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The service life for the assemblies represents a key factor when it comes to the product robustness. The concern for this factor starts from the beginning of each component manufacturing process. The parameters of the assembly process must be very well established, so that a compact, functional and reliable product to be the result. Thus, the existence of a testing step in the process is indispensable for the proper product functionality checking. Performing of the test procedures that simulate the components operation under certain conditions can take long period of time. This is caused by the multitude of the parameters that must be perfectly adapted according to the product operating capacity. In order to highlight these, our paper performs a comparative analysis between two automotive high-pressure pumps, using two special tests. After testing the two pumps, we noticed that the first one completed the test successfully and the second one failed the test. The purpose of this exercise is to demonstrate that the operating limits of an assembly must be precisely set. Also, a small deviation from the test parameters can lead to the total pump malfunction.

Studies on box girders bridges that treats domains such as: its seismic response, fire resistance of the structure, effect of web inclination of the bridge, shear force distribution in webs of the bridge, loading conditions for the bridge with dead load and live load were reviewed and concluded. Our paper aims to describe different research from the dedicated literature using software such as Ansys, Midas, CSi Bridge with FEM (finite element method) and to highlight the points where the maximum stress values are found. This will help us in the future to compare these results obtained by experts with new analyzes that we want to accomplish regarding the efficacy and reliability of the box girder structure. The main motivation to study this domain is represented by the previous experience and knowledge and to detect new dangerous sections in this type of structure. By counteracting the dangerous sections, we can improve the reliability degree and efficiency of the box girder bridge structure.

Heating ventilating and air-conditioning systems which equip our buildings/rooms represent noise sources unfavorable affecting the people decent living and working conditions. Usually, silencers are used to reduce the annoying sound from these systems. They are lined with different materials and they have various geometries in order to satisfy the consumer needs, in terms of acoustic comfort. Sound absorption and sound transmission loss characterize the materials acoustic properties, but it is not mandatory that a good absorbent material to be also an efficient one from transmission loss (attenuation) point of view. Our paper is focused on an acoustic study of different materials lining three commercial silencers of same geometry and size. We have recorded the sound data according to standards: ISO 10534-1:1998 for the sound absorption coefficient and ISO 7235:2009 for the transmission loss rating. Third octave analysis with LabView soft is used to process the sound information and then the two parameters values are calculated. The acoustic characteristics of the tested materials are discussed and features that recommend them to be used as lining materials for silencers are highlighted.

In the context of an urban environment assaulted by noise from different sources, the possibility of using composite materials made of concrete and various materials considered as waste was investigated, for the purpose of using them in acoustic barriers. Five different types of sustainable concrete have been developed, incorporating polystyrene granules, polyethylene terephthalate granules, corn cob granules, shredded sunflower stalk and balls made of sheep wool. Two different thicknesses were adopted, of 40 mm and 80 mm. The influence of the material's thickness was investigated. For these materials, the acoustic absorption coefficient was determined, using Feng's modified procedure of the ISO 10534:1998 standard. The sound absorption coefficient's meaning suffers changes and its measured value can be considered the real one, smaller than the usual reported standard values. Each of the sustainable concrete has sound absorption coefficients higher than those of the conventional concrete. The results highlighted that these types of materials represent a sustainable solution for both waste and noise problems of our cities.

In the materials area there are many theoretical and experimental investigations concerning their sound absorption behaviour, covering a wide range of applications. An alternative approach consists in identifying the ensemble acoustic field-propagation environment with a fractal gives its functionality in the form of structure parameters that is dependent on scale resolution. These fractal parameters can be matched with “classical” ones typical for sound absorption experiments in various materials. The mathematical methodology presented here implies the substitution of a dynamics with constraints on continuous but differentiable curves, in an Euclidian space, with “synchronous” dynamics, free from any constraints, on continuous but non-differentiable curves with various fractal dimensions but on a fractal space (i.e. the geodesics of that space). In a very special representation, the external constraints select the fractal geodesics type. In our study this “type selection” refers to the geodesics tunnel effect of fractal (acoustic) type for which we calculate the reflectance and the transparency of an external fractal barrier. An experimental procedure, using a modified impedance tube technique, to determine the sound absorption coefficients for various composite materials was conducted. The procedure uses an anechoic room and the measured sound absorption coefficients also include the sound transmission. The fractal approach of the acoustic behaviour, through the fractal parameters determined (transparency and reflectance) matched the experimental results, in terms of sound absorption, emphasizing the high degree of generality of the fractal theory in the dynamics of physical processes.

