Soft body armour is usually constructed by layering numerous layers of the same fabric. Such a construction, however, may not be the most efficient in providing the required protection due to different ballistic resistant efficiency of each layer. This research aims to optimise the construction of the panels for soft body armour by hybridisation in order to achieve the improvement of ballistic performance and reductions in weight. Twaron woven fabrics with different weave structures and Dyneema uni-directional (UD) laminates were used as components for the hybrid design of panels. Two complementary research approaches were employed in this study, namely the empirical method and the Finite Element (FE) analysis. The first part of this research systematically revealed the different ballistic characteristics of each layer in different positions of an armour panel and the way of energy absorption in the panel. The fabric layers in the front, middle and back of the panel exhibited different extent of transverse deformation and stress distribution. The energy absorption increases from front layer and reaches to the maximum value in the last perforated layer and then decreases gradually in the following back layers. Such pattern of energy absorption was not affected by either the striking velocity or the total number of layers in the panel, but the position, in the thickness, of the peak value in energy absorption was shifted more towards the back of the panel when the striking velocity increases. Such findings contribute to the understanding of different ballistic responses in different positions of an armour panel under ballistic impact. The second part of this research put forward a new hybrid design concept. According to above theoretical understandings of different ballistic characteristics in different positions of an armour panel, the fabric layers in the panel were discretely divided into three groups. In addition to the performance of different components for the panel and the influences of the laying sequence, a procedure for constructing hybrid armour panels has been established. The first group was composed of the first few layers on the striking face. The heavyweight fabrics as heat resistant layers were used in this group to resist the heat generated on the striking face. The second group contained some middle layers close to the last perforated layers. The lightweight fabric was combined in this group due to the higher energy absorption capacity. All back layers were classified into the third group. Dyneema UD laminates were placed in this group to constrain the large transverse deflection of the lightweight fabric and to minimize BFS of the panel. Two hybrid panels were designed and evaluated. In the perforation ballistic tests, the hybrid panel was more likely to stop the projectile compared to Twaron woven panels with the same areal density. In the non-perforation ballistic tests, the hybrid panel exhibited significantly lower BFS and achieved the reductions in weight. Such hybrid design makes best use of different available materials to achieve the improvement of ballistic performance and lightweight of a panel. It has a practical significance for the soft armour panel design.

This research investigated the residual stresses in narrow-gap API 5L X65 pipe girth welds in as-welded and after post weld heat treatment (PWHT) conditions. The PWHT included global furnace and local practices. Non-destructive neutron diffraction (ND) strain scanning was carried out on selected pipe spools and strainfree reference samples for the determination of the lattice spacing before and after PWHT. The as-welded and post-heat treatment residual stresses measured in the pipe spools were examined and compared. Experimental work also included full residual stress mapping in the weldment and through-thickness measurement at weld centre and close to the external and internal pipe surfaces. The measured profiles were compared with the recommendations given in British flaw assessment procedure BS 7910 "Guide to methods for assessing the acceptability of flaws in metallic structures" and the UK nuclear industry's R6 procedure. The design, preparation and experimental neutron diffraction measurement procedures for the determination of the strain-free lattice parameter in various configurations of reference samples and in the required directions were discussed. The variability of the lattice spacing in the reference samples was found depended on the specimen manufacture methods and thermal process. Welding residual stresses were also simulated using finite element analysis (FEA) modelling approach. The simulated thermal cycles and transient strains at specific locations were compared with the experimental readings. The residual stress profiles derived from finite element model were compared with the measurements from neutron diffraction. It was found, the measured and simulated, as-welded - residual stress profiles showed good consistency in terms of stress distribution and magnitude to reasonable extent. Measurement results also indicated that local PWHT was effective in reducing the residual stresses in the pipes to a level similar to that achieved by a global approach.

