Langley aerospace test highlights, 1985

The role of the Langley Research Center is to perform basic and applied research necessary for the advancement of aeronautics and space flight, to generate new and advanced concepts for the accomplishment of related national goals, and to provide research advice, technological support, and assistance to other NASA installations, other government agencies, and industry. Significant tests which were performed during calendar year 1985 in Langley test facilities, are highlighted. Both the broad range of the research and technology activities at the Langley Research Center and the contributions of this work toward maintaining United States leadership in aeronautics and space research, are illustrated. Other highlights of Langley research and technology for 1985 are described in Research and Technology-1985 Annual Report of the Langley Research Center

Sound source contributions for the prediction of vehicle pass-by noise

Current European legislation aims to limit vehicle noise emissions since many people are exposed to road traffic noise in urban areas. Vehicle pass-by noise is measured according to the international standard ISO 362 in Europe. More recent investigations of urban traffic have led to the proposal of a revised ISO 362 which includes a constant-speed test in addition to the traditional accelerated test in order to determine the pass-by noise value. In order to meet the legal pass-by noise requirements, vehicle manufacturers and suppliers must analyse and quantify vehicle noise source characteristics during the development phase of the vehicle. In addition, predictive tools need to be available for the estimation of the final pass-by noise value. This thesis aims to contribute to the understanding of vehicle pass-by noise and of the characteristics of the vehicle noise sources contributing to pass-by noise. This is supported through an extensive literature review in which current pass-by noise prediction methods are reviewed as well. Furthermore, three vehicle noise sources are replicated experimentally under laboratory conditions. This involves an orifice noise source, represented by a specially designed loudspeaker on a moving trolley, shell noise, represented by a metal cylinder structure, and tyre cavity and sidewall noise, represented by an annular membrane mounted on a tyre-like structure. The experimentally determined directivity characteristics of the acoustically excited noise sources are utilised in the pass-by noise prediction method. The predictive results are validated against experimental measurements of the three vehicle-like noise sources made within an anechoic chamber

Applications of aerospace technology in the public interest: Pollution measurement

This study of selected NASA contributions to the improvement of pollution measurement examines the pervasiveness and complexity of the economic, political, and social issues in the environmental field; provides a perspective on the relationship between the conduct of aerospace R and D and specific improvements in on site air pollution monitoring equipment now in use; describes the basic relationship between the development of satellite-based monitoring systems and their influence on long-term progress in improving environmental quality; and comments on how both instrumentation and satellite remote sensing are contributing to an improved environment. Examples of specific gains that have been made in applying aerospace R and D to environmental problem-solving are included

Road Condition Estimation with Data Mining Methods using Vehicle Based Sensors

The work provides novel methods to process inertial sensor and acoustic sensor data for road condition estimation and monitoring with application in vehicles, which serve as sensor platforms. Furthermore, methods are introduced to combine the results from various vehicles for a more reliable estimation

Road Condition Estimation with Data Mining Methods using Vehicle Based Sensors

The work provides novel methods to process inertial sensor and acoustic sensor data for road condition estimation and monitoring with application in vehicles, which serve as sensor platforms. Furthermore, methods are introduced to combine the results from various vehicles for a more reliable estimation

Relationship between tyre cavity noise and road surface characteristics on low-noise pavements

Abstract In this work, a protocol to study Tyre Cavity Noise (TCN) was developed. Using this new method, TCN was measured on 24 different road pavements, together tyre noise emission measured with the Close-Proximity (CPX) method and road texture measurements. The results were used to model the relationship between TCN and road surface parameters. The analysis shows that the Standard Reference Test Tyre's (SRTT) TCN is correlated to megatexture at low frequencies and that the correlation between TCN and outside noise emission is significant for frequencies lower than 1 kHz. The use of sensors placed inside the tyre for monitoring the acoustic performance of road pavements presents several advantages compared to the CPX method, such as a more compact design, lower cost and lower hazards both for the instrumentation and for other vehicles

A HIERARCHICAL FRAMEWORK FOR STATISTICAL MODEL VALIDATION OF ENGINEERED SYSTEMS

As the role of computational models has increased, the accuracy of computational results has been of great concern to engineering decision-makers. To address a growing concern about the predictive capability of the computational models, this dissertation proposed a generic model validation framework with four research objectives as: Objective 1 &mdash to develop a hierarchical framework for statistical model validation that is applicable to various computational models of engineered products (or systems); Objective 2 &mdash to advance a model calibration technique that can facilitate to improve predictive capability of computational models in a statistical manner; Objective 3 &mdash to build a validity check engine of a computational model with limited experimental data; and Objective 4 &mdash to demonstrate the feasibility and effectiveness of the proposed validation framework with five engineering problems requiring different experimental resources and predictive computational models: (a) cellular phone, (b) tire tread block, (c) thermal challenge problem, (d) constrained-layer damping structure and (e) energy harvesting device. The validation framework consists of three activities: validation planning (top-down), validation execution (bottom-up) and virtual qualification. The validation planning activity requires knowledge about physics-of-failure (PoF) mechanisms and/or system performances of interest. The knowledge facilitates to decompose an engineered system into subsystems and/or components such that PoF mechanisms or system performances of interest can be decomposed accordingly. The validation planning activity takes a top-down approach and identifies vital tests and predictive computational models of which contain both known and unknown model input variable(s). On the other hand, the validation execution activity takes a bottom-up approach, which improves the predictive capability of the computational models from the lowest level to the highest using the statistical calibration technique. This technique compares experimental results with predicted ones from the computational model to determine the best statistical distributions of unknown random variables while maximizing the likelihood function. As the predictive capability of a computational model at a lower hierarchical level is improved, this enhanced model can be fused into the model at a higher hierarchical level. The validation execution activity is then continued for the model at the higher hierarchical level. After the statistical model calibration, a validity of the calibrated model should be assessed; therefore, a hypothesis test for validity check method was developed to measure and evaluate the degree of mismatch between predicted and observed results while considering the uncertainty caused by limited experimental data. Should the model become valid, the virtual qualification can be executed in a statistical sense for new product developments. With five case studies, this dissertation demonstrates that the validation framework is applicable to diverse classes of engineering problems for improving the predictive capability of the computational models, assessing the fidelity of the computational models, and assisting rational decision making on new design alternatives in the product development process

