Rozprawy doktorskie na temat „CRANK ANGLE”

Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace. It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough. The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly. The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC.
Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen. Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter. Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen. Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.

This thesis report elucidates the experimental and analytical methods of determining the axial thrust loads of a twin scroll turbocharger mounted on a 6-cylinder diesel engine, tested at Scania CV AB, Sodertalje. Literature survey revealed several methods to experimentally determine the thrust loads but the concept of using strain gauges was nally selected. The key objectives of this thesis are to determine an experimental method to measure axial thrust loads, develop an analytical model to predict axial loads and to perform a root cause analysis. It was noted that axial load peaks are of immense interest here than the average values of the axial loads. The method adopted to measure axial loads consists of a weakened bearing that was capable of withstanding an estimated axial load and at the same time undergo strains that could be sensed by strain gauges. The test operating points consisted of a series of engine speeds and loads. Root cause analysis results suggested that there was a minimal drift of 0.25 N force per 10 degree rise in temperature on the bearings. Also, the main reason for the drift in strain gauge measurements was the plastic deformation of the axial bearing that experienced higher axial loads due to transient testing. A 1D model based on the Control Volume approach including both the pressure and impulse contributions predicting the thrust loads was modelled. The factored axial force measurements during most of the operating conditions were negative (forces acting from the turbine towards the compressor) with the highest value recorded as -90 N at 1400 rpm and 80 % engine load. The highest factored axial force (negative) predicted by the model during the same operating point was -100 N. The di erence between the predicted and measured max load varied between 10 % to 15% among all the operating conditions considered for correlation. It could be concluded that the experimental method established could be used to measure axial loads. Further, future work in terms of non-invasive measurements, CFD methods and usage of fast pressure sensors on compressor side to predict transient conditions would improve the current method.
Denna avhandling rapport belyser de experimentella och analytiska metoder for att bestamma de axiella tryckbelastningar av en Twin Scroll turboaggregat monterat paen 6-cylindrig dieselmotor, testas vid Scania CV AB, Sodertalje. Litteraturstudie visade era metoder for att experimentellt bestamma axialbelastningar men begreppet att anvanda tradtojningsgivare slutligen valts. De viktigaste mlen for denna avhandling ar att bestamma en experimentell metod for att mata axiella tryckbelastningar, utveckla en analytisk modell for att forutsaga axialbelastningar och utfora en orsaksanalys. Det konstaterades att de axiella belastningstoppar ar av stort intresse har an medelvardena for de axiella belastningar. Den metod som for att mata axiella belastningar bestar av en forsvagad lager som kunde motstaen uppskattad axiell belastning och samtidigt genomgar stammar som kan kannas av tojningsgivare. Testdriftpunkter bestod av en serie av motorhastigheter och belastningar. Rotfelsanalys resultat antydde att det fanns en minimal avdrift av 1N kraft per 10 graders temperaturokning palagren. Aven den framsta orsaken till drift i tradtojningsgivare matningar var plastisk deformation av det axiella lagret som haft en hogre axiella belastningar pagrund av transient provning. En 1D modell baserad pakontroll Volym tillvagagangssatt innefattande bade tryck och impuls bidrag forutsaga axialbelastningar modellerades. De vgas axiella kraftmtningar under strre delen av driftsfrhallandena var negativa (krafter som verkar fran turbinen mot kompressorn) med det hogsta vardet registreras som -90 N vid 1400 rpm och 80 % motorbelastning. Den hogsta vagas axialkraften (negativ) forutsags av modellen under samma arbetspunkt var -100 N. Skillnaden mellan forutsagelsen och matning befanns variera mellan 10 % 15 % bland alla driftfrhallanden vagas for korrelation. Det kan konstateras att den experimentella metod som faststallts kan anvandas for att mata axiella belastningar. Vidare skulle det framtida arbetet i termer av icke-invasiva matningar, CFD-modeller och anvandning av snabba trycksensorer pakompressorsidan for att forutsaga transienta forhallanden forbattra den nuvarande metoden.

