<p>The design process includes many different activities inwhich various computational mechanics tools are used forbehaviour modelling of mechanical systems and their buildingblocks, e.g. machine elements. These tools usually supportlarge and complex models and they produce large quantities ofdata with a high degree of complexity. In these situations,efficient data management and the ability to search and sharedata are important issues to achieve an efficient designprocess. Today, this ability is usually not supported by theindividual applications even though this probably would improveand facilitate the ability to search for data on a higher levelin the engineering information system.</p><p>This work investigates the ability of searching andcomparing analysis data within behaviour models of technicalsystems as well as over the analysis results. This is done byinvestigating the potential benefits of integrating moderndatabase technology with a multibody system (MBS) analysissoftware in the same manner that has been successfully done forbusiness and administrative applications. This has resulted inan implemented pilot system, named MECHAMOS, that integratesthe main-memory resident object-relational database managementsystem (DBMS) AMOSwith the symbolic multibody system (MBS)software SOPHIA operating in MapleV. This provides MECHAMOSwith both symbolic and numeric mathematical capabilities forMBS analysis and data management capabilities to search andcompare engineering data in the database.</p><p>The approach, making data managing tools available in acomputer aided engineering software, considerably improves theanalysis of technical systems. The analysis is brought to ahigher level through the available query language and thedesired data is specified, fairly intuitively, in a query. Whenthe query is processed, the DBMS knows how to retrieve andautomatically derive the required data. As shown in someexamples, the ability to search over stored and derived data inthe database is not restricted to a single MBS-model inMECHAMOS. Because of the implemented materialisation handling,it is also possible to search, combine, and compare data fromseveral simulation results which are based on several differentmodels in the database. This extends the ability to performoptimisation from a traditional parameter study to thepossibility to analyse and compare different technical conceptsthrough the query language and hereby retrieve those conceptsthat fulfil certain requirements. If submodel techniques aresupported, queries over a set of components in the databasewould automatically create, analyse and compare the possibleconcepts. This would assist the designer in choosing the bestcomponents for a design.</p>

Computational efficiency of solving the dynamics of highly oscillatory systems is an important issue due to the requirement of small step size of explicit numerical integration algorithms. A system is considered to be highly oscillatory if it contains a fast solution that varies regularly about a slow solution. As for multibody systems, stiff force elements and contacts between bodies can make a system highly oscillatory. Standard explicit numerical integration methods should take a very small step size to satisfy the absolute stability condition for all eigenvalues of the system and the computational cost is dictated by the fast solution. In this research, a new hybrid integration scheme is proposed, in which the local linearization method is combined with a conventional integration method such as the fourth-order Runge-Kutta. In this approach, the system is partitioned into fast and slow subsystems. Then, the two subsystems are transformed into a reduced and a boundary-layer system using the singular perturbation theory. The reduced system is solved by the fourth-order Runge-Kutta method while the boundary-layer system is solved by the local linearization method. This new hybrid scheme can handle the coupling between the fast and the slow subsystems efficiently. Unlike other multi-rate or multi-method schemes, extrapolation or interpolation process is not required to deal with the coupling between subsystems. Most of the coupling effect can be accounted for by the reduced (or quasi-steady-state) system while the minor transient effect is taken into consideration by averaging. In this research, the absolute stability region for this hybrid scheme is derived and it is shown that the absolute stability region is almost independent of the fast variables. Thus, the selection of the step size is not dictated by the fast solution when a highly oscillatory system is solved, in turn, the computational efficiency can be improved. The advantage of the proposed hybrid scheme is validated through several dynamic simulations of a vehicle system including a flexible tire model. The results reveal that the hybrid scheme can reduce the computation time of the vehicle dynamic simulation significantly while attaining comparable accuracy.

This paper was presented at CJK-OSM 7, 18–21 June 2012, Huangshan, China.

