Dissertations / Theses on the topic 'Riveted joints'

The objective of this study is to model and analyze a three dimensional single riveted lap joint (with and without a crack). By using finite element method, stress and fracture analyses are carried out under both the residual stress field and external tensile loading. Using a two step simulation, riveting process and subsequent tensile loading of the lap joint are simulated to determine the residual and overall stress state. Residual stress state due to riveting is obtained by interference and clamping misfit method. By employing different interference and clamping misfit values, the effects of riveting process parameters on stress state are examined. Two cracks namely the semi elliptical surface crack at faying surfaces of plates and the quarter elliptical corner crack at rivet hole are the most widely observed crack types in riveted joints. Fracture analysis of cracked riveted joints is carried out by introducing these two crack types to the outer plate at a plane perpendicular to the loading. The mixed mode stress intensity factors (SIFs) and energy release rates (G) around the crack front are obtained by using displacement correlation technique (DCT). Effects riveting process parameters (interference and clamping ratios) and geometrical parameters (crack shape and size) on fracture parameters are studied. The stress intensity factor solutions presented herein could be useful for correlating fatigue crack growth rates, fracture toughness computation, and multiple site damage (MSD) analysis in aircraft bodies.

The introduction of alternative materials and in particular aluminium alloys, for vehicle body applications has impelled the development of new joining techniques. Traditional joining methods such as spot-welding and arc-welding are being challenged. Self-piercing riveting has attracted considerable interest by the automotive industry and has been used as an alternative to spot-welding in vehicle body assembly. However, self-piercing riveting is a relatively new joining method and as such it is not well understood. The aim of this project was therefore to develop an understanding of the mechanical behaviour of self-piercing riveted joints. The effects of paint-baking, shelf-life, pre-straining and surface condition of the sheet material on the joint quality and behaviour were therefore examined. Aluminium alloy sheet materials, 5754 and AA6111, were used in this investigation. The project began with a metallographic inspection of cross-sections of samples that were joined under different conditions in order to examine the effect of process variables on the joint quality. This part of the investigation led to the identification of suitable setting parameters that produced joints which, by metallographic inspection, were of good quality. It was also observed that some process variables, such as sheet thickness combination, rivet and die design and setting force, affected the joint quality and therefore needed to be taken into consideration in the choice of the processing parameters. Subsequent work focused on mechanical testing. Lap shear, T-peel, pull-out and fatigue tests were carried out in order to examine the mechanical behaviour and to analyse the failure mechanisms of the joints. The work showed that the strength, the thickness and the surface condition of the riveted sheets affected the strength and the failure mechanisms of the joints. The joint strength was also observed to be dependent on the rivet and anvil design as well as the setting force. In addition, the joint strength and behaviour differed as the specimen geometry thus emphasising the need for a test standard for self-piercing riveted joints. Paint baking led to a marginal and insignificant reduction in the static strength, whilst resulting in a reduction in the fatigue strength of the joints as a consequence of recovery of the 5754 alloy and the removal of the wax-based surface lubricant. The effect of 3%, 5% and 10% pre-straining of the 5754 sheet on the quality and performance of the self-piercing riveted joints was also examined. It was established that it was possible to produce joints of good quality, higher strength and superior fatigue performance by using the same setting parameters as for joints without additional pre-straining. An investigation of the effect of the shelf-life of AA6111 indicated that this only had a minor and insignificant effect on the joint quality and behaviour. It was therefore deduced that the quality and performance of joints would not be compromised even after an AA6111 self-life of 21 months. The effect of the interfacial characteristics on the joint quality and behaviour was examined by placing a PTFE layer at the interface between the riveted sheets. It was observed that the PTFE insert significantly reduced the joint strength and changed the failure mechanism. Three distinct failure modes, referred to as rivet pull-out, rivet fracture and sheet material failure, were observed during this investigation. All shear tested samples failed by rivet pull-out. The same failure mechanism was the only one observed for the pull-out tests. The failure mechanism for the peel test depended on the thickness of the rivet sheet. For joints with a (1 mm+2mm)/(0.9mm+2mm) combination, fracture of the thinner sheet material dominated the failure mechanism, whilst for joints with a (2mm+2mm) combination, rivet pull-out was the only failure system. Rivet fracture and sheet material failure were also observed during fatigue testing. Examination of samples following fatigue testing led to the observation of fretting which had not been reported by previous investigators working with self-piercing rivets. Fretting had an important effect on the fatigue strength and fatigue failure mechanisms. Inspection of fatigue fractured samples which were tested at maximum applied loads ranging from 50% to 85% of the ultimate shear load of the joints exhibited fretting scars at three different interfaces. Flange-face fretting was observed to take place at one side of the interface between the two riveted sheets and led to the formation of mainly A1203 debris. Pin-bore fretting was observed to occur between the rivet shank and the aluminium alloy sheet and led to debris containing oxides of aluminium and iron together with the oxides of zinc and tin from the wear of the corrosion protective coating of the rivet. Both types of fretting were affected by the applied load and the surface condition of the riveted sheets. Further examination indicated that fretting contributed to the initiation and propagation of fatigue cracks. The failure modes during fatigue testing were affected by the fretting behaviour and were dependent on the applied load and the interfacial conditions. A PTFE layer introduced a very low coefficient of friction leading to a significantly reduction in the amount of fretting. However, this was accompanied with a change in the load transfer mechanism resulting in rivet fracture and a shorter fatigue life. The paint-baking process led to the removal of the wax-based surface lubricant and fretting cracks therefore initiated at an earlier stage of the fatigue test. In addition, fretting also led to a significant work-hardening of the riveted sheets. It was observed that there was an increase in microhardness at the regions immediately below the fretting area from the riveted sheets. The depth of the work-hardened area below the fretting interface after different periods of fretting represented the depth of damage as a result of fretting fatigue. It was therefore further indicated that fretting played an important role in the fatigue behaviour and would probably affect the crash behaviour of the joints. The effect of secondary bending, an inherent feature of lap joints, was examined and analysed using strain gauge measurements. It was established that secondary bending contributed to the failure mechanism and led to a significant reduction in the fatigue strength of such joints. Using the experimental data an analysis has been carried out to predict the fatigue strength in the absence of secondary bending.