Este estudo teve como objetivo analisar as tensões do osso periimplantar, analisando as forças axiais e oblíquas incidentes em um modelo 3D usando Método de Elementos Finitos (MEF) a partir de modelo experimental in vitro, que consistiu em: 1 implante Brånemark System MkIIIGroovde (3,75 mm de diâmetro, 13,0 mm de comprimento); 1 pilar multi-unit de 5mm de altura com parafuso de titânio e torque de 20Ncm; infraestrutura de cobalto-cromo revestida com cerâmica feldspática aparafusada com torque de 10 Ncm, e poliuretano simulando o osso. Para obter dados de deformação, extensômetros lineares elétricos (Strain Gauges) foram utilizados e os valores obtidos foram comparados com o MEF gerado a partir do escaneamento do modelo em Micro CT e reconstruído tridimensionalmente no software Simpleware. Uma vez construído o modelo do MEF, as propriedades mecânicas dos implantes de titânio foram substituídas pelas propriedades dos implantes de zircônia Y-TZP no programa ANSYS. Uma carga vertical e uma oblíqua, cada uma de 300N, foram aplicadas no centro da face oclusal da coroa de cada modelo e, em seguida, as tensões foram verificadas na região do osso periimplantar. As tensões encontradas no modelo de EF com força vertical aplicada foram 0,92 MPa na região vestibular, 1,15 MPa na lingual, 0,98 MPa na mesial e 1,00 MPa na região distal para implante de titânio. Quando utilizado implante de zircônia com carga aplicada vertical os valores de tensão foram em vestibular 11,66 MPa, em lingual 9,73 MPa, em mesial 9,76 MPa e em distal 9,59 MPa. No modelo de EF com força oblíqua de 30o os valores foram em vestibular 0,92 MPa, em lingual 1,14 MPa, em mesial 0,97 MPa e em distal 0,99 MPa com o mesmo implante de titânio. O mesmo implante com carga inclinada (30o) gerou valores de tensão de 10,23 MPa em vestibular, 8,30 MPa em lingual, 8,48 MPa em mesial e 9,51 MPa em distal. A tensão diminuiu numericamente com o implante de zircônia, com as incidências de cargas verticais e oblíquas. / This study aimed to analyze the tensions of the periimplant bone around a single implant, analyzing axial and oblique incident forces in a 3D Model using Finite Element Method. Experimental in vitro model consisted of: Brånemark System MkIIIGroovde implant (3.75 mm diameter, 13.0 mm length); multi-unit set abutment of 5mm height with titanium screw and trque of 20Nm; cobalt-chromium coping coated with feldspathic ceramic screwed with a torque of 10Nm, and olyurethane simulating the bone. Strain gauges were used to set up this experimental model and the values obtained were compared with FEM generated from the model scanning in Micro CT and developed in Simpleware software. After this, the mechanical properties of the titanium implants were replaced by the properties of Y-TZP zirconium implants in ANSYS software. A vertical and an oblique load, each one of 300N, were applied on the center of the occlusal aspect of the crown of each model and then the tensions were verified in the periimplant bone region. The tensions generated in the FE model with vertical force applied were 0.92 MPa on vestibular region, 1.15 MPa on lingual, on mesial 0.98 MPa and 1.00 MPa on distal region for titanium implant. When applied vertical load in zirconia implant, the values were 11.66 MPa on vestibular, 9.73 MPa on lingual, 9.76 MPa on mesial and 9.59 MPa on distal. In the FE model under 30o oblique load, the values were 0.92 MPa on vestibular, 1.1457 MPa on lingual, 0.97 MPa on mesial and 0.99 MPa on distal with the same titanium implant. Zirconium implant with oblique load (30o) generated tension values of 10.23 MPa on vestibular, 8.30 MPa on lingual, 8.48 MPa on mesial and 9.51 MPa on distal. The stress numerically decreased with zirconia implant with vertical and oblique loads.

