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White Paper

Innovative Assembly Systems for the Aerospace Industry

2017-10-31
WP-0004
The aerospace industry is facing new challenges to meet burgeoning customer demand. An unprecedented number of orders for commercial aircraft is forcing aerospace manufacturing to make gains in efficiency throughout aircraft production and operation. However, current manufacturing systems are using technologies and production methods unsuited to a future dynamic market. To ensure its profitability, the aerospace industry must seize the opportunity to innovate and readdress approaches to manufacturing. This whitepaper looks at four advanced manufacturing (AM) solutions designed to improve assembly process efficiency, automation, and accuracy.
White Paper

The Use of Imaging for Powder Metal Characterization and Contamination Identification

2018-04-05
WP-0008
As AM technologies are being used with higher frequencywithin the automotive and aerospace industries, the interest in powder characterization and contaminant identification is growing—especially for suppliers looking to gain entry into these highly regulated industries. Standards for powder materials and methods used for aerospace applications are still be developed, and regulatory agencies such as the Federal Aviation Administration have been requesting that standards be developed as guidance for the industry. Methods such as CCSEM and HLS could be viable options for suppliers needing to adhere to a powder specification by demonstrating compliance. Solutions exist to integrate such methods into a production environment as exemplified by RJ Lee Group.
Solution Notes

Drilling Material Stacks: Can it be both automated and affordable?

2017-06-26
SN-0001
Automating a manufacturing process often comes with substantial investment or sustained operational costs of complex subsystems. But, by reducing complexity and using technologically mature components, it is possible to develop viable scaled and robust automated solutions. For the past several years, aerospace manufacturers have endeavored to automate manufacturing processes as much as possible for both production efficiencies and competitive advantage. Automating processes like drilling, fastening, sealing, painting, and composite material production have reaped a wide range of benefits; from improving quality and productivity to lowering worker ergonomic risks. The results have improved supply chains from small component manufacturers all the way up to airframe assemblers. That said, automation can be very expensive, and difficult to introduce when a product is anywhere beyond the beginning of its life cycle.
Technical Paper

A Low-cost Modular Small Engine System Utilizing Extruded Aluminum

2001-03-05
2001-01-1208
The use of modularized aluminum extrusions for the block, crankcase and head in small engine systems allows a range of engines to be mass produced without resort to casting for the stationary components. The use of modern accurately dimensioned extrusions greatly reduces the machining required. The versatility and strength of extruded aluminum alloys enables the elimination of load bearing threads and most other finish machining, thus significantly reducing the labor costs of manufacture. A range of strokes and hence of different capacity engines can be produced from a single extrusion form. For extended life, bores can be coated with a variety of finishes, including simple anodizing. Extrusion technology allows cost-effective engines to be manufactured with a significantly lower investment than with other technologies.
Technical Paper

A New High Strength Aluminium Alloy for Controlled Atmosphere Brazing

2001-05-14
2001-01-1727
A new high strength aluminium alloy intended for tubes in automotive radiators has been developed. The material is an age hardening alloy containing Mg, Si, Cu, and Mn. Titanium is added for corrosion protection. The post-braze strength of the material is dependent on the cooling rate after brazing. With 1°C/s cooling rate between 400 and 200°C, the Rp0.2 will be about 75 MPa. The corrosion resistance of the material is excellent. It is more noble than standard fin materials and will be protected by sacrificial action. Any attack in the material will be forced into a lamellar mode due to the Ti addition.
Technical Paper

Interactions Between the Materials in the Tube-Fin-Joints in Brazed Copper-Brass Heat Exchangers

2001-05-14
2001-01-1726
The paper describes the interactions between the filler material and the copper fin in the joint in the CuproBraze® process. Due to the influence of the filler metal, part of the copper fin is alloyed. The influence of the time above the melting point of the filler material and of the maximum process-temperature were investigated. It was found that the time has the strongest influence. After laboratory tests and production scale tests a brazing window for the process has been established. That can be used to set up brazing cycles for different kind of furnaces. From a number of wind tunnel tests it has been confirmed that when the brazing is done within this window the alloying of the fin is limited that it does not have practical influence on the thermal performance of the heat exchanger.
Technical Paper

Aging Response and Elevated Temperature Strengthening in Brazing Sheet Core Alloys of 3xxx Series Aluminum

2001-05-14
2001-01-1725
In this study, the age hardening effect in different braze sheet core alloys with varying levels of Mg was evaluated through tensile tests performed at their respective aging temperatures. The investigated temperature range was room temperature to 250°C. As the Mg content of the material increased, the extent of age hardening increased and the gain in yield strength was retained up to a higher temperature. For the material with 0.5 Mg, the yield strength at 175°C following peak aging at 175°C was about 60 % greater than the as-brazed yield strength. While the overaging did not occur after 2500 hours of aging at 104°C, the yield strength of material with 0.5 Mg following aging for 1500 hours at 175°C was higher than its as-brazed yield strength.
Technical Paper

