Modeling and rendering for development of a virtual bone surgery system

A virtual bone surgery system is developed to provide the potential of a realistic, safe, and controllable environment for surgical education. It can be used for training in orthopedic surgery, as well as for planning and rehearsal of bone surgery procedures...Using the developed system, the user can perform virtual bone surgery by simultaneously seeing bone material removal through a graphic display device, feeling the force via a haptic deice, and hearing the sound of tool-bone interaction --Abstract, page iii

Machine learning and interactive real-time simulation for training on relevant total hip replacement skills.

Virtual Reality simulators have proven to be an excellent tool in the medical sector to help trainees mastering surgical abilities by providing them with unlimited training opportunities. Total Hip Replacement (THR) is a procedure that can benefit significantly from VR/AR training, given its non-reversible nature. From all the different steps required while performing a THR, doctors agree that a correct fitting of the acetabular component of the implant has the highest relevance to ensure successful outcomes. Acetabular reaming is the step during which the acetabulum is resurfaced and prepared to receive the acetabular implant. The success of this step is directly related to the success of fitting the acetabular component. Therefore, this thesis will focus on developing digital tools that can be used to assist the training of acetabular reaming. Devices such as navigation systems and robotic arms have proven to improve the final accuracy of the procedure. However, surgeons must learn to adapt their instrument movements to be recognised by infrared cameras. When surgeons are initially introduced to these systems, surgical times can be extended up to 20 minutes, maximising surgical risks. Training opportunities are sparse, given the high investment required to purchase these devices. As a cheaper alternative, we developed an Augmented Reality (AR) alternative for training on the calibration of imageless navigation systems (INS). At the time, there were no alternative simulators that using head-mounted displays to train users into the steps to calibrate such systems. Our simulator replicates the presence of an infrared camera and its interaction with the reflecting markers located on the surgical tools. A group of 6 hip surgeons were invited to test the simulator. All of them expressed their satisfaction with the ease of use and attractiveness of the simulator as well as the similarity of interaction with the real procedure. The study confirmed that our simulator represents a cheaper and faster option to train multiple surgeons simultaneously in the use of Imageless Navigation Systems (INS) than learning exclusively on the surgical theatre. Current reviews on simulators for orthopaedic surgical procedures lack objective metrics of assessment given a standard set of design requirements. Instead, most of them rely exclusively on the level of interaction and functionality provided. We propose a comparative assessment rubric based on three different evaluation criteria. Namely immersion, interaction fidelity, and applied learning theories. After our assessment, we found that none of the simulators available for THR provides an accurate interactive representation of resurfacing procedures such as acetabular reaming based on force inputs exerted by the user. This feature is indispensable for an orthopaedics simulator, given that hand-eye coordination skills are essential skills to be trained before performing non-reversible bone removal on real patients. Based on the findings of our comparative assessment, we decided to develop a model to simulate the physically-based deformation expected during traditional acetabular reaming, given the user’s interaction with a volumetric mesh. Current interactive deformation methods on high-resolution meshes are based on geometrical collision detection and do not consider the contribution of the materials’ physical properties. By ignoring the effect of the material mechanics and the force exerted by the user, they become inadequate for training on hand- eye coordination skills transferable to the surgical theatre. Volumetric meshes are preferred in surgical simulation to geometric ones, given that they are able to represent the internal evolution of deformable solids resulting from cutting and shearing operations. Existing numerical methods for representing linear and corotational FEM cuts can only maintain interactive framerates at a low resolution of the mesh. Therefore, we decided to train a machine-learning model to learn the continuum mechanic laws relevant to acetabular reaming and predict deformations at interactive framerates. To the best of our knowledge, no research has been done previously on training a machine learning model on non-elastic FEM data to achieve results at interactive framerates. As training data, we used the results from XFEM simulations precomputed over 5000 frames for plastic deformations on tetrahedral meshes with 20406 elements each. We selected XFEM simulation as the physically-based deformation ground-truth given its accuracy and fast convergence to represent cuts, discontinuities and large strain rates. Our machine learning-based interactive model was trained following the Graph Neural Networks (GNN) blocks. GNNs were selected to learn on tetrahedral meshes as other supervised-learning architectures like the Multilayer perceptron (MLP), and Convolutional neural networks (CNN) are unable to learn the relationships between entities with an arbitrary number of neighbours. The learned simulator identifies the elements to be removed on each frame and describes the accumulated stress evolution in the whole machined piece. Using data generated from the results of XFEM allowed us to embed the effects of non-linearities in our interactive simulations without extra processing time. The trained model executed the prediction task using our tetrahedral mesh and unseen reamer orientations faster per frame than the time required to generate the training FEM dataset. Given an unseen orientation of the reamer, the trained GN model updates the value of accumulated stress on each of the 20406 tetrahedral elements that constitute our mesh during the prediction task. Once this value is updated, the tetrahedrons to be removed from the mesh are identified using a threshold condition. After using each single-frame output as input for the following prediction repeatedly for up to 60 iterations, our model can maintain an accuracy of up to 90.8% in identifying the status of each element given their value of accumulated stress. Finally, we demonstrate how the developed estimator can be easily connected to any game engine and included in developing a fully functional hip arthroplasty simulator