Environmental, aesthetic and political pressures continue to push for siting off-shore wind turbines beyond sight of land, where waters tend to be deeper, and use of floating structures is likely to be considered. Savings could potentially be realized by reducing hull size, which would allow more compliance with the wind thrust force in the pitch direction. On the other hand, these structures with large-amplitude motions will make dynamic analysis both more challenging and more critical. Prior to the present work, there were no existing dynamic simulation tools specifically intended for compliant wind turbine design. Development and application of a new computational method underlying a new time-domain simulation tool is presented in this dissertation. The compliant floating wind turbine system is considered as a multibody system including tower, nacelle, rotor and other moving parts. Euler's equations of motion are first applied to the compliant design to investigate the large-amplitude motions. Then, a new formulation of multibody dynamics is developed through application of the conservation of both linear momentum and angular momentum to the entire system directly. A base body is prescribed within the compliant wind turbine system, and the equations of motion (EOMs) of the system are projected into the coordinate system associated with this body. Only six basic EOMs of the system are required to capture 6 unknown degrees of freedom (DOFs) of the base body when mechanical DOFs between contiguous bodies are prescribed. The 6 x 6 mass matrix is actually composed of two decoupled 3 x 3 mass matrices for translation and rotation, respectively. Each element within the matrix includes the inertial effects of all bodies. This condensation decreases the coupling between elements in the mass matrix, and so minimizes the computational demand. The simulation results are verified by critical comparison with those of the popular wind turbine dynamics software FAST. The new formulation is generalized to form the momentum cloud method (M- CM), which is particularly well suited to the serial mechanical N-body systems connected by revolute joints with prescribed relative rotation. The MCM is then expanded to multibody systems with more complicated joints and connection types.

Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-02-07T12:18:55Z No. of bitstreams: 1 DIEGO DAVID SILVA DINIZ – DISSERTAÇÃO PPGEM 2014.pdf: 4871335 bytes, checksum: cfbb94b91722df0a50916a777f1ec43e (MD5) / Made available in DSpace on 2018-02-07T12:18:55Z (GMT). No. of bitstreams: 1 DIEGO DAVID SILVA DINIZ – DISSERTAÇÃO PPGEM 2014.pdf: 4871335 bytes, checksum: cfbb94b91722df0a50916a777f1ec43e (MD5) Previous issue date: 2014-12-03 / CNPq / Atualmente, o desenvolvimento da indústria automotiva e uma maior exigência do mercado estimularam a intensificação dos estudos na dinâmica veicular, levando os fabricantes a focarem seus esforços em produzir e otimizar tecnologias capazes de obter veículos mais rápidos, seguros e confortáveis. Com a evolução da computação, tornou-se viável a realização de simulação numérica para modelos complexos de veículos que fosse capaz de otimizar e compreender o real comportamento dinâmico do veículo, submetidos às situações adversas. Dentro desse contexto, este trabalho visa apresentar um estudo de modelagem computacional (modelo quarter car, half car e multicorpos) aplicados para avaliação do comportamento dinâmico vertical de um veículo do tipo off-road (Baja) com suspensão dianteira e traseira do tipo duplo A. Para este fim, foram feitos levantamentos experimentais dos parâmetros de suspensão associados a estudos da dinâmica vertical de um veículo off-road, do tipo baja, com auxílio da máquina de ensaio dinâmica (MTS 321.21), além de estudos dinâmicos numa mesa inercial por meio de um analisador de vibrações. Mediante os parâmetros, foram construídos e simulados os modelos matemáticos, quarter car e half car no software MATLAB e o carro completo no ambiente multicorpos. Como resultados, foram avaliadas a influência da pressão interna dos pneus, a variação das rigidezes das molas e o efeito do amortecimento em situações comuns, que o veículo fora de estrada pode ser submetido, permitindo avaliar o seu comportamento dinâmico vertical. Assim, os perfis de pistas idealizadas nestes trabalhos foram: lombada, valas e swept sine. Nos experimentos, destaca-se a variação da rigidez radial dos pneus, quando ocorrem mudanças na sua pressão interna, o efeito da variação dos valores das massas não suspensa do sistema, modificando o comportamento dinâmico do veículo no momento de excitação pelas adversidades do solo, e a variação da força de contato pneu/solo com a mudança da pressão interna dos pneus. Ambos esses efeitos causam mudança no comportamento dinâmico vertical e, em alguns casos, até na dinâmica lateral, influenciando no desempenho do veículo, o que torna imprescindível realizar estes tipos de estudos para um melhor entendimento dos fenômenos existentes, durante situações que um veículo off road são submetidos. / Currently, the development of the automotive industry and greater market demand stimulated the intensification of studies on vehicular dynamics, leading manufacturers to centralize their efforts to produce and optimize technologies capable of faster, safer and comfortable vehicles. Through the evolution of computation, it became viable the realization of numerical simulation of complex models of vehicles that would be able to optimize and understand the real dynamic behavior of the vehicle subjected to adverse situations. Within this context, this paper presents a study of computational modeling (quarter car, half car and multibody models) used for assessment of the vertical dynamic behavior of a vehicle type off-road (Baja) with front and rear suspension Double A. To make it possible, surveys of experimental parameters associated with studies of suspension of a vehicle off-road, the baja type, with the aid of dynamic testing (MTS 321.21) vertical machine dynamics were made in addition to dynamic studies in one inertial table through a vibrations analyzer. Through parameters, mathematical models (quarter car and half car) were built and simulated in MATLAB software. The complete car were built and simulated in multibody environment. With the results, there were evaluated the influence of the internal tire pressure, the variation of springs stiffness and the dampening effect throughout ordinary situations to this kind of vehicle and then allowing evaluates its vertical dynamic behavior. Therefore, the profiles of these works were idealized clues: speed bump, ditches and swept sine. In the experiments stands out a variation of the radial stiffness of the tire, when changes occur in their internal pressure, the effect of varying the values of the unsprung mass of the system, modifying the dynamic behavior of the vehicle at the time of excitation by the adversities of the soil, and the variation of contact force tire / ground with the change of the internal pressure of the tires. These effects cause changes in the vertical dynamic behavior, and in some cases even in the lateral dynamics may influence the performance of the vehicle, which makes it essential to make these types of studies to better understand the phenomena existing in situations that are off-road vehicle submitted.

