Micromechanical simulations are conducted to quantify the influence of microstructure attributes to the formation of small fatigue cracks. Three wrought aluminum alloys (7075-T651, 2024-T3, virtual material) with fractured particle are studied to quantify the influence of material’s yield strength and ultimate strength to material’s fatigue resistance. Laser Engineered Net Shaping (LENS) material with pores of various spatial distribution and particles are simulated for the microplasticity and its effects on fatigue incubation. A cohesive zone model is used to study the interface cohesive behavior’s influence to the cyclic driving mechanisms. Different simulations based on different interfacial crack geometries and particle shapes are studied. A cohesive law with unloading-reloading cyclic behavior is introduced. A damage factor D is proposed to study the possibility of interfacial crack propagation. With this factor, plastic wake zone behind the debonding is studied.

In this thesis, the author proposes and presents a novel simulation technique for the analysis of multilayered Flexural Plate Wave (FPW) devices based on the convergence of the Finite Element method (FEM) with classical Surface Acoustic Wave (SAW) analysis techniques and related procedures. Excellent agreement has been obtained between the author's approach and other more conventional modelling techniques. Utilisation of the FEM allows the performance characteristics of a FPW structure to be critically investigated and refined before undertaking the costly task of fabrication. Based on a series of guidelines developed by the author, it is believed the proposed technique can also be applied to other acoustic wave devices. The modelling process developed is quite unique as it is independent of the problem geometry as verified by both two and three dimensional simulations. A critical review of FEM simulation parameters is presented and their effect on the frequency domain response of a FPW transducer given. The technique is also capable of simultaneously modelling various second-order effects, such as triple transit, diffraction and electromagnetic feedthrough, which often requires the application of several different analysis methodologies. To verify the results obtained by the author's novel approach, several commonly used numerical techniques are discussed and their limitations investigated. The author initially considers the Transmission Matrix method, where it is shown that an inherent numerical instability prevents solution convergence when applied to large frequency-thickness products and complex material properties which are characteristic of liquids. In addition the Stiffness Matrix method is investigated, which is shown to be unconditionally stable. Based on this technique, particle displacement profiles and mass sensitivity are presented for multilayered FPW structures and compared against simpler single layer devices commonly quoted in literature. Significant differences are found in mass sensitivity between single layer and multilayered structures. Frequency response characteristics of a FPW device are then explored via a spectral domain Green's function, which serves as a further verification technique of the author's novel analysi s procedure. Modifications to the spectral domain Green's function are discussed and implemented due to the change in solution geometry from SAW to FPW structures. Using the developed techniques, an analysis is undertaken on the applicability of FPW devices for sensing applications in liquid media. Additions are made to both the Stiffness Matrix method and FEM to allow these techniques to accurately incorporate the influence of a liquid layer. The FEM based approach is then applied to obtain the frequency domain characteristics of a liquid loaded FPW structure, where promising results have been obtained. Displacement profiles are considered in liquid media, where it is shown that a tightly coupled Scholte wave exists that is deemed responsible for most reported liquid sensing results. The author concludes the theoretical analysis with an in-depth analysis of a FPW device when applied to density, viscosity and mass sensing applications in liquid media. It is shown that a single FPW device is potentially capable of discriminating between density and viscosity effects, which is typically a task that requires a complex and costly sensor array.