Mathematical Modelling of the Drilling Process for Real-time Applications in Drilling Simulation, Interpretation and Assistance

For the last thirty years, mathematical modelling has been used to develop software solutions that support drilling engineering activities at the planning stage of drilling operations. But it is only for the last decade that mathematical models have been used for the real-time support of drilling operations. Moving from a pure engineering perspective to having models that can respect real-time requirements, necessitates many improvements of the subjacent mathematical modelling of the drilling process. First, it is not anymore possible to ignore transient behaviors that were somewhat irrelevant at the planning stage. Second, there is a need for solutions that should be fast enough to cope with the real-time constraints of the drilling process. With the perspective of creating applications that can support the drilling process in real-time, the following mathematical models have been developed: • Drilling fluid behavior. The properties of drilling fluids depend on their composition and pressure-temperature conditions. For instance, the pressure-temperature dependence of the mass density of drilling fluids, depends on the individual PVT-properties (Pressure-Volume-Temperature) of each of the components and their relative volume fractions. Therefore, the addition of drill-cuttings in the drilling fluid also changes the drilling fluid PVT-behavior. Furthermore, the rheological behavior of drilling fluids depends also on its composition. We have found that the rheological behavior of a KCl/polymer water-based mud is simultaneously modified by the relative proportion of barite and sand. Furthermore, it is known that drilling fluids are thixotropic. Yet, we found that the thixotropic behavior of drilling fluids is different from the one of other thixotropic fluids and we have determined that one of the causes for the discrepancy is related to the presence of solids in the fluid mix. We have developed a method to estimate the rheological behavior and its associated uncertainty, as a function of the modification of the solid proportions. • Drill-string mechanical sub-models coupled with hydraulic effects. Hydraulic pressure has also an impact on drill-string mechanical forces not only because the fluid mass density modifies buoyancy but more generally because viscous pressure gradients generate net forces along the drill-string. These hydraulic related forces are superposed to those engendered by mechanical friction and elastic deformation. • Steady state and transient drill-string mechanical models. Steady state torque and drag models utilizing the above-mentioned drill-string mechanical sub-models can be used to assess some characteristics of the drilling process when constant velocities are prevalent. But, during a drilling operation, there are many moments during which the drill-string displacement is in transient mode. Therefore, it is also important to have access to transient torque and drag models with a fast response time. • Transient cuttings transport model. The transport of cuttings is obviously influenced by hydraulic circulation but also drill-string rotational speed, at least in the deviated parts of a well. On the other hand, the presence of drill-cuttings in suspension or settling on the low-side of the borehole, influences pressure losses and mechanical forces along the drill-string. Therefore, the estimation of the transient displacement of drill-cuttings plays an important role in the overall estimation of the actual drilling conditions during a drilling operation. However, a transient cuttings transport model shall also be sufficiently fast, especially when it is used in real-time applications. Equipped with such models of the drilling process that are compatible with real-time constraints, then it is possible to solve problems that are relevant for the assistance of drilling operations. A first domain of application is related to the estimation, in real-time, of surface and downhole sensor values as a function of external commands like the block position and speed, the top-drive rotational velocity and the pump rates. We will refer to this domain of application as “drilling simulation”. However, comparison of measured values with simulated ones, require the proper modelling of the sensors and the impact of their actual position on the readings. For instance, drilling fluid is retained in the flowline and mud treatment equipment. Therefore, to simulate pit volumes, it is important to model the retention mechanism. Transient hydraulic, mechanical and heat transfer models, associated with precise modelling of sensor measurements, can then be used to interpret the current actual drilling conditions, because if their estimated parameters differ from the measurements, then a possible reason is that something unexpected is happening downhole. However, such drilling symptom detection method necessitates two additional conditions to be fulfilled: • The models shall be calibrated. Regardless of the quality of the drilling models, the inputs to these models are always known with a limited degree of accuracy and therefore their outputs may differ from measurements for that simple reason. However, it is important to distinguish between uncertainties that are related to properties that do not change substantially during a given drilling operation, from those that can change at any time. To avoid influencing the calibration of time invariant properties with possible side effects of the deterioration of the drilling condition, it is important to utilize drilling conditions by which undesirable side effects have no or little influence on the measurements that are used to calibrate the property. • Uncertainty of the modelled outputs shall be estimated. Calibration may reduce the uncertainty on the model outputs, but it does not eliminate it completely. It is therefore important to estimate the uncertainty of the predicted values. To achieve this, it is necessary to capture the precision by which the inputs of the process are known and to propagate that uncertainty throughout the modelling of the outputs. With continuously calibrated models and an estimation of the current downhole conditions, then it is possible to address some preliminary drilling process assistance functions: • Safety triggers. During the execution of automation functions, the situation awareness of the driller is reduced as he does not drive the drilling machines himself. Therefore, it shall not be attempted to automate any functions before a minimum set of protection functions are in place. Such safety triggers shall detect and react to incidents related to the axial and rotational movement of the drill-string and, of course, associated with pressure. Example of such safety triggers are: o Reactions to overpulls and set-down weights. o Reactions to abnormal torques. o Reactions to abnormal pressures. • Safeguards. Any drill-string or drilling fluid movements shall not generate a drilling incident. Therefore, commands to the drilling machines shall be kept within safe operational envelopes. For instance, upward movement of the drill-string shall not decrease the downhole pressure below the pore pressure or the collapse pressure of the open hole formations. Similarly, the applied flowrate combined with a possible downward movement and rotation of the drill-string shall not overpass the fracturing pressure of open hole formation rocks. • Automated procedures. Protected by safety triggers and operating within acceptable safeguards, then it is possible to automate some standard procedures. However, such automatic procedures must continuously be adapted to the current drilling conditions. For instance, the length of a friction must be modified to account for the current drill-string length and mechanical friction, or the flowrate applied during the ream-down sequence of a reciprocation procedure shall be reduced as a function of the current potential surging risk

Empirical analysis of localized casing wear with variations in contact pressure and drilling conditions