The ventilation and air conditioning system is a complex and energy-consuming one. So far there is a lot of research in this area, but most of it is related to the study of soundproofing materials behind the dashboard and the modification of the air ducts. Our paper presents a more efficient constructive solution, which will reduce energy, noise and vibration. The purpose is to study air distribution systems with multiple fans. The number of small fans will be directly proportional to the seats in the car (depending on the type of car). The difference between the system proposed by us and the classic one is that the fans will start depending on the seats occupied by the passengers. Favourable results of studies can lead to high passenger comfort. Also, vibration reduction solutions for ventilation and air conditioning systems are all the more necessary in the case of silent electric cars.

This paper proposes the concept of electronic noise and vibration diagnostic system for vehicles that aims to avoid wrong or unreasonable replacement of their components in the repair process. Our concept for a vibroacoustic diagnostic system consists of a set of sensors that receive noise and vibration, judiciously arranged and connected to a DAQ (Data Acquisition System). This allows the ECU (Electronic Control Unit) to accurately determine, by three-dimensional detection, the area in which vibroacoustic anomalies are manifesting (due to current or incipient defects). The data storage memory works according to the first in - first out principle, retaining only significant information to save resources. Establishing a mathematical model is one of the focuses for this concept for predicting the failure of various components of the vehicle based on vibroacoustic and then developing an artificial intelligence program capable of identifying and classifying new behaviours are the steps which we follow in the development of this tool. Also, the benefits of early detection of a subassembly failure are found in increasing traffic safety.

High pressure injection pumps use removable assemblies with screws. They allow the subsequent assembly and disassembly, without destroying the components and the entire assembly, whenever is necessary. Our paper is an experimental analysis highlighting the influence of tightening parameters on components deformations. We perform the study using controller, Janome screwdriver, ZEISS measurement system and SEM (Scanning Electron Microscope) used in the metallographic analysis. Various torques applied on the screws give us results that show the interactions and their impact on the pumps components, producing deformation on the screws, gaskets and even front plate. A trial was done to establish the upper limit for the torque of the screws. After applying several tightening’s at different values, we conclude that the optimal upper limit for screws tightening between front plate and housing is 45 Nm. Applying a torque bigger than 50 Nm, the screws are destroyed, shear. This can generate numerous defects on the sealing gasket area and on the front plate in the screws holes area. The circularity of the front plate is impacted by the thickness of the wall and the inner / outer diameters.

The acoustic human comfort includes the protection from noise and it is closely related to the sound absorption concept. The paper presents an experimental study on sound absorption coefficients, including transmission, for some combined materials: waste materials (rubber particles, polypropylene, crumbled plastic, wood flour, jute and cord fabrics) with different backing plates (plasterboard, oriented strand board - OSB, polystyrene). The tests were realized following the impedance tube method (ISO 10534-1:1998 standard), except for that the end of the tube was inserted into an anechoic room. The effect of this “backing room” on the samples sound absorption performances is discussed. Also, the experimental results emphasize the influence of the combined materials placed in series on the sound absorption performances and promote the idea of environmentally friendly solutions in their improvement.