The topic of thesis is estimation of the crank angle based on pulse signals from an induction sensor placed on the flywheel. The engine management system performs many calculations in the crank angle domain which means that a good accuracy is needed for this measurement. To estimate the crank angle degree the torque balance on the crankshaft based on Newtons 2nd law is used. The resulting acceleration is integrated to give engine speed and crank angle. This approach is made for two crankshaft models, the rigid crankshaft approach and the lumped mass model. The latter can capture the torsional effects of the crankshaft twisting and bending due to torques acting on it. This is then compared to a linear extrapolation of the engine speed which is the chosen method today. To validate results experiments was performed where data for 36 stationary operating points was gathered. The results indicate that using a torque based model and predicting torsion improves the accuracy of the crank angle measurement especially for higher engine speeds. The rigid crankshaft approach does not give enough improvement of the accuracy to warrant further work.
Detta examensarbete handlar om att ta fram en metod för att uppskatta vevvinkel från pulser från en induktionssensor placerad på svänghjulet. Motorns styrsystem utför många beräkningar med vevvinkeln som bas och därför krävs hög noggrannhet. Den valda metoden ärr att använda momentbalans på vevaxeln baserat på Newtons andra lag. Accelerationen som fås från denna ekvation integreras sedan för att ge motorvarv-tal och vevvinkel. Denna metod görs för två fall av vevaxel modell. En stel vevaxel och en fler-mass modell som används för att förutspå förvridningar i axeln. Detta jämförs sedan med en linjär extrapolation av hastigheten vilket är tillvägagångsättet idag. För att kunna validera modellerna samlades data in i experiment som utfördes för 36 stationära arbetspunkter. Resultaten visar på att en momentmodell som även förutspår förvridningar ger en förbättrad uppskattning av vevvinkeln. Den stela vevaxel modellen ger inte tillräckligt förbättrad prestanda för att vara värd fortsatt arbete.

The in-cylinder pressure is an important signal that gives information about the combustion process. To further improve engine performance, this information can be used as a feedback signal in a control system. Usually a pressure sensor is mounted in the cylinder to extract this information. A drawback with pressure sensors is that they are expensive and have issues with aging. This master’s thesis investigates the possibility to create a virtual sensor to estimate in-cylinder pressure based on crank angle degree sensor (CAD-sensor) data and physical models of the heavy-duty engine. Instead of using the standard mounted CAD-sensor an optical high-precision sensor measures the elapsed time between equidistant angles. Based on this signal the instantaneous angular acceleration was estimated. Together with the inertia of the crankshaft, connecting rods and pistons, an estimation of the engine torque was calculated. To be able to extract in-cylinder pressure from the estimated torque, knowledge about how the in-cylinder pressure signal propagates in the drivetrain to accelerate the flywheel needs to be known. Two engine models based on the torque balance on the crankshaft are presented. The fundamental difference between them is how the crankshaft is modeled, rigid body or spring-mass-damper system. The latter captures torsional effects of the crankshaft. Comparisons between the estimated torque from sensor data and the two engine models are presented. It is found that torsional effects of the crankshaft is present at normal engine speeds and has a significant influence on the flywheel torque. A separation of the gas torque contribution from one cylinder is done with CAD-sensor data together with the rigid body engine model. The in-cylinder pressure is then estimated by using the inverse crank-slider function and a Kalman filter estimator. The estimated pressure captures part of the compression and most of the expansion at engine speeds below 1200 RPM. Due to the crank-slider geometry the pressure signal disappears at TDC. The torsional effects perturb the estimated pressure during the gas exchange cycle. Further development must be made if this method is to be used on heavy-duty applications in the future.

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xxiv, 266 p. : ill. (some col.). Advisor: Yann G. Guezennec, Dept. of Mechanical Engineering. Includes bibliographical references (p. 259-266).