Constrained optimization is used to derive human postures and movements. In the first study a static 3D model with 30 muscle groups is used to analyse postures. The activation levels of these muscles are minimized in order to represent the individual's choice of posture. Subject specific data in terms of anthropometry, strength and orthopedic aids serve as input. The aim is to study effects from orthopedic treatment and altered abilities of the subject. Initial validation shows qualitative agreement of posture strategies but further details about passive stiffness and anthropometry are needed, especially to predict pelvis orientation. In the second application, the athletic long jump, a problem formulation is developed to find optimal movements of a multibody system when subjected to contact. The model was based on rigid links, joint actuators and a wobbling mass. The contact to the ground was modelled as a spring-damper system with tuned properties. The movement in the degrees of freedom representing physical joints was described over contact time through two fifth-order polynomials, with a variable transition time, while the motion in the degrees of freedom of contact and wobbling mass was integrated forwards in time, as a consequence. Muscle activation variables were then optimized in order to maximize ballistic flight distance. The optimization determined contact time, end configuration, activation and interaction with the ground from an initial configuration. The results from optimization show a reasonable agreement with experimentally recorded jumps, but individual recordings and measurements are needed for more precise conclusions.

his work deals with the methods of creating computational models for the analysis of the chain drive of camshafts in combustion engines. Methods are compared of the simulation of the drive mechanism; a new method is also presented for the simulation of the tensioning and guide bar by means of a modal reduction of an elastic body in the Multibody system. The work describes individual parts of the chain gear and the mathematical formulation of differential equations of motion. Algorithms are also indicated describing the mutual interaction of bodies in contact. Computations are here described for the determination of individual parameters necessary for setting up a chain drive model. The tensile characteristics of the chain is determined by the FEM programme. The chain model is analyzed in several alternatives of arrangement. FEM calculations are described here of the rigidity of contacts between the chain and the chain wheels and between the chain and the guide bars. The computational model has been created in the MSC ADAMS programme. The computation is carried out for a stabilized speed of the crankshaft of 3,000, 4,500 and 6,000 rpm and for a continuous start from the idle state up to the speed of 6,000 rpm with a constant load of the crankshafts by the torsion moment. Computation is also carried out for loading the crankshafts with a torsion moment deduced from the cam shape. The courses of the quantity obtained are processed by means of FFT; Campbell diagrams have been constructed for their evaluation. The results have been compared with the modal analyses of the individual parts of the chain gear for the determination of their mutual interaction.

Wheel loaders are fundamental construction equipment to assist handling of bulk material e.g. gravel and stones. During digging operations, it withstands forces that are both large and very complicated to predict. Moreover, it is very expensive to develop prototypes of wheel loader for verification. Consequently, the Discrete Element Method (DEM) was introduced for gravel modeling a couple of years ago to enable prediction of these forces. The gravel model is connected with a Multibody System (MBS) model of the wheel loader, in this thesis a Volvo L180G. The co-simulation of these two systems is a very computer intensive operation and hence, it is important to investigate which parameters that have the largest influence on the simulation results. The aim of this thesis is to investigate the simulation sensitivity with respect to co-simulation communication interval, collision detection interval and gravel normal stiffness.The simulation results are verified by comparison with measurement data from previous tests performed by Volvo CE. The simulations are compared to investigate the relevant parameters. The conclusion of this thesis is that DEM is a method that in a very good way can predict the draft forces during digging operations.

