Dissertations
Sebastian Flock
Simulation of Active Aerodynamic Flaps to Reduce Rotor Load on a Wind Turbine
ISBN: 978-3-95886-176-3
Jörg Karl Berroth
The Influence of Rotor Blade Pitch Dynamics on Loads in Wind Turbine Blade Adjustment Systems
The rapid development of WT, short for wind turbines, toward ever-larger rotor diameters also leads to increasing requirements on their BAS, short fot blade adjustment systems. Load-reducing regulation concepts are also being developed and are intended to dampen the load dynamics directly on the rotor blade. These concepts are mostly based on additional blade adjustment, thus also resulting in increased demands on the wind turbine's BAS.
The main objective of this dissertation was to investigate influences on the dynamic loads in blade adjustment systems and attain reliable load assumptions to realize highly dynamic blade pitch adjustment for active load reduction. BAS modeling methodologies were therefore extended using MBS, short for multi-body simulation to enable component-level analysis of the dynamic loads in regulated turbine operation under different control strategies within a total system approach.
Core of the implemented extensions is integration of the BAS as rotating subsystem within the overall WT system model, which includes aerodynamic, mechanical, electrical and control-related system elements. This approach enables the coupled analysis of mechanical subsystems under the additional influence of potentially reactive overall system dynamics, as well as the internal system dynamics within the blade adjustment drives.
The modeling methodologies presented here have been validated based on field measurement data for a reference wind turbine in the 2 MW class and finally used to discuss the increased demands on the BAS by applying an additional load-reducing individual blade pitch control, IPC for short.
ISBN 978-3-95886-176-3
Andreas Paulus:
Tribolayer Formation on Lead-Free Bronze and Brass Materials in the Contact between Cylinder and Valve Plate in an Axial Piston Pump
The purpose of this work is to replace the lead-containing alloy by lead-free alloys in thecontact between the cylinder and the valve plate of an axial piston pump. This has to beachived without loss in performance or service life of the axial piston pump. In order toachieve this goal, the wear-reducing effect of the lead content in the surface region of thematerial has to be substituted. One possibility for this is the targeted generation of functionalsurface layers ,so-called boundary layers, which are caused by a tribological load, incombination with lubricants. Those layers can reduce both friction and wear in gears androlling bearings.Within the scope of this study, experiments have shown that boundary layers are alsogenerated in lubricated sliding contacts on bronze and brass materials and can reduce frictionand wear. A methodology has been developed with the aid of which it is possible to examinecertain tribological systems with regard to the formation and effect of boundary layers. Thismethodology has been successfully applied to replace the lead-containing bronze in thecontact between the cylinder and the valve plate in an axial piston pump by a lead-free bronzeor brass material.After the analysis of the tribological system and the definition of suitable replacementsystems, five lead-free bronze and brass materials as well as two additivated lubricants wereinvestigated. In addition to experimental model and component tests, the boundary layerswere analyzed systematically in microanalytical investigations.The lead-free alloy CuSn12Ni2 was qualified in the tests as a possible alternative to the leadcontainingseries alloy. The positive properties of the CuSn12Ni2 alloy are based, inter alia,on the formation of a stable boundary layer in operation, which can be investigated andcontrolled using the methodology presented here.
Kevin Helmut Schmitz:
Establishing Modular Product Architectures Based on Corporate Knowledge
Increasing globalization enables companies to enter new markets. A concomitant intensification of the competitive situation motivates many companies to introduce new product variants to the market. This sometimes results in a huge increase in product and process complexity, which often outweighs the positive aspects of enhanced customer orientation. To compete successfully in the market on a persistent basis, it is important to offer market-oriented product variants representing only those functional features for which the customer is also willing to pay. It is expedient to discover what variants of a product the market is demanding to assure appropriate external diversity with the lowest possible internal corporate diversity.
This current dissertation demonstrates that the knowledge necessary for this is implicitly available in the bills of materials for past orders and that it can be exploited for product development using suitable analytical methods. The novel data mining approach of correlation-based modularization, CoMod for short, identifies computer-based dependencies between features and collates these into variant-optimized modules using a clustering algorithm. The modular product architecture thus generated realizes high market coverage with a small number of module variants. Targeted, metrics-based optimization also ensures the practical feasibility of products structured using CoMod. The relevance and hence the development priority for module variants is moreover quantified, thereby enabling increased development efficiency.
