The thesis deals with quasi-static and fatigue simulations of thick composite lugs subjected to three-dimensional stress states. This includes damage prediction of hybrid laminates made of GRFP and CRFP containing unidirectional and woven fabric plies.Focus lies on the development of a progressive damage model in fatigue which accounts for sti˙ness and strength degra-dations. Two methods based on Puck’s failure criterion are proposed to predict failure of unidirectional plies: one for plane stress analysis and and the other which takes out-of-plane damage into account.Virtual testing in FEM is conducted in quasi-static and fatigue analysis on thick composite lugs subjected to uni-axial loading. Damage, strength and life predictions are then compared with experimental results to validate the numerical models under investigations. / In der vorliegenden Arbeit wird die Berechnung der Festig-keit von dickwandigen Lochleibungslaminaten im Faserver-bundwerksto˙en unter dreidimensionalen Spannungszustän-den untersucht. Nichtlineare Materialverhalten von Hybrid-laminaten in CFK und GFK werden für Unidirektionalfa-serlagen und Gewebelagen berücksichtigt.Der Schwerpunkt liegt auf der Entwicklung von progressi-ven Versagensmodellen unter der Berüsichtigung von Rest-festigkeit und Reststeifigkeit des Materials. Zwei Modelli-erungsmethoden nach Puck-Kriterium zur Vorhersage des Versagens in UD-Lagen werden vorgeschlagen: eine Degra-dierungstechnik für ebene Spannungszustände und ein me-hrachsiges Modell.Numerische Simulationen mit der Finite-Elemente-Methode werden in Statik- und Ermüdungsanalyse an dickwandigen Lochleibungslaminaten unter einachsiger Belastung durch-geführt. Beschädigungen, Festigkeiten und Ermüdungsle-bensdauer werden dann mit experimentiellen Daten ver-glichen, um die numerischen Methoden zu validieren.

Im Zuge eines Forschungsprojektes werden Möglichkeiten untersucht, die Schallemissionen eines Bühnenpodiums unter einen für Zuschauer wahrnehmbaren Schalldruckegel zu reduzieren. Daraus ergibt sich u.a. die Motivation, die Schalleistung für spezifische Antriebe zu bestimmen um bühnen- und antriebsspezifische Lösungskonzepte zur Schallemissionsreduzierung zu entwickeln. Zur Ermittlung entsprechender Lösungen werden an erster Stelle die Geometrien der antriebsspezifischen Zahnradpaarungen in einem CAD-Modell dargestellt. Erlauben die Flankengeometrien die Abbildung eines Überrollvorganges mit ununterbrochenem Zahnflankenkontakt, können die Zahnradmodelle weiterführend in einer nichtlinearen FEM-Simulation verwendet werden. Ziel dieser nichtlinearen Simulation ist die Bestimmung der aus dem Überrollvorgang resultierenden Erregerkräfte im Zeitbereich. Anschließend ist die Übertragung dieser Kräfte in den Frequenzbereich möglich, was nachfolgend eine harmonische Simulation sowie final die Feststellung der antriebsspezifischen Schallleistung erlaubt.

This dissertation concerns quasistatic torsional mirror's for optical applications. The intended main area of application is the use as switch in optical network's, replacing the conventional optical-electro-optical conversation. With these actuator's a new concept of electrostatic actuation has been realised. While the drive electrodes are integrated into the deflectable mirror, the whole counter electrode below the mirror plate remains at equal ground potential. The device is manufactured out of two parts using method's of silicon bulk mikro machining. A deflectable mirror plate, torsional spring's and the surrounding support structure are fabricated within the thin device layer at the top of BSOI material. The counter electrode is manufactured out of a highly doped silicon wafer. Both part's are assembled together by adhesive bonding at die level at the end. Since the driving potential is supplied to the mirror plate and the counter electrode is at ground level, lateral tolerances because of device assembly mismatches does not appear with the use of the new concept. In detail the mirror plate itself is divided into two seperate electrodes by a parallel arrangement of filled isolating trenches. The highly doped device layer provides electrical connection via the torsional spring's to the mirror electrodes. A quasistatic torsional actuation is performed if a dc-voltage is applied between one mirror side and the counter electrode. Several design's have been fabricated. The lateral dimension of the torsional mirror plate vary from 0,5 mm to 2,0 mm. The designed characteristic frequencies vary from 0,5 to 3 kHz. For quasistatic actuation the pull in angle vary from 1 to 5 degree and the pull in voltage goes up to several hundred volts. Accessorily the mirror plate is enclosed by a comb drive structure. So that the device could be used for low voltage resonant actuation or an capacitive position read out becomes feasible. Within this thesis the new concept has been verified and functionality has been demonstrated. Depending on their characteristic frequency, devices are suitable to perform quasistatic actuation within 10 ms. Experiments indicated that the electrical isolation damages irreversible at drive voltage's above 400 volt. It limits the maximum deflection of nearly all design's. At prototype actuators repeatability has been studied. No drift was observed in the static characteristic within several cycles for certain designs. Closed-loop position control is not mandatory for the actuators fabricated within this thesis. Mechanical stress inside the mirror plate causes deformation of the reflective surface larger than permitted by optical criteria. This paves the way for further device optimization, yield improvement and system integration.