Recentemente, uma mudança de paradigma vem impactando toda a engenharia e manufatura na forma de se planejar, projetar, testar e construir produtos. A forma mais tradicional de desenvolvimento, que se caracterizava pelo processo seriado de múltiplos ciclos de design-construção-teste, vem sendo substituída gradativamente por processos de desenvolvimento guiados por simulação computacional. Decorrentes disso, os primeiros protótipos físicos são freqüentemente capazes de atingir os objetivos quando testados. Esta mudança, chamada também de projeto baseado em simulação, permite reduzir drasticamente o tempo de desenvolvimento de produtos e trazer a inovação para o mercado. Este trabalho apresenta uma forma computacional, via técnica de multicorpos, para se analisar a dinâmica de uma lavadora de eixo vertical. É proposto um protótipo virtual no software ADAMS, para estudo dinâmico de uma lavadora durante o processo crítico de centrifugação. O modelo virtual é posteriormente confrontado com dados experimentais, para sua validação. Uma extensa pesquisa bibliográfica foi realizada, com a intenção de capturar as técnicas mais usuais de modelamento e estudo dinâmico em lavadoras, bem como de compreender melhor o papel de seus componentes durante o processo crítico de centrifugação. / Recently a paradigm shift has impacted the engineering and manufacturing in the way of planning, designing, testing and building products. The most traditional way of product development, characterized by multiple cycles of design-build-test, has been substituted by a process based on computational simulation, where the first physical prototypes are capable of delivering the desired performance. This new way of developing products is called simulation based design and allows organizations to reduce drastically the product lead time and bring innovation to the market. This work presents a computational way to analyze the dynamic behavior of a top load washing machine using multibody system (MBS). It\'s proposed a virtual prototype developed in the ADAMS software, for dynamic study of a commercial washing machine during spin cycle. The virtual model is compared to experimental data for validation. An extensive research in the literature has been done in order to find the most usual ways of modeling and analyzing washing machine dynamics during spin.

Recentemente, uma mudança de paradigma vem impactando toda a engenharia e manufatura na forma de se planejar, projetar, testar e construir produtos. A forma mais tradicional de desenvolvimento, que se caracterizava pelo processo seriado de múltiplos ciclos de design-construção-teste, vem sendo substituída gradativamente por processos de desenvolvimento guiados por simulação computacional. Decorrentes disso, os primeiros protótipos físicos são freqüentemente capazes de atingir os objetivos quando testados. Esta mudança, chamada também de projeto baseado em simulação, permite reduzir drasticamente o tempo de desenvolvimento de produtos e trazer a inovação para o mercado. Este trabalho apresenta uma forma computacional, via técnica de multicorpos, para se analisar a dinâmica de uma lavadora de eixo vertical. É proposto um protótipo virtual no software ADAMS, para estudo dinâmico de uma lavadora durante o processo crítico de centrifugação. O modelo virtual é posteriormente confrontado com dados experimentais, para sua validação. Uma extensa pesquisa bibliográfica foi realizada, com a intenção de capturar as técnicas mais usuais de modelamento e estudo dinâmico em lavadoras, bem como de compreender melhor o papel de seus componentes durante o processo crítico de centrifugação. / Recently a paradigm shift has impacted the engineering and manufacturing in the way of planning, designing, testing and building products. The most traditional way of product development, characterized by multiple cycles of design-build-test, has been substituted by a process based on computational simulation, where the first physical prototypes are capable of delivering the desired performance. This new way of developing products is called simulation based design and allows organizations to reduce drastically the product lead time and bring innovation to the market. This work presents a computational way to analyze the dynamic behavior of a top load washing machine using multibody system (MBS). It\'s proposed a virtual prototype developed in the ADAMS software, for dynamic study of a commercial washing machine during spin cycle. The virtual model is compared to experimental data for validation. An extensive research in the literature has been done in order to find the most usual ways of modeling and analyzing washing machine dynamics during spin.