Due to the rapid development of electric and hybrid motorisations, gear manufacturers have encountered an increasing need to create high level quality gear flanks. While the main goals are to increase the load-carrying capacity and the wear resistance, reducing gear noise has become more and more important. To answer this, macro- and micro-geometry defects have long been studied as well as their effect in amplifying the vibrations of gears. However, the impact of tooth flanks micro-scale roughness on gear noise has not well been studied and understood, even though the teeth surface contacts are essential in the gear mechanics. This paper aimed to discriminate the influence of the tooth finishing process (grinding, powerhoning) on single stage spur gear noise. A two-dimensional finite-element simulation model of a one-stage gear system was hence developed. The transmission system was composed of two identical loaded gears with one degree of freedom. Topological features of teeth surfaces finished by grinding and powerhoning were measured with a three-dimensional white light interferometer. These real topographic profiles of the tooth surfaces were integrated in the model. The meshing stiffness was determined as an output of this dynamic model. It is a parameter directly linked to the acoustic behaviour of the gear. Results show that gear noise could be reduced by the right choice of the finishing process kinematic.

Very often processes associated with rotating machinery entail two general types of random processes: (i) quasi-periodic processes linked directly to the machine rotational frequency (including harmonics and sub-harmonics), and (ii) regular processes such as those associated with random vibration of machinery elements. Variability of the rotational frequency and slow-time variability can both be induced by factors such as time-varying external loading and changing thermodynamics (e.g. the influence of road grade and engine temperature on automobiles using cruise control). In this work we incorporate and extended Kalman filter (EKF) model guided by estimates of the family of AR and MV spectral estimates to arrive at a method of decomposing and tracking these two types of processes, along with related parameters (e.g. frequency jitter bandwidth/intensity and the strength, damping and natural frequency of randomly excited narrowband resonances). This work may be viewed in some ways as an extension of the work presented in [1]. Our findings include (i) for the case of constant nominal speed, the EKF estimates of the time-varying frequency, sine and colored noise processes are quite good; whereas the estimate of the time-varying amplitude is not as good, and (ii) in the case of linearly increasing speed (where the colored noise resonance behavior is only excited in that portion of the observation time where the sine frequency is in close proximity), the estimated root mean-squared errors related to both the frequency and the noise increase linearly with the nominal frequency rate of change.

Automotive manufacturers invest a lot of effort and money to enhance the vibro-acoustic performance of their products. In a complex dynamic system such as a truck cabin, the enhancement effort may be very difficult and time-consuming if only the ‘trial and error’ method is used without prior knowledge about the noise contributors. The purpose of this paper is to identify the most influential noise radiating panel in a passenger cabin compartment of a heavy duty truck. The noise inside the vehicle cabin originates from various sources and travels through many pathways. The first step of sound quality refinement is to find the pathways and corresponding operational internal forces. Operational acceleration responses and frequency response functions (FRFs) are measured on a prototype truck to determine the excitation forces while engine is running in operational conditions. Once these internal forces are identified using the experimental force identification (FI) technique, they are utilized to predict the total sound pressure level inside the cabin and also perform the panel acoustic contribution analysis (PACA) to determine the most problematic panel of the cabin. A coupled vibro-acoustic finite element model (FEM) is used to predict the sound pressure level inside the cabin. Sound pressure levels at the driver’s and passenger’s right and left ears are determined numerically for excitation coming from the cabin mounts ranging between 20–200 Hz. When the most noise radiating panel is identified, it can be redesigned to improve the sound pressure level inside the cabin.

