Search Results

The rolling bearing is a fundamental component of rotating machines and its failure may lead to a catastrophic damage of the system. The incipient and correct identification of faults contribute to an early predictive maintenance plan, which avoids additional costs and sudden breakdowns. The resonant demodulation technique, envelope analysis, is a well-established method widely used to identify failures in rolling bearings. However, this method requires the identification of the frequency region that contains enough information about the faults. Thus, the spectral kurtosis gives the impulsiveness measure of a vibration signal and it is used to identify the frequency region of failure. This paper presents the use of the bat algorithm as an optimization methodology to identify the resonant demodulation parameters using spectral kurtosis as the objective function.

More and more, the automotive vehicle consumers tend to opt for internal combustion engines which use chain in their timing system, since the chain drive system presents high durability, avoiding the usual maintenance common to the belt timing system. The necessity of developing parts which increase the fuel consumption efficiency and minimize noise and vibration leads to the study and comprehension of some physical phenomena such as “polygonal action” and the ability of predicting the fluctuation of angular velocity of the sprockets used for timing the crankshaft and camshaft. The study of mathematic models in parallel to the physical test guides the development of the present work.

One of the steps towards higher efficiency internal combustion engines (ICEs) is the application of new improved subsystems, with lower power consumption. One of such subsystems is the needle roller bearing valvetrain, where rolling bearings replace the common sliding bearings designs as camshaft supports, hence decreasing the frictional torque and increasing liquid power at the crankshaft. However, the first question to arise is the vibration characteristic of the system for the new design. In order to initiate the assessment of the vibration behavior of the camshaft, some fundamental investigations should be made, such as natural frequency identification. For that, one might benefit from virtually evaluate these characteristics via FEA / Rotordynamics algorithm, reducing the need for expensive experimental setups of the complete valvetrain. This work intends to assess the applicability of these both methods to the camshaft vibration problem.

Lately the simulation of driving cycles through the vehicle's longitudinal dynamics has become increasingly important and common for engineering design. Consequently is essential to evaluate the performance of the simulation through consistent validation metrics that allows a qualitative and quantitative analysis of the data. This paper presents a simple systematic mechanical model that estimates the fuel consumption of an arbitrary small-size hatch back in a specific driving cycle, with all the modeling details of the energy balance throughout the system, as well as, the procedure of the test that reproduces the simulated conditions and the validation methods with different validation metrics. Besides, this work examines how the present metrics should be interpreted for assessing computational model accuracy, as well as, the impact of experimental measurement uncertainty on the accuracy assessment.

The basic function of the clutch, transmitting torque when running, interrupting the flow of power between the engine and gearbox in the changing gears and stopping and protecting the engine and transmission against overload and dampen vibration transmission. The plateau clutch with spring membrane is the system used today. The modern clutches are small and save space in the engine compartment reducing the total weight of transmission, minimizing the resistance to rotation of the motor, providing less mechanical losses. The construction and assembly of the membrane spring clutch assembly is very important, since misalignment of reeds could result in chatter or vibration in clutch pedal, along with the hard drive of the pedal, which can also generate a deformation of the components and thus premature wear of the clutch.

In the track to fuel efficiency increase and green house gases emissions reduction, systemic friction reduction in mechanical components starts to play a big role in the complete automotive system design. When thinking on design for friction efficiency, most of the common applied mechanical components still have enough room for improvement, so as to greatly impact the whole mechanical efficiency. Following the results obtained by a Design and Analysis of Computer Experiments - DACE investigation on the most influencing friction torque parameter of roller bearings, different designs of raceway profiles were examined in order to reduce the bearing friction, i.e., increase its efficiency. In this work a DACE methodology was applied alongside a friction model for the roller bearings to evaluate the effects of the variables and its interactions.

Each year more strict laws and regulations concern the environmental impact of green house gases of general vehicles. Hence, any step taken towards a systemic efficiency increase of internal combustion engines and power-trains revels great a deal of emission reduction downstream the fuel consumption chain. Most of such mechanical systems depend on friction reduction elements, such as special low-friction coats and rolling element bearings, even so there is still some power loss on these components. In order to reduce such losses due to friction, in other words increasing the component's efficiency, this work applies the Design of Experiments -DoE methodology along with the frictional torque simulation in an automotive application to asses the effects of the variables and its interactions involved in the friction torque theory. For simulation studies a Response Surface Design is generated and Box-Behnken Design is carried out.

The primary belt drive is required to synchronize the crankshaft and camshaft of internal combustion engines, keeping the belt tensioned. In order to provide optimum setting of the belt force (compensation of fluctuations in the belt force due to temperature, wear or dynamic effects) automatic belt tensioning system is used, nevertheless, the components of such systems are liable to high dynamic loading condition. Oscillatory loading and noise arise from the engine internal combustion and primary belt drive components can present failures even with conservative designs concerning to static loading. This paper intends, by means of numerical methods, such as Finite Elements Method (FEM) through the commercial software Abaqus, analyze the dynamic behavior of critical components of the primary belt drive system, in order to avoid failures due to dynamic excitation and resonance.