Rene Boonen

On the determination of fatigue properties of Ti6Al4V produced by selective laser melting

This paper provides new insights into the fatigue properties of Selective Laser Molten components made from Ti6Al4V powder particles. The SLM-process parameters are optimized and high quality SLM-parts with a relative density of 99.7% are produced. Uniaxial fatigue experiments are then performed on notched and unnotched specimens and the endurance limits are determined using the staircase method and the theory of Dixon and Mood. The presented results indicate inferior fatigue strength in comparison with conventionally produced components from Ti6Al4V. Microstructural analysis shows that this is mainly due to the anisotropy in the microstructure and the weak grain boundaries between epitaxial grains. However, the failure mechanism is consistant leading to low statistical scatter in the fatigue data. Furthermore, the critical volume method and the critical distance theory have proven to be accurate and efficient design tools to account for the notch-effect in SLM-Ti6Al4V.

Development of an active exhaust silencer for internal combustion engines using feedback control

A silencer to attenuate engine exhaust noise using active control methods is developed. The device consists of an electrically driven valve, combined with a buffer volume, which is connected to the exhaust outlet. Using the mean flow through the valve and the pressure fluctuations in the volume, the valve regulates the flow in such a way that only the mean flow passes through the exhaust outlet. The fluctuations of the flow are temporally buffered in the volume. To carry out optimization and validation experiments, a cold engine simulator is developed. This device generates realistic exhaust noise and the matching gas flow using compressed air. The simulator allows quick and reliable acoustic and fluid dynamic experiments on exhaust prototypes. The active silencer is capable to reduce the exhaust noise from 91 dBA to 78 dBA after the tail pipe outlet, with a back pressure of 3 kPa to the engine.

The effect of external dynamic loads on the lifetime of rolling element bearings: accurate measurement of the bearing behaviour

Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasizes an important influence of external dynamic loads on the lifetime of bearings. However, most lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting this influence. For bearings subjected to highly varying loads, this leads to inaccurate estimations of the lifetime, and therefore excessive safety factors during the design and unexpected failures during operation. This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. Since bearings are very precise machine components, their motion can only be measured in an accurately controlled environment. Otherwise, noise from other components and external influences such as temperature variations will dominate the measurements. The test rig is optimised to perform accurate measurements of the bearing behaviour. Also, the test bearing is fitted in a modular structure, which guarantees precise mounting and allows testing different types and sizes of bearings. Finally, a fully controlled multi-axial static and dynamic load is imposed on the bearing, while its behaviour is monitored with capacitive proximity probes.

Experimental Validation of Input Torque Balancing Applied to Weaving Machinery

This paper considers a class of high-speed airjet weaving machines that is characterized by excessive harness frame vibration, resulting in premature failure. This problem is tackled through addition of an auxiliary, input torque balancing mechanism: A centrifugal pendulum, of which the pendulum motion is imposed by an internal cam. While earlier work by the same authors focused on the design, optimization, and robustness analysis of this mechanism, the current paper presents experimental results. The considered setup is an industrial weaving machine a blanc equipped with a centrifugal pendulum prototype. Below a critical speed, the prototype functions as predicted and significantly improves the machine dynamics: The drive speed fluctuation is reduced by a factor of 2.5 and the vibration level of the harness frames is halved. Above the critical speed, however, torsional resonance dominates the machine dynamics. This phenomenon is verified on simulation by extending the rigid-body setup model, on which the centrifugal pendulum design is based, with a torsional degree of freedom.