In this study a numerical study of a suction muffler in a hermetic reciprocating compressor of a domestic refrigerator is performed using a finite volume based flow solver (Fluent). In order to reveal the behavior of the flow realistically, unsteady experimental pressure data has been used in the outlet boundary condition for the simulations. Detailed investigations are carried out to reveal the instantaneous flow behavior in different muffler sections such as channel and chambers based on the mass flow rate variation with respect to crankshaft angle. Power spectrum of pressure fluctuations at selected points help to reveal the noise characteristics of the muffler. This study gives a comprehensive insight into the interaction of muffler chambers with flow through the channel. In a previous study, the ratio of the chamber volumes were shown to be an important design parameter. To verify this assumption, three prototype muffler geometries were simulated. In these prototypes, the plate that divides the muffler into two chambers was moved by 7 mm and 10 mm in the direction to enlarge the second chamber. The flow through the prototype geometries were investigated numerically. The results showed that the aerodynamic performance increased while the aero-acoustic performance slightly decreased. Furthermore, this study aims to be an initial step to a more complicated optimization process which involves the inlet valve dynamics.

Most of the mechanical systems are composed of different subsystems coupled by several links. Any excitation acting on the system is divided into several internal forces which propagate through these links or so called transfer paths. This paper presents the use of experimental transfer path analysis in identifying the transmission paths for a heavy duty truck in order to estimate the vibration and noise transmitted from the cabin and engine mounts. The most challenging part of the TPA analysis is estimation of the internal operational forces so that the total response can be predicted accurately. At the circumstances where direct measurement of the operational forces is impossible, especially for complex structures, a common approach to address the problem is based on a measured frequency response function (FRF) matrix and a set of operational responses. The main problem of this approach is the inversion of the FRF matrices which can be ill-conditioned. Once the internal operational forces are estimated, the vibration or noise response for the selected location in the truck can be calculated. To validate the predicted results, coherence of the collected data and the condition numbers of FRF matrices are investigated so that the accuracy of the predicted results can be quantified for the frequency band of interest. The predictions of the total response are compared with the experimentally measured data such that the coherence and condition number related observations are validated.

This work is related to the design and development of instrumentation, data acquisition and graphical user interface of Photovoltaic driven Reverse Osmosis system for monitoring and performance evaluation purposes. Installed PV system comprises of 12 PV panels, trackers, batteries and inverter whereas RO system is equipped with pre filters, pumps, energy recovery devices and filtration membranes. Proper instrumentation is carried out in PV system to measure the irradiation, temperatures, voltage and current at various points. Moreover various sensors are used to measure the pressures, flows, salinities at RO unit. Signal conditioning circuits are designed to adjust sensor output signals for computer interface. A simple moving average filter is used to suppress the measurement noise. The experimental investigation of PVRO system is carried out by using LabVIEW interface capabilities. The developed system reveals and stores the pronounced impact of measured variables on the PV output power and specific energy consumption of the RO filtration system. The online data display in multi-scale window frame is very informative for system operation and analysis. During the experimental run of PVRO system using the developed DAQ system, the PV system generated 7.5kWh of energy during the whole day operation. Feed water having 7100ppm salinity and its flow rate was set to 850 lit/hour by adjusting the RPM of the high pressure pump. Clean water flow rate is recorded to be at 465 lit/hour having salinity of 115 ppm during the RO operation. Specific energy consumption of RO system comes out to be 2.083kWh/m 3 for 7100ppm salinity of feed water.

In roads building, classical asphalt mix manufacturing commonly requires the heating (at 160°C) and the complete drying of aggregates. The induced energy cost has opened the way to develop alternatives processes and materials with low energy/carbon materials such as Warm Mix Asphalt (WMA). In warm mixes processes, aggregates manufacturing temperatures are different and lower than the Hot Mix ones. However, manufacturing temperature reduction can locally lead to poor bonding between bitumen and aggregate during the mixing step, due to the bitumen viscosity increasing, although bonding quality measurement remained a challenge. The aim of our study was to presents two thermal inverse methods for bonding quality assessment. These methods are based on Thermal Contact Resistance (TCR) assessment between bitumen and aggregate, during asphalt mix manufacturing. The experimental test principle consisted of heating both bitumen and cylindrical aggregate to their manufacturing temperatures (over 100°C) and to put them into contact thanks to a special experimental device. According to initial samples temperatures, heat transfer occurs from the bitumen to the aggregate. Two variants of the sequential Beck’s method were used to solve the inverse heat conduction problem. The first one consisted of determining the TCR from heat flux and temperatures and the second one consisted of identifying directly the TCR. The TCR values were interpreted as bonding quality criteria. Results showed low sensitivity to temperature measurement noise in the second variant of the inverse method. Moreover our study showed that bonding quality depends on bitumen and aggregate temperatures. The higher the component’s temperatures, the lower the TCR values and better is the bonding quality.

