Papers by Keyword: Noise

Abstract: This paper explains and demonstrates how miniature gears of excellent surface quality can be manufactured by modern machining methods. Necessity of gear finishing by post processes such as grinding, lapping, honing etc. is the major limitation of all conventional methods of miniature gear manufacturing. To overcome this limitation, modern machining methods such as wire-EDM, abrasive waterjet machining, and laser beam machining etc. have been explored. It resulted in significant achievements in geometric accuracy, surface finish, and integrity of miniature gears. Using modern machining methods, it is possible to manufacture gears equipped with precision finish (average roughness 1 μm), high geometric accuracy (DIN quality 5), and defect-free tooth surfaces at significantly low cost. This paper aims to facilitate researchers by providing information on important aspects as regards to the manufacturing of miniature gears by modern machining methods and hopes research and development in this area to establish the field further.

Abstract: Hospital refurbishments often take place in parallel to regular operation, resulting in a scheduling problem: Construction activities must located such as they do not clash with daily work activities and vice versa. To be able to see this mutual influence, we have devised a tool in which we are able to visualize the adverse effects of construction on daily operation. The approach uses a cellular automaton to represent the three-dimensional hospital environment and uses a particle simulation for computing the distribution of dust, noise and vibrations. By interactively relocating work activities and construction activities, our tool can be used to solve the mentioned scheduling problem. It also enables us to show the sequence of construction and relocation activities in 3D, which might be easier to interpret than a classical project plan in tabular form.

Abstract: This paper describes a multiphase computational fluid dynamics (CFD) based numerical study about aeroacoustics response of NACA0012 airfoil for both normal and icing conditions. Three different turbulence models (RANS, DES & LES) are tested where Detached Eddy simulation (DES) turbulence modelling approach is found suitable for this case study. Aeroacoustics numerical results for clean NACA 0012 are compared with the experimental data obtained from NASA report 1218 [1], where a good agreement is found. An extended CFD study is carried out for iced NACA 0012 airfoil, where results show more boundary layer flow separation in case of iced blade profile that leads to a change in the aerodynamic characteristics of the blade profile and increase in sound level for iced airfoil as compared to the clean NACA0012 airfoil.

Abstract: SIGMA-class warship one of warship type is designed up to sea state 6. The ship was redesigned in enlarged dimensions, and called SIGMA extended class warships. A control system can give a performance of response in accordance to the set point when the value of controlled variable can be transmitted to the controller accurately. The characteristic of sensor is not usually able to tranmit a proper value, due to the noise on the sensor and also the environment disturbances. This paper describe a strategy of Kalman filter to estimate variables controlled when the presence noise on the compass or gyrocompas. The result of Kalman filter implementations give the magnitude of the integral absolute error of yaw and sway less than 5%, when there are noise on the measurement and the disturbances.

Abstract: We have carried out a new geometric type spiroid worm gear drive having arched profile in axial section. We prepare the computer aided model (CAD) of this gear drive for other geometric and production analysis. The objectives of the publication are measuring of this spiroid worm using three coordination measuring machine and after doing noise analysis of this gear box.

Abstract: The transportation policies focusing on minimizing the environmental impact aim at an improved quality of life and health of the population, the urban one in particular. Noise pollution is one of the biggest problems associated with the European urban environment at the present moment, mainly because of the ever-increasing road traffic. SUNET system (System for Urban Noise and Eco-Traffic) was designed to improve the management of the noise pollution in Cluj-Napoca and to provide up-to-date public data on a user-friendly interface. The implementation of the application over the entire municipality is highly advantageous as it creates a link between the town’s administration (the local authorities, the City Hall of Cluj-Napoca) and the user (the citizens) through this system which is dynamic, modern and compliant with the European regulations. The graphic interface uses the HTML (HyperText Markup Language) code, while the database is set up in an SQL (Structured Query Language) format and contains information about the characteristics of the system and users alike, all organized in specific tables. The need for an online urban noise pollution monitoring system, such as the SUNET one, appears to allow the provision of fairly realistic and up-to-date information and encourage the community to actively assist in the application of proper action plans and the decision-making process when it comes to the population’s exposure to high levels of noise pollution.