Im Wettkampf die Grenzen der Kohlenwasserstoff- und Geothermie Förderung sowie Speicherung stetig zu übertreffen und optimieren, wurden horizontale Bohrungen, tiefe Ablenkungsbohrungen und Bohrungen mit großem Neigungswinkel (ERD Bohrungen) zum heutigen Standard. Bei der Planung solcher Projekte sowie Ablenkungen, wirken sich Vorgänge wie Räumen (reaming), Bohren (drilling), Rotation off-bottom und das Ein- und Ausfahren der Bohrgestänge enorm auf die Futterrohr Beschaffenheit aus. Durch das Aufeinandertreffen und dem herrschenden Kontakt zwischen dem Bohrstrang und der Innenwand des Futterrohrs, tritt eine stärkere Abnutzung des Materials auf seitens des Futterrohrs, besonders an den Verbindungsstellen des Bohrstrangs, auf. Dies führt entweder zu einem ungleichmäßigen kreisförmigen Schwund der Futterrohr-Stärke, oder bei längerem kontinuierlichem Kontakt gegen die Innenwand des Futterrohrs, zu einer punktuellen tiefen Verschleißrille. Ein dynamischer Futterrohr-Verschleiß ist aufgrund der Vielzahl von Variablen, ein komplexes, zu simulierendes Phänomen, da die Variablen das nicht-lineare Verschleißverhalten beeinflussen. Die Verschleißintensität wird durch individuelle Kombinationen von Betriebsbelastungen (verändernde Kraft-Flächen-Verteilungen) beeinflusst. Metallurgische Eigenschaften (Werkstoffhärte und Streckgrenze) und vorherrschende tribologische Mechanismen (Oberflächenrauheit, Reibungsfaktoren und Verschleißart) kommen zum Tragen. Damit Verschleißsimulationsgleichungen möglichst genau sind, müssen die erforderlichen Reibungs- und Verschleißfaktoren experimentell durch umfangreiche Versuche bestimmt werden. Um diese Anforderung zu erfüllen, besteht der erste Schritt dieser Forschung darin, vorhandene mathematische Modelle und konventionelle Bohrlochplanungssoftwares zu analysieren. Daraus folgt die Bestimmung von Parametern, die für ein umfassendes Verschleißtestverfahren in Bezug auf variable Seitenkraft, Bohrstrangdrehzahl, axiale Bewegung und Fluidtyp, notwendig sind. Der zweite Schritt und somit der Fokus dieser Studie ist die Planung, Konstruktion und Anwendung eines vollwertigen Verschleißmodels zur Reproduktion von Reibungs- und Verschleißfaktoren unter Feldbedingungen. Die entwickelte Verschleißanlage ermöglicht Abrieb verschiedener Futterrohr-Materialien unter diversen Betriebslasten und verschieden Arten von Schmiermitteln zu simulieren. Unter Anwendung nahezu gleicher Betriebslasten, wurden die Verschleißprozesse für Stahl-, Glasfaser- und Kohlefaser-Futterrohrs untereinander verglichen. Der Umfang der Testreihe beinhaltete bislang 14 Tests unter Anwendung eines Schlammbasierenden Schmiermittels oder Wasser. Vergleiche zwischen den erbrachten Ergebnissen, in Bezug auf Reibungs- und Verschleißfaktoren, zeigen eine starke Ähnlichkeit und stehen somit im Einklang mit früheren experimentellen Studien. Nachdem der höchste Verschleißfaktor binnen kurzer Testdauer erreicht wurde, ist zu beobachten, dass dieser nach einer Verringerung des Druckkontaktes drastisch und stetig sinkt. Dieses Phänomen ist bei allen getesteten Materialien unter bestimmten Betriebslasten und Bohrszenarien zu verzeichnen und kann als einen genaueren Richtwert für Feld Ereignisse genutzt werden. Des Weiteren können mithilfe der gemessenen Werte des Reibungsfaktors, die Spanne der Belastungsdruckgrenze (Contact Pressure Threshold) an den Futterrohren genauer bestimmt werden. Eine Verschleißvolumengleichung, basierend auf den experimentellen Ergebnissen, wird als Teil der Testergebnisse präsentiert. Anhand der ermittelten Werte sowie Trends der Versuchsergebnisse, können Vorhersagen, bezüglich des Verschleißes, getroffen werden. Indem weiterer Stahlsorten, Durchmesser und neue Futterrohr-Materialien in den experimentellen Umfang einbezogen werden, kann die Anlage unter praxisnahen Bedingungen Verschleißverhalten darstellen. Hersteller für Futterrohre und