nÃo hà / O Ãngulo mandibular tem sido descrito como uma Ãrea frÃgil e, acredita-se que, com a presenÃa do terceiro molar, a mandÃbula perde parte de sua estrutura para abrigar tecidos que nÃo contribuem para sua resistÃncia estrutural. Neste contexto, o artigo produzido nessa tese teve como objetivo identificar Ãreas de concentraÃÃo e distribuiÃÃo de estresse na regiÃo do Ãngulo em uma mandÃbula portando os dois terceiros molares erupcionados, outra portando apenas um terceiro molar erupcionado e outra sem terceiros molares apÃs a aplicaÃÃo de um trauma mentual por meio de simulaÃÃes computacionais por elementos finitos. Foi reconstruÃda uma mandÃbula atravÃs da discretizaÃÃo de mÃscaras por um processo de identificaÃÃo digital e atribuiÃÃo de propriedades de acordo com a densidade tomogrÃfica para o osso cortical e medular, ligamento periodontal, cemento, dentina, esmalte e polpa. Para diferenciar as estruturas, a mandÃbula portando os terceiros molares recebeu uma substituiÃÃo digital das propriedades correspondentes a esses tecidos dentÃrios por mÃscaras correspondente aos tecidos Ãsseos, assim produzindo as duas outras estruturas do estudo. De modo a reproduzir a condiÃÃo anatomia real, os nÃs da vertente posterior dos cÃndilos foram deixados imÃveis e foram criados elementos para reproduzir a aÃÃo da musculatura mastigatÃria. Cada um dos corpos recebeu um impacto mentual perpendicular ao plano frontal de 250 quilograma-forÃa. Os resultados foram avaliados por anÃlise descritiva do diagrama cromÃtico da dispersÃo de estresses de Von Misses. Um modelo detalhado, relacionado ao paciente, de alta resoluÃÃo foi produzido com uma alta densidade de elementos finitos (914.952 elementos para mandÃbula 01, 867.183 para a 02 e 831.897 para a 03). Devido ao mÃtodo detalhado de obtenÃÃo dos corpos e à metodologia do estudo foi possÃvel obter resultados adequados para a resposta ao impacto. De acordo com o diagrama de dispersÃo de tensÃes, sempre que o terceiro molar esteve presente, seja bilateral ou unilateralmente, houve uma maior concentraÃÃo de tensÃes ao redor da porÃÃo cervical do alvÃolo desse dente. No entanto, quando o dente estava ausente, houve uma concentraÃÃo de energia maior no colo do cÃndilo. O presente trabalho apresentou um modelo experimental que reproduz adequadamente a dinÃmica mandibular e que evidenciou o comportamento da estrutura mandibular frente à um impacto mentual. Neste caso, o terceiro molar à responsÃvel pela concentraÃÃo de tensÃes na regiÃo da linha oblÃqua externa e trÃgono retro-molar, justificando que esse dente contribui para uma maior fragilidade do Ãngulo mandibular. / The mandibular angle has been described as fragile area, the presence of the third molar has been suggested to contribute to increased mandibular fragility because the mandible loses parts of its bone structure to harbor an organ that does not contribute to its strength. In this context, the article produced on this thesis had the objective of identify areas of tension concentration and its distribution on the mandibular angle if both third molar were present, if only one was present, and without third molars. Each mandible was submitted to blunt mentual trauma and evaluated by a finite element methodology. A mandible was reconstructed through the discretization of masks by a digital process of identification of structures considering the tomographic density to the cortical and medullar bone, periodontal ligament, cement, dentin, enamel and pulp. To differentiate the structures, the first mandible with both third molars was submitted to a digital replacement of the mask from the third molar structures to the masks of the cortical and medullar bone. Therefore, producing the two other structures of the study. To reproduce the normal anatomic situation, the external nodes of the most posterior and superior part of the mandibular condyle were fixated in all degrees of freedom bilaterally, and elements were created to reproduce the actions of the masticatory muscles. Each structure was submitted to a blunt mentual trauma, perpendicularly to the frontal plane, with 250 kilograms of magnitude. The results were evaluated by the description of the chromatic stress distribution diagram of Von Misses. A highly detailed, patient-specific, custom-made, high-resolution model of the mandible could be generated with a very dense volume mesh (914.952 elements for the mandible 01, 867.183 for 02, and 831.897 for 03). Due to the detailed method of body prove attainment and to the study methodology it was possible to obtain adequate results to the dynamic of the impact. According to the diagram of the dispersion of tensions, whenever the third molar was present, unilateral or bilateral, there was a greater concentration of tensions around the cervical part of the alveolus. However, when absent the stress concentration was more significant on the condylar neck. The present study showed an experimental model that reproduces the mandibular dynamics and the behavior of the mandibular structure to a mentual trauma. As a conclusion, the third molar is responsible to a tension concentration on the region of the external oblique ridge and retromolar area justifying that these teeth contribute to the mandibular angle fragility.