Traffic microsimulation models use the movement of individual driver-vehicle-units (DVUs) and their interactions, which allows a detailed estimation of the traffic noise using Common Noise Assessment Methods (CNOSSOS). The Dynamic Traffic Noise Assessment (DTNA) methodology is applied to real traffic situations, then compared to on-field noise levels from measurement campaigns. This makes it possible to determine the influence of certain local traffic factors on the evaluation of noise. The pattern of distribution of vehicles along the avenue is related to the logic of traffic light control. The analysis of the inter-cycles noise variability during the simulation and measurement time shows no influence from local factors on the prediction of the dynamic traffic noise assessment tool based on CNOSSOS. A multifractal approach of acoustic waves propagation and the source behaviors in the traffic area are implemented. The novelty of the approach also comes from the multifractal model&rsquo, s freedom which allows the simulation, through the fractality degree, of various behaviors of the acoustic waves. The mathematical backbone of the model is developed on Cayley&ndash, Klein-type absolute geometries, implying harmonic mappings between the usual space and the Lobacevsky plane in a Poincar&eacute, metric. The isomorphism of two groups of SL(2R) type showcases joint invariant functions that allow associations of pulsations&ndash, velocities manifolds type.

The sealing of the high-pressure pump is carried out by means of a seal between the pump drive shaft and the front plate to keep the fuel inside them. The literature presents numerous studies carried out on how these seals last in time and on their composition. Due to the fact that during assembly or during the mounting of the pump on the engine may occur accidental defects on the sealing area, our interest in this paper is to investigate their impact on pump operation. The damages were explored on a test bench a certain number of kilometres and later analysed their impact on the pump using an ultraviolet chamber in a dark room. The experimental analyses were carried out using the EvoCam optical microscope, but also with the help of computer tomography procedure.

A dynamical system with one degree of freedom is modelled in two manners: the first one considers that only the dynamical sliding friction is present and the second considers the presence of both dynamic friction and static friction. It is difficult to apply the model of revealed static friction only for the zero relative velocity. For this reason, an approximate model for the static friction was identified, that accepts that the static friction occurs when the magnitude of relative velocity in contact decreases under a certain value, the critical value. The integration of the equations of motion of the two models reveals that for important values of the relative velocity, the two models estimate the same behaviour of the system. An experimental set-up was used to validate the theoretical results.

Most of electric and hybrid cars are city oriented due to their reduced pollution and small range. In this paper we intend to analyse kinematics and energy distribution during braking in the scope of city use cases. The purpose is to identify optimization criteria based on system limitations. Our proposal is to describe each case from point of view of kinematics (velocity, acceleration), energy (kinematic energy, instantaneous power). Having relations between data and the results helps us to form optimization strategies: a strategy oriented on driver comfort and two resulted from regenerative braking system component limits. Based on results, maximizing acceleration until its comfort value, in city conditions, does not generate unsupported instantaneous power for generator or energy storage system for an average electric car. Power limitation became more important when keeping same strategy for speed higher than 50 kph. In this case electric vehicles with small battery capacity and hybrid vehicles could show lower efficiency, as more kinetic energy will be dissipated by friction brakes. Presented strategies can be used to implement braking system controlling algorithm for regenerative brakes/friction brakes ratio on-the-fly optimization.

The high-pressure pump is a component of the automotive common-rail system and has as main assemblies: housing, driveshaft, gaskets and front plate. Literature presents analyses of the threaded fastening assemblies, especially for those with the critical joints with screws, those involving torque and angle. The assembly process that we have studied performs the sealing of the components with the gasket through the screws, thus preventing the fuel from leaking from the pump. Our paper presents an analysis of the influence of the tightening process with screws of the housing, gasket and front plate. The experiment was conducted using the Zeiss measuring system and the screwdriver Janome. The tests analysis demonstrates that screwing process can influence the distortion.

Research in deployable structures increased in the last decade, due to the need of building structures that can change their shape or functionality in response to varying of different aspects: climatic conditions, environment, functional requirements or emergency situations. Depending on how the transformation is doing, transformable structures can be deployable or demountable, as a kit-parts system. These structures can be classified in four main groups: structures based on spatial articulated bar mechanisms; foldable plate structures; tensegrity structures; and membrane structures. In this paper, some geometric design aspects of curvilinear bar mechanisms are discussed and a curvilinear structure mechanism is proposed. More results on the geometric design, dimensional synthesis and simulation of this scissor structural mechanism will be presented in future work.