A computer-based parametric study of the effect of reinforcement architectures on fracture response of aluminum compact-tension (CT) specimens was performed using the finite element code ABAQUS. A three-dimensional crack propagation procedure based on the crack tip opening angle (CTOA) was developed using Python. Eleven different reinforcement architectures consisting of rectangular and triangular cross-section reinforcements were evaluated. Reinforced specimens produced between 13 and 28 percent higher fracture load than achieved with the non-reinforced case. Reinforcements with blunt leading edges (rectangular reinforcements) exhibited superior performance relative to the triangular reinforcements with sharp leading edges. Relative to the rectangular reinforcements, the most important architectural feature was reinforcement thickness. At failure, the reinforcements carried between 58 and 85 percent of the load applied to the specimen, suggesting that there is considerable load transfer between the base material and the reinforcement. The amount of load transfer is linked to strains experienced by the reinforcement ahead of the crack tip.
Master of Science

The work in this report, financed by the European Union through the Marie Curie Fellowship Association, was carried out at the FZ-Rossendorf. The subject of the research was to develop a method to investigate the damage, the high defect gradients at the tip of a ductile crack by means of Small Angle X-ray Scattering. The work explains the objectives and entails a brief introduction and background; it portrays and discusses the results which can be summarized as follows. Different damage parameters were investigated: the integral intensity, the total intensity on the detector, the anisotropy parameter and the fractal dimension. Of these, the anisotropy parameter is the most robust and most clearly depicts a damage region and the fractal dimension provides an idea of the structure of the scattering defect. The integral and total intensity provide comparable results only in some cases and are therefore not reliable. From supportive investigations: Scanning and Transmission Electron Microscopy (S-TEM), Finite Element Analysis and X-Ray Diffraction, it is suggested that the scatterer created after deformation is related to large oriented dislocation networks.

The work in this report, financed by the European Union through the Marie Curie Fellowship Association, was carried out at the FZ-Rossendorf. The subject of the research was to develop a method to investigate the damage, the high defect gradients at the tip of a ductile crack by means of Small Angle X-ray Scattering. The work explains the objectives and entails a brief introduction and background; it portrays and discusses the results which can be summarized as follows. Different damage parameters were investigated: the integral intensity, the total intensity on the detector, the anisotropy parameter and the fractal dimension. Of these, the anisotropy parameter is the most robust and most clearly depicts a damage region and the fractal dimension provides an idea of the structure of the scattering defect. The integral and total intensity provide comparable results only in some cases and are therefore not reliable. From supportive investigations: Scanning and Transmission Electron Microscopy (S-TEM), Finite Element Analysis and X-Ray Diffraction, it is suggested that the scatterer created after deformation is related to large oriented dislocation networks.

Master of Science
Department of Mechanical and Nuclear Engineering
Kevin Lease
Over the past several years the crack tip opening angle (CTOA) has been identified as one of the key fracture parameters to characterize low constraint stable tearing and instability in structural metallic alloys. This document presents the results of experimental stable tearing characterizations. Characterization methods include optical microscopy and marker band measurements of crack front tunneling. Specific attention is given to the measurement methods used, and also the correlation between CTOA and Delta-5. The effect of tunneling and comparisons with computational results are discussed, and the effect of material and measurement method on CTOA is observed and a clear relationship is seen. Preliminary work on future studies into internal features and behavior is also presented.

Theoretical part of this thesis presents summary of material and testing parameters which influence SCG and consequently the duration of the FNCT test. The experimental part focuses on modification of testing conditions of FNCT test in order to minimize the test time. FNCT tests were performed for four types of surfactants: Arkopal N110, Sodium dodecylbenzensulfonate (NaDBS), Disponil LDBS55 and Simulsol SL8. The most pronounced accelerating effect was observed for NaDBS surfactant, which in comparsion with commonly used Arkopal N110 doubled the test speed at the same concentration (11 %) and other test conditions. The accelerating effect of NaDBS was also observed for two different PE grades: Liten VB85 and VL 20N. Under the test conditions 80 °C and 4 MPa, 5% NaDBS water solution caused for VL 20N almost 12,5-fold acceleration compared to conventional 2% Arkopal N110 and almost 8,5-fold acceleration for VB 85. The correlation between wettability of surfactant solution and FNCT time to fracture was found.

A container crane of STS-type, Ship To Shore, consists of a spreader hanging underneath a railrunning trolly. As the container is under the influence of wind, it is likely that it starts to turn in a torsional pendulum. This report handles how the torsional pendulum of a container crane can be damped.