Proximal humerus fractures are the third most common fractures in the over-65 patient population and their stable fixation remains a key challenge in orthopaedic and trauma surgery. While Open Reduction Internal Fixation by plate has become a well-known treatment modality in the last few decades, clinical studies associate high complication rate with its use. The overall aim of this project was to create a computer-aided design framework for proximal humerus plates using a validated subject-specific humerus-plate finite element model. The framework consisted of three stages: (1) reverse engineering of bone and plate geometry, (2) creation and validation of a finite element model simulating the in vitro testing of the bone-implant construct and (3) parametric optimisation study of implant design using this model. In vitro biomechanical tests were conducted to not only compare the mechanical performance of three key commercially available proximal humerus plates (S3-, Fx- and PHILOS plate) but also the effect of different screw zones. Sixty-five humeri specimens with two-part surgical neck fractures were treated and grouped based on their different screw configurations. Extension, flexion, varus and valgus bending were applied in the cantilever fashion in the elastic tests whereas only varus bending was applied in the plastic tests. The load required to apply 5 mm displacement was measured to determine bone-plate construct stiffness. The S3 plate yielded the stiffest constructs and while the removal of the inferomedial support had the most impact on varus bending stiffness, type of medial support was important: inferomedial screws in the Fx plate achieved higher bending stiffness than blade insertion. Stability of constructs treated with the plate was an interplay of factors such as the plate’s and screws' number, orientation and position. Next, a subject-specific finite element model of the humerus-plate construct was successfully developed that simulated the stiffest of the constructs from the in vitro varus bending tests conducted in this project. The model was validated against the in vitro results. The validated model was then used to perform a parametric optimisation study where the combination of design parameters (height and divergence angle of S3 plate’s inferomedial screws) was determined that achieved optimum bone-plate construct stability (minimum fracture gap change). Out of the 538 designs tested, the optimum design (16o divergence angle and 33o height angle) yielded the lowest fracture gap change (0.156 mm) which was 4.686% lower than the standard finite element model while achieving 5.707% higher varus bending load (54.753 N). The validated model was also used to investigate the issue of using smooth pegs and threaded screws. Twenty-six models with different percentages of screw threading were run to compare their bone-plate construct stiffness. While threading the smooth pegs was found to increase the varus bending stiffness by up to 4.546%, it did not affect all screws equally. Finally, the successful completion of the optimisation study of screw orientation and the clinical investigation promises the implementation of the computational framework for a range of future multi-objective optimisation studies of multiple design parameters especially for the design of implants for other parts of the human body and also for investigations into other clinically relevant questions.

Timber is an inherently sustainable material which is important for future construction in the UK. In recent years many developments have been made in relation to timber technology and construction products. As the industry continues to look to construct more efficient, cost effective and sustainable buildings a number of new engineered timber products have emerged which are principally manufactured off-site. In terms of light timber frame, products such as structural insulated panels (SIPs) and engineered floor joists have emerged. For heavy timber construction, systems such as glulam and cross laminated timber (CLT) are now increasingly common. Despite many of the obvious benefits of using wood as a construction material a number of concerns still exist relating to behaviour in fire. Current fire design procedures are still reliant upon fire resistance testing and 'deemed to satisfy' rules of thumb. Understanding of 'true' fire performance and thus rational design for fire resistance requires experience of real fires. Such experience, either gathered from real fire events or large fire tests, is increasingly used to provide the knowledge required to undertake 'performance based designs' which consider both fire behaviour and holistic structural response. At present performance based structural fire design is largely limited to steel structures and less frequently concrete buildings. Many of the designs undertaken are in accordance with relevant Eurocodes which give guidance on the structural fire design for different materials. For the same approaches to be adopted for timber buildings a number of barriers need to be overcome. Engineered timber products, such as SIPs and engineered joists, are innovative technologies. However, their uptake in the UK construction market is increasing year on year. Little is known about how such systems behave in real fires. As a result the development of design rules for fire is a difficult task as failure modes are not well understood. To overcome this barrier the author has undertaken a number of laboratory and natural fire tests on SIPs and engineered floor joists to establish how such products behave and fail in real fires. The data gathered can be used to develop design approaches for engineered timber products in fire, thus negating the need to rely upon fire resistance testing. The development of design rules from the data gathered would be a progressive step towards performance based design. Realising performance based fire design for timber structures at present has three obvious barriers. Firstly, thermo-physical properties for timber exposed to natural fires are not well defined. Current guidance in standards such as EN 1995-1-2 provides data for standard fire exposure only. Movement towards design for parametric fires requires a better understanding of timber thermo-physical behaviour under different rates of heating and durations of fire exposure. Secondly, particularly in the UK, the fire performance of timber buildings is heavily influenced by the behaviour of gypsum plasterboard which is commonly used as passive fire protection. The thermal behaviour of gypsum under both standard and natural fire conditions is still not well understood. The majority of research available relating to gypsum in fire is dated, whilst board products continually evolve. Finally, the whole building behaviour aspects utilised in the fire design of steel and other structures have arisen as a result of complex numerical simulations. At present most commercial finite element codes are not appropriate for modelling entire timber buildings exposed to fire due to complexities relating to the constitutive behaviour of timber. Timber degrades differently depending upon stress state (i.e. tension or compression), temperature and importantly temperature history. In recognition of the above barriers, the author has made a number of developments. Firstly, a modified conductivity model for softwood is proposed which is shown to give acceptable depth of char and temperature predictions in timber members exposed to the heating phase of parametric fires. This model is suitable for adoption in any computational heat transfer model. Secondly, the finite element software TNO DIANA has been modified, via user supplied subroutines, to simulate large timber buildings exposed to fire by considering stress state, temperature and state history. The developments made in this engineering doctorate are intended to facilitate the progression of performance based design for timber structures. The numerical approaches adopted herein have been supported using multi-scale experimental approaches. As a result a number of novel tools for implementation in FEA models are proposed which should ultimately lead to a more rational approach to the fire design of timber buildings.

