and throughout the C-17 Cargo Door Assembly Jig. It is ultra-lightweight and will have a C-Frame constructed from carbon-epoxy composite material.

This paper describes the application of an automated machine tool system used in the assembly process of a military aircraft wing torque box, manufactured by The Boeing Company. Traditional approaches to the wing assembly production involve manual framing, drilling, and installation steps. This program first introduced an automated drilling system during the Engineering/Manufacturing Development phase of this project. In a continuous search to optimize the wing assembly process, Boeing decided to go beyond this level of automation. The idea was to introduce an automated system to drill, ream, countersink, inspect holes, seal prior to fastener insertion, and install various types of fasteners. This paper will examine and outline the production constraints that lead to the requirements of the automated system. System capabilities as they apply to the wing production requirements are presented. The current and proposed assembly techniques are described.

At The Boeing Company, the advent of a Determinant Assembly (DA) program and the subsequent production of accurate fuselage subpanels created a need to be able to position subpanels accurately and repeatably during fuselage assembly. The tool engineering organization of The Boeing Company and Advanced Integration Technology, Inc. (AIT) as the prime contractor, are developing and installing automated positioning and alignment systems throughout major 747 fuselage assembly areas which enable DA techniques. The benefits of this assembly approach and this automated precision tooling are flexibility, assembly accuracy, ease of assembly and associated speed, reduced downtime for tool maintenance, and improved shop-floor ergonomics.

Friction Stir Welding (FSW) can achieve high quality welds in aluminum alloys that are of interest to the aerospace industry (e.g. alloys 2014, 2219, 7050 and numerous aluminum-lithium alloys). The low distortion solid-phase welds exhibit metallurgical and mechanical properties, including fatigue, which are superior to conventional fusion welds achieved by arc processes. FSW, although a relatively new welding technique, has been systematically developed and proved by The Welding Institute (TWI) under contract to an international group of sponsors, one of which is The Boeing Company. To further validate the process, The Boeing Company conducted separate development activities including detailed mechanical testing of welds made from the FSW process.

The following will be a discussion of techniques, and considerations regarding the use of portable coordinate measurement machines (PCMM) in the aerospace industry. The focus will be the use of articulated arm PCMM's in soft tooling and assembly applications. The key elements to consider when evaluating proposed systems will be covered as well as a look at current trends in this industry segment.

Several years ago Raytheon Aircraft Production Managers were faced with four looming problems: 1. Rising medical charges due to Carpal Tunnel and related illness. 2. Rising labor costs caused by antiquated, ineffecient, ineffective assembly methods. 3. Inability to meet production schedules. 4. Inferior quality, excessive rework. The popular consensus for improvement of all of the above noted conditions was automation through machine riveting.

British Aerospace needed an automated wing riveting system for fastening the A320 wing sections. The E4000 Wing Riveting System was designed and installed at their Airbus factory in Chester, UK and is now in production. It uses a five axis solid yoke with workheads on each end of the yoke. It accurately installs both rivets and lockbolts over the entire wing panel, including offset areas.

Business case analysis of projects has become a valuable tool in the way a company makes decisions in today's manufacturing environment. The business case is an attempt to closely analyze the financial ramifications of implementing a new procedure or piece of equipment. Contained within the business case is a Return On Investment (ROI) spreadsheet, calculations, and background information.