A number of different models have been developed to analyze how different placement of the actuators affects the system. Two differens types of controllers, LQG and MPC, have been developed and applied to these models. The different models and controlers were evaluated and compared by studying simulation results in timedomain. Moreover in order to make the simulations more realistic, a wind model has been developed and applied.

The models and controllers have been analyzed with bodediagrams and sensitivity functions.

The analyses shows clearly that the best placement of the actuators for control of the torsional pendulum on an STS-crane is in the trolly, pulling and relaxing the wires. This control is best handled by a state feedback control (LQG). Furthermore, the control should in this way, with addition of in the horizontalplane movable suspensions in the trolly, work acceptably in the whole operational area of a STS-crane.

Structural adhesives are widely used with great success, and yet occasional failures can occur, often resulting from improper bonding procedures or joint design, overload or other detrimental service situations, or in response to a variety of environmental challenges. In these situations, cracks can start within the adhesive layer or debonds can initiate near an interface. The paths taken by propagating cracks can affect the resistance to failure and the subsequent service lives of the bonded structures. The behavior of propagating cracks in adhesive joints remains of interest, including when some critical environments, complicated loading modes, or uncertainties in material/interfacial properties are involved. From a mechanics perspective, areas of current interest include understanding the growth of damage and cracks, loading rate dependency of crack propagation, and the effect of mixed mode fracture loading scenarios on crack path selection. This dissertation involves analytical, numerical, and experimental evaluations of crack propagation in several adhesive joint configurations. The main objective is an investigation of crack path selection in adhesively bonded joints, focusing on in-plane fracture behavior (mode I, mode II, and their combination) of bonded joints with uniform bonding, and those with locally weakened interfaces. When removing cured components from molds, interfacial debonds can sometimes initiate and propagate along both mold surfaces, resulting in the molded product partially bridging between the two molds and potentially being damaged or torn. Debonds from both adherends can sometimes occur in weak adhesive bonds as well, potentially altering the apparent fracture behavior. To avoid or control these multiple interfacial debonding, more understanding of these processes is required. An analytical model of 2D parallel bridging was developed and the interactions of interfacial debonds were investigated using Euler-Bernoulli beam theory. The numerical solutions to the analytical results described the propagation processes with multiple debonds, and demonstrated some common phenomena in several different joints corresponding to double cantilever beam configurations. The analytical approach and results obtained could prove useful in extensions to understanding and controlling debonding in such situations and optimization of loading scenarios. Numerical capabilities for predicting crack propagation, confirmed by experimental results, were initially evaluated for crack behavior in monolithic materials, which is also of interest in engineering design. Several test cases were devised for modified forms of monolithic compact tension specimens (CT) were developed. An asymmetric variant of the CT configuration, in which the initial crack was shifted to two thirds of the total height, was tested experimentally and numerically simulated in ABAQUS®, with good agreement. Similar studies of elongated CT specimens with different specimen lengths also revealed good agreement, using the same material properties and cohesive zone model (CZM) parameters. The critical specimen length when the crack propagation pattern abruptly switches was experimentally measured and accurately predicted, building confidence in the subsequent studies where the numerical method was applied to bonded joints. In adhesively bonded joints, crack propagation and joint failure can potentially result from or involve interactions of a growing crack with a partially weakened interface, so numerical simulations were initiated to investigate such scenarios using ABAQUS®. Two different cohesive zone models (CZMs) are applied in these simulations: cohesive elements for strong and weak interfaces, and the extended finite element method (XFEM) for cracks propagating within the adhesive layer. When the main crack approaches a locally weakened interface, interfacial damage can occur, allowing for additional interfacial compliance and inducing shear stresses within the adhesive layer that direct the growing crack toward the weak interface. The maximum traction of the interfacial CZM appears to be the controlling parameter. Fracture energy of the weakened interface is shown to be of secondary importance, though can affect the results when particularly small (e.g. 1% that of the bulk adhesive). The length of the weakened interface also has some influence on the crack path. Under globally mixed mode loadings, the competition between the loading and the weakened interface affects the shear stress distribution and thus changes the crack path. Mixed mode loading in the opposite direction of the weakened interface is able to drive the crack away from the weakened interface, suggesting potential means to avoid failure within these regions or to design joints that fail in a particular manner. In addition to the analytical and numerical studies of crack path selection in adhesively bonded joints, experimental investigations are also performed. A dual actuator load frame (DALF) is used to test beam-like bonded joints in various mode mixity angles. Constant mode mixity angle tracking, as well as other versatile loading functions, are developed in LabVIEW® for use with a new controller system. The DALF is calibrated to minimize errors when calculating the compliance of beam-like bonded joints. After the corrections, the resulting fracture energies ( ) values are considered to be more accurate in representing the energy released in the crack propagation processes. Double cantilever beam (DCB) bonded joints consisting of 6061-T6 aluminum adherends bonded with commercial epoxy adhesives (J-B Weld, or LORD 320/322) are tested on the DALF. Profiles of the values for different constant mode mixity angles, as well as for continuously increasing mode mixity angle, are plotted to illustrate the behavior of the crack in these bonded joints. Finally, crack path selection in DCB specimens with one of the bonding surfaces weakened was studied experimentally, and rate-dependency of the crack path selection was found. Several contamination schemes are attempted, involving of graphite flakes, silicone tapes, or silane treatments on the aluminum oxide interfaces. In all these cases, tests involving more rapid crack propagation resulted in interfacial failures at the weakened areas, while slower tests showed cohesive failure throughout. One possible explanation of this phenomenon is presented using the rate-dependency of the yield stress (commonly considered to be corresponding to the maximum traction) of the epoxy adhesives. These experimental observations may have some potential applications tailoring adhesive joint configurations and interface variability to achieve or avoid particular failure modes.
Ph. D.