<p>Problemformulering: Bakgrunden till vår uppsats startade när vi själva började söka extrajobb vid sidan av studierna och upptäckte ganska snart att de flesta jobb av intresse som var vakanta på arbetsmarknaden gick att söka via bemanningsföretag. Därför blev vi intresserade av att få veta varför företag väljer att gå via bemanningsföretag istället för att anställa själva. Syfte: Syftet med denna studie är att få reda på hur företag ser på de kostnader som uppstår vid inhyrning av personal. Metod: I det här avsnittet kommer vi att presentera vårt val av metod. Vi kommer att berätta utförligt hur vi ska gå tillväga för att genomföra vår undersökning. Även förhållningssättet kommer att presenteras som utmynnar i senare delen av uppsatsen i analys och slutsats. Teori: I teoriavsnittet presenterar vi de teorier som vi valt att använda oss av, bland annat "Det Intellektuella kapitalet" och "Porters fem konkurrenskrafter". Även här presenteras de vetenskapliga artiklar som vi har funnit intressanta att studera inför arbetet. Empiri: I det här avsnittet presenteras våra intervjufrågor respektive svar. Analys: Här analyserar vi de svar vi har fått vid intervjuerna med hjälp av de teorier som vi presenterar i teorikapitlet. Slutsats: Slutsatsen är den väsentligt viktiga delen i vår uppsats. Här drar vi slutsatser med hjälp av de nya perspektiv vilka vi har fått vid intervjuerna. Källkritik: Här presenterar vi vår egen åsikt om de artiklar, böcker och svar som vi fått vid intervjuerna. Nyckelord: Intellektuellt kapital, Porters fem krafter, Bemanningsföretag, Bemanningsbranschen.</p>

<p><p>In order to be competitive in the markets of today, more and more companies try to make their production more effective by automation. Consequently more money is invested in robots and the operability of the robots becomes increasingly important. Undetected faults may result in damages, both to the robot itself and to the operator, which make detection and prediction of faults important.</p><p>The gearboxes responsible for controlling the motions of the robots are essential for their functionality. In order to increase the understanding about them this project focuses on creating a model of the stress distribution inside a gearbox.</p><p>First, the geometry of the gearbox is measured and digitalized using a vernier caliper, a protractor, a ruler and the CAD-program Solid Works. Then the geometry is imported into the finite element program Samcef.</p><p>In Samcef, the interaction between the parts in the gearbox is modeled and a dynamic simulation of the stresses inside the gearbox during a robot cycle performed.</p><p>Since there are almost no experience about Samcef at ABB SECRC, part of the project is to evaluate the program and comment the experiences received when using it.</p><p>Two main power transmission steps are identified, modeled and simulated. They are merged together into a big model where both steps are present. This model consists of all the essential power transmission inside the gearbox, from input to output. The load applied is a rotational movement on the input axle during a robot cycle.</p></p>

<p>This master thesis is intended to give an increased understanding of the stress state in an axle, which is assembled in one of Atlas Copco’s mountain drilling rigs. The main problems investigated were how the axle is affected when the bearing is worn, when the pretension is varied, and how to dimension the axle. Answers to these questions were found by using hand calculations, practical testing and with Finite Element analyzes. The dimensioning of the axle is currently based on the bending stress, but the author’s opinion is that the axle should be dimensioned considering the equivalent stress. Wear and pretension had large influence on the strain along the axle, but almost no influence on the shear stress and on the equivalent stress. Maximum equivalent stress occurs in the same place on the axle independently on wear and pretension, except for one case. This particular case is, however, not likely to occur. The maximum equivalent stress occurs inside the axle, at the hole which the pretension bolt goes through. This equivalent stress depends mostly on a shear stress concentration which occurs inside the axle. Theshear stress concentration was verified with a number of different FEM-models with various geometries, and with theory. The concentration depends on the geometry of the axle, and it occurs where the expansion bushings ends, but on the inside of the axle. The shear stress concentration is approximately two and a half time bigger than the stress on the outside of the axle. Finally a new design method is proposed which is based on the shear stress, that is recalculated into an equivalent stress.</p>

<p>This report is the result of a thesis as been implemented during the spring term 2009 at</p><p>the University of Gävle.</p><p>The company Bruks produces mobile chippers which are used for chipping logging</p><p>slash, roundwood and parts of trees. The chipper is powered by a separate diesel engine</p><p>and the chipper can be assembled on trucks, trailers or some other carrier vehicles.</p><p>When the chip has passed the chipper drum, the chip is collected in an integrated bin</p><p>which is mounted on the vehicles frame with dumping yokes. When these dumping</p><p>yokes were designed they were probably created with large material dimensions. The</p><p>aim with the degree project is hence to study the strengths of materials and, if possible,</p><p>to suggest an arrangement that can decrease the total weight on the dumping yoke on</p><p>Bruks´ mobile chippers 805 CT.</p><p>The CAD-program Pro/ENGINEER was used during the project for outlining the 2Ddrawings,</p><p>as distributed of constructors on Bruks, to solid 3D-parts. The three-dimensional</p><p>assembly from Pro/ENGINEER was transferred to Pro/MECHANICA. The construction is</p><p>complex and contains many components, and therefore the model has been divided into two</p><p>different parts, the external and the internal dumping yoke.</p><p>The conclusion of the degree project is that the product generally is not over dimensioned.</p><p>However there are many options for optimizing, mainly on the external dumping yokes.</p>