Verbindungen profitieren von diesen Simulationen, um genauere Werte bei ihrer Herstellungsweise integrieren zu können. Durch die Anlage simulierten Feld Bedingungen, können die Werte der Belastungsdruckgrenzen (Contact Pressure Threshold) und Verschleißfaktoren erlangt werden. Diese Werte werden benötigt, um eine empirische Daten Gliederung zu erstellen, welche daraufhin in eine Software integriert werden. Dies vermag den Futterrohr-Verschleiß im Voraus abzuwägen und zu reduzieren, aber ermöglicht gleichzeitig die Flexibilität bei Betriebslasten beizubehalten.In the race to push the limits of hydrocarbon and geothermal production (and storage), deep inclined, horizontal, and ERD wells have become the drilling norm. In building such well trajectories, processes such as drilling, reaming, rotation off-bottom and tripping always affect casing wall thickness due to its interaction with the drillstring (particularly at the tool joints) under high contact forces. This results in either an uneven circumferential thickness reduction or, in case of long continuous contact of a tense drillstring pressed against the casing inner wall, a localized deep wear-groove. Localized dynamic casing wear is a complex phenomenon to simulate due to the number of control variables influencing the non-linear wear behavior. Wear intensity is influenced by individual combinations of service loads (changing force-area distributions), metallurgical properties (material hardness and yield strength) and prevailing tribological mechanisms (surface roughness, friction factors and wear type). For wear simulation models to be accurate, the required friction- and wear factors must be experimentally determined by full-scale tests. To fulfill this requisite, the first step of this research is to analyze existing mathematical models and conventional well planning software to establish parameters for a full-scale wear test method in terms of variable side force, drillstring RPM, axial reciprocation, and fluid type. The design, construction, and application of a full-scale wear frame to reproduce friction- and wear factors under field conditions is the second step, and the core focus of this study. The wear frame is designed to incorporate different casing materials under a range of operational loads and lubrication conditions, and wear scenarios under similar service loads have been compared for steel, fibered glass and fibered carbon casings. A total of 14 wear tests have been carried out in the study time-frame for the casing materials under water and mud lubrication conditions. A comparison of test results shows good consistency and agreement with previous experimental studies in terms of friction and wear factors. After the initial peak values, the wear factor is observed to decline drastically to a steady-drop range upon contact pressure reduction. For all tested materials, this steady range of values can provide a good estimate of field wear volume over time under particular service loads and drilling scenarios. Also, the measured steady values of friction factors help determine close ranges on contact pressure threshold for the casings. A proposed wear volume equation based on the experimental results is presented as a part of test results. It has been observed from the detected trends in the test results that repeated wear tests can make casing wear predictable. With the inclusion of more steel grades, diameters and new casing materials into the experimental scope, the wear frame can be used to develop a comprehensive record of wear performance under different field scenarios for casing and tool joint manufacturing industry. Attribution of wear factors and contact pressure thresholds to specific field conditions via a wear test database, and its integration into a software solution, can fill gaps to help reduce casing wear while retaining flexibility on operational loads