This Master´s thesis deals with the determination of the propagation directions of primary crack in the rail vehicles wheel under operating conditions. The aim of this work is the stress-strain analysis with using fracture mechanics to examinate behaviour of primary cracks for different operating conditions, i.e. rotation, rotation with contact and assessment of refracted cracks with applied rotation and contact.

Connecting rod is an important dynamic link rod between piston and crank shaft. This undergoes a complex state of stress during working and adds to the problem in design for strength. Mostly connecting rods are manufactured using carbon steel and in recent days composite materials are finding its application in connecting rod. In the present paper a finite element model was developed to study the effects of various stress patterns on the design of the rod. To achieve the objective, connecting rod is modelled by taking the dimensions from actual component captured from a blue light scanner. The practical load-data points as a function of crank angle are directly collected from the four cylinder diesel engine. Simulation software is used to determine the pressure in the cylinder. The values of angular velocity and acceleration are calculated theoretically using analytical equations. Using the above data, static and dynamic finite element simulation is carried out successfully and connecting rod is replaced by carbon based composite material reinforced with silicon carbide. And it describes the modelling and analysis of connecting rod. Finite Element Analysis was carried out by considering two materials. The parameter like von misses stress, von misses strain and displacement was obtained from Abacus software. Over the past years, improvements in performance efficiency have been achieved by simplifying the design of the structural components and using composite materials to reduce the overall weight.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
O objetivo deste trabalho é prever a alteração do ângulo de camber em função do deslocamento vertical da roda. Para o estudo foram selecionados dois tipos de suspensão, triângulos sobrepostos e McPherson, os quais foram comparados com dois modelos cinemáticos de dois mecanismos, mecanismo de quatro barras e mecanismo de biela-manivela invertido, respetivamente. Os resultados obtidos pela comparação dos dados teóricos e medidos, são bastante satisfatórios uma vez que os valores se encontram bastante próximos, o que permite confirmar a validade dos modelos adotados.
The main objective of this work is to predict the camber angle change due to the vertical displacement of the wheel. Two types of suspension, Double-Wishbone and McPherson, have been selected, which were compared with two kinematic models of two mechanisms, four-bar linkage and inverted slider-crank mechanism respectively. The results obtained, by comparing the theoretical and measured data, are quite satisfactory since the values are quite similar, allowing to confirm the validity of the adopted models.

