Objective - To evaluate a surgical technique for performing laparoscopic bilateral ovariectomy in standing horses. Study Design - Experimental study. Animals or Sample population - 8 mares, age 2-20 years, weight 410-540 kg. Methods - Standing laparoscopic bilateral ovariectomy was performed in 8 mares with normal anatomy of the reproductive tract. The Harmonic Scalpel (an ultrasonically activated instrument) was used to transect the ovarian pedicle and to obtain hemostasis simultaneously. Necropsy was performed on 4 mares 3 days after surgery and 30 days following surgery on the remaining 4 mares. Gross and histopathologic evaluation of the ovarian pedicles was performed to characterize the effects of the Harmonic Scalpel on the transected tissue. Results - The Harmonic Scalpel achieved complete hemostasis of the vasculature of the ovarian pedicles in all mares. Median transection time for the ovarian pedicle was 28 minutes. Postoperative complications included transient fever in one mare, moderate subcutaneous emphysema in another, and incisional seroma formation in a third mare. Post-mortem examination 3 and 30 days postoperatively revealed no signs of generalized peritonitis, postoperative hemorrhage or adhesion formation. Mild to moderate acute inflammation, and scar formation with moderate chronic inflammation at the ovarian pedicle was found 3 and 30 days after surgery, respectively. Median depth of coagulation necrosis 3 days postoperatively was 2.87 mm. Conclusions - The Harmonic Scalpel appears to provide reliable hemostasis of the ovarian pedicle during elective laparoscopic ovariectomy in horses. Clinical Relevance - The Harmonic Scalpel represents a safe alternative to other means of hemostasis during elective laparoscopic ovariectomy in horses. / Master of Science

Micro drilling has been applied in the interconnection and precision manufacturing industries extensively. As a promising machining technique, Ultrasonically Assisted Drilling (UAD) has become increasingly popular in both academia and industry in recent years. In this thesis, modelling techniques and experiments for Ultrasonically Assisted Micro Drilling (UAMD) are investigated. Representative work on modelling of micro drills and UAD has been documented and categorised. Existing gaps in the literature are identified and the aims of this research are formulated. Using the Finite Element (FE) technique, a hybrid model is developed to realise modelling for the whole drill bit without compromising the computation efficiency, even when the drill has a complicated geometry (small diameter flute, multiple step shanks, etc). A specific drill model (Φ0.3 mm diameter, 2 step shanks) is chosen for a case study in order to evaluate the model. The hybrid tool shows sufficiently accurate results and impressive computation efficiency in the evaluation. For vibration modelling, force modelling and experimental work, a standard Φ1 mm drill with 1 step shank is used across the chapters. First of all, FE analysis is conducted on the whole drill and normal modes are solved with boundary condition as fixed simply supported. A 2 Degree-of-Freedom (DOF) model is then built considering rotation and the ultrasonic excitation to solve the transverse vibration with boundary conditions consistent with the FE model. The asymmetric geometric characteristics of the drill bit are taken account of through using the first two fundamental modes in the FE model. Potential parametric resonances are discussed in the numerical simulation. Other vibration characteristics are also discussed with varying parameters such as ultrasonic frequency, ultrasonic amplitude and rotational speed. In order to extend the vibration model, a nonlinear thrust force model has been developed for incorporation into the 2 DOF model. The force model considers ultrasonic parameters, feed rate, material properties and the nonlinearity of the UAMD process. Force reduction during the UAMD process is explained qualitatively with the model and a full range of feed rates have been simulated to study their effect on the force reduction. The limitations of this model have also been explained. A high speed UAMD system was designed to examine the effects of key parameters. Experiments with different ultrasonic frequencies, amplitudes and rotational speeds were conducted and the influences of these parameters on thrust force were investigated. With the thrust force data from these experiments, a correlation study to the simulation results based on the force model is carried out. The study identifies the limitations on the current one dimensional force model and leads to recommendations for the further development of the force model. Further work is identified for both modelling and experiments, and the present models can be expanded to suit the research and development of UAMD techniques.