The overall aim of the project is to examine the rivetability of new steels and to investigate the mechanical behaviour of self-piercing riveted (SPR) aluminium-steel hybrid structures for automotive applications. Interstitial Free Steel (I.F.) of 1.2 mm thickness was joined to Aluminium 5754 of 2 mm thickness and Aluminium 5182 (coated and uncoated) of 1.5 mm thickness. The work began by initially conducting a quality assessment of the various joints that were produced in order to establish the optimum conditions for joining the various sample combinations to be investigated. A relationship was established between the head height and the interlock distance on the one hand and between the interlock distance and the lap shear strength of samples. It was also established that for higher lap shear strength, it is preferable to use the stronger material (I.F. steel) as the pierced sheet and the weaker material (5182) as the locked sheet. However, the results showed that this rule could not be applied for predicting the fatigue behaviour of SPR joints between I.F. steel and 5182. An investigation of the fatigue failure mechanisms was undertaken and possible reasons for this behaviour are discussed. The influence of fretting was also investigated by using scanning electron microscopy and reported. The fatigue behaviour of Dual Phase (DP600 + 5182) SPR joints was investigated. It was observed that the position of fatigue crack initiation differed with the maximum applied load. An explanation for this observation was provided by considering the failure mechanism of the samples under different load levels. The study also showed how fretting led to the initiation of fatigue cracks. The corrosion behaviour of (I.F. steel + 5182) samples was investigated by conducting tests in a salt spray according to the ASTM B117-97 standard. Three types of corrosion were observed; galvanic corrosion, differential aeration corrosion, uniform corrosion and are discussed. The weight change with time was monitored and was used to describe the corrosion behaviour. The lap shear strength was measured as a function of corrosion time. The presence of the corrosion product within the overlap was observed to greatly influence the lap shear strength behaviour. A further study was carried out in order to examine the influence of the individual alloys on the corrosion of the SPR samples. In this part the potential influence of pulse current treatment on corrosion was also investigated and was observed to increase greatly the corrosion resistance of the I.F. steel. Principal findings for this observation are also provided.

Thesis (M.S.)--Wichita State University, Dept. of Industrial and Manufacturing Engineering.
" December 2006." Title from PDF title page (viewed on January 29, 2007). Thesis advisers: Hossein Cheraghi, Krishna Krishnan. Includes bibliographic references (leaves 62-64).