Modeling the Sound Source of an Intake and Predicting the Intake Sound Pressure Level for a Motorcycle

In order to accurately estimate the intake sound pressure level, it is important to improve the accuracy of the air cleaner simulation model and precisely estimate the sound source of the intake. It has been confirmed that the modeling accuracy of an air cleaner can be improved by considering the vibro-acoustic coupling. Meanwhile, the sound source of the intake depends not only on the engine specifications, but on the intake system and even the exhaust system design. In this reported example, since it is difficult to estimate the sound source of the intake only by calculation, due to the aforementioned reasons, actual measurements were carried out to define the sound source. The method is such that the sound source is modeled by acoustic impedance and volume velocity in the engine, and the acoustic impedance is measured using an impedance tube. Then, the sound pressure at the intake opening is measured. Then, the volume velocity is calculated backwards using the results of measurement and the intake system unit model. This method allows defining the sound source by experiments. In addition to that, estimation of sound pressure level at the intake opening has become possible by using measured acoustic impedance and volume velocity, which are determined by experiments, as the boundary conditions of the air cleaner model.

Development of an active exhaust silencer for combustion engines

A silencer is developed to attenuate engine exhaust noise using active control. The device consists of an electrically driven valve, combined with a buffer volume. Using the mean flow through the valve and the pressure fluctuations in the volume, the valve regulates the flow such that only the mean flow passes the tail pipe outlet. The flow fluctuations are temporally buffered in the volume. A cold engine simulator is developed to experiment with exhaust systems. This device generates realistic exhaust noise and the matching gas flow using compressed air. It allows quick and reliable acoustic and fluid dynamic experiments on exhaust prototypes. The valve is controlled using a nonadaptive feed‐forward algorithm. The active silencer reduces the exhaust noise 13 dBA. However, the nonlinear relation between valve stroke and pressure drop limits the performance of the controller. Currently, a feedback controller is being implemented. It improves the performance, but is now limited by the time delay between con...

Estimating Rolling Element Bearing Stiffness Under Different Operational Conditions Through Modal Analysis

This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. The design is optimised to measure the bearing behaviour, free from dynamics of the surrounding structure. In the current study, the test rig is used to evaluate the stiffness of a deep groove ball bearing under different operational conditions. The bearing behaviour is measured using the modal analysis technique. Then, an analytical model of the test structure is fitted on the data to estimate the bearing stiffness. The stiffness estimation is validated using a dummy bearing with a known stiffness. Finally, the stiffness of a mounted ball bearing is estimated. The paper evaluates the effect of a radial static load on the bearing stiffness. Stationary and operational conditions are compared as well. A clear difference between the stiffness of a rotating and non-rotating bearing is observed.

Active control of sound transmission through an industrial sound encapsulation

In this paper, an active control system is developed to enhance the sound transmission loss of a sound encapsulation at low frequencies. The sound encapsulation is used to shield a noise source, such as an air compressor. The control systems comprise two control loudspeakers and two error microphones. The Filtered‐X LMS adaptive feedforward control algorithm is used to drive the signals at the error microphones to a minimum. The reference signal for the control algorithm is taken from the noise source, i.e., the tacho signal of the compressor. This study deals with the optimization of the location of control sources and error sensors in view of the achieved control performance. From this perspective it is important to note that minimizing the sound‐pressure level at the error microphones, which are constrained to be located inside the sound encapsulation, does not necessarily reduce the acoustic intensity measured in the far field of the encapsulation (or at least, not to the same degree). Relevant issues which are considered are: the coupling of control sources with the acoustic modes of the enclosure, changes to the interior sound field due to active control, etc.

Development of a Test Rig for Multi-Axial Static and Dynamic Loading of Bearings

Condition monitoring of bearings has been a major research topic for more than five decades. To validate and improve the condition monitoring techniques, this paper focuses on the development of an innovative and versatile bearing test rig. The rig allows applying a fully controlled multi-axial static and dynamic load on different types and sizes of bearings. Easy adjustment to mount bearings with different inner diameter, outer diameter and width is possible, without compromising on performance. Furthermore, the behaviour of the bearing is monitored by accelerometers, proximity probes and thermocouples. During the design of the rig, several techniques were applied to ensure clean measurements, with maximum repeatability, and to reduce errors due to temperature variations. Finally, introducing an additional dynamic force on the bearing makes it possible to load the bearing as if it were built into a real machine, for example a gearbox. At the time this paper is written, results of the test rig were not yet available. However, the authors expect to be able to report on the first test results during the conference.Copyright