The wear of the high-pressure pump is directly proportional with the engine operating mode of the vehicle. Due to the urban areas congestion, the engine assembly components can be affected and they can lose their reliability. The engine operation can be described as a cyclical model, reaching all the operating points: idle, cranking, maximum torque and maximum power. Thus, the discontinuous operation (proportional with car engine cycles) of the high pressure pump can create different types of wear for its components. Our paper presents an experimental test that simulates the behaviour of the pump after the operation of the vehicle in urban regime with a cyclical type in a course of 10.000 km. It aims to achieve the most important engine operating points. In order to do this, an electronic control unit is installed on the test machine, which has the role of controlling the electronic pump valve. All data (pressure, speed, temperature) are recorded in real time and stored in the memory unit of the test machine. The obtained data are analyzed and the pump is disassembled. Wear is observed on the main components (roller, shoe and driveshaft), but this does not lead to pump malfunction. After this analysis, the main components of the tested pump are compared with new components in order to evaluate the wear level.

The paper presents a theoretical analysis of a nonlinear system with dry friction and unbalanced rotational mass. The equations of motion are deduced and integrated numerically. Then, the size and orientation of the normal reaction force can be obtained. The model predicts a rotation motion phase followed by an oscillation one. The experimental results obtained using a laboratory set-up are in very good agreement to the predictions of the theoretical model. DOI: http://dx.doi.org/10.5755/j01.mech.24.6.22470

Plenum boxes are used for supply and exhaust of air through diffusers and grilles from heating and ventilating air conditioning (HVAC) systems. The plenum boxes ensure a continuous flow and moreover, they are usually lined with different materials in order to realize an acoustic insulation. These silencers/attenuators are of great importance in realizing a comfortable acoustical environment. The paper presents a theoretical and experimental investigation on some commercial plenum boxes with various sizes and lined with different sound absorbing materials. The sound transmission loss TL is the performance criterion for the silencers acoustical behaviour. The test procedure agrees the requirements of ISO 7235:2010 and the measurements were made in an anechoic room. Third-octave band analysis of experimental data is compared with theoretical ones. The results evidence the importance of silencer design which must take account of its geometry and the proper sound absorbing material as a function of frequency in order to optimize its acoustic efficiency.

The paper presents the results obtained by investigating some functional parameters as the noise level, the pressure – drop and the temperatures of three different manufacturing solutions for mufflers. The results emphasize the corroboration between these parameters and contribute to the improvement of the muffler fabrication and design since it is a complex function that affects noise characteristics, emission and fuel efficiency of engine. It was designed a measurement chain for the noise level evaluation of the mufflers including a microphone Bruel&Kjaer type 4133, a Impulse Precision Sound Level Meter Bruel&Kjaer, type 2209, with standard filters and a multifunctional external data acquisition board type-NI DAQPad-6015 . We assessed the noise level, using two based LabVIEW virtual instruments, measuring total band power and the equivalent continuous sound pressure level. It was also created a measurement chain for the pressure – drop evaluation and temperature distribution on the external surface of the mufflers.

Internal combustion engines are typically equipped with an exhaust muffler to suppress the acoustic pulse generated by the combustion process. The paper presents the procedure and the experimental setup for some functional parameters determination as the noise level, the pressure drop and the temperatures through investigating three different manufacturing solutions for mufflers. An algorithm and a dedicated method have been proposed in order to emphasize more direct the mufflers influence on the engines performances. The procedure equally includes particular cycles of the engine and it is highlighted the relation between the engine operating conditions and the functional parameters of the automotive mufflers.

