Open Access

High-precision, multidimensional holes are required in many technical applications. Due to its undercut shape, these kind of holes are usually manufactured from two sides of the work piece including a time-consuming co-axial alignment. Compared to current state of the art, a one-sided drilling strategy has numerous advantages regarding flexibility, precision and process efficiency. In this work, a helical drilling optic and an ultrashort pulse laser are utilized to fabricate a rotationally symmetric multidimensional-shaped hole in one single process step. The influences of single pulse energy, pulse repetition rate, rotation speed of laser beam as well as the drilling time on ablation depth are investigated. By varying the pulse energy and pulse density, the deposited energy per unit length on the single helical path can be adapted and thus the ablation depth can be scaled. With the adapted laser energy deposition, a T-shaped hole with a uniformed depth of about 80 mu m inlet is fabricated. Morphological analysis on the hole wall show excellent drilling quality without recast layers or heat-affected zones and roughness Rq < 0.35 mu m.

Pseudopotential (PP)-basierte Lattice-Boltzmann-Methoden werden zunehmend für die Simulation von Mehrphasenströmungen eingesetzt. Da sie auf einem phänomenologischen Ansatz basieren, ist ihr Einsatz mit einem hohen Modellierungsaufwand verbunden. Zudem entstehen an den Phasengrenzen sogenannte Scheingeschwindigkeiten, welche Genauigkeit und numerische Stabilität beeinträchtigen. Daher werden PP-Modelle in dieser Arbeit um drei neue Aspekte erweitert. Erstens wird gezeigt, dass bei der Modellierung unterschiedlicher Kontaktwinkel mit gängigen Methoden in Kombination mit verbesserten Kräfteschemata Scheintröpfchen entstehen. Diese werden durch einen neuartigen Ansatz eliminiert, der auf zusätzlichen Randbedingungen für alle Wechselwirkungskräfte basiert. Diese Technik verhindert nicht nur das Auftreten der Scheintröpfchen, sondern erhöht auch die Stabilität in wandgebundenen Strömungen. Zweitens wird ein neuartiges Verfahren zur Reduktion von Scheingeschwindigkeiten eingeführt. Dabei wird die Diskretisierung der Interaktionskräfte erweitert und die zusätzlichen, freien Koeffizienten in Simulationen statischer Tropfen numerisch optimiert. Die resultierende Diskretisierung wurde in Simulationen stationärer und dynamischer Testfälle validiert, wobei Scheingeschwindigkeiten deutlich reduziert werden konnten. Drittens und letztens wurden die Diffusionseigenschaften in Mehrstoffsystemen detailliert untersucht, wobei eine kritische Abhängigkeit zwischen den makroskopischen Diffusionskoeffizienten und dem Kräfteschema aufgezeigt wird. Diese Analyse bildet die Grundlage für den Vergleich und die zukünftige Entwicklung neuer Potentialfunktionen (für Mehrstoffsysteme) und reduziert den Modellierungsaufwand.

Bond graph software can simulate bond graph models without the user needing to manually derive equations. This offers the power to model larger and more complex systems than in the past. Multibond graphs (those with vector bonds) offer a compact model which further eases handling multibody systems. Although multibond graphs can be simulated successfully, the use of vector bonds can present difficulties. In addition, most qualitative, bond graph–based exploitation relies on the use of scalar bonds. This article discusses the main methods for simulating bond graphs of multibody systems, using a graphical software platform. The transformation between models with vector and scalar bonds is presented. The methods are then compared with respect to both time and accuracy, through simulation of two benchmark models. This article is a tutorial on the existing methods for simulating three-dimensional rigid and holonomic multibody systems using bond graphs and discusses the difficulties encountered. It then proposes and adapts methods for simulating this type of system directly from its bond graph within a software package. The value of this study is in giving practical guidance to modellers, so that they can implement the adapted method in software.

Hartmut F. Binner: Organisation 4.0: MITO-Konfigurationsmanagement Hardcover-ISBN: 978- 3-658-2066-1, eBook-ISBN: 978-3-658-20662-8 5, 99 Seiten 2018, Springer Vieweg

This paper discusses the analysis of mechanical power flow in an electric motor drive operating under variation of conditions. The drive system vibration generates the oscillation in the supplied active power which can reduce performance of the system and increase the actual load on the shaft. It is shown that the vibration damper installation significantly decreases the oscillations in mechanical power flow on the motor shaft and improves characteristics of the system operation. The paper provide analysis of two models of the electric drive installed on the platform - the system which is quipped with vibration dampers and without.

The paper is about finding the global optimum for a wheel loader work cycle in a gravel application. This includes simulating the gravel and extracting the trajectories for the main actuators; propulsion, lift and tilt, during the work cycle. The optimal control method is dynamic programming and the optimum is calculated with regard to fuel efficiency [ton/l] but can be weighted towards productivity [ton/h].

The main requirements of efficient steganographic systems are transparency, robustness and security. In this work, the proposed system is designed to achieve these requirements, as follows: to increase the transparency and robustness, the proposed system uses the transform domain technique, in this case the wavelet domain technique to embed the color secret image into the color cover image. To achieve high security, chaotic systems are used to accomplish the following two purposes: firstly to scramble the secret color image before hiding it into the color cover image, secondly to randomly select the embedding positions in the cover image. Three chaotic systems with many combinations are used for the scrambling and the embedding process. Experimental results including Mean Square Error (MSE), Peak Signal to Noise Ratio (PSNR), Correlation, Signal to Noise Ratio (SNR) and embedding capacity demonstrate that the proposed system has good performance as compared with other existing methods without attack and under different types of attacks such as filtering and noise attacks. Simulation results show that the combination of chaotic systems providing the best performance include the use of Logistic and Hénon maps for the embedding process and Arnold's cat map for the encryption process. The MSE, PSNR, correlation, SNR and embedding capacity obtained in this case reach up to 0.0010, 78.1dB, 0.9999, 67.2dB and 0.39% respectively when the secret image is Airplane with 32×32 pixels and the cover image is Girl with 512×512 pixels. For the extracted secret image, the chaotic system set that provides the best performance includes the use of Arnold's cat map for the encryption process. The MSE, PSNR, correlation and SNR obtained in this case reach up to 0.0846, 58.9dB, 1 and 56.1dB respectively. As compared with other methods, the proposed method achieves gains without any attack of 8.2dB for the stego image and 32.4dB for the extracted secret image in PSNR when the secret image is Airplane with 256×256 pixels and the cover image is Girl with 512×512 pixels.

The requirements of an efficient communication scheme for wireless sensing applications have been investigated. The noncoherent direct chaotic communication scheme called chaos on-off keying (COOK) has presented itself as a promising candidate. This paper proposes a modified version of the COOK scheme to improve its performance in noisy and fading environments. The proposed scheme is designed to increase the signal space of the decision variable by using the concept of differential correlation keeping implementation requirements simple. The results show that the proposed modified version of the COOK scheme achieves less bit-error probability in noisy and fading channels at moderate signal-to-noise ratio values and almost constant detection threshold as compared with the original version.