Aircraft fuselage skin panels are joined together by rivets. The initiation and propagation of fatigue cracks in aircraft structures at and around the rivet/skin interface is directly related to residual stress field induced during the riveting process and subsequent service loads. Variations in the manufacturing process, such as applied loading and presence of sealant can influence the induced residual stress field. In previous research, the riveting process has been simulated by a 2D axisymmetric force-controlled analysis. The 2D analysis cannot capture the unsymmetrical residual stress state resulting from process variations. Experimental work has also been limited to observing effects of squeeze force on fatigue crack initiation in the riveted lap joint. In this work, a 3D finite element model of the riveting process that incorporates plasticity and contact between the various surfaces is simulated using ABAQUS finite element code to capture the residual stress state at the rivet/skin interface. The finite element model is implemented to observe the effects of interference, sealant and hole quality on the residual stress state using Implicit and Explicit solvers. Effects of subsequent load transfer are also analyzed with the developed model. A set of controlled lap joint fatigue experiments for the different conditions provides validation to the model.

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering.
"December 2006." Title from PDF title page (viewed on Oct 31, 2007). Thesis adviser: S. Hossein Cheraghi. Includes bibliographic references (leaves 63-64).

Orientador: Fernando de Azevedo Silva
Banca: José Elias Tomazini
Banca: Silvana Aparecida Barbosa
Resumo: Juntas rebitadas sobrepostas representam elementos críticos na construção de estruturas aeronáuticas quando projetadas à fadiga. Por serem elementos de fixação largamente utilizados na indústria aeronáutica, o estudo de suas propriedades e variáveis à fadiga tem sido cada vez mais amplo. A variável que tem mostrado possuir alta influência na resistência à fadiga de juntas rebitadas é a força de aperto aplicada no processo de rebitagem. A vida da peça tende a ser maior quando o valor dessa força é aumentado. O método dos elementos finitos, que é uma ferramenta de cálculo aplicada nos mais diversos campos de atuação e tem se tornado parte indispensável de projetos mecânicos, é utilizado nesta dissertação para a análise de uma junta rebitada sobreposta de uso aeronáutico. A junta é simulada levando em conta as etapas do processo de fabricação e aplicação, a fim de realizar a análise de seu comportamento mecânico e calcular sua vida em fadiga. Através de um teste experimental de tração monotônica foram obtidos valores de deformação com extensômetros, e é feita a correlação desses dados com o modelo numérico a fim de validar a modelagem. Em seguida são feitas mais duas análises com diferentes forças de aperto, com o objetivo de verificar a influência dessa variação na vida em fadiga da peça.
Abstract: Riveted lap joints represent a critical element in metallic airframe construction when designing against fatigue. These elements are widely used in the aerospace industry, so the study of the fatigue's properties and variables has been increasingly broad. The variable that has shown to have a high influence on the fatigue strength of riveted joints is the clamping force applied to the riveting process. The life of the part tends to be higher when the clamping force applied is increased. The finite element method, which is a calculation tool applied in various fields of activity and has become an indispensable step of mechanical design, is used in this dissertation for the analysis of a riveted lap joint of aeronautic use. The joint is simulated considering the stages of the manufacturing process and application, in order to perform analysis of mechanical behavior and calculate the fatigue life. Through an experimental test of monotonic tensile, strain values were obtained with strain-gauges, and is made the correlation of these data with the numerical model to validate the modeling. Finally two more tests are made with different clamping forces, in order to check the influence of this variation in fatigue life of the joint.
Mestre