Vibration based fault detection and diagnose analysis is a well established field in machine or monitoring supervision. The vibration diagnose is also suited for the miniature ball bearings monitoring. The typical balls size starts at 3 mm with the bearing outer diameter of maximum 20 mm. Ball bearings of this size are ideal for precision mechanisms, they are able to carry light loads and they are perfect for handheld medical equipment and tools which must be very small but also very precise and durable. The paper presents experiments carried out on a fully instrumented universal CETR micro-tribometer at room temperature. The tested miniature ball bearing, lightly loaded and operating at low speeds, is subjected to dry and lubrication conditions with two different oil viscosities. A comparative study is realized concerning the vibration diagnose potential using the FFT analysis of the bearing acquired signals. Statistical analysis of the vibration signals is a key point in the detection of the overall vibration level of bearings lubricated with oils of different viscosities.

Some of the aspects of the vehicle suspension limiting performances from stress and vibrations point of view have been explored in this study. The vehicle is modeled as two DOF system and the suspension is considered a passive one. 3D CATIA model was built for both the spring and spring-damper ensemble, neglecting the tire influence. This can reasonably covers the studies of geometries and forces (bending or tensile stress), masses and stiffnesses (meaning vibration profiles). The theoretical analysis on the vibration behaviour of the spring-damper ensemble, regarded as the vehicle suspension, suggests a convenient operation regime at low frequencies below 15 Hz, if the damper piston displacement is limited.

High-pressure pumps are the most important components of modern fuel injection systems. A modern system is the common rail one, equipping vehicles with a diesel or a gasoline engine. Depending on the fuel type, the design of the pumps is completely different, and it is more complex for diesel engines that are more prone to wear. The components subjected to wear are those in contact and continuous motion like drive shaft with roller and shoe, plunger and hydraulic head assembly with valves. Wear is initiated as a result of a process and product deviations or inadequate exploitation of the high-pressure pump. The factors influencing the wear can be improper material hardness, improper coating, incomplete or wrong machining, wrong clearance or misalignment between components, inadequate surface finish, dimensions out of tolerances, wrong assembly process, poor lubrication, contamination or running at high loads and temperatures. Our paper aims to identify, describe and discuss the types of wear encountered at common rail high-pressure pumps, highlighting the effects on their functionality. The wear occurrence can be prevented by paying more attention to the design details, manufacturing processes and correct exploitation of the high-pressure pumps.

Gear mechanisms are widely used in technical applications, mainly for transmitting rotational motion between two axes with constant transmission ratio via a higher pair. Significant friction energy loss in the pair between teeth highlights the importance of estimating the mechanical work lost by friction within this contact. In a previous study, the coefficient of rolling friction between a cylindrical body and a flat face body was found based on the decrease of oscillations amplitude of a cycloidal pendulum. The basic idea of the present paper follows the observation that in the case of a gear mechanism, the relative motion between the wheels can be taken as relative motion of their axodes. In this regard, a pendulum obtained from a mobile cylindrical gear with attached rod and a fixed corresponding rack is considered. The law of motion of the cycloidal pendulum is applied for the proposed pendulum and an “equivalent rolling friction coefficient” which characterises the friction between the teeth of the pinion and the rack is found. The differential equation modelling the motion of the pinion-rack pendulum is difficult to obtain, which is explained by the analysis of the involute gear field of a general cylindrical gear mechanism.

The paper presents the determination of the yield stress for copper, Cu_99.75, at standard ambient temperature, by means of upsetting of cilyndrical specimens, taking account the allowable degree of deformation of this material. The outcomes achieved can be used both plastic deformation processes and volumic deformation simulation of copper Cu_99.75.

Bearing condition monitoring confronts the most machine users. Diagnostic methods used to include bearing problems represent one of the most important challenges. The scuffing phenomenon initiation of the bearing elements produces an important increase in the vibration level and can be emphasized by the analysis of the bearing friction forces which are the most sensitive indicator of the bearing failure. Commonly used technique for damage detection is the vibration signature analysis that must be carefully utilized in conjunction with the friction torque monitoring through the strain gauges measurements. In order to detect the scuffing onset, the paper presents an experimental setup for the scuffing tests performed on a 7206 ball bearing. A virtual instrument monitoring the friction force respectively the braking torque was created. An accelerometer captures the signal from the bearing outer ring then it is processed using PCI-4451 National Instruments data acquisition board and LabVIEW soft.