Implementation of hierarchical design for manufacture rules in manufacturing processes

In order to shorten the product development cycle time, minimise overall cost and smooth transition into production, early consideration of manufacturing processes is important. Design for Manufacture (DFM) is the practice of designing products with manufacturing issues using an intelligent system, which translates 3D solid models into manufacturable features. Many existing and potential applications, particularly in the field of manufacturing, require various aspects of features technology. In all engineering fields geometric modelling wluch accurately represents the shape of a whole engineering component has become accepted for a wide range of applications. To apply DFM rules or guidelines in manufacturing processes, they have to be systematised and organised into a hierarchical rule system. Rules at the higher level of the hierarchical system are applied to more generic manufacturing features, and specific rules are applied to more detailed features. This enables the number of rules and amount of repetition to be minimsed. Violation of the design for manufacture rules in the features, their characteristics and manufacturing capabilities are further examined in this hierarchical system. Manufacturabillty analysis, such as production type, materials, tolerances, surface finish, feature characteristics and accessibility, are also taken into consideration. Consideration of process capabilities and limitations during the design process is necessary in order to minimise production time and as a result, rnanufactunng cost. The correct selection of manufacturing processes is also important as it is related to the overal cost. As a result of this research, a hierarchical design for manufacture rule system is proposed which would aid designers in avoiding designs that would lead to costly manufacturing processes