<p>This thesis describes the work process and the results for the development of a newkind of ergonomic cleaning mop, ranging from basic concept to a virtually productionready digital prototype. The project was made in cooperation with, Ömer Altun, whowas also the project supervisor, and whose plan it is to launch this new product onthe market in a foreseeable future. The mop is meant to be used by both professionalcleaning staff and ordinary home users. What makes this product unique is that it hasa movable center piece that simplifies the cleaning under low furniture.The work began with the establishment of a product requirements specification andlater a study of similar products and existing functional models was conducted. Afterthese surveys the work began with refining the existing concepts in order to makethem more complete. In consultation with Ömer, further refining of one of these newconcepts was conducted, but was split into seven smaller steps.After the initial refining process, effort shifted into the investigation and selection ofappropriate materials and manufacturing methods. At this stage, two experimentswere also conducted and subsequently used to support the final decisions concerningthe choice of materials and design.When the materials and methods were adopted, a detailed CAD model of the wholeproduct and related technical drawings was made and also a number of FEM-analyseson all critical details, to ensure that performance requirements were met, wasconducted. These CAD models are closer described in detail in the chapter“Detaljkonstruktion”.In the final sections of discussion and evaluation are suggestions for furtherimprovements. And also some evaluation of the work process and the problems andsolutions encountered during the project execution.</p>

<p>Tractors of today come equipped with a CAN-system. A CAN-system sends information from sensors to electronic control units who process the signals. The sensors measure several interesting parameters such as force, pressure and speed for various components of the tractor. This thesis discuss a force sensor which is placed in the pivot of the tractors three point linkage, the sensor measure the horizontal reaction force from the load that the tractor is exposed to. Signals from this sensor can be used to measure the force from any implement that the tractor is exposed to during an operation. The results from this thesis can be used for research purposes, for example, to compare implements from different manufacturer or to optimize the implement settings during an operation. However, there is a problem that this thesis aimed to solve by developing a method which can be put into practice. When a constant force from an implement is acting on the three point linkage, the reaction force in the pivot of the three point linkage (where the force sensor is attached) is going to vary depending on the angel of the lower lift arm. It is not uncommon that the angel of the lower lift arm is varying, because different implement and soil require different settings on the linkage. This means that the force which is measured by the sensor may vary in size even though the actual force does not vary. To solve this problem, theoretical calculations have been performed and equations to describe the variation of the reaction force depending on the geometry have been created. The theory has also been verified by a finite element analysis and a practical verification test. The conclusions from these three parts correspond to each other. Theoretically that means by knowing the horizontal reaction force (measured by the force sensor) and the angles of the geometry on the three point linkage (can be measured with a position sensor) you can calculate the force an implement influence the tractor with. However, there is a problem which prevents this method from being completely reliable. It is only working when the impact force is completely parallel to the horizontal plane. Since many implements are being pulled to the soil (plow, cultivator, etc.) in practice there are also vertical forces affecting the tractor. This is no problem to solve in theory, but in practice this method does not compensate for the vertical force. This vertical force should be examined more carefully before the method can be used reliably in full scale.</p>