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Juntas rebitadas sobrepostas representam elementos críticos na construção de estruturas aeronáuticas quando projetadas à fadiga. Por serem elementos de fixação largamente utilizados na indústria aeronáutica, o estudo de suas propriedades e variáveis à fadiga tem sido cada vez mais amplo. A variável que tem mostrado possuir alta influência na resistência à fadiga de juntas rebitadas é a força de aperto aplicada no processo de rebitagem. A vida da peça tende a ser maior quando o valor dessa força é aumentado. O método dos elementos finitos, que é uma ferramenta de cálculo aplicada nos mais diversos campos de atuação e tem se tornado parte indispensável de projetos mecânicos, é utilizado nesta dissertação para a análise de uma junta rebitada sobreposta de uso aeronáutico. A junta é simulada levando em conta as etapas do processo de fabricação e aplicação, a fim de realizar a análise de seu comportamento mecânico e calcular sua vida em fadiga. Através de um teste experimental de tração monotônica foram obtidos valores de deformação com extensômetros, e é feita a correlação desses dados com o modelo numérico a fim de validar a modelagem. Em seguida são feitas mais duas análises com diferentes forças de aperto, com o objetivo de verificar a influência dessa variação na vida em fadiga da peça.
Riveted lap joints represent a critical element in metallic airframe construction when designing against fatigue. These elements are widely used in the aerospace industry, so the study of the fatigue’s properties and variables has been increasingly broad. The variable that has shown to have a high influence on the fatigue strength of riveted joints is the clamping force applied to the riveting process. The life of the part tends to be higher when the clamping force applied is increased. The finite element method, which is a calculation tool applied in various fields of activity and has become an indispensable step of mechanical design, is used in this dissertation for the analysis of a riveted lap joint of aeronautic use. The joint is simulated considering the stages of the manufacturing process and application, in order to perform analysis of mechanical behavior and calculate the fatigue life. Through an experimental test of monotonic tensile, strain values were obtained with strain-gauges, and is made the correlation of these data with the numerical model to validate the modeling. Finally two more tests are made with different clamping forces, in order to check the influence of this variation in fatigue life of the joint.

Dans le cadre de la conception des structures aéronautiques et de la modélisation de leur tenue mécanique, la représentation des comportements non linéaires locaux conduisant à la rupture est nécessaire et notamment ceux des liaisons. Ainsi en situation de crash survivable, les liaisons sont soumises à des charges dynamiques qui peuvent conduire à la rupture et à la désarticulation. Pour caractériser la tenue au crash des assemblages rivetés, une méthodologie dite de plans d'expérience numériques est proposée ; son intérêt est de limiter le cout des procédures expérimentales. Fondée sur les techniques de modélisation par éléments finis et d'optimisation par méthode inverse, la méthode repose sur la détermination des paramètres du comportement non linéaire et à la rupture des matériaux constitutifs de la liaison rivetée. Le développement de l'outil informatique d'optimisation est présenté dans la première partie du mémoire. Les modèles de comportement de deux alliages d'aluminium composant l'assemblage sont identifiés grâce à l'optimiseur. Ils seront utilisés pour mener les simulations de différents essais effectués sur les assemblages. L'évaluation des contraintes et des déformations résiduelles dues au procédé de rivetage est abordée dans la deuxième partie. Les mécanismes de mise en forme des rivets sont analyses expérimentalement. Des simulations sont d'autre part entreprises à l'aide du code de calcul explicite pam-solid#t#m, afin d'introduire, une fois validées, les contraintes et les déformations résiduelles post-rivetage dans le calcul de la tenue mécanique de l'assemblage. La faisabilité des plans d'expérience numériques est démontrée dans la troisième partie. Les paramètres d'endommagement du modèle de Gurson sont identifiés par méthode inverse pour les deux matériaux composant l'assemblage. La qualité de l'ensemble des résultats obtenus permet notamment d'envisager l'emploi de l'outil de simulation dans le cadre de la caractérisation de modèles équivalents macroscopiques du rivet. Ces techniques de modélisation simplifiée des liaisons sont abordées dans la dernière partie. Un critère de rupture de la liaison est caractérisé par l'expérience à l'aide du dispositif Arcan et par plan d'expérience numérique. Un nouveau modèle non linéaire de la liaison est développé dans le code de calcul pam-solid#t#m et ses paramètres identifiés. L'ensemble des résultats obtenus est finalement appliqué à la simulation de l'écrasement d'une structure comportant 700 rivets.