The demand for a high quickly measuring angle in the port crane system should be considered when the container has been transferred from one place to another place. It is significant to build the feedback linking of payload's angle in the integrated crane system. The value of accurate measurement of the angle can be used to optimize the crane control system. In this context, the design and implementation of the experimental setup associated with emulated cranes will be carried out. Several solutions for remote angle measurement were considered one of the considered solutions being represented by millimeter microwave radar sensors. Special developments of algorithms to calculate the sway angle of payload or container were considered as so as the real-time processing using Arduino Uno computation platform. The following objectives were successfully reached. 1. Development of remote sensing system for payload's swing angle measurement considering radars such the sensing devices; 2. Development of a novel angle algorithm measurement and real-time processing of data; 3. Development of a prototype characterized by real-time processing and remote detection capabilities considering short-range and long-range measurements, such as lidar sensor or radar sensor.
A demanda por um ângulo de medição rápido e alto no sistema de guindaste portuário deve ser considerada quando o contêiner for transferido de um local para outro. É significativo construir a ligação de feedback do ângulo da carga útil no sistema de guindaste integrado. O valor da medição precisa do ângulo pode ser usado para otimizar o sistema de controle do guindaste. Neste contexto, será realizada a concepção e implementação da configuração experimental associada a gruas emuladas. Diversas soluções para medição remota de ângulos foram consideradas uma das soluções consideradas sendo representadas por sensores de micro-ondas milimetrados. Desenvolvimentos especiais de algoritmos para calcular o ângulo de oscilação da carga útil ou contêiner foram considerados, assim como o processamento em tempo real usando a plataforma de computação Arduino Uno. Os seguintes objetivos foram alcançados com sucesso. 1. Desenvolvimento de sistema de sensoriamento remoto para medição do ângulo de oscilação da carga útil considerando radares como os dispositivos de detecção; 2. Desenvolvimento de um novo algoritmo de medição de ângulos e processamento de dados em tempo real; 3. Desenvolvimento de um protótipo caracterizado por processamento em tempo real e capacidade de detecção remota considerando medições de curto e longo alcance, como sensor LIDAR ou sensor de radar.

Understanding the mechanical behavior of composite materials requires extensive knowledge of fracture behavior as a crack approaches an interface between the bulk material and the reinforcement structure. Overall material toughness can be greatly influenced by the propensity of an impinging crack to propagate directly through the substrate or deflect along an interface boundary. As the basis for this thesis; the assertion that an impinging crack may encounter a reinforcement structure at various incident angles is explored. This requires the ability to predict crack penetration/ deflection behavior not only normal to the reinforcement, but at various incident angles. Previous work in the area of interface fracture mechanics has used a stress or energy based approach, with recent advances in the field of a combined cohesive-zone method. Work presented here investigates the interaction between strength and toughness when using the cohesive-zone method on the problem of an impinging crack not normally incident to the interface of a composite material. Computational mechanics methods using Abaqus and user-define cohesive elements will be applied to this angled incident crack problem. A circular model based on the displacement field equations for mode-I fracture loading is introduced and verified against well-established LEFM solutions. This circular model is used to study the effects of incident crack angle on the penetration vs. deflection behavior of an impinging crack at various angles of incidence. Additionally, the effects of angle on the load applied to the model at fracture are explored. Finally, a case study investigating how the interaction between strength and toughness found using the cohesive-zone method helps to explain some of the inconsistencies seen in the interface indentation fracture test procedure.
Graduation date: 2013