This paper illustrates that a method for identification of pick up noise and an analysis the cause of pick up noise by substituting components of a laser printer. The operating sound radiated from a laser printer includes the tonal noise components caused by the rotating mechanical components such as gear, shaft, motor, fan, etc. A sound operated by laser printers has become important competitiveness in printer industries as the demand of laser printers increases. Especially, a noise between a friction pad and a paper in the process of printing has become an essential issue in an aspect of quality evaluation. However the existing criteria for determining the above noise have solely relied on human’s subjective judgments; which highlights the requirement to objectify these criteria. In this paper, the standard of existing pick up noise is established by finding the tonality, which is a psychoacoustic parameter, of noticeable limit sound level. Based on the findings of the method, the study has found factors which cause pick-up noise and suggests the substitution of following components of printers such as: spring constants, spring force, and the quality of friction pads. As a result, it is confirmed that the proposed pick up noise index has usefulness to classify whether existence of pick up noise with an objective evaluation and not to occur the noise based on design optimized combination of laser printer components.

To perform 3D inspection, the most common digitizing system is a coordinate measuring machine (CMM) equipped with a touch trigger probe. Because of their large time consuming, a large number of industrial digitizing systems presenting different characteristics have recently emerged, but collected data quality strongly depends on the sensor technology combined with the associated displacement system. The works presented here focus on a novel approach that help users to select the most appropriate digitizing system in regard of the specification to be verified. This selection is performed in two steps: an ability selection that removes non convenient systems and a performance selection to select the system that provides sufficient data quality in the minimum time. This quality can be noise, trueness, density, depending on the specification to be verified. To store all necessary information, databases that contain intrinsic and qualified information have been developed. An example with GPS specifications is treated.

It is a well known fact that Reverse Engineering techniques involve the following steps: scanning the object, pre-processing a cloud of points, processing the cloud of points, redesigning, and manufacturing the part. Difficulties arise when processing clouds of points resulted from digitization, obtaining geometrical parameters of the scanned object itself and getting the final associated CAD model. This paper presents an algorithm for the recognition of a rotational part form. The part has been previously scanned and will be redesigned for re-manufacturing. To determine the surfaces of a rotational part, it is necessary to scan the part in order to obtain the cloud of points which is afterwards cleared of noise points. Beginning with the cloud of points, an algorithm is built that automatically determines the part’s axis. The axis is then used to generate the required sections. The same tool also facilitates the recognition of simple, basic shapes like cylinders, cones and spheres. The points cloud data are stored in a text file. The text file contains all the points’ coordinates of the cloud. After running the software on the data file we obtain the geometrical data necessary for the parametric model. This data can then be exported to a 3D design environment to redesign the digitized part. This paper contains two case studies in which a part was scanned and then, following the steps outlined above, the geometrical data of the part are obtained. With the geometrical data, the part can be modelled like a parameterized object.

The “gear rattle” phenomenon is a research topic of great interest for the NVH (Noise, Vibration and Harshness) automotive sector, concerning driveline noise and vibrations coming from the manual gear boxes. It is due to the internal combustion engine variable torque producing impacts and rebounds, and consequently noise, between the teeth of the unloaded gear pairs of the gear box because of the unavoidable presence of backlashes. Discrete Wavelet Transform (DWT) is used to decompose the angular relative motion signal and the wavelet decomposition details are adopted to analyze the dynamic behaviour of gears under rattle conditions. The DWT has been chosen because it is a particularly suitable instrument to recognize discontinuities, such as jumps or instantaneous changes in the slope of the signals, due to their localization in the time domain. Wavelet analysis allows to characterize an event by the localization, the kind, and the amplitude of the event. This technique enables, moreover, to define new indices for metrics of gear rattle especially useful in order to conduct comparisons among different operative conditions. Some examples of application of the proposed technique are reported in the paper. The theoretical investigations regard comparative analysis with respect to the amplitude and to the frequency of speed fluctuations and to the gears lubrication regime.

