Visual perception is the most important of the human senses. Lack of visual perception is one of the main causes of accidents. The safety of vehicle traffic depends on how well automotive lighting ...supports the visual perception of the driver. This book explains the fundamentals of visual perception, like e.g. physiology of eye and brain, as well as those of automotive lighting technology, like e.g. design of headlamps and signal lights. It is an interdiciplinary approach to a fastly evolving field of science and technology, answering questions like `How does information enter our brain when driving a car?` and `What are the benefits and dangers of LED signal lighting?`
Abrasive processes, primarily the local slip, are the dominant contributor to friction and wear of vehicle tires in service. The time history of forces accompanying acceleration, braking, and ...cornering in particular, lead constantly to changing contact conditions under the tire. Consequently, a laboratory test taking into account not only surface texture but also tire contact times (in the range of milliseconds) as well as realistic contact forces in a freely controllable temporal sequence is desirable. This paper presents the study of the dynamic contact between a rubber block and the abrasive surface at conditions close to those in a tire footprint. In our case, the test samples are a miniaturized tread block allowing to reproduce the intermittent tire contact including correct contact timings, pressure and friction coefficients in dependence on the driving maneuver to be tested. An analysis and comparison of friction and wear mechanisms for continuous contact and defined contact times is presented surpassing the characterization capabilities of DIN abrasion testers.
Two different compounds with a variation of stiffness are examined. The grip and wear rates are analyzed and compared. It is shown that understanding the dominant mechanisms and quantifying tire tread friction and wear in detail require the consideration of realistic transient dynamics of a tire tread block impacting the road at each revolution of the tire.
•Intermittent tire contacts (contact timings, pressure, friction coefficients) are reproduced with a miniaturized tread block.•Effect of rubber dynamic modulus on the contact conditions, direct high-speed cam observations of sample deformations.•Grip and abrasion depend very much on the snap-out conditions in the trailing edge.•Contrasting the DIN-Abrader, significant differences in friction energy between compounds are revealed in dynamic test mode.•Rubber wear in such kind of dynamic system can be correlated well to frictional energy.
•A control system to treat wastewater with ms pulsed ultrasound is presented.•A special focus is the vibration behavior of the ultrasonic system.•The control efficacy is analyzed on the ultrasonic ...timescale.
Sonochemical processes applied to wastewater treatment have an influence on the behavior of ultrasonic systems. This is especially due to the load characteristic of the sonochemical process itself and the temperature increase caused by internal damping within the converter. Hence, a controlling device is needed to guarantee the operation in resonance and to keep the vibration amplitude constant. This paper presents a digital control system for the operation of weak to strong damped ultrasonic devices and its application for inactivating Escherichia coli in wastewater. In an experimental investigation, the electric data during a sonochemical process to inactivate E. coli in wastewater is taken into account to analyze the efficacy of the treatment process and the reaction of the vibration system to the process. Frequency response measurements depict that the resonance frequency changes with the sonicated medium and the vibration amplitude decreases with driving current. In addition to a common continuous operation of the system, different pulsed modes are investigated. The experiments prove the common dependencies between inactivation and power level or treatment time. Additionally, it is pointed out that the control of the sonochemical device is of utmost importance to guarantee an efficient treatment of water, because fast process changes, especially in pulsed operation modes, need to be controlled to a steady state as fast as possible. Although a water treatment efficiency increase using pulsed modes was not proved, it is shown, that the performance of the control unit is capable of using different driving modes in water treatment.
Laser beam welding is a commonly used technology for joining similar and dissimilar materials. In order to improve the mechanical properties of the weld, the introduction of ultrasonic vibration into ...the weld zone has been proposed 5. The ultrasonic system consists of an electronic control, a power supply, a piezoelectric converter and a sonotrode, which introduces the vibration into the weld zone. Its proper design is of great importance for the process performance. Furthermore, the effects of ultrasound in a melt pool need to be understood to evaluate and optimize the process parameters. In addition, it is important to find out the limits of ultrasonic excitation with respect to a maximum vibration amplitude. Therefore, firstly different methods of ultrasonic excitation are investigated and compared with respect to their performance. A system which is based on using longitudinal vibrations turns out to be the best alternative. Secondly, the system design is described in detail to understand the boundary conditions of the excitation and finally, simulations about the influence of ultrasonic vibrations are done by using a simplified model. The system is used to perform experiments, which aim at detecting the maximum vibration amplitude doing bead on plate welds of EN AW-6082 aluminum alloy. The experiments reveal a significant change of the weld shape with increasing ultrasonic amplitude, which matches the simulative findings. If the amplitudes are small, there is a marginal effect on the weld shape. If the amplitudes are high, melt is ejected and the weld shape is disturbed. In the present case, amplitudes over 4 µm were found to disturb the weld shape.