Aluminum Rail Rivet and Steel Rail Weld DOE and CAE Studies for NVH

2001-04-30
2001-01-1608
Vehicle body with aluminum riveted construction instead of steel welded one will be a big challenge to NVH. In this paper, aluminum and steel rails with the dimensions similar to the rear rail portion of a typical mid-size sedan were fabricated. Rivets were used to assemble the aluminum rails while welds were used to assemble the steel rails. Adhesive, rivet/weld spacing, and rivet/weld location were the three major factors to be studied and their impact on NVH were investigated. The DOE matrix was developed using these three major factors. Modal tests were performed on those rails according to the DOE matrix. The FEA models corresponding to the hardware were built. CAE modal analysis were performed and compared with test data. The current in-house CAE modeling techniques for spot weld and adhesive were evaluated and validated with test data.
Technical Paper

Rapid Electrochemical Characterisation of Corrosion Properties of Aluminium Brazing Sheet by Stepwise Dissolution Measurement

2001-05-14
2001-01-1693
For aluminium heat-exchangers one of the most accepted corrosion tests is the SWAAT. It is widely used by both aluminium producers and manufacturers of heat-exchangers. However, in alloy development programmes, as well as in production environments even faster characterisation of corrosion properties of aluminium brazing sheet would be advantageous. The Stepwise Dissolution Measurement (SDM), which is an electrochemical technique, was developed in our laboratory to enable rapid screening of corrosion properties of aluminium brazing sheet. Within approximately 6 hours it is possible to distinguish between Long Life (over 25 days SWAAT performance) and non Long Life materials. Cross section showed that the mode of attack in SDM is similar to the mode of attack in SWAAT exposure.
Technical Paper

Micromachined Servo Accelerometer for Harsh Environments

2001-04-30
2001-01-1583
Endevco has developed the Model MSA100A micromachined servo accelerometer. It utilizes a force-balance approach that demonstrates superior performance over a conventional “open loop”. the accelerometer is small and rugged, with superior low frequency response down to DC. It has been optimized to provide low level measurements in the presence of severe vibrational inputs and temperatur e extremes after being subjected to large shock impacts. This paper details the design and operational features of the sensor element. The micromachined silicon sensor uses MEMS technology (microelectromechanical systems) in its fabrication. Also described is the electronic circuit used in the force-balance system, as well as the packaging of the accelerometer. Test results and application experience are presented.
Technical Paper

Investigation of Disc Brake Squeal via Sound Intensity and Laser Vibrometry

2001-04-30
2001-01-1604
This paper presents an experimental investigation of methods for disc brake squeal source localization. The underlying data for the localization methods considered here was obtained through the use of a sound intensity probe and a scanning laser vibrometer. The ability to correctly identify the squeal sources is an essential first step in diagnosing brake squeal. Localization methods based upon the use of sound intensity and laser vibrometry, when used together, are shown to converge successfully upon squeal sources. The sound intensity probe is used to spatially locate regions of airborne squeal noise in the near field of the brake rotor and caliper system mounted on a brake squeal dynamometer. The scanning laser vibrometer is then used to further investigate the vibration behavior of the brake assembly within these suspect regions.
Technical Paper

Analysis of Instabilities and Power Flow in Brake Systems with Coupled Rotor Modes

2001-04-30
2001-01-1602
Recent investigations by others have indicated that the dynamic response of automotive brake rotors in the squeal frequency range involves the classic flexural modes as well as in-plane motion. While the latter set creates primarily in-plane displacements, there is coupling to transverse displacements that might produce vibrational instabilities. This question is investigated here by analyzing a modal model that includes two modes of the rotor and two modes of the pad and caliper assembly. Coupling between in-plane and transverse displacements is explicitly controlled. Results from this model indicate that the coupling does create vibrational instabilities. The instabilities, whose frequencies are in the squeal range, are characterized by power flow through the transverse motion of the rotor.
Technical Paper

“Digital Prototype” Simulations to Achieve Vehicle Level NVH Targets in the Presence of Uncertainties

2001-04-30
2001-01-1529
“Digital Prototype” simulations have been used at DaimlerChrysler to achieve vehicle level NVH objectives. The effectiveness of these simulations to guide the design when faced with vehicle parameter uncertainties is discussed. These uncertainties include, but are not limited to, material properties, material gauges, damping, structural geometry, loads, boundary conditions and weld integrity. Manufacturing and assembly processes introduce variations in the nominal values of these parameters resulting in a scatter of vehicle level NVH simulation responses. An example of a high frequency NVH concern will be studied and modified to arrive at robust design guidance when faced with uncertainty. The validity of a “deterministic digital prototype” simulation model and its relevant role as a “trend predictor” rather than “absolute predictor” tool in guiding the design is also discussed.
Technical Paper

Estimation of Statistical Distribution of Composite Manufactured Transmission Error, A Precursor to Gear Whine, for A Helical Planetary Gear System