The vibration analysis aims to extract features from the measurements in order to be used for fault detection and diagnosis. Vibration response measurement is an important and effective technique for the detection of the defects in rolling element bearings. The corresponding analysis methods operate in the time domain, in the frequency domain and recently in the time-frequency domain. A quantitative determination of the defect severity and its development are useful to be determined in order to estimate the remaining useful ball bearing life. Experimental data from a bearing with a defect are collected by an accelerometer then processed to identify the passing time of a ball over a defect. The paper presents a computation model corroborated to an experimental investigation to establish the defect length of a ball bearing inner race.

To realize an efficient car suspension control (for instance in technical inspection) it is important to use easy measurable variables. This is the reason for developing optimization techniques in order to simplify and improve the engineering design process. The paper presents an optimization process of a torsion bar spring included in the car suspension involving the following steps: modeling and analyzing the torsion bar spring behaviour, definition of the optimization objective and the specifications for the proposed solution choosing an appropriate methodology to satisfy the design objectives. It has been used a Min-Max optimization method to highlight the vibration response (in terms of RMS) of the system. CAD analysis and MatLAB optimization are performed on the car suspension elastic element and the obtained results provide an optimum vibrational response and constructive design. This combination of these analyses can be considered an efficient tool in order to ensure the driver and passengers comfort according to the standards.

Transformable structures in architecture can change their shape or function in response to varying climatic conditions, changing environment and needs for different functional requirements or to emergency situations. Depending on how the transformation is doing, transformable structures can be deployable or demountable, as a kit-parts system. Deployable structures can also be divided in four main groups: spatial bar structures; foldable plate structures; tensegrity structures; and membrane structures. In this paper, some planar bar mechanisms proposed by Ten Fold Engineering company, which can be integrated in deployable structures, will be discussed.

One of the problems of the modern era that we are facing nowadays, besides the pollution caused by fuel burning, is the level of noise pollution in constant growth in agglomerated cities. The main source of noise is the transport sector where the number of passenger cars had dramatically increased in recent years. Most of the vehicles around the world are powered by internal combustion engines equipped with a fuel injection system and a small percentage with an electric one. Researchers have shown that noise pollution affects human health from a psychological and physical point of view. Due to the manufacturing process of high-pressure pumps, some pumps mounted on the engine and running under certain conditions can produce a higher audible noise than the engine. The paper presents an experimental investigation on a high-pressure pump that provides a comparison between the noise level at the beginning of its lifetime and that resulting after an endurance test performed on a special test bench. It has been found that the greatest contributor to noise emissions is the high-pressure pump outlet valve when it opens. To improve the sound quality of the high-pressure pump, it is essential to further develop the outlet valve design and better control over the manufacturing process.

In rigid dynamics theory the gyroscope has a special role, as one of the bodies with the most complex motion, having three degrees of freedom. As consequence of the complexity of the motion is the fact that only for three situations, the equations of motion can be analytically integrated. For all the three situations, it is assumed that the principal moments of inertia (PMI) with respect to the principal axes that are normal to the rotation axes, are equal, condition fulfilled by the shape of body of revolution of the gyroscope. The paper analyses the case when the two principal moments of inertia are unequal. The equations of motion are numerically integrated for different values of the ratio between the two PMI. The effect of the disparity between the two PMI upon the motion of the gyroscope is proved by comparison with the motion of the axisymmetric gyroscope, both obtained by numerical integration.