L'accroissement des performances des équipements de Traction ferroviaire, reposait essentiellement jusqu'à maintenant, sur l'intégration des innovations dans le domaine des composants électriques et des matériaux diélectriques mais la standardisation de sous-ensembles réutilisables nous conduit à reconsidérer les assemblages structuraux des coffres de traction (convertisseurs de puissance). Ces coffres de traction sont assemblés actuellement avec des éléments de fixation mécanique (boulon, rivet), le but est donc d'améliorer la connaissance des comportements mécaniques de ces types d'assemblages à travers d'une étude expérimentale basée sur des essais statiques et dynamiques sur des joints boulonnés et rivetés. Ces essais nous ont permis de valider des modèles numériques par des éléments finis en utilisant les codes de calcul ABAQUS et ANSYS. La deuxième partie de la thèse concerne les assemblages par collage structural. Nous avons étudié la possibilité de remplacer les assemblages mécaniques classiques par l'assemblage par collage structural. La première phase de notre travail a été de recenser et sélectionner des adhésifs structuraux susceptibles de répondre à notre cahier de charge. Dans cette partie les travaux suivants ont été réalisés : - Etude des comportements des adhésifs en tant que matériau, ce qui a nécessité de réaliser des éprouvettes massiques. - Réalisation d'essais expérimentaux en statique et en dynamique sur des joints collés avec l'adhésif sélectionné. - Création des modèles numériques non linéaires en 3D sur ABAQUS pour les joints collés. - Etude hygrothermique accélérée afin d'étudier l'effet du vieillissement sur les assemblages collés en fonction de l'humidité et de la température
Increased performance of railway traction equipment, until now relied primarily on the integration of innovations in the field of electrical and dielectric materials, but the standardization of subassemblies reusable us to reconsider the structural assemblies of the traction cubicles (power converters). These cubicles are assembled now with mechanical fasteners (bolts, rivets), the first goal is to improve knowledge of the mechanical behaviour of these types of joints through an experimental study based on statics and dynamics tests of bolted and riveted joints. These tests have allowed us to validate numerical models of finite elements by using the computer codes ABAQUS® and ANSYS®. The second part of the thesis deals with the structural adhesive joints. We studied the possibility of replacing conventional mechanical assembly structural bonding. The first phase of our work was to identify and select structural adhesives that could meet our specifications. In this section the following work has been made: - Study of thermo-mechanical behaviour of the adhesive with the bulk Adhesive Test Specimens. - Statics and dynamics test in the bonded joint. - Non-linear 3D finite elements models. - Hygrothermal accelerated to study the effect of aging on the adhesive according to the humidity and temperature

Uniões por prendedores são elementos amplamente utilizados na indústria aeronáutica para a união de partes constituintes da aeronave. Contudo, devido à sua geometria e aos carregamentos sofridos, estes elementos estão frequentemente sujeitos a falhas por fadiga. Assim, para um projeto e dimensionamento bem executado dessas juntas, é necessário conhecer seu comportamento mecânico e o campo de tensões ao qual estão sujeitas. O método dos elementos finitos certamente atende a estas necessidades; porém, o uso de elementos sólidos tridimensionais para a representação destas uniões pode levar a análises demasiadamente demoradas e custosas, sendo desejável o uso de modelos mais simplificados. Nesse trabalho, juntas de topo assimétricas são modeladas pelo método dos elementos finitos, utilizando tanto elementos sólidos tridimensionais quanto elementos de casca, com o objetivo de encontrar um modelo relativamente simples que apresente resultados satisfatórios e requeira um menor tempo de solução. Os resultados numéricos obtidos são comparados com resultados experimentais, que utilizam extensômetros e fotoelasticidade.
Riveted joints are structural elements widely used in the aeronautic industry to connect different parts of the aircraft. However, due to their geometry and working load, they are frequently subjected to fatigue failure. Therefore, to a well executed project of this type of joint, it is necessary to understand the mechanical behavior and the stress field to which they are subjected. The finite element method can certainly answer those needs; however, the use of tridimensional elements to represent this type of joint can lead to time consuming and expensive analysis, being desirable the use of simpler models. In this work, asymmetric butt joints are modeled using the finite element method using both, tridimensional and shell elements, with the objective of finding a model that provides satisfactory results at smaller solution time. The numerical results obtained are compared with experimental results using strain gage and photoelastic procedures.

This thesis describes proposal of a methodology for evaluating fatigue life of riveted joints. The first section summarizes the theory used to evaluate fatigue life, description of the structure of operation load spectra and construction principles for the design joints for optimum durability. The second part of the thesis focuses on the proposal of a methodology enabling analytical solutions in closed form suitable for the initial structural design and also numerical solutions for use in detailed analyzes of the structure. The applicability of the methodology is demonstrated on an example of analysis of a real structural detail and subsequent comparison of the analysis with available test results.