Noise and vibration are factors affecting the marketability of automobiles. It is required for the drivetain design not to transmit unpleasant noise and vibration to the passengers when driving. As for continuous variable transmission (CVT), noise that is considered to be generated from the metal pushing V-belt has been studied. A research project on this matter reported an estimated mechanism that attributes the noise to self-inducing vibration between the metal pushing V-belt and the pulleys. The self-induced vibration occurs when dynamic friction characteristics exhibit a negative gradient in relation to the sliding speed. However, the effect of the gradient on frequency spectrum of the noise has not been quantitatively elucidated in a consistent manner. In this research, noise at the vehicle start-up phase was studied based on the already reported prediction technology for metal pushing V-belt behavior. In other words, this study focuses on the effect of the friction characteristic gradient between the metal pushing V-belt and the pulleys on each element’s behavior and frequency components of belt pushing force. The results revealed that self-induced vibration on the element V-surface at the exit of the drive pulley excites high-order string vibration at the belt string, generating noise via the transmission case. In addition, it was also found that acoustic energy that excites the high-order string noise is affected by the change in belt pitch diameter at the exit of the pulley, and this determines the magnitude of frequency spectrum of the noise. It was concluded from the above findings that the change in the pitch diameter can be suppressed by narrowing the radial clearance between the shaft and the movable pulley and this measure is effective in reducing noise.

Independent modal control technique allows to change the eigenvalues of a system, without changing its eigenvectors. From a mechanical point of view, it means it is possible to modify the natural frequencies and the damping of a n-DoF system, letting modal shapes unchanged. Independent modal control can be profitably used in active vibration control increasing the damping of the system without changing its natural frequencies and vibration modes. A control of this type can improve the dynamic performance, reduce the vibratory phenomenon (and the resulting acoustic noise) and increase the fatigue strength of the system. This work demonstrates how the performance of the control depends on the number and position of sensors and actuators used besides, obviously, on the reduced model used to synthesize the control itself. Finally the paper suggests a simple optimum function to minimize the spillover effects due to unmodeled modes. Theoretical aspects are supported by numerical simulations.

In this paper the effect of geometry shape of the Helmholtz resonator on its resonant frequency and on its noise attenuation capability is discussed. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one and two degrees of freedom. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.

Helmholtz resonators are known to be efficient resonators for ducts if they are properly designed. A design procedure is suggested in this paper to identify the size of the resonators in one and two degrees of freedom. The procedure is supported by a through numerical simulation of acoustic wave propagation that is presented and is verified using published experimental results. The overall procedure shows achievable great attenuation of noise in pipeline.

This paper presents a method for reconstructing 3D buildings and updating Geographic Information System (GIS) data from video. We use 2D-GIS data and a ground-based video sequence as inputs. The main approach consists of three parts. In the first part, the data is captured and analyzed: besides the 2D-GIS data, we capture a video from a street view; then we can obtain thousands of3D feature points by our extracting algorithm and design a noise filter to remove outliers. In the second part, we present a generation process, which contains the footprint extraction and basic facades reconstruction. The last part is the correction and updating process: after correcting the footprint and computing the height of the building, our method will update the data into GIS. In addition, we use some user knowledge to make the results much more accurate. In the filtering and the correcting process, our method can deal with several interactive operations.

In this paper the Sequential Function Specification Method is used to estimate the transient heat flux imposed on the rake face of the cutting tool during the cutting operation. The cutting tool is modeled as a three dimensional object. The capabilities of the geometric modeling, mesh generation as well as solver of the commercial software ANSYS is utilized in order to reduce the time expended for modeling and direct heat conduction solution. This way the inverse heat conduction algorithm employs ANSYS as a subprogram through the ANSYS Parametric Design Language (APDL). The stability as well as accuracy of the heat flux estimation is investigated using familiar triangular as well as step heat flux test cases. The effect of noise level, the number of temperature sensors as well as their locations are investigated in order to arrive at an optimal experimental procedure. Finally, a typical temperature data during the working condition are used to recover the heat flux at the cutting tool surface.