The CoMod methodology was developed and optimized in the context of several industrial projects.
ISBN: 978-3-8440-5395-1
Matthias Wegerhoff
Methodology for the numerical NVH analysis of an electrified passenger vehicle drive train
The interior acoustics is important for customer acceptance or as a criterion for purchasing a passenger car. This applies to conventionally driven passenger cars as well as to electrified vehicles. Today's customer has demands on acoustics, based on the results of a longtime research history on the internal combustion engine. For the electric drives, this history is still relatively young, correspondingly there are still methodologies missing for the virtual identification of possibly inadequately fulfilled acoustic product requirements.
This work presents a methodology for simulating high-frequency structure-borne noise events over a wide operating range of a vehicle with a purely electrically driven drive train. The methodology for simulating and analyzing the acoustic behavior of the drive train is made up of numerous methods for mapping and validating the components involved. Therefore, the work is also a guide for the transparent validation of a model formation in the high frequency range =5000Hz. Accordingly, the Iimits of the model, as a result of the methodology, are pointed out and further research needs are derived. Finally the most dominant resonance m the drive train is analyzed and the drive train is acoustically optimized.
ISBN 978-3-95886-167-1
Felix Johannes van der Beek
Configuration-based Modularization of Multi-variant Capital Goods
Ever-increasing customer requirements for individual, especially configurable products and technical solutions are resulting in increased external diversity on the part of the manufacturer. The challenge here is to map this external diversity to an internal diversity as efficiently as possible, yet in a manner that is economically acceptable. The wide variety of required product assemblies and components results in product complexity that extends over the entire product life cycle.
Modularization whilst applying the principle of independence provides a promising way to withstand this product complexity. The core concepts of modularization are the complete structuring of a product and simultaneous establishment of standards. These standards permit a module definition that divides the product into separate units. The choice of module interfaces and their functional and physical definition are therefore crucial. These interfaces are binding and constructively determine the product structure. All future modules must be compatible with these interfaces. Product components can thus be developed and produced simultaneously, which here means time-efficiently.
The degree of modularization is strongly context-bound, product-specific, and company-specific. Its optimum can only be found via a systematic approach. Computer-aided validation of newly developed product architectures can make a significant contribution to this.
Against this background, a novel concept for modularization was developed in this dissertation based on the structure of bills of material for realized orders. The complex definition of a modular product architecture is supported and thus objectified by the statistical analysis of large data sets. The module definitions will be validated and the number and relevance of module variants can be assessed before commencing the design of new products.
ISBN 978-3-8440-5198-8
Stephanie Dallmeier:
Sensitivity Analysis of the Preload Loss in Single-shear Screw Connections for Carbon Fiber Reinforced Plastics
The screw connection currently represents the most widely used combination of highly loaded, thick-walled CFK laminates. Although this is widely used, it is not yet adequately possible to depict its mechanical behavior via models. One of the open questions relates to design of the connection partner, with the aim of minimizing preload loss. That is where this dissertation starts. The objective of this dissertation is to identify the essential parameters that can be influenced by the designer to achieve targeted reduction of preload loss. This dissertation's methodology comprises the combination of two methods, namely the application of both numerical models using the finite element method and sensitivity analysis. Sensitivity analysis is to be understood here as the generic term for methods of statistical planning and evaluation of computer experiments. Numerical models are used because experimental investigation of the issues is so complex that it is only feasible at high cost. The results will lead to initial constructive recommendations facilitating a screw connection with low preload loss.
ISBN 978-3-8440-4467-6
Tim Kamper:
Validated modeling method for the calculation of structure-borne noise of gearboxes in wind turbines
The increasing number of wind energy turbines, WET for short, Ieads to additional plants being built closer to residential areas. Thus the acoustic emission of WET becomes an especially importance issue. Tonal noise; which is excited by the gearbox and transferred to the surrounding structure as structure borne noise, is especially annoying to affected residents when it is emitted by planar structures.