Multi-angle valve seat machining: experimental analysis and numerical modelling

Modern automotive manufacturers operate in highly competitive markets, heavily influenced by Government regulation and ever more environmentally conscious consumers. Modern high-temperature, high-pressure engines that use high hardness multi-angle valve seats are an attractive environmental option, but one that manufacturers find requires more advanced materials and tighter geometric tolerances to maintain engine performance.Tool manufacturers meet these increasingly tougher demands by using, higher hardness cutting materials such as polycrystalline cubic boron nitride (pcBN), that on paper, promise to wear at a lower rate, require less coolant and deliver tighter tolerances than their carbide counterparts.The low brittle fracture toughness of pcBN makes tools that use it vulnerable to minute chipping. A review of literature for this work pointed to no clear answer to this problem, although suggestions range from manufacturing defects, dynamic and flexibility problems with the production line machinery and fixtures, and radial imbalances in the cutting loads.This work set about experimentally investigating those potential explanations, coming to the conclusion that the high radial imbalance of the cutting loads is responsible for pcBN cutting insert failure during multi-angle valve seat machining, and that by simply relocating the cutting inserts around the multi angle cutting tool, the imbalance can be reduced, thus extending the life of the cutting inserts.It is not always easy to predict the imbalance due to the multiple flexibilities in the system, and simulating such a system in 3D with all its associated cutting phenomena such as friction, thermal expansion, chip flow and shearing, would call upon extraordinary computational power and extremely precise experimental inputs to reduce cumulative error.This thesis proves that such a 3D simulation can be made, that runs in exceptionally short durations compared to traditional methods, by making a number of simplifications.MSC Marc was used to host the simulation, with a parametric script written in Python responsible for generating the model geometry and cutter layout. A Fortran program was developed that is called upon by Marc to calculate the required cutting load outputs and generate new workpiece meshes as material is removed.</div

Ultra-Deepwater Production Systems

The report herein is a summary of the work performed on three projects to demonstrate hydrocarbon drilling and production methods applicable to deep and ultra deepwater field developments in the Gulf of Mexico and other like applications around the world. This work advances technology that could lead to more economic development and exploitation of reserves in ultra-deep water or remote areas. The first project is Subsea Processing. Its scope includes a review of the ''state of the art'' in subsea components to enable primary production process functions such as first stage liquids and gas separation, flow boosting, chemical treatment, flow metering, etc. These components are then combined to allow for the elimination of costly surface production facilities at the well site. A number of studies were then performed on proposed field development projects to validate the economic potential of this technology. The second project involved the design and testing of a light weight production riser made of composite material. The proposed design was to meet an actual Gulf of Mexico deepwater development project. The various engineering and testing work is reviewed, including test results. The third project described in this report encompasses the development and testing of a close tolerance liner drilling system, a new technology aimed at reducing deepwater drilling costs. The design and prototype testing in a test well are described in detail

Mastering Uncertainty in Mechanical Engineering

This open access book reports on innovative methods, technologies and strategies for mastering uncertainty in technical systems. Despite the fact that current research on uncertainty is mainly focusing on uncertainty quantification and analysis, this book gives emphasis to innovative ways to master uncertainty in engineering design, production and product usage alike. It gathers authoritative contributions by more than 30 scientists reporting on years of research in the areas of engineering, applied mathematics and law, thus offering a timely, comprehensive and multidisciplinary account of theories and methods for quantifying data, model and structural uncertainty, and of fundamental strategies for mastering uncertainty. It covers key concepts such as robustness, flexibility and resilience in detail. All the described methods, technologies and strategies have been validated with the help of three technical systems, i.e. the Modular Active Spring-Damper System, the Active Air Spring and the 3D Servo Press, which have been in turn developed and tested during more than ten years of cooperative research. Overall, this book offers a timely, practice-oriented reference guide to graduate students, researchers and professionals dealing with uncertainty in the broad field of mechanical engineering