The paper presents the results of the responses of a concrete trough of a new lightweight rail track system (LR55) to full scale non destructive tasting. The system which is made from three main components; low profile steel rail, elastomeric pad and prestressed concrete trough is developed for light rail transits in cities streets, which can significantly help in improving the traffic flow, reducing the traffic congestion and thus providing opportunities for minimising serious environmental problems such as level of noise, vibration and air pollutions and in this regards it can be considered as environmentally friendly means of transport. A mathematical model was developed where the LR55 track system was treated as multilayer beams on elastic foundations, and the model was then validate experimentally through a series of non-destructive tests on full scale model subjected to a full scale service load specified by the current BS codes of practises.

The human hand works in a perfect accord with the brain for an efficient exploration of physical world and objects perception according to man’s purposes. During the haptic sensing, the fingertip slides on a surface activating the receptors located under the skin allowing the brain to identify objects and information about their properties. In fact, in order to create the contact, the hand must exercise a force causing the fingertip to deform, generating a stress-state that contains the information on the object in contact. The information concerning the object surface is represented by the vibrations induced by the friction between the skin and the rubbed object in contact. The mechanoreceptors have the key role of transducing the stress state into an electrical impulse conveyed to the brain. Nevertheless, the vibration spectra induced by the finger/surface rubbing and the consequent activation of the mechanoreceptors on the skin were rarely investigated. A clear understanding of the mechanisms of the tactile sense is basilar for manifold applications, like the development of artificial tactile sensors for intelligent prostheses or robotic assistants, and for the ergonomics. In this context, it is fundamental to realize appropriate dynamic analysis of the signals that characterize the characteristics of the contact. In other words, it is necessary to investigate the vibration spectrum measured on the finger, in order to identify the frequency range of measured spectra (that should correspond to the expected one given by the mechanoreceptors activation frequency range [2–500 Hertz]). An experimental set-up is developed to recover the contact global dynamics by detecting the contact force and the induced vibrations; the bench test has been designed to guarantee the measurements reproducibility and, at cause of the low amplitude of the vibrations of interest, to perform measurements without introducing external noise. In particular, in this paper, the interest will be focused on the changes shown in vibration spectra with respect to variations of the scanning velocity and surface roughness characteristics.

In this paper, two terminals, doubly clamped, nano-switch has been studied. Here the interest of this study is the situation in which the pull-in and pull-out voltages not be same as each other and the pull-in/pull-out trend follows a hysteresis loop. This property could be used to introduce a double threshold switch with greater stability or noise immunity. With only one input threshold, a noisy input voltage signal near that threshold could cause the output to switch rapidly back. The model comprises a clamped-clamped carbon nanotube (CNT) suspended over a graphite ground electrode plate from which a potential difference is imposed. The actuation is based on DC applied voltages and it is assumed that the neutral axis of bending is stretched when the beam is deflected, and also, due to closeness of the substrate and the CNT, the van der Waals interaction forces between CNT and ground plate is considered. The versatile Galerkin’s method is employed to reduce the nonlinear integral-partial-differential equation of motion to a nonlinear ordinary differential equation in time, and then, the reduced equation is solved by direct numerical integration. The pull-in/pull-out phenomena, hysteresis characteristic are studied. The obtained results are compared to Molecular Dynamic (MD) method. Eventually, a nano-switch immune to input noise is proposed which relies on the hysteresis characteristic of the system. The proposed CNT-based nano-switch can operate in nano-scale electronics similar to the well known Schmitt trigger circuit in classical electronics. When the input voltage is higher than a certain pull-in voltage threshold, the output of the switch is in “ON” state; when the input voltage is below the pull-out voltage threshold, the output is in “OFF” state; when the input voltage is between the two threshold values, the output retains in the previous state.