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 (Ph. D.)--Technische Universiteit Delft, 1997. / Cover title. Summary in Dutch. Includes bibliographical references.

Thesis (Ph. D.)--Technische Universiteit Delft, 1997. / Cover title. Summary in Dutch. Includes bibliographical references.

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.

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.