<p>The effect of ultrasonic absorptive coatings on hypersonic boundary-layer transition on a 3 degree half-angle cone was investigated in Purdue's Boeing/AFOSR Mach 6 Quiet Tunnel for Reynolds numbers from 9.0-14.3 X 10⁶ /m. Silicon-carbide coated carbon foam with two densities, estimated at 100 and 200 pores per inch, are referred to throughout this work as X1 and X2 respectively. Both foams were fabricated as three frustums applicable to different locations on the cone. Matching solid pieces were made to test solid-porous configurations to analyze the effect of porous material length and location. Ultrasonic benchtop experiments have been carried out to characterize absorption coefficient values for the X1 and X2, quantifying the levels of acoustic energy absorbed by each foams, and enable companion linear stability calculations. </p> <p><br></p> <p>The most effective placement of both X1 and X2 foams towards achieving transition delay was in their most downstream position, spanning 59.2 cm to 74.3 cm downstream of the nosetip. The overall length of the cone was 109.1 cm. When the X1 foam covered more area, spanning from 44.1 cm to 74.3 cm, the same delay is observed with an unexpected increase in second-mode amplitude. In the same configuration, the X2 foam caused an increase in amplitude, without achieving delay. Agreement is observed against companion linear-stability theory calculations for the impermeable case, and for X1 and X2 foam in the configuration spanning from 44.1 cm to 74.3 cm. Finally, numerical modeling predicts the insurgence of an unexpected low-frequency mode. This was consistent with experimental results observed with the upstream placement of the foam inserts.  </p>

The target of the research is to employ the autoresonant control technique in order to maintain the nonlinear oscillation mode at resonance (i.e. ultrasonic vibration at the tip of a drill bit at a constant level) during vibro-impact process. Numerical simulations and experiments have been executed. A simplified Matlab-Simulink model which simulates the ultrasonically assisted machining process consists of two parts. The first part represents an ultrasonic transducer that contains a piezoelectric transducer and a 2-step concentrator (waveguide). The second part reflects the applied load to the ultrasonic transducer due to the vibro-impact process. Parameters of the numerical models have been established based on experimental measurements and the model validity has been confirmed through experiments performed on an electromechanical ultrasonic transducer. The model of the ultrasonic transducer together with the model of the applied load was supplemented with a model of the autoresonant control system. The autoresonant control intends to provide the possibility of self-tuning and self-adaptation mechanism for an ultrasonic transducer to maintain its resonant regime of oscillations automatically by means of positive feedback. This is done through a signal to be controlled (please refer to Figure 7.2 and Figure 7.3) transformation and amplification. In order to examine the effectiveness and the efficiency of the autoresonant control system, three control strategies have been employed depending on the attributes of the signals to be controlled . Mechanical feedback control uses a displacement signal at the end of the 2nd step of the ultrasonic transducer. The other two control strategies are current feedback control and power feedback control. Current feedback control employs the electrical current flowing through the piezoceramic rings (piezoelectric transducer) as the signal to be controlled while power feedback control takes into account both the electrical current and the power of the ultrasonic transducer. Comparison of the results of the ultrasonic vibrating system excitation with different control strategies is presented. It should be noted that during numerical simulation the tool effect is not considered due to the complexity of a drill bit creates during the Ultrasonically Assisted Drilling (UAD) process. An effective autoresonant control system was developed and manufactured for machining experiments. Experiments on Ultrasonically Assisted Drilling (UAD) have been performed to validate and compare with the numerical results. Two sizes of drill bits with diameters 3mm and 6mm were applied in combination with three autoresonant control strategies. These were executed during drilling aluminium alloys with one fixed rotational speed associated with several different feed rates. Vibration levels, control efforts, feed force reduction were monitored during experiments. Holes quality and surface finish examinations supplement analysis of the autoresonant control results. In addition, another interesting research on the investigation of the universal matchbox (transformer) has been carried out. Introducing a varying air gap between two ferrite cores allows the optimization of the ultrasonic vibrating system, in terms of the vibration level, effective matchbox inductance, voltage and current level, phase difference between voltage and current, supplied active power etc (more details please refer to Appendix I).

Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials.