2001-04-30
2001-01-1507
Gear whine is one of the NVH attributes that have become noticeable as performance of other NVH attributes is improved. The predominant root cause of gear whine is transmission error, defined as the deviation of angular position of driven gear/s from the ideal conjugate position/s. Presence of Transmission error can be attributed to three major sources: 1) dimensional variability of individual gears during manufacturing, 2) misalignment during assembly and 3) dynamic tooth deflections during operation. This paper describes a method to estimate statistical distribution of Composite Manufactured Transmission Error (cMTE) for a planetary gear system based on measured surface variation of the gear tooth profiles. The statistical distribution of the surface variation is derived from measured left and right profiles for four equally spaced teeth per gear in both lead and involute directions.
Technical Paper

Errors in the Driveline System Balancing Process

2001-04-30
2001-01-1504
Single-plane balancing is a very well-understood process, whereby an imbalance vector is determined and then opposed by a similar vector of equal magnitude but 180° out of phase. This is used in many situations to improve machine performance, vibration, noise etc. However, there is inherent in this process a sensitivity to errors of measurement and correction, since a large imbalance vector and the equally large correction vector must be of exactly equal magnitude and exactly 180° apart for perfect balance. This paper examines the effect of errors in measurement of the initial imbalance and correction of it on the residual balance of automotive drivelines. In particular, it examines the effects of the errors present in a system whereby a system balance correction is made, on a driveline assembly, at discrete points around a given plane (at bolt locations). Errors occur in measurement of vibration, in calculating correction masses and in applying those correction masses.
Technical Paper

Gear Whine Improvements for an Automatic Transmission through Design Retargeting and Manufacturing Variability Reduction

2001-04-30
2001-01-1505
Gear whine in 1st gear for an automatic transmission that has been in production for nearly thirty years was identified as an NVH issue. Due to advances in vehicle level refinement, and reduction of other masking noises, the automatic transmission gear whine became an issue with the customer. Since the transmission was already in production, the improvements had to be within the boundaries of manufacturing feasibility with existing equipment to avoid costly and time consuming investment in new machines. The approach used was one of identifying optimum values of existing gear parameters to provide a reduction in passenger compartment noise. The problem was in a light truck application. Objective noise measurements were recorded for 10 transmissions from more than 50 driven in vehicles. The transmissions were disassembled and the gears inspected.
Technical Paper

Pass-by Noise on Different Concrete Surfaces - A Canadian Experiment

2001-04-30
2001-01-1567
A comprehensive study was undertaken to evaluate the effectiveness of different proposed low-noise surface treatments for concrete road pavements. The acoustical results of that study are described in this paper. Several consecutive 500 metre long trial sections were integrated as part of a newly constructed concrete freeway. These trial sections included several control sections of regular transversely tined concrete, a randomly tined section, and a number of different exposed aggregate concrete (EAC) surfaces of different aggregate types and sizes, all surfaced using a shotblasting method. Controlled tests were performed prior to opening of the highway, and uncontrolled tests were performed just after the highway was opened using the statistical pass-by (SPB) method.
Technical Paper

New Developments in Molded Polyurethane for Sound Insulation Applications

2001-04-30
2001-01-1555
The continual trend towards weight reduction resulted in the implementation of molded polyurethane carpet underlay at a density of 43 kg/m3 in early 2000. Now, through new formulation developments, coupled with the production introduction of carbon dioxide co-blown technology, additional weight reductions have been achieved. This has resulted in molded densities of 34 kg/m3 to be reached in prototype moldings. In addition to weight reductions, there has also been a renewed focus on improving the acoustical performance of the sound insulation material. As a result, a new family of formulations has been developed which have shown acoustical improvement while not sacrificing weight. This paper will showcase these new developments and highlight the benefits of polyurethane in sound insulation applications.
Technical Paper

Pump Noise Reduction Using Shainin Statistical Engineering Methods

2001-04-30
2001-01-1542
Historically, pump noise can be a contributor to customer dissatisfaction with automatic transmissions. In this paper, a Shainin experiment was conducted to identify all probable root causes for pump noise on a production RWD transmission. Sample transmissions were selected following subjective evaluations. Noise was objectively measured in the lab using a microphone and an accelerometer. The study was conducted following a systematic Shainin statistical engineering methodology, which included the following major steps: selection of the test measure using the isoplot technique, selection of Best of Best (BOB) and Worst of Worst (WOW) transmissions, assessment of assembly variation, component search, and pair-wise comparisons. The study successfully highlighted the key variables on the drive gear involute profile, which are now being tightly controlled for improved noise characteristics.
Technical Paper

Experimental Determination of Automotive System Response Characteristics

2001-04-30
2001-01-1477
Vehicle NVH performance is significantly affected by the dynamics of various primary systems. In the automotive industry, different design activities or vendors are responsible for designing various different systems simultaneously. Therefore, it is highly desirable to gain a better understanding of the individual system characteristics and the interaction between the primary systems to achieve a desirable overall NVH performance. Unfortunately, it is usually quite difficult to construct a proper fixture to accurately measure and quantify the actual uncoupled system characteristics. This paper examines an alternate approach of applying the FRF-based substructuring method to back-calculate the system response characteristics from the full vehicle system measurements. The results are then used to forward-compute the dynamic response of the vehicle, which are also validated by comparison to the direct response function measurements.
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