Track stiffness is the one of the most critical parameters of the track structure. Its evaluation is important to assess track quality, component performance, localised faults and optimise maintenance periods and activities. Keeping the track stiffness within acceptable range of values is connected with keeping the railway network in a satisfactorily performing condition, allowing thereby upgrade of its capacity (speed, load, intensity). Current railway standards are changing to define loading and stiffness requirements for improved ballasted and ballastless performance under high speed train traffic. In recent years various techniques have been used to measure track deflection which have been also used to validate numerical models to assess various problems within the railway network. Based on recent introduction of the Video Gauge for its application in the civil engineering industry this project provides the proof of effective applicability of this DIC (Digital image correlation) tool for the accurate assessment of track deflection and the calculation of track stiffness through its effective applicability in various track conditions for assessing the stiffness of various track forms including track irregularities where abrupt change in track stiffness occur such as transition zones and rail joints. Attention is given in validation of numerical modelling of the response of insulated rail joints under the passage of wheel load within the goal to improve track performance adjacent to rail joints and contribute to the sponsoring company s product offering. This project shows a means of improving the rail joint behaviour by using external structural reinforcement, and this is presented through numerical modelling validated by laboratory and field measurements. The structural response of insulated rail joints (IRJs) under the wheel vertical load passage is presented to enhance industry understanding of the effect of critical factors of IRJ response for various IRJ types that was served as a parametric FE model template for commercial studies for product optimisation.

Seismic events around the globe directly affect all ranges of structures, from complex and expensive ‘skyscrapers’ to simple frame structures, the latter making up a higher proportion of the number of structures affected as they are a much more common type of structure. The impact of a seismic event can be devastating, especially if adequate predictions of their impact and imposed structural response are not made during the design stage of the structure. Knowing what response to expect allows the engineer to design the structure to survive an event and protect the occupants. The structural response to a seismic event is very complex and can be affected by a wide range of structural, geotechnical and environ parameters. While larger, expensive structures make use of expensive, time consuming, finite element analytical procedures to determine their response the cheaper, simpler, frame structures have to make do with existing, simplified, spectral method predictions. This research firstly involves finite element analysis of simple frame structures, considering different structural and geotechnical parameters which may influence the seismic response, namely the stiffness of the structural joints, the geometry of the structure (influencing the individual structural element flexibility) and the foundation conditions (fixed base or shallow foundations with soil structure interaction). A range of frames, of varying geometry, are considered which mobilise different amounts of inter-storey drift, local rotation and global rotation response. The influence of soil structure interaction (SSI) and frame rigidity (i.e. the properties of the joints) on the response behaviour is investigated. The finite element database is then used to validate improved methods for predicting the spectral response parameters, specifically the natural period and damping of equivalent single degree of freedom (SDOF) systems, which include the effects of frame rigidity, geometry and SSI. Dynamic centrifuge testing is also carried out in order to further validate the improved spectral model for the case of real soil with shear dependant stiffness. The physical model testing is also extended to consider how environs, such as other structures in close proximity, influence the response of a structure.