Titanium alloys have outstanding mechanical properties such as high hardness, a good strength-to-weight ratio, excellent fatigue properties and high corrosion resistance. However, several inherent properties including their low thermal conductivity and high chemical affinity to tool materials impairs severely their machinability with conventional machining techniques. Conventional machining of Ti-based alloys is typically characterized by low depths of cuts and relatively low feed rates, thus adversely affecting the material removal rates during the machining process. Recently, a non-conventional machining technique known as ultrasonically assisted turning (UAT) was introduced to machine modern alloys, in which low-energy, high-frequency vibration is superimposed on the movement of a cutting tool during a conventional cutting process. This novel machining technique results in a multi-fold decrease in the level of cutting forces with a concomitant improvement in surface finish of machined modern alloys. Also, since the late 20th century, machining of wear resistant materials that soften when heated has been carried out with hot machining techniques. In this work, a new hybrid machining technique called Hot Ultrasonically Assisted Turning (HUAT) is introduced for processing of a Ti-based alloy Ti-15V3Al3Cr3Sn. In this technique, UAT is combined with a traditional hot machining technique to gain combined advantages of both schemes for machining of intractable alloys. HUAT of the studied alloy was analysed experimentally and numerically to demonstrate its benefits in terms of reduction in cutting forces over a wide range of industrially relevant speed-feed combinations. Thermal evolution in the cutting process was assessed, and the obtained results were compared with FE simulations to gain knowledge of temperatures reached in the cutting zone. The developed novel turning process appeared to improve dry turning of the Ti alloy with significant reduction of average cutting forces without any substantial metallurgical changes in the workpiece material. Nano-indentation, light microscopy and SEM studies were performed to get an insight into the development of hardness in a zone near the machined surface in the workpiece. Backscatter electron microscopy was also used to evaluate the formation of α-Ti during the novel HUAT. No grain changes or α-precipitation were observed in machined workpieces in conventional and hybrid turning processes. 3D elasto-plastic thermomechanically coupled finite-element models for the orthogonal turning process were developed for conventional turning (CT), hot conventional turning (HCT), UAT and HUAT, followed by a more realistic novel 3D finite-element model for the oblique turning process. These 3D models were used to study the effects of cutting parameters (cutting speed, feed rate and depth of cut, ultrasonic vibration, ultrasonic frequency, rake angle and tool nose radius) on cutting forces, temperature in the process zone and stresses. The later model was used to analyse the effect of vibration and heat on the radial and axial components of cutting forces in HUAT, which was not possible with the developed 3D orthogonal-turning model. Comparative studies were performed with the developed CT, HCT, UAT and HUAT finite-element models and were validated by results from experiments conducted on the in-house prototype and in literature. The HUAT for the Ti-15333 was analysed experimentally and numerically to demonstrate the benefits in terms of a significant reduction in the cutting forces and improvement in surface roughness over a wide range of industrially relevant speed-feed combinations.