No description available.

Scannende MEMS-Mikrospiegel stellen eine vielversprechende technologische Entwicklung mit potentiellen Anwendungen im Bereich der miniaturisierten Bildprojektion und Umgebungssensierung dar. Im Regelfall oszilliert das Spiegelelement hierbei resonant um die horizontale Achse, während die vertikale Achse statisch ausgelenkt wird. Somit ergibt sich ein sogenannter Raster-Scan. Während eine resonante Aktuierung in MEMS-Technologie im Frequenzbereich mehrerer kHz effizient umgesetzt werden kann, stellt die Implementierung statischer Antriebe eine Herausforderung dar. In dieser Arbeit wird ein neuartiges Aktuierungskonzept vorgestellt, das effizientere quasi-statische Auslenkung ermöglicht. Hierfür wird der Drehimpuls, der durch die hochfrequente horizontale Schwingung erzeugt wird, durch eine weitere resonante Oszillation ähnlicher Frequenz gestört, wodurch sich ein für die quasi-statische Auslenkung nutzbares Drehmoment ergibt. Da gyroskopische Effekte ausgenutzt werden, die nicht in aktuellen auf Modalanalyse basierenden Simulationsmethoden berücksichtigt sind, werden Starrkörper- und transiente FEM-Modelle entwickelt, um die Realisierbarkeit des Antriebskonzepts simulatorisch zu verifizieren. Im Rahmen der durch den genutzten Prozess gegebenen Randbedingungen werden daraufhin Aktuierungselemente für die resonanten Achsen erarbeitet und mit diesen zwei Designvarianten eines 2D-Mikrospiegels erstellt. Nach modellbasierter Verifikation werden diese in einer MEMS-Fertigungslinie prozessiert. Mit den generierten Mustern wird dann eine vollständige experimentelle Charakterisierung unter Nutzung eines speziell erstellten FPGA-basierten Evaluations-Boards durchgeführt. Beide Design-Varianten zeigen hierbei voll funktionsfähige Sensierungs- und Aktuierungselemente. Es kann ein erfolgreicher Nachweis der Funktionsfähigkeit des neuartigen Antriebskonzepts vollbracht werden. Die dabei gezeigte 2D-Projektion erreicht Winkel von 12° x 1.8° / Scanning MEMS micromirrors are an emergent technology for compact form factor image projection and environment sensing applications. Commonly the mirror element oscillates resonantly along the horizontal axis, whereas it is deflected statically along the vertical axis, performing a so called raster scan. While resonant actuation can be implemented efficiently in MEMS, static deflection however remains challenging. In this thesis a novel actuation concept for 2D MEMS micromirrors is introduced that potentially enables efficient quasi-static actuation. Therefore the angular momentum that is generated by the high frequency resonant axis is disturbed by an orthogonal resonant oscillation of similar frequency, leading to a torque that can be utilized to achieve an indirect quasi-static deflection. As in this case gyroscopic effects are exploited that are usually not considered in state of the art modal finite element based MEMS simulation, in order to validate the feasibility of the actuation concept rigid body and transient finite element based models are developed and simulation studies conducted. Using an existing manufacturing process as a framework, actuation schemes for the resonant axes are introduced and two distinct micromirror designs are developed and verified by simulation. These are processed in a MEMS manufacturing line. A thorough characterization study is then carried out using a custom FPGA based evaluation board with closed loop control capabilities. Both design variants are functional with regard to all actuation and tilt angle detection elements. A successful implementation of the proposed actuation concept is shown achieving 2D projection of a laser beam with tilt angles of 12 ◦ × 1.8 ◦ in frequency and amplitude controlled operation.