The roller-shoe assembly is a known and efficient mechanism used for movement transmission in order to obtain mechanical energy. This mechanism is found in high pressure pumps and its role is to change the rotating motion in a translation one. During the running time, some wear types can be identified such as scuffing, corrosion, material removal. Scuffing is the main type of wear appearing in this mechanism. The aim of our paper is to analyse the behaviour of these two components (roller and shoe) over an aggravating test. The main defect is low clearance between components. The roller and shoe assembly is mounted in a diesel fuel pump for test. The test chosen for this experiment is Low Sommerfeld Number. It was stopped after 10% from time set. After visual analysis, it was observed the roller-shoe scuffing. The shoe was analysed and it was observed that the diamond like carbon (DLC) layer is non-conform. In the same pump, the affected components were replaced with new components to be convinced that the wear was caused by low clearance between them correlated to non-conform DLC layer. The test results confirm the reason of scuffing.

Currently, the common-rail injection system is composed from a high-pressure pump, injectors, an electronic control unit and a common rail. Over time, the common-rail system has been simplified and optimized, but it remains that the high-pressure pump can still be affected by distortion which occurs during the pump assembly process and in turn has an effect in mounting the pump to the engine. The main assemblies of the diesel pump are the front plate, housing, driveshaft and hydraulic head. Our paper presents a solution for minimizing the distortion and also any external leaks that may occur due to a change in design of the sealing gasket between the body and front plate. This modification realizes the connection interface with the engine block and facilitates the pump mounting. The tests analysis is performed on high pressure pumps to determine where and when the distortion occurs.

The pollutant gases entering the car through the ventilation system are very harmful and the effect they have on the human body is often lethal. The European Environmental Agency is talking about over 45000 “premature deaths” that occur annually due to the particles in the atmosphere. A rigorous monitoring of pollutant content in the passenger compartment is absolutely necessary, therefore the appearance of the first pollen filter in 1940 by Nash Motors on the Weather Eye ventilation system. Studies conducted by researchers in Germany show that not all systems work the same way, and the degree of air filtration is only 40% for some cars, while other cars filter outdoor air up to 90%. The most car manufacturers recommend the filters replacing, and huge gaps exist between a classic particle filter (it captures and retains dust, pollen and soot) and one with active carbon that also captures unpleasant odours. In reducing the amount of pollutant gases entering the passenger compartment, the air quality sensor (AUC), mounted in the pollen filter housing, also controls the activation of the recirculation function when the car enters a polluted area. Our paper presents an overview in the field of pollution in the passenger compartment, the main types of passenger car filters launched on the market and the importance of their use according to the manufacturer’s indications.

The goal of vibration analysis is to extract features from the measurements x (t) or x (kT0), T0 sampling time, to be used for fault detection and diagnosis. The corresponding analysis methods operate in the time domain (autocorrelation functions, power cepstrum, crest and kurtosis factors), in the frequency domain (Fast Fourier Transform FFT, maximum entropy spectral estimation, envelope analysis) and recently in the time-frequency domain. Time-frequency analysis methods represent efficient alternatives to detect bearings damage due to non-stationary impact signals. In this case, the short-time Fourier transform (STFT) or the Wavelet transform are applied. The paper presents a comparative study of some methods used in bearing faults detection (the envelope spectrum and the wavelet transform). A monitoring tool acquires experimental data from a bearing vibration control test rig. An accelerometer captures the signal from the bearing outer ring then it is processed using PCI-4451 National Instruments data acquisition board and LabVIEW soft.

Heating, ventilating and air-conditioning (HVAC) systems represent a major source of inside buildings noise with a negative effect on the acoustical environment. Therefore, it is necessary to add attenuation to the system. This is provided by sound attenuators or silencers manufactured in different geometrical configurations and with various absorptive lining materials. The paper deals with the insertion loss, as a performance criterion for in-duct noise, of some dissipative silencers types. The measured data are compared in order to establish the efficiency of every tested silencer type. Third-octave band analysis of random noise of an air handling unit (AHU) from a HVAC system is realized without and with silencers (ducts fitted). Insertion loss measurements are made in an anechoic room using a test facility that agrees the requirements of ISO 7235:2009. The results highlight the effects of the silencers geometry, pressure-air flow and loading relations upon the sound attenuation level. The silencers selection could be a difficult task for the designers which have to consider all these parameters.