This thesis is a summary of my research works at the MSM department of the University of Liège since 1989. These research works are devoted to the numerical simulation of the three-dimensional sheet metal forming processes by the finite element method. Several research areas, including the finite element modelling, the time-integration technique of material constitutive laws and the 3D contact treatments are covered. The theoretical methodologies, the numerical implementation and industrial applications will be presented. The thesis begins with a brief overview made in chapter 1. In chapter 2, a 8-node mixed brick element based on the HU-WASHIZU variational principle is developed (JET3D element). Special attention is paid to avoid hourglass modes as well as locking phenomena, including "shear locking" and "volumetric locking" in nonlinear analysis. Numerical examples are used at the end of this chapter to assess the performance and applicability of this element. In chapter 3, a 3D four-node shallow element, which was originally developed by Ph. JETTEUR and then has been improved by him and his co-workers, is recalled (COQJ4 element). Special care is taken to the finite rotation problems and a new formulation for the finite rotation is developed. An example is used at the end of the chapter to show the performance of the proposed formulation for the finite rotation problems. A special contact element is developed for the shell element in chapter 4. In this chapter, some basics aspects of numerical tretments of contact problem are discussed and some attentions are paid to the contact searching algorithms, which has proved to be very important in 3D cases. In chapter 5, the appropriate constitutive equations are examined together with the techniques of time-integration and the evaluation of the tangent stiffness matrix. Much attention is paid to the implicit integration methods, which have proved to be very efficient for large increments of deformation. Finally, in chapter 6, two benchmark tests are used as validation of the code. Special attention is paid to the possibility of using dynamic explicit procedure in the numerical simulation of sheet metal forming, although it is often characterised as a quasi-static process. All the developments made in the thesis have been implemented into the finite element code LAGAMINE developed since 1982 at the MSM department of the University of Liège.

The demands the automotive gear designer has to considerduring the gear design process have changed. To design a gearthat will not fail is still a challenging task, but now lownoise is also a main objective. Both customers and legalregulations demand noise reduction of gears. Moreover, thequality of the product is more in focus than ever before. Inaddition, the gear design process itself must be inexpensiveand quick. One can say that the gear designer faces a newdesign environment. The objective of this thesis is tocontribute to the answer to some of the questions raised inthis new design environment. In order to respond to the new design situation, the geardesigner must consider new phenomena of gears that werepreviously not a matter of concern. One such phenomenon is anew gear failure type, Tooth Interior Fatigue Fracture (TIFF).As the gear teeth are made more slender in an attempt to reducethe stiffness variation during the mesh cycle, therebypotentially reducing the noise, the risk of TIFF is increased.The phenomenon of TIFF is explored in detail (paper III-VI)through fractographic analysis, numerical crack initiationanalysis using FEM, determination of residual stress by meansof neutron diffraction measurements, testing for determiningmaterial fatigue properties, fracture mechanical FE-analysis,sensitivity analysis and the development of an engineeringdesign method. The main findings of the analysis of TIFF arethat TIFF cracks initiate in the tooth interior, TIFF occursmainly in case hardened idlers, the fracture surface has acharacteristic plateau at approximately the mid-height of thetooth and the risk of TIFF is more pronounced in slender gearteeth. Along with the more optimised gear design, there is atendency for the gear to be less robust. Low robustness, i.e.,great variation in performance of the product, implies a highincidence of rejects, malfunction and/or bad-will, all of whichmay have a negative effect on company earnings. As the use ofoptimisation decreases the safety margins, greater attentionhas to be paid to guaranteeing the products' robustness.Moreover, in order to be cost-effective, the qualities of thegear must be verified early in the design process, implying anextended use of simulations. In this thesis, two robustnessanalyses are presented in which the analysing tool issimulation. The first one considers robust tooth root bendingfatigue strength as the gear is exposed to mounting errors, thesecond one considers robust noise characteristics of a gearexposed to manufacturing errors, varying torque and wear. Bothof these case studies address the problem of robustness ofgears and demonstrate how it can be estimated by use ofsimulations. The main result from the former robustnessanalysis is that wide gears are more sensitive to mountingerrors, while the latter analysis showed that to achieve robustnoise characteristics of a gear it should have large helixangles, and some profile- and lead crowning should beintroduced. The transverse contact ratio is a trade-off factorin the sense that both low average noise levels and low scatterin noise due to perturbations cannot be achieved. <b>Keywords</b>: robust design, Taguchi method, gear, idler,simulations, Finite Element Method, Tooth Interior FatigueFracture, TIFF