The Coffin-Manson equations of Sn/Ag/Cu and Sn/Pb solder joints are presented in this thesis. The experimental results of CSP thermal cycle fatigue test and ball shear test are used to formulate Coffin-Manson equations. The maximum amplitude of equivalent plastic shear strain corresponding to these two experiments are employed. The MARC finite element package is used to calculate the plastic shear strain. Different published fatigue experiment results have been used to show the accuracy and the feasibility of these proposed equations. The 3-D finite element models of the BGA type