Self-piercing riveting (SPR) is a high-speed mechanical fastening technique for point joining of sheet-material components. SPR is becoming important in automotive applications for aluminium vehicle body assembly. However, compared with current sheet-metal joining processes in the automotive industry, the effects of various parameters such as mechanical properties, rivet setting methods and systems, methods of removing self-piercing rivets, etc. A study examining the effect of specimen configuration on the mechanical behavior of self-piercing riveted, dual-layer joints in aluminium alloys was conducted. It has observed that the specimen configuration had a significant effect on the strength and failure mechanism of a self-piercing riveted dual-layer joint. The basic aspects of SPR process forming by conducting both explicit and implicit analysis have been investigated in this thesis. It was found that the operating force-deformation curve of SPR process was determined by the rivet deformation force and its displacement. Under certain process conditions, an increase in inertia effect due to high velocity of metal forming process results was not significant to an extent. In this research, the springback characteristic parameters of the SPR process were also studied. The springback analysis carried out at the end of the forming process showed that the dimensional change in the part due to springback was not significant.
Wichita State University, College of Engineering, Dept. of Mechanical Engineering
Includes bibliographic references (leaves 51-53)

Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
Copyright 2008 by Uma Shankar Krishnappa. All Rights Reserved. Includes bibliographical references (leaves 51-53).

In a structure, a joint is considered as the weakest part, and it should not get separated when subjected to loading, so that an unstable collapse of structure can be avoided. It is important to investigate the failure in joint before it is used in a structure. Failure of a joint depends on various factors such as the geometry of joint configuration, sheet strength that are joined, rivet material used, cracks developed during joining, and many other. Self-Piercing riveting process is a new technology for joining sheet metals in automobile and aircraft industries. This process has many advantages over conventional joining processes. In this thesis, the failure of a self-piercing riveted joint is investigated. Failure of three different riveted configurations under 35m/s and 60m/s velocities were predicted using the general purpose non-linear finite element software LS-DYNA. This research is divided into three stages of work. In the first stage, a 2D simulation of riveting process is carried out over two Aluminum sheets. An r-adaptive methodology is utilized to acquire a higher accuracy of results and to avoid high element distortion. A parametrical study is then conducted to study the effect of rivet penetration velocity and adaptive mesh size varies the quality of the joint. In the second stage of work, a spring back analysis of joint is conducted to study the deformations of work piece after the riveting process. In the third stage, a Peel specimen, a U-shaped single riveted connection, and a U-shaped double riveted connection were investigated for failure under 35 m/s and 60 m/s velocities in both shear and tension testing conditions. Three different loading conditions were used for testing. The results from this study will show how process parameters can influence the quality of riveted joint, amount of deformations that occur in the work piece after the removal of rigid bodies, and failure load of SPR joint in different configurations.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.

Foi realizado um estudo comparativo da capacidade de duas variantes do método de radiografia por raios- X em detectar trincas de fadiga em juntas sobrepostas rebitadas de laminado híbrido metal-fibra Glare® de uso aeronáutico. Durante os ensaios mecânicos de fadiga sob amplitude constante de tensão, diversos corpos de prova rebitados foram periodicamente inspecionados por raios-X, em ambas as modalidades convencional e digital. Raios-X em filmes convencionais digital. Raios-X em filmes convencionais proporcionaram ótimo detalhamento de trincas nas juntas mecânicas, enquanto que as imagens geradas pela modalidade digital apresentaram qualidade muito inferior, prejudicando ou até mesmo impedindo a avaliação do grau de integridade estrutural das juntas rebitadas.
A comparison is performed on the ability of two modalities of nondestructive X-ray radiography method in detecting fatigue cracks in riveted lap joints of aeronautical grade fiber-metal laminate Glare™. During constant amplitude loading in fatigue testing riveted specimens were periodically inspected using both the conventional and digital X-ray methodology. Conventional film X-ray modality provided high quality images of growing cracks in the mechanical joints, whereas digital radiography generated faulty images, which impaired or even prevented the structural integrity assessment of the riveted joints.

Diplomová práce je zaměřena na optimální modelování nýtového spoje pro tři různé konfigurace pomocí metody konečných prvků v programu MSC. Nastran/Patran. Na základě prezentovaných výsledků je možné virtuálně simulovat chování nýtových spojů při zatížení, za účelem správného návrhu před provedením statických pevnostních zkoušek. Použitím těchto MKP simulací v procesu certifikace výrobku lze významně redukovat časovou i finanční náročnost pevnostních zkoušek. Při lepším porozumění chování konstrukce lze také lépe predikovat reálnou únosnost nýtových spojů.