Abstract: The research is aimed to the investigation of the microstructure defects in the silicon and the thin-film CIGS solar cells. These defects have their origin mainly in the technological process of a production but they can be caused by an accidental mechanical stress during a normal operation, too. That leads to a formation of the micro-cracks and the fractures, which have a significant effect on a device efficiency and reliability. The reverse-bias conditions are usually used for the defects charac- terization purposes. The mechanical induced defects increase a reverse current which leads to a strong overheating in the local breakdowns and the surroundings areas, thus for the defects localization pur- poses an infrared imaging and an electroluminescence method is used. Beyond these commonly used methods the results from the electrical current noise fluctuations observed in a frequency domain are presented in this work. The noise fluctuations measurement is a reliable indicator of a device quality and allow us to qualify the device damage extent. Using combination of these methods it is possible to localize the particular defects, assess the degree of a damage and classify the elimination process of the particular defects.

Abstract: Current requirements for the reduction of the noise pollution in inhabited areas are constantly increasing. Acoustic wearing courses represent the real measures how to directly mitigate sources of road traffic noise created by a tire/road contact. Directly reduced noise emissions created by a tire/road contact don't need further mitigation by expensive noise barriers. Noise emissions on two different types of wearing courses of asphalt mixtures (Asphalt concrete for very thin layers and Low-noise stone mastic asphalt) were measured using the specialized device operating on the basis of CPX (Close Proximity method) and compared with the standard mixture of Asphalt concrete. Differences were between 1 dB and 5 dB depending on the wearing course and the vehicle speed. The efficiency of the low-noise asphalt pavements was also compared with the initial costs of the pavements. The economical evaluation confirmed that the initial costs of the acoustic wearing courses are higher than the costs of the standard asphalt concrete mixture. However the noise reduction by 1 dB using the asphalt concrete for very thin layers increases the costs just by 350 USD (considering the same length and width of the road segment), which makes acoustic wearing courses the economically efficient noise reducing measure.

Abstract: Currently the fatigue testing of bevel gears are being done by using non rotating type of fixtures that applies fatigue load on a single tooth, which does not resemble the actual loading condition in an automotive differential gear box. This paper discusses the experimental setup with the noise and vibration analysis approach to determine the signature of failures of spiral bevel gears. The proposed experimental setup seems promising for further research and development in the fatigue testing of spiral bevel gears. The Crown pinion and wheel assembly is used for the testing. The pinion is connected to the electric 3 phase AC motor of 75HP with a suitable coupling and the crown wheel is mounted on the half axle shaft, which in turn is connected to an electric dynamometer. The speed/torque of electric motor and the load applied by the dynamometer can be varied. The acoustic sensor is mounted near the differential gear box and the accelerometers are mounted on the Pinion bearing, Crown wheel bearing and the half axle bearing. A four channel data acquisition system is used to log data in time domain (raw data) by three accelerometers and an acoustic sensor. The variations of sound pressure(dB) v/s time, sound Pressure(FFT-(RMS)) amplitude v/s Frequency, Acceleration v/s Time, Octave analysis i.e., Band power v/s Frequency, Noise spectrum Power v/s Frequency, Histogram, Power density v/s Time can be obtained. These data are then used to plot vibration and SPP levels in frequency domain to develop the noise and vibration signature of that crown pinion for given cycles of operation. The tests on Bevel pinion and gear set were performed in the BEC, Bagalkot NVH lab facility. The gear set run successfully at double the rated torque for 30 million pinion cycles. And the signature of pinion failure was obtained. The results demonstrated the suitability of using the given bevel crown pinion and gears set for specified speed, high load application in differential gear box of an automobile.

Abstract: Openness is of great importance in centrifugal fan design. An experiment research has been designed to study how the openness distribution affects the performance of multi-blade centrifugal fan, which is designed with limited size. The results show that the openness adopted proper acceleration-deceleration distribution curve has a better performance.