This thesis focuses on the development and validation of a method, which can be used to determine structure borne noise emitted by a WET gearbox in actual operation on the WET based on measurements on the test rig. As a first step measurement campaigns on a test rig and on a WET are analyzed. Based on this, the state of the art possibilities of Multi Body Simulation are extended in order to evaluate the excitation of structure borne noise of one gearbox ahead of commissioning in different types of WET. This enables the early determination and evaluation of corrective measures in case of acoustic anomalies. The developed method is validated by means of measurements on a WET and on a test rig. Additionally, the improvement of results compared to the state of the art of MBS modeling is shown.
ISBN 978-3-95886-130-5
Daniel Schrömbgens:
Lifetime of grease lubricated roller bearings with a standstill period under humid conditions
High temperatures will occur during operation of roller bearings. These temperatures will help to avoid damage, affected by water inlet. But, if there are many standstill periods, humidity could condense at the bearing, so water inlet could damage the contact surfaces. Failures with corrosion can be found in some applications. The failure mode suggests damage by stress corrosion cracking. Tests at the present study could create corrosive pre-damages with an enormous reduction of lifetime. But none of the tests could create stress corrosion cracking at roller bearings. Contrariwise all damages whether with or without a radial load show the same failure mode. A radial load at the present tests will create the needed stresses for stress corrosion cracking. Else stress corrosion cracking is impossible. Summarized it seems unlikely, that stress corrosion cracking may occur in roller bearings. Extensive corrosion could pre-damage the surface, which will lead to premature failure.
ISBN: 978-3-95886-093-3
Christian Bongardt:
Micro Pitting on Roller Bearings
Roller bearings are machine elements whose task is to transfer forces between parts rotated against each other. The service life of roller bearings can be designated according to DIN ISO 281, or according to DIN 26281. There are however forms of damage that are not covered by the standardized calculation procedures. Micro pitting on roller bearings is one of these. Micro pitting involves fatigue damage to the surface, which results in failure of the roller bearing. There are not currently any findings in the field of roller bearing technology, under which operating conditions this damage form occurs, meaning that only an inadequate design of roller bearings is possible. The present dissertation will therefore use the test bed to determine the critical operating conditions for micro pitting on roller bearings. There will be a targeted investigation of the impacts made with respect to damage symptoms by the specific lubricating gap height, operating temperature, contact pressure, and lubricant. Both the mechanical contact conditions and the chemical interaction between lubricant and contact surface will be evaluated. A test procedure based on the test results will be proposed, whereby the risk posed by lubricants towards micro pitting on roller bearings can be determined on the FE-8 test bed.
ISBN 978-3-95886-089-6
Jan Neis:
Analysis of Product Portfolio Complexity When Using Data Mining Procedures
The challenge to companies for survival in modern markets no longer lies merely in determining advantageous production locations. Much more important nowadays is the question of how inherent company know-how can be secured and expanded to respond flexibly to the needs of the market with ever new variations whilst preserving the know-how advantage compared to low-wage countries. Companies are often not aware of just how much explicit and tacit knowledge is tucked away in their data. Numerous stored documents on the wide variety of products contain the entire corporate knowledge about the configuration, function, and technical structure of the products and their variants. This knowledge should be externalized for product related optimization procedures. The approach developed in this dissertation provides efficient methods for each working sequence in an optimization process for targeted data evaluation, with the result that an informed decision can be made about the progress of the procedure.
ISBN 978-3-8440-4120-0
Benedikt Günther:
Functional Expansion of Capital Goods in the Retrofit Market
Capital goods are purchased to operate them over a long period of time and use them to generate a turnover. This requires a one-off high investment during purchase, which only pays off if the capital goods are able and permitted to provide a monetary return over the planned period. Yet requirements, applications, and laws can change within the period of use, which severely restricts the period of use if the capital goods no longer satisfy them. This dissertation proposes a methodology for functional expansion of capital goods in the retrofit market. This is based on an analysis–synthesis loop and considers that the focus is always on two systems in the development of a retrofit component – the existing product and retrofit component to be developed.