<div>The huge gamut of today’s internet-connected embedded devices has led to increasing concerns regarding the security and confidentiality of data. To address these requirements, most embedded devices employ cryptographic algorithms, which are computationally secure. Despite such mathematical guarantees, as these algorithms are implemented on a physical platform, they leak critical information in the form of power consumption, electromagnetic (EM) radiation, timing, cache hits and misses, and so on, leading to side-channel analysis (SCA) attacks. Non-profiled SCA attacks like differential/correlational power/EM analysis (DPA/CPA/DEMA/CEMA) are direct attacks on a single device to extract the secret key of an encryption algorithm. On the other hand, profiled attacks comprise of building an offline template (model) using an identical device and the attack is performed on a similar device with much fewer traces.</div><div><br></div><div>This thesis focusses on developing efficient side-channel attacks and circuit-level low-overhead generic countermeasures. A cross-device deep learning-based profiling power side-channel attack (X-DeepSCA) is proposed which can break the secret key of an AES-128 encryption engine running on an Atmel microcontroller using just a single power trace, thereby increasing the threat surface of embedded devices significantly. Despite all these advancements, most works till date, both attacks as well as countermeasures, treat the crypto engine as a black box, and hence most protection techniques incur high power/area overheads.</div><div><br></div><div>This work presents the first white-box modeling of the EM leakage from a crypto hardware, leading to the understanding that the critical correlated current signature should not be passed through the higher metal layers. To achieve this goal, a signature attenuation hardware (SAH) is utilized, embedding the crypto core locally within the lower metal layers so that the critical correlated current signature is not passed through the higher metals, which behave as efficient antennas and its radiation can be picked up by a nearby attacker. Combination of the 2 techniques – current-domain signature suppression and local lower metal routing shows >350x signature attenuation in measurements on our fabricated 65nm test chip, leading to SCA resiliency beyond 1B encryptions, which is a 100x improvement in both EM and power SCA protection over the prior works with comparable overheads. Moreover, this is a generic countermeasure and can be utilized for any crypto core without any performance degradation.</div><div><br></div><div>Next, backed by our physics-level understanding of EM radiation, a digital library cell layout technique is proposed which shows >5x reduction in EM SCA leakage compared to the traditional digital logic gate layout design. Further, exploiting the magneto-quasistatic (MQS) regime of operation for the present-day CMOS circuits, a HFSS-based framework is proposed to develop a pre-silicon EM SCA evaluation technique to test the vulnerability of cryptographic implementations against such attacks during the design phase itself.</div><div><br></div><div>Finally, considering the continuous growth of wearable and implantable devices around a human body, this thesis also analyzes the security of the internet-of-body (IoB) and proposes electro-quasistatic human body communication (EQS-HBC) to form a covert body area network. While the traditional wireless body area network (WBAN) signals can be intercepted even at a distance of 5m, the EQS-HBC signals can be detected only up to 0.15m, which is practically in physical contact with the person. Thus, this pioneering work proposing EQS-HBC promises >30x improvement in private space compared to the traditional WBAN, enhancing physical security. In the long run, EQS-HBC can potentially enable several applications in the domain of connected healthcare, electroceuticals, augmented and virtual reality, and so on. In addition to these physical security guarantees, side-channel secure cryptographic algorithms can be augmented to develop a fully secure EQS-HBC node.</div>

<p dir="ltr">Decades of semiconductor technology scaling and breakthroughs in communication technology have miniaturized computing, embedding it everywhere, enabling the development of smart things connected to the internet, forming the Internet of Things. Further miniaturization of devices has led to an exponential increase in the number of devices in and around the body in the last decade, forming a subset of IoT which is increasingly becoming popular as the Internet of Bodies (IoB). The gradual shift from the current form of human-electronics coexistence to human-electronics cooperation, is the vision of Internet of Bodies (IoB). This vision of a connected future with devices in and around our body talking to each other to assist their day-to-day functions demands energy efficient means of communication. Electro-Quasistatic Human Body Communication (EQS-HBC) has been proposed as an exciting alternative to traditional Radio Frequency based methodologies for communicating data around the body. In this dissertation, we expand the boundaries of wearable and implantable IoB nodes using Electro-Quasistatic Human Body Communication and Powering by developing advanced channel models and demonstrating novel applications.</p><p dir="ltr">Leveraging the advanced channel models developed for wearable EQS-HBC, we demonstrate wearable applications like ToSCom which extend the use cases of touchscreens to beyond touch detection and location to enable high-speed communication strictly through touch. We further demonstrate an application of EQS Resonant Human Body Powering to demonstrate Step-to-Charge, allowing mW-scale wireless power transfer to wearable devices. With increasing connected implanted healthcare devices becoming a part of the IoB space, we benchmark RF-based technologies for In-Body to Out-of-Body (IBOB) communication using novel in-vivo experiments. We then explore EQS-HBC in the realm of IBOB communication using advanced channel modeling, revealing its potential for low-power and physically secure data transfer from implantable devices to wearable nodes on the body, demonstrating its potential in extending the battery life span of implantable nodes. Finally, an overview of the potential of IoB devices is analyzed with the use of EQS-HBC where we propose a human-inspired distributed network of IoB nodes which brings us a step closer to the potential for perpetually operable devices in and around the body.</p>