Ziel: In der vorliegenden In-vitro-Studie sollte der Einfluss unterschiedlicher endodontischer Schall (S)- und Ultraschallansätze (US) auf Dentinabtrag und Instrumentenversagen untersucht und quantifiziert werden, der bei der Anwendung im standardisierten bovinen Wurzelkanal (WK) entsteht. Zusätzlich sollte eine neue Methode zur tribologischen Untersuchung des erfolgten Dentinabtrags mithilfe von 3D-Digitalisierung etabliert werden. Methodik: In 90 bovine Inzisivi wurden CNC-gesteuert, standardisierte WKs mit drei verschiedenen Kanalkrümmungsradien (r = 3 mm, n = 30; r = 6 mm, n = 30; und gerader WK, n = 30) gefräst. Die WK wurden mithilfe des 3D Digitalisierers ATOS SO 4M (Gom, Braunschweig, Deutschland) photogrammetrisch eingescannt (Scan Nr. 1). Daraufhin erfolgte die Aktivierung der Ansätze „IRRI S“ (VDW), „EDDY' (VDW) und „PEEK“ (ILK, UKD) für 3 x 20 s im WK bei Anwendung eines standardisierten Spülprotokolls mit NaOCl 3 %, EDTA 20 %. Scan Nr. 2 erfolgte anschließend analog zu Scan Nr. 1. Mit Hilfe der Software Atos v.6.3.0-6 wurden beide Scans transformiert, polygonisiert und über die Funktion „Flächenvergleich“ ausgewertet. Jeder WK wurde in 4 Regionen unterteilt (1: Kanaleingang; 2: gerader Kanalteil; 3: Kanalinnenkurvatur; 4: Kanalaußenkurvatur/Apex) und pro Region wurde der größte Dentinabtrag in µm ermittelt. Zusätzlich wurde jeder Messwert anhand eines selbst entwickelten Dentinal Damage Index (DDI) eingeordnet. Die Versagensanalyse der Ansätze erfolgte rasterelektronenmikroskopisch. Ergebnis: Die optische 3D-Digitalisierung zeigte, dass der US-Ansatz „IRRI S“ im 3 mm-WK in allen Regionen zu sichtbarem Dentinabtrag führte: Region 1- MW 48,56 ± 13, 91 µm; Region 2- MW 36,06 ± 8,35 µm; Region 3- MW 41,05 ± 15,89 µm; Region 4- MW 71,88 ± 54,96 µm. Im 6 mm-WK erfolgte sichtbarer Dentinabtrag in Region 1 durch „IRRI S“ (MW 41,08 ± 11,94 µm) und S-Ansatz „EDDY“ (MW 41,10 ± 10,37 µm), in Region 3 und 4 durch „IRRI S“ (MW 33,34 ± 6,61 µm, MW 40,50 ± 13,56 µm). Interessanterweise wird der gerade WK in Region 1 und 4 von „IRRI S“ (MW 43,59 ± 15,32 µm, MW 43,39 ± 15,48 µm) geschädigt. Der US-Ansatz „PEEK“ schädigte das Dentin nicht. Die rasterelektronenmikroskopische Auswertung von „IRRI S“ ergab nach Anwendung in allen WKs minimale Oberflächenalterationen und leichte Begradigungen der Instrumentenspitze. „EDDY“ zeigte deutliche Oberflächenaufwerfungen und Abnutzungen an der Instrumentenspitze in allen WK. US-Ansatz „PEEK“ zeigte nur in den 3 mm-WK leichte Auffaserungserscheinungen. Schlussfolgerung: Der Schallansatz „EDDY“ und der Ultraschallansatz „PEEK“ sind für die klinische Anwendung in gekrümmten Wurzelkanälen geeignet, da sie nicht zu unerwünschten Dentinschädigungen der Kanalwand führen.:Abkürzungsverzeichnis III 1 Einleitung 1 2 Stand der Forschung 3 2.1 Dentin-Eigenschaften 3 2.2 Rinderdentin 4 2.3 Dentinabtrag 5 2.3.1 Erwünschter Dentinabtrag 5 2.3.2 Unerwünschter Dentinabtrag 5 2.3.3 Bisherige Messmethoden für den Dentinabtrag 8 2.4 Wurzelkanalkrümmungen 11 2.5 Ultraschall- bzw. schallaktivierte Spülung (US-AS) 13 2.5.1 Anwendung 13 2.5.2 Ultraschallansatz „IRRI S“ 15 2.5.3 Schallansatz „EDDY“ 16 2.5.4 Der „PEEK“- Ansatz 17 2.6 Photogrammetrische Methoden für die 3D-Koordinatenmesstechnik 18 3 Ziel der Studie 21 4 Material und Methoden 23 4.1 Übersichtsdarstellung des Versuchsplans 23 4.2 Materialliste 26 4.2.1 Chemikalien und Reagenzien 26 4.2.2 Geräte, Instrumente und Verbrauchsmaterialien 26 4.2.3 Software 28 4.3 Entwicklung des Kanalmodells 28 4.4 Modellherstellung 33 4.5 Vorversuche 36 4.6 Etablierung des Scan-Protokolls für bovine Wurzelkanalmodelle 39 4.6.1 Titantiumdioxid-Applikation 40 4.6.2 3D optischer Scan der Wurzelkanalmodelle 41 4.7 Haupt-Versuch: Applikation der Schall-/ US-Ansätze im bovinen Wurzelkanalmodell 42 4.7.1 Versuchsaufbau 42 4.7.2 Ausrichtung der Schall- und Ultraschallansätze 43 4.7.3 Anwendung der Schall- und Ultraschallansätze 45 4.7.4 Spülkonzept 47 4.8 Messdatenerhebung 47 4.8.1 Vermessung der Schall- und Ultraschallansätze 47 4.8.2 3D optischer Scan nach erfolgter Applikation der Schall- und Ultraschallansätze 48 4.8.3 Transformation und Polygonisierung der 3D-Scans 48 4.8.4 Flächenvergleich und Auswertung 50 4.8.5 Dentinal-Damage-Index nach Tetzner und Weber 56 4.9 REM-Aufnahmen 57 4.10 Statistische Auswertung 58 5 Ergebnisse 59 5.1 Dentinabtrag im Regionen-Vergleich 60 5.1.1 Ultraschallansatz „IRRI S“ 60 5.1.2 Schallansatz „EDDY“ 69 5.1.3 Ultraschallansatz „PEEK“ 78 5.2 Dentinabtrag-Vergleich zwischen den verschiedenen Kanalkrümmungen bei gleichem Ansatztyp 84 5.2.1 Ultraschallansatz „IRRI S“ 84 5.2.2 Schallansatz „EDDY“ 86 5.2.3 Ultraschallansatz „PEEK“ 88 5.3 Dentinabtrag-Vergleich zwischen den verschiedenen Ansatztypen bei gleicher Kanalkrümmung 90 5.3.1 Wurzelkanalmodell mit 3 mm Kanalkrümmungsradius 90 5.3.2 Wurzelkanalmodell mit 6 mm Kanalkrümmungsradius 92 5.3.3 Wurzelkanalmodell ohne Kanalkrümmung 94 5.4 Massenänderung 96 5.5 Längenänderung der Ansätze 96 5.6 Rasterelektronenmikroskopische Auswertung 97 6 Diskussion 103 6.1 Material und Methoden 103 6.1.1 Wurzelkanalmodell 103 6.1.2 Messmethoden 106 6.2 Ergebnisse 109 6.2.1 Dentinabtrag 109 6.2.2 REM-Aufnahmen 113 6.3 Klinische Konsequenzen 115 7 Schlussfolgerungen 119 8 Zusammenfassung 121 9 Summary 122 Abbildungsverzeichnis 123 Tabellenverzeichnis 137 Literaturverzeichnis 139 Lebenslauf 157 Danksagung 159

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