The piston ring is one of the main elements in an internal combustion engine. Together with the cylinder sleeve, the piston ring has two basic functions: (1) contacting the cylinder sleeve to prevent the gases formed above the piston from migrating to the crankcase and (2) as a translation couple, formed of the piston-ring and cylinder-sleeve assembly. Complex tribological phenomena occur in the piston-ring and cylinder-sleeve tribosystem, according to variations in sliding speed, gas pressure, and temperature. This paper presents a method of calculation of the thickness of the lubricant film in the piston-ring and cylinder-sleeve tribosystem, using the Reynolds equation, integrated in specific conditions. According to the Newtonian behaviour of the lubricant, the shear stresses in the lubricant film between the piston ring and cylinder sleeve are determined. A computational procedure to determine flash temperatures in the piston-ring and cylinder-sleeve tribosystem is presented. The theoretical results, including film thickness, sliding speed, gas pressure, and flash temperatures for a complete crankshaft cycle are also presented.

This research was focused on the damping capacity study of two types of silicone rubbers proposed as layers within total lumbar disc prostheses of ball-and-socket model. In order to investigate the damping capacity, the two silicone rubber types mainly differing by the molecular mass of polymeric matrix and the filler content, as was emphasized by scanning electron microscopy and differential scanning calorimetry, were subjected to free vibration testing. Using an adapted experimental installation, three kinds of damping testing were realised: tests without samples and tests with three samples of each type of silicone rubber (69 ShA and 99 ShA). The free vibration tests were performed at a frequency of about 6 Hz using a weight of 11.8 kg. The relative damping coefficient was determined by measuring of two successive amplitudes on the vibrogram and calculating of the logarithmic decrement. The test results with silicone rubber samples showed a relative damping coefficient of 0.058 and respectively 0.077, whilst test results without samples showed a relative damping coefficient of 0.042. These silicone rubbers were found to have acceptable damping properties to be used as layers placed inside the prosthetic components.

The HVAC (Heating, Ventilating and Air Conditioning) beneficiaries are in particular annoyed by the noise generated from the radiant unit and the air circulating ducts, since they are located inside the rooms and buildings. The comparatively experimental results highlight the relations between the air flow, pressure, power-charging and the sound level. The measurements are carried out at different fan's speeds, ranging the power-charge from 30-100% while the duct air flow is slowly adjusted from full open to full closed, between 0-500 Pa. Third-octave band analysis of random noise of the handling units is realized in an anechoic room, using the measurement procedures that agrees the requirements of the ISO 3744:2011 and ISO 5136:2010 standards. For an accurate design of the HVAC system, the designer needs to know not only the sound power of the radiant unit, but also from all of the air paths, since the sound travels along with the conditioned air. The experimental methodology used in the paper is of real interest for the HVAC manufacturers, in order to rate the sound level of their products and to improve the noise attenuation.

HVAC system represent major source of buildings internal noise and therefore they are designed to provide a human acoustic comfort besides the thermal and air quality requirements. The paper experimentally investigates three types of commercial air handler units (AHU) with different ducts cross-section sizes and inlet-outlet configuration. The measurements are performed in an anechoic room. The measurements are carried out at different fan's speeds, ranging the power-charge from 30-100% while the duct air flow is slowly adjusted from full open to full closed, between 0-500 Pa. The sound pressure levels of the radiant units are rated using NR curves. Also, the supply and the outdoor ducts sound levels are compared in order to point the frequencies where the noise must be reduced. Third-octave band analysis of random noise of an air handling unit from a HVAC system is realized, using measurement procedures that agrees the requirements of the ISO 3744:2011 and ISO 5136:2010 standards. The comparatively results highlight the effects of the geometry, air flow pressure and power-charging dependencies upon the sound level. This is the start for a noise reduction strategy.