Dissertação apresentada para obtenção do grau de Mestre em Engenharia Mecânica, na Faculdade de Engenharia da Universidade do Porto, sob a orientação dos Professores Paulo M.S.T. de Castro e Artur Portela

Dissertação apresentada para obtenção do grau de Mestre em Engenharia Mecânica, na Faculdade de Engenharia da Universidade do Porto, sob a orientação dos Professores Paulo M.S.T. de Castro e Artur Portela

This thesis presents a study of the effect of controllable riveting parameters, mainly squeeze force, rivet length, rivet diameter tolerance, hole countersunk depth and hole diameter tolerance, on the quality of formed rivet. The quality of a formed rivet is determined by the geometry of its head formation and the extent to which the hole is filled. The study determines maximum allowable tolerance on drilled hole in a 0.064” thick aluminum sheet for a 1/8” rivet. The study is performed using finite element simulation of the riveting process. Theoretical relations between squeeze force and formed rivet head geometry derived in this study is used to validate the finite element model. Statistical design of experiment is employed to analyze the simulation data of riveting and determine the effect of individual factors, their interactions and relationship with the quality of formed rivet head. The results demonstrate that the correct formation of rivet head geometry depends upon all the factors studied. However, correct geometry of rivet head is not enough to determine the quality of a riveted joint, because the countersunk rivet head does not expand enough to fill up the hole completely, thereby creating a gap and leading to a loose rivet. The gap increases with the increase in tolerances in drilled hole, limiting its allowable tolerances to 0.006”. The length of rivet has no significant effect on the gap formation. To ensure the elimination of gap formation, an alternate procedure with reduced countersunk depth is studied, which allows for increased allowable tolerance in drilled hole. Results show that with as little as 0.01” reduced countersunk depth, the allowable tolerances on drilled hole could be increased to 0.03”, without compromising on the quality of the joint.
"December 2006."
Includes bibliographical references (leaves 62-64)

This thesis presents a study on the effect of controllable process parameters in riveting (i.e., such as the sequence of riveting, distance between rivets (pitch) and gap between sheets) on the quality of riveted lap joint and formed rivet. The quality of a riveted lap joint is characterized by sheet metal bulging, sheet material growth, residual stress level on sheets and rivets, and post riveting clearance in the joint. The quality of a formed rivet is often determined by the geometry of its head formation. This study is to determine the best riveting sequence for riveted lap joint in sheet metal assembly with 1/8" nominal diameter of flat head tinner rivet on 0.064" thick aluminum sheet. The study is performed using finite element simulation of riveting process. Statistical design of experiment is employed to analyze the simulation data of riveting process along with the effect of individual factors, their interactions and relationship with the quality parameters of riveted lap joint in sheet metal assembly. A good combination of riveting process parameters is found that minimizes the residual stress in sheets and rivets, bulging and material growth in sheets and reduces the chance of post riveting clearance in riveted lap joint.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering

碩士
中華技術學院
飛機系統工程研究所
96
The purpose of this proposal is first to develop the new model riveted bolt that includes two functions such as 1 the components are nailed by a riveted joint at one side working, 2 the parts are fastened by the thread of bolt and nut with twisting way. Combining the advantages of two functions effectively fabricates a rigid joint to fix the connection of the specimen-lapped. And, the design of new load cell was obtained the clamping force of the joint as applying the torque by using new model riveted bolt. Then, the carbon fiber/epoxy (TC35/Y15037P) prepregs were stacked into two typical lay-ups, cross-ply and quasi-isotropic by hot press. After drilling a hole, =4mm, at the center of overlap with connecting of cross-ply & cross-ply laminates and quasi-isotropic & quasi-isotropic laminates, respectively, we inserted the new model riveted bolt with adhesive at the interface of overlap to form a rigid mixed joint and the experiment was performed tensile test by MTS-810 to obtain the basic mechanical properties, stress-strain relationship with software Grapher. According to the theory of Rule of Mixtures compare strength and stiffness with experimental result, and actual error of result most more in under 35%, with the heaviest to error amount of pile. Finally, the overlap tensile strength of joint was higher than that of joint. Additionally, the pictures of tested specimens were taken by SEM to investigate fracture model. Through, drafting is function model for CATIA that intact show to in the process be of construction for the new model riveted bolt.