ISBN 978-3-8440-3677-0
Laiye Bi:
Dynamic simulation of full-scale wind turbine nacelle system test benches
A virtual replica of a system test bench for full-scale wind turbine nacelle is built up in the framework of this dissertation. The primary objective of the Simulation study is to reveal the overall dynamics of the test bench and expose the difference between test bench dynamics and wind turbine field dynamics. The secondary objective is to make proper use of the developed models and design active control schemes for test bench operation. The virtual test bench is formulated in a multi-body simulation environment, with flexible drive train dynamics validated with experimental modal testing. The model also integrates the operation control and DUT control, having a similar hardware-in-the-loop architecture as the physical test bench. The data exchange between multi-body model and controllers is realized through Co-simulation interface. Test scenarios with aeroelastic wind Ioad calculation can be simulated. By comparing the interface force/torque response with the reference turbine model, it is found that the open-loop behavior of the tested nacelle explicitly differs from field operation. The changed boundary conditions of the tested nacelle are the root cause of the difference since the inertia and stiffness of the Ioad application system largely differ from the original rotor system of the turbine. It is also found that the rheonomic joint is the reason why coupled rotor-drive train dynamics are lost when using the wind Ioad software simulator. The difference of open-loop behavior is compensable via active control. A virtual rotor system can be artificially created to excited realistic Ioad response inside the DUT as in field operation. However, the existing multi-body model has hundreds of states and thus computationally expensive. Therefore, low-order plant models in form of transfer elements were derived from the multi-body model by truncating high-order modes at designed operation points. The low-order models are feasible to represent the dominant dynamics of the test bench while maintaining the accuracy. This model-based approach enables convenient design and tuning of control frameworks. Control schemes corresponding to torque and non-torque Ioad control are proposed respectively and then put together. Resonances inside the tested nacelle can then be effectively excited as observed in the simulated turbine field operation. The Ioad application bandwidth is however limited by the dominant dynamics of the test bench.
ISBN 978-3-95886-072-8
Marco Ramm:
Systematic Development and Analysis of a Continuously Variable Transmission With Internal Power Distribution for Mobile Machines
Steadily rising operating costs and requirements for convenience require an optimization of existing drive strategy concepts for mobile work machines. These are used as building material machines, agricultural and forestry machines, and municipal and special vehicles. The highest efficiency is demanded of the machines in these sectors in relation to energy and time, which can only be achieved by a drive technology optimized for the respective range of applications. In contrast to most passenger and commercial vehicles, mobile work machines require a distinction between the propulsion and work drive, whereby the focus in this work is on the propulsion drive.
ISBN 978-3-95886-045-2
Hermann van Lier:
Risk of Renewed Tempering of Radial Cylindrical Roller Bearings due to Load Impact in Operating Points With Cage Slip
Bearings should transmit forces between components moving relative to each other as far as possible without wear and friction. Mechanical and plant engineering uses different active principles to do this. One machine element often used here is the roller bearing. In principle, these consist of an inner and an outer ring, between which the rolling elements are arranged. The rolling action of the rolling elements enables a low-friction rotary motion between the inner and outer ring with simultaneous transmission of forces.
ISBN 978-3-95886-052-0
Felix Straßburger:
Hydraulic-mechanical Hybrid Drive for Counterbalanced Trucks
The two possible molecules are called enantiomers which, apart from the direction of rotation of linear polarized light, admittedly exhibit the same physical characteristics, but often provoke different physiological reactions within the organism. This is due to the high substrate specificity of biological target molecules and their extraordinary selectivity in relation to stereochemistry. Natural and active ingredients often have one or several stereo centers and are therefore in most cases chiral. Such molecules differ in their visual and mirror-image design and are therefore not identical. One sufficient condition for chirality is the absence of a rotating mirror axis Sn.