O emprego dos implantes osseointegráveis na odontologia moderna tem sido crescente. Dentre os tipos de conexões existentes, o cone Morse tem se mostrado com vantagens e atrativos interessantes. Com relação ao comprimento, a aplicabilidade de implantes curtos para casos de perda óssea vertical intensa se faz muito presente, principalmente em áreas mandibulares posteriores, a fim de se evitar procedimentos cirúrgicos mais complexos que envolvam maior morbidade. Juntamente com a perda óssea, a necessidade da manutenção do plano oclusal nivelado é inquestionável, sendo necessário o uso de próteses sobre implantes curtos com dimensões maiores, podendo haver sobrecarga sobre tais implantes e estruturas de suporte. O método dos elementos finitos (MEF) possibilitou avaliar as tensões na superfície dos implantes e componentes, e na interface entre implantes e rebordo ósseo. Neste estudo foram usados modelos de implantes cone Morse e próteses sobre implantes do tipo metalocerâmicas, individualizadas, de diferentes dimensões, alojados em diferentes rebordos com reabsorção óssea vertical. Todas as estruturas foram desenhadas por meio do programa SolidWorks (SolidWorks Corporation, Massachusetts, USA), e análises qualitativas e quantitativas das tensões equivalentes de Von Mises foram realizadas nos rebordos ósseos e implantes por meio do programa AnsysWorkbench10.0 (Swanson, Analysis Systems, Inc., Houston, USA). Os grupos foram: grupo controle (3 implantes de 11mm comprimento), grupo 1 (implantes de 13mm, 11mm e 5mm comprimento), grupo 2 (1 implante de 11mm e 2 implantes de 5mm comprimento) e grupo 3 (3 implantes de 5mm comprimento). As alturas dos pilares usados foram 3.5mm para implantes de 13mm e 11mm (regulares) e 0.8mm para implantes de 5mm (curtos). Foram simuladas forças oblíquas de 365N em molares e 200N em pré-molares. Os resultados mostraram que, com relação aos implantes e componentes, os pilares com 0.8mm de altura geraram menores tensões equivalentes de Von Mises comparativamente aos de 3.5mm de altura. A associação de implantes curtos com coroas de maiores dimensões concentrou maiores valores e distribuição de tensões na superfície destes implantes, principalmente na face vestibular (direção das cargas oblíquas). O implante mais distal sempre concentrou maiores tensões. Já com relação ao osso, houve 50% mais tensão no osso cortical para os implantes de 5mm do que os de 13mm e 11mm de comprimento. Houve 80% mais tensão no osso esponjoso para os implantes de 5mm do que os de 13mm e 11mm de comprimento. Houve maior concentração de tensão na região óssea cervical aos implantes curtos. No entanto, tais implantes foram capazes de realizar boa dissipação das tensões aos ossos frente às cargas aplicadas, apesar de atingir seu limiar próximo entre deformação elástica e plástica para o osso trabecular. Implantes mais distais e/ou com maior mesa oclusal geraram regiões de maior tensão no osso circunjacente. Concluiu-se que pacientes que se faz necessária a instalação de implantes curtos associados a próteses sobre implantes de dimensões aumentadas necessitam de cuidadosa avaliação e ajuste oclusal, já que uma eventual sobrecarga nestes implantes curtos, e até mesmo nos de comprimento regular, podem gerar tensões que vão além do limiar fisiológico do osso circunjacente, podendo acarretar danos a todo o sistema. / The use of dental implants is increasing in dentistry. Among the different types of connections existent, the Morse taper has been highlighted on several positive features. Regarding to the length, the use of short implants in cases of severe vertical bone loss are becoming frequent, especially in mandibular posterior areas, avoiding more complex surgical procedures and greater morbidity. As a consequence of bone loss, the need for rehabilitation to maintain the occlusal plane level is unquestionable, leading to the use of implants prostheses with larger dimensions, which may cause overload on these short implants and the supporting structure. This finite element analysis (FEA) compared stress distribution on external surface of Morse taper implants, their abutments and at bone/implant interface of different bone ridges, varying implants length and dimensions of each metal-ceramic crowns. All structures were designed using the SolidWorks software (SolidWorks Corporation, Massachusetts, USA), and qualitative and quantitative analysis of the equivalent Von Mises stresses were ran on AnsysWorkbench10.0 (Swanson Analysis Systems, Inc., Houston, USA). Three-dimensional FE models were designed representing a posterior left side segment of the mandible: group control, 3 implants of 11mm length; group 1, implants of 13mm, 11mm and 5mm length; group 2, 1 implant of 11mm and 2 implants of 5mm length; group 3, 3 implants of 5mm length. The abutments heights were 3.5mm for 13mm and 11mm implants (regular) and 0.8mm for 5mm implants (short). Evaluation was performed on Ansys software, with oblique loads of 365N for molars and 200N for premolars. The results, for implants and abutments, showed that abutments with 0.8mm height generated less von Mises stresses compared with 3.5mm height. The use of short implants associated with bigger crowns concentrated higher stress distribution and stress values on the surface implants, mainly on the vestibular side (oblique loads). The more distal implants had the higher stress mesures. The results for the bone showed that there was 50% higher stress on cortical bone on the 5mm implants length than 13mm and 11mm implants. There was 80% higher stress on trabecular bone for the 5mm implants length than 13mm and 11mm implants. There was higher stress concentration on the bone region of the short implants neck. However, these implants were capable to dissipate the stress to the bones, given the applied loads, but achieving near the threshold between elastic and plastic deformation to the trabecular bone. Distal implants and/or with biggest occlusal table generated greatest stress regions on surrounding bone. It was concluded that patients requiring short implants associated with increased proportions implant prostheses need careful evaluation and occlusal adjustment, as a possible overload in these short implants, and even in regular ones, can generate stress beyond the physiological threshold of the surrounding bone, which may compromise the whole system.