Pseudo-random excitation with low crest factor is less likely to force a structure under test into nonlinear behavior, which should be avoided, or at least minimized, in the practice of experimental ...modal analysis. However, simply cutting high peaks and removing them from the excitation time history is not an option because such clipping of the signal introduces frequency distortions of the amplitude spectrum. A better approach is to manipulate phases of the harmonics before generating the time history instead of clipping it afterwards. To do so a new parameter, kurtosis, is used in this paper to characterize the high peak behavior of pseudo-random excitations. An analytical solution is obtained for how the phases should be selected in order to reduce kurtosis and make modal testing excitations smoother with less extreme peaks. This solution was implemented for evaluation of the damping ratio of a SDOF system by the half-power method in the presence of an additional cubic term in the equation of motion. The system response obtained by numerical integration was treated as modal analysis data and the result is that the kurtosis-optimized excitation has compensated for the effect of nonlinearity and allowed to identify the damping ratio with good precision whereas an ordinary Gaussian excitation with randomized phases caused an error of 75 percent. Comparison with the numerical crest factor minimization by time-frequency-domain swapping has been made and experimental results from a modal testing rig with a realistic turbine blade are also presented in the paper.
This work deals with a novel piezoelectrically driven vibro-impact drilling tool which is designed to drill holes and take rock samples in NASA's future space missions. The drilling device consists ...of an ultrasonic transducer with a piezoelectric stack, a free flying mass and a drill stem. Excited by the high-frequency vibration of the transducer the free mass oscillates between the horn tip of the transducer and the drill stem. The shock waves in the drill stem caused by the impacts with the free mass affect hard and brittle materials so effectively that small holes can be performed with extremely low additional downforce and low power consumption. This paper provides measurements with a modified actuator which show an irregular motion of the free mass. For further optimization two model approaches are investigated: the finite element method and a discrete lumped parameter model. Each model is capable of predicting actuator's parts motion similar to measurements.
Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping ...performance. Recently, semi-active switching techniques-namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques-have been proposed, which are capable of adapting to variations of the excitation frequency without reduction in performance. Crucial for the damping performance is the tuning of the shunt parameters and the precise switching sequence.
The transport and dosage of granular materials are an important part of Process Engineering. Thereby, the food, chemical, pharmaceutical and coating industries set high demands on the transport and ...dosage performances of the used plants. In this context, Ultrasound Process Technology in the past years has developed itself into an attractive alternative compared to presently used classical technologies.
This paper describes the application of ultrasonic progressive waves in a powder-feeding device. The use of a specific pipe material with appropriate damping characteristics allows to generate a progressive wave using a single piezoelectric actuator. Small objects can be carried along the surface of a pipe by the elliptic motion at the surface, which is the result of a flexural progressive wave. The operational principle is the same as in travelling wave ultrasonic motors.
It was experimentally confirmed that the device can be used for feeding and supplying small amounts of powder. The powder-fed performance, however, strongly depends on environmental conditions, so that a control of the system is required. Construction and characteristics of a trial device are shown.
At present the machining of highly ductile electrolytic copper ECu 57 with gun drills is carried out at very low feed values, as the material tends to form very long and unfavourable chips. In ...addition, high frictional forces on the guide rails cause high torsional strain on the gun drill. This paper first reports on the results of ultrasonically assisted deep hole drilling in ECu 57 with tools of 5
mm diameter. The actuator system for exciting axial vibrations in the ultrasonic range is described and experimental results which were obtained from cutting tests are reported. Particular emphasis is put on the improvements compared with the conventional drilling technology without superimposed vibrations. The effect of different input amplitudes is investigated in detail. The performance criteria are drilling moment, surface quality, chip form as well as the surface zone. By optimising the vibration amplitude, cutting speed and feed, the machining result was improved compared with conventional machining, and at the same time the stability of the machining process was simultaneously increased.
Welding round bars of large diameters in a rotational laser beam welding process corresponds with weld pool bulging and the risk of weld defects. Power modulation is a promising approach for bulge ...reduction and for keyhole stabilisation to achieve superior weld quality. The following investigations are about the specific effects of power modulation for round bars with a diameter of 30 mm. The welding speed is 0.95 m/min and argon is used as shielding and process gas. Triangle shaped power modulation at 8 kW average laser beam power, 0/2/4/6 kW amplitude power and 2/10/50 Hz modulation frequency is used for the round bar welding of a 1.4301 steel alloy. The welds are evaluated by visual inspection, metallographic cross sections and scanning acoustic microscopy. The amount of weld defects increases at medium and high power modulation, but weld pool bulging is already reduced at low power modulation. Weld pool bulging can be impeded by a low normalised power modulation frequency of 0.05 and a high modulation depth of 0.86. The power modulation’s advantages of weld mixing and degassing do not apply to rotational round bar welding because of the linear welding speed’s gradient from the specimen surface to the centre.
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