Experimental investigations into the air pumping effect at the tyre/road interface

Introduction: Environmental noise pollution is an important issue that affects health and quality of life of millions of people in the modern world. One of the main sources of environmental noise pollution is the noise generated by road traffic. To reduce road traffic noise, the automotive industry has done a great deal of research and development in the recent decades. As a result of these efforts, such earlier important contributors to the overall automotive noise, as powertrain and exhaust noise, have been reduced considerably for nearly all driving conditions, so that the dominant contributor has become tyre/road noise. According to the tyre/road noise reference book written by Sandberg and Ejsmont, there are two different groups of generation mechanisms for tyre/road noise: (i) tyre vibrations; and (ii) aerodynamical effects in or around the tyre. In contrast to noise generated by tyre vibrations, the aerodynamical mechanisms of tyre noise generation have received relatively little attention in the past. Therefore, the main aim of the research reported in this paper was to undertake comprehensive experimental investigations of aerodynamically related mechanisms of tyre/road noise

<i>I</i>-optimal or <i>G</i>-optimal: Do we have to choose?

When optimizing an experimental design for good prediction performance based on an assumed second order response surface model, it is common to focus on a single optimality criterion, either G-optimality, for best worst-case prediction precision, or I-optimality, for best average prediction precision. In this article, we illustrate how using particle swarm optimization to construct a Pareto front of non-dominated designs that balance these two criteria yields some highly desirable results. In most scenarios, there are designs that simultaneously perform well for both criteria. Seeing alternative designs that vary how they balance the performance of G- and I-efficiency provides experimenters with choices that allow selection of a better match for their study objectives. We provide an extensive repository of Pareto fronts with designs for 17 common experimental scenarios for 2 (design size N = 6 to 12), 3 (N = 10 to 16) and 4 (N = 15, 17, 20) experimental factors. These, when combined with a detailed strategy for how to efficiently analyze, assess, and select between alternatives, provide the reader with the tools to select the ideal design with a tailored balance between G- and I-optimality for their own experimental situations.</p

A study on how small changes to vehicle panel boundary conditions vary the overall system response

An experimental investigation carried out on a luxury sedan door observed the effect of making small changes to trim boundary conditions by removing and replacing a series of small polymer clips that held the trim to the aluminium door. Structural testing was carried out by exciting the system with a shaker and recording the response with accelerometers placed at three different locations about the door. Acoustic response measurements were also taken with the use of a sound intensity probe. The study found that the removal of even a single clip could vary the response significantly for certain clip locations. The spread of structural data was also found to range by more than 15 dB for certain frequency bands. Similar large deviations were observed for the noise transfer response measurements. This is significantly large spread of data for what might be perceived as a relatively small change to the structure, highlighting the importance of reduced variability at material joints

An investigation of ultrasonic transducer loading on a workpiece

Arrays of dry-coupled thickness-shear transducers are often employed in the guided wave sector to inspect pipelines and plate-like structure. The dry coupling permits to dismiss any coupling material between the transducer and the waveguide, but as a drawback a preload must be applied on the transducers to guarantee an effective coupling between the two surfaces. Although the influence of the preload on the natural frequencies is studied in the literature, the frequency response function of a transducer relating the input voltage to the displacement output is not present in the literature. Moreover, the distribution of force on the backing mass and the effect of the preload on the uniformity of vibration of the transducers are still missing. A natural frequency analysis and a forced analysis are then computed numerically with finite element analysis to quantify the influence of the preload on a thickness-shear transducer. Furthermore, these results are compared with experimental results obtained with a Laser Vibrometer. It is then shown how the geometrical layout of the transducer coupled with the preload influences the vibration of the transducer