O objetivo deste estudo foi analisar, por meio do método dos elementos finitos, como ocorreram as distribuições de tensões nos dentes, osso e aparelho ortodôntico, durante a fase de retração por deslizamento (150g), em um caso com extrações. Simularam-se duas posições do gancho (mesial e distal de canino), duas alturas do gancho (4 e 9mm) e duas alturas posteriores (gancho do tubo do molar e no miniimplante, a 9mm do arco). A amostra consistiu do corte axial da TCFC, de uma mulher de 17 anos de idade, com dentes bem nivelados. Foi desenvolvido um modelo 3D, da geometria da hemi-maxila direita e um modelo numérico, para obter os regimes de tensões e deformações gerados em um sistema de movimentação ortodôntica, por meio do software ANSYS® versão 12.0. Os sólidos dos braquetes e do fio ortodôntico foram incluídos a partir das dimensões fornecidas pelo fabricante. A montagem de todos os componentes foi feita por meio do SolidWorks 2009 SP4.1. A partir do cálculo das respostas do modelo, às cargas a que foi submetido, verificou-se que, os dentes que sofreram maiores concentrações de tensões foram os justapostos aos ganchos, sendo mais intensas as do gancho mesial, particularmente nos incisivos laterais. Embora, a solicitação de tensões no arco tenha sido semelhante em todos os modelos, na posição distal do gancho, houve maior concentração de tensões na extensão imediatamente distal. Os modelos com ganchos de 4mm, diferente aos de 9mm, apresentaram distribuições de tensões mais uniformes, causando menos estresse aos dentes e osso e semelhante ao arco. O modelo com vetor de força direcionado do gancho da mesial do canino ao miniimplante foi o único que mostrou variações, mostrando distribuições de forças mais elevadas na região anterior e posterior ao ser comparado com o vetor de força direcionado ao tubo do primeiro molar. / The aim of this study was to evaluate, by means of finite element analysis, the tensions distrubutions on the teeth, bone and orthodontic appliance, during en-masse retraction sliding mechanics (150g), in an extraction case. It was taken into account two hook positions (mesial and distal to the canine), two hook heights (4mm and 9mm) and two posterior heights ( the first molar tube and the mini-implant, located 9mm from the archwire). The sample of this study consisted of an axial cut realized in a cone beam computed tomography of a 17 years old woman with leveling teeh. It was developed a 3D computed model of a right hemi-maxilla and a computednumerical model capable of getting the systems tensions and deformations generated from an orthodontic moviment system, through a finite element software, ANSYS® 12.0. Observing manufactores specifications, brakets and archwire solids were included in this solid geometric model. The assembly of all componentes were made though the SolidWorks 2009 SP4.1 software. The loads model responses were calculated. The bigger concentration of tension were on the teeth located between the hook. The model with the mesial hook, suffered more intense tensions, mainly on lateral incisors. Although, the tensions request on the archwire were similars in all models, when the hook was located distaly, there were more intense tensions in its immediately distal extension. The 4mm hook models, compared with the 9mm, presented more uniform tensions distribution causing less stress to the teeth and bone and similar to the archwire. The only model that demonstrated variations, was the model with the vector force from the mesial hook and to the mini-implant. This model, demostrated higher tensions distributions on the anterior and posterior region if compared to the first molar tube vector force.