Falscher Text. Bitte das Original-Abstract hier verwenden
ISBN 978-3-95886-030-8
Savas Kurutas:
Prediction and Optimization of Transmission Vibrations at the Interface to the Foundation
Noise in this day and age is considered as a huge burden to mankind and the environment. Requirements for the acoustic behavior of transmissions result both from statutory regulations regarding noise emissions, environmental and occupational health and safety, and from the industrial demands for comfort. The structure-borne noise emission of a transmission in industrial application therefore represents an attribute for assessment of noise behavior and can therefore also inter alia be regarded as a purchase criterion over competitive products. The transmission of vibrations in the form of structure-borne noise represents a specific problem in many cases. The rigid coupling of components to the machine frame, in part caused by design requirements, can direct vibrations with low attenuation over long distances and generate undesirable emission. Consideration of structure-borne noise is therefore indispensable for effective noise reduction. Various types of vibration sources with different characteristics can be identified in a drivetrain. Narrowband excitations proportional to rotation speed are typical in the case of internal combustion engines, for example. The periodically changing network frequency in the case of induction motors induces excitations with a largely constant frequency. Gear drives should be mentioned as a further important source of vibration. Variable sprocket stiffness over the travel path results in a parameter-evoked oscillation, which induces narrowband excitations within the system. The transmission manufacturer can contractually warrant compliance with the acoustic emission limits upon sale to the customer, which can therefore also be regarded as a purchase criterion. Compliance with these limits often requires the ability to predict the structure-borne noise, even in the early design phase for a new transmission. The sector for small series and individual production of transmissions has no possibility of determining measurement results for each prototype, which would support a prediction in the early stages of a project. The reason is that until now the corresponding transmission type was not yet produced in the specific version. Incorrect assessments can however result in substantial additional costs due to time-consuming rework for noise reduction on the engineered transmission.
ISBN: 978-3-95886-037-7
Judith Pollmanns:
A Construction Process Information Model for Estimation of Development Costs
This dissertation presents a method that allows estimation of the expected development costs in light of defined criteria, even at a very early stage of development. An information model is introduced that portrays the construction process from the request list to the created drawing based on the processed information.
ISBN 978-3-8440-3055-6
Thomas Hohnen:
Metric-based Optimization of Product Modularity to Reduce Product Costs
Product modularization is still very popular in everyday corporate practice. This dissertation will derive metrics to provide holistic quantification of product modularity. A method will also be presented with which the modularity of a product can be systematically evaluated. In addition to the metrics, the cost relationships of the modularity will be qualitatively represented based on pronounced literary research.
ISBN 978-3-8440-3055-6
Christoph Alexander Warkotsch:
Local Tension Fields in Sandwich Elements With a Discontinuous Core Layer
This dissertation investigates the issue of a discontinuous core layer in the form of a gap in the core of a sandwich element. There is a comprehensive phenomenological description of the local tension fields that can be caused by a gap in sandwich core. Among potential influencing factors, moreover, those that have made a decisive contribution to the emergence of local tension fields are identified.
ISBN 978-3-8440-2386-2
Sebastian Schubert:
Methodology for Planning Diversely Optimized Product Families
The methodology presented here for planning diversely optimized product families targets optimization of product family planning and presentation of results in the form of product structures. This methodology means that product families can be planned such that the required external diversity can be realized based on minimal internal diversity. Internal costs are thus minimized creating the basis to offer the products at mass market prices.
ISBN 978-3-8440-3055-6
Manuel Löwer:
PDM-based Innovation Planning Within Integrated Product Lifecycle Management
Considering the special limiting conditions as found in SMEs, this dissertation presents a concept that firstly depicts the strategic and as yet insufficiently covered system innovation aspect, and then the operational support from existing PDM systems throughout the entire process.
ISBN 978-3-8440-1351-1
Frank Dehen:
Bayesian Networks for Cost Forecasting in the Early Phase of Product Development
The method developed enables assessment of the manufacturing costs for products with a high degree of novelty at a very early stage of development. It closes the gap in the calculation procedure that presupposes known functions and solution principles for estimating the costs. A methodical and systematic approach to cost forecasting using Bayesian networks will therefore be developed and illustrated by means of a detailed example.
ISBN 978-3-8440-1086-2
Martin Josef Benders:
Methodology for the Combined Synthesis of Material, Manufacturing Process, and Geometry
This dissertation will develop a systematic approach to the combined synthesis of material, manufacturing process, and geometry in line with VDI Guideline 2223. This initially requires explanation of the dependencies to be considered between material, manufacturing process, and geometry as well as existing approaches. A methodology will then be presented based on these results before various supporting methods and tools are finally outlined.
ISBN 978-3-8440-0427-4