Literature review of tire-pavement interaction noise and reduction approaches

Tire-pavement interaction noise (TPIN) dominates for passenger vehicles with the speed of above 40 km/h and for trucks with the speed of 70 km/h. With the prevailing trend of electric vehicles, TPIN can become more NVH (Noise, Vibration, and Harshness) issue in the future. In this paper, the vehicle noise and tire noise were briefly reviewed in the background introduction. Then the motivation of and approaches to reducing tire noise was reviewed from open literature. It was found that the tire industry and the pavement industry have been working individually on designing and building quiet tire and quiet pavement for many decades. However, the interaction between tire and pavement was less investigated. The future research on reducing TPIN can be the combined consideration of both tire and pavement characteristics while maintaining other performances, such as traction, handling, rolling resistance, hydroplaning, and durability

Solid rocket motor internal insulation

Internal insulation in a solid rocket motor is defined as a layer of heat barrier material placed between the internal surface of the case propellant. The primary purpose is to prevent the case from reaching temperatures that endanger its structural integrity. Secondary functions of the insulation are listed and guidelines for avoiding critical problems in the development of internal insulation for rocket motors are presented

Utilisation d'une stratégie de contrôle actif vibratoire pour la réduction du bruit de roulement dans l'habitacle des automobiles

La réduction du bruit de roulement transmis jusqu'à l'habitacle automobile est étudiée en utilisant une stratégie de contrôle actif vibratoire (ASAC). Premièrement, la conception d'un banc de test vibro-acoustique, constitué d'un ensemble pneu/roue/suspension a été développé dans le but d'identifier les chemins de transmission vibro­ acoustique (jusqu'à 250 Hz) pour une excitation quasi identique au moyeu de la roue. Des mesures de fonctions de réponse en fréquence (FRF) entre l'excitation primaire au moyeu de la roue et chacune des jonctions de la suspension et du chassis ont été utilisées dans le but de caractériser et de préciser l'identification du trajet qu'emprunte l'énergie vibratoire, par des mesures du champ vibratoire aux jonctions suspension/châssis, partant du contact du pneu/route, passant par le châssis et se dirigeant jusqu'à l'habitacle. En second lieu, un modèle constitué d'élément finis (FEM) et d'éléments de frontière (BEM) a été développé afin de simuler la réponse acoustique d'un habitacle automobile. Ce modèle FEM/BEM a été utilisé dans le but de prédire le comportement vibro-acoustique d'un caisson de voiture suite aux forces mesurées aux jonctions de la suspension et du châssis. Finalement, un algorithme de contrôle actif vibratoire optimal a été développé afin de prédire l'effet la réduction de l'énergie vibratoire des différents chemins de transmission sur la mesure du niveau de pression acoustique à l'intérieur de l'habitacle automobile. L'approche du contrôle actif optimale est basée sur l'utilisation d'un actionneur électrodynamique, permettant de mo­difier le comportement vibratoire de la suspension et du châssis automobile, de façon à réduire le rayonnement acoustique de la structure du caisson de voiture. Afin de prédire la réduction du niveau de pression à l'intérieur de l'habitacle automobile, des fonctions de réponse en fréquence (FRF), d'un actionneur de contrôle positionné au centre du bras de suspension triangulé, ont été mesurées expérimentalement et ont été introduites dans l'algorithme de contrôle actif optimal. La contribution de l'actionneur de contrôle a été évaluée par une mesure de réduction du niveau de force mesuré aux jonctions de la suspension et du châssis et d'une diminution du niveau de bruit interne de l'habitacle par une mesure du niveau de pression acoustique localisé à la tête du conducteur.Abstract: The reduction of the structure-borne road noise inside the cabin of an automobile is investigated using an Active Structural Acoustic Control (ASAC) approach. First, a laboratory test bench consisting of a wheel/suspension/lower suspension A-arm assembly has been developed in order to identify the vibro-acoustic transmission paths (up to 250 Hz) for realistic road noise excitation of the wheel. Frequency Response Function (FRF) measurements between the excitation/control electrodynamic shakers and each suspension/chassis linkages are used to characterize the different transmission paths that transmit energy through the chassis of the car. Secondly, a FE/BE model (Finite/Boundary Elements) was developed to simulate the acoustic field of an automobile cabin interior. This model is used to predict the acoustic field inside the cabin as a response to the measured forces applied on the suspension/chassis linkages. Finally, an implemented optimal active control algorithm using a feedforward structure to perform the simulation of an optimal active structural acoustic control (ASAC) by using experimental and numerical FRFs is presented. The control approach relies on the use of an electrodynamic actuator to modify the vibration behavior of the suspension and the automotive chassis such that its noise radiation efficiency is decreased. To predict the noise level reduction inside the passenger compartment, the measured FRFs of a control actuator, connected to the lower suspension A-arm, have been implemented by using the optimal active control algorithm in MATLAB ª . Its contribution to noise reduction has been evaluated in term of acoustic radiation efficiency, as measured by the sound pressure level (SPL) located at the driver's head