碩士
國立臺灣科技大學
營建工程系
98
Most of the experimental studies in rock mechanics and engineering were conducted in the viewpoint of macro-scale, and fewer micro-view researches focus on the fracture characterizations such as crack initiation and propagation in stressed rock due to the limitation of nondestructive techniques.This experimental study, therefore, aims at the synchronization of both acoustic and optical nondestructive techniques to investigate the effects of shear angle and pre-exist crack on rock-like material (mortar) under inclined shear tests. Based on the plane strain condition of shearing specimen under COD (crack opening displacement) control, a series of experimental tests were performed to obtain entire loading curves by varying: (1) the inclined angle??nranged from 50 to 75°, and (2) the material geometry with or without pre-existing crack (penny and circular shapes in the middle of specimen). In conjunction of both AE (acoustic emission), used to detect the micro-seismic activities within the rock, and ESPI (electronic speckle pattern interferometry) techniques detected the deformation field on the rock surface, the evolution of fracture can be examined during the shearing process. The results show that three fracturing characterizations have been verified corresponding to the inclined shear test: localization, crack initiation and propagation. In addition, this study presents the effect of the inclined angle ? on the shear stiffness, strength at failure, the crack propagation angle ? as well as the different failure modes: mixed compression-shearing failure mode as ?殈??n-50°due to the relatively high normal stress; dilation-allowed shearing mode with either forming a single shear zone (?殈 50-60°) or bi-shear zone (?殈 60-75°) due to the relatively low normal stress. Specimen with pre-existing circular crack shows the stress concentration surrounding circular hole and the crack propagation angle ? increases as increasing the shear angle ?? Furthermore, experiments without pre-existing crack show that the larger the shear angle ??n, the wider the width of the AE events, λd. Similarly, experiments with pre-existing circular crack display the wider λd. comparing with the one without pre-existing crack. The use of AE can be used to detect the localization while ESPI can be used to verify crack initiation and propagation. Both results were compared each other and depicted a good agreement. By synchronizing both AE and ESPI techniques could also be adopted to examine the shearing mechanism in rock mass and joined rock as well.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
As ligas de alta resistência apresentam uma vasta gama de propriedades deveras interessantes para componentes em engenharia. Mais concretamente, a liga de alta resistência DIN 34CrNiMo6, que será alvo de estudo no presente trabalho, apresenta elevada ductilidade, alta temperabilidade, tenacidade e resistência. Estas propriedades, fazem desta liga uma excelente escolha para a produção de elementos críticos, tais como: veios, eixos, pinhões, barras de torção, componentes aeronáuticos, entre muitos outros. Sendo estes materiais utilizados, na maioria dos casos, sob condições severas de serviço e ainda com carregamentos combinados e de forma aleatória, e que por razões de projeto na maioria dos casos, apresentam descontinuidades geométricas que causam concentrações de tensões, o que torna a situação ainda mais crítica na região do entalhe e que ao final de um determinado número de ciclos levarão o material à rotura por fadiga. Deste modo, é importante e através de um modelo numérico prever a vida à fadiga de forma fiável.O principal objetivo da presente dissertação passa por estudar o comportamento da liga DIN 34 CrNiMo6, com entalhes severos e sujeita a carregamentos combinados de flexão-torção, mais especificamente, para duas relações (B=T e B=2T). Foram ainda variados os ângulos de aplicação de carregamento para 0º, 45º e 90º. Para a constituição da malha de elementos finitos para a simulação numérica, representativa do provete em estudo, foi utilizado um modelo elasto-plástico. A previsão de vida foi estudada através de um modelo baseado na energia de deformação (Ellyin, 1997).Os resultados obtidos foram, no geral, bastante satisfatórios em comparação com resultados experimentais, e também com modelos linear-elásticos.
High strength alloys have a wide range of interesting properties for engineering components. In specific the high strength alloy DIN 34CrNiMo6, which will undergo study in this work, presents itself to be a material which high ductility, hardenability as well as tenacity and toughness. These properties make this alloy an excellent choice for the conception of critical elements such as, shafts, pinions, torsion rods, aeronautical components and so on. In most cases, this type of materials is used under sever operating conditions with random combined loadings, which means that sometimes, because of the project conception, they are designed to have geometric discontinuities which cause stress concentration. This situation is more critical under the region of a notch and after a number of work cycles this situation will lead to fatigue failure. By this being said it is important to predict, in a reliable way, the components fatigue life cycle, and a way of studying this is through a numerical model.The main goal of the work is the analysis of the behaviour of the DIN 34CrNiMo6 alloy with sever notches under combined loadings of torsion-bending, specifically for two relations (B=T and B=2T). The loading application angle was studied for the values of 0º, 45º and 90º. For the construction of the finite element mesh of the numerical simulation, which describes the sample in study, an elastic-plastic model was utilized, having the prediction of the life cycle been studied through a strain energy based model (Ellyin, 1997).The obtained results were, in general, satisfactory in comparison with the experimental results as well as the linear-elastic models.

Soy flour (SF), a by-product of the soybean oil extraction processing, was investigated for its application in soy-polypropylene composites for interior automotive applications. The emphasis of this work was the understanding of this new type of filler material and the contribution of its major constituents to its thermal stability and impact properties. For this reason, reference materials were selected to represent the protein (soy protein isolate (SPI)) and carbohydrate (soy hulls (SH)) constituents of the soy flour. Additional materials were also investigated: the residue obtained after the protein removal from the soy flour which was called insoluble soy (IS), and the remaining liquid solution after acid precipitation of the proteins, containing mostly sugars and minerals, which was called soluble sugar extract (SSE). Two treatments, potassium permanganate and autoclave, were analyzed for their potential to modify the properties of the soy composite materials. An acid treatment with sulfuric acid conducted on soy flour was also considered. The soy materials were studied by thermogravimetric analysis (TGA) under isothermal (in air) and dynamic (in nitrogen) conditions. SPI had the highest thermal stability and SSE the lowest thermal stability for the early stage of the heating process. Those two materials had the highest amount of residual mass at the end of the dynamic TGA in nitrogen. The two treatments showed minimal effect on the isothermal thermal stability of the soy materials at 200 ??C. A minor improvement was observed for the autoclave treated soy materials. Fourier transformed infrared (FTIR) spectroscopy indicated that the chemical surface composition differed according to type of the soy materials but no difference could be observed for the treatments within one type of soy material. Contact angle analysis and surface energy estimation indicated differences of the surface hydrophobicity of the soy materials according to type of material and treatment. The initial water contact angle ranged from 57 ?? for SF to 85 ?? for SH. The rate of water absorption increased dramatically after the autoclave treatment for IS and SPI. Both materials showed the highest increase in the polar surface energy fraction. In general, the major change of the surface energy was associated with change of the polar fraction. After KMnO4 treatment, the polar surface energy of SF, IS and SPI decreased while SH showed a slight increase after KMnO4 treatment. A relationship between protein content and polar surface energy was observed and seen to be more pronounced when high protein containing soy materials were treated with KMnO4 and autoclave. Based on the polar surface energy results, the most suitable soy materials for polypropylene compounding are SPI (KMnO4), SH, and IS (KMnO4) because their polar surface energy are the lowest which should make them more compatible with non-polar polymers such as polypropylene. The soy materials were compounded as 30 wt-% material loading with an injection moulding grade polypropylene blend for different combinations of soy material treatment and coupling agents. Notched Izod impact and flexural strength as well as flexural modulus estimates indicated that the mechanical properties of the autoclaved SF decreased when compared to untreated soy flour while the potassium permanganate treated SF improved in impact and flexural properties. Combinations of the two treatments and two selected (maleic anhydride grafted polypropylene) coupling agents showed improved impact and flexural properties for the autoclaved soy flour but decreased properties for the potassium permanganate treated soy flour. Scanning electron microscopy of the fractured section, obtained after impact testing of the composite material, revealed different crack propagation mechanisms for the treated SF. Autoclaved SF had a poor interface with large gaps between the material and the polypropylene matrix. After the addition of a maleic anhydride coupling agent to the autoclaved SF and polypropylene formulation, the SF was fully embedded in the polymer matrix. Potassium permanganate treated SF showed partial bonding between the material and the polymer matrix but some of the material showed poor bonding to the matrix. The acid treated SF showed cracks through the dispersed phase and completely broken components that did not bind to the polypropylene matrix. In conclusion, the two most promising soy materials in terms of impact and flexural properties improvement of soy polypropylene composites were potassium permanganate treated SF and the autoclaved SF combined with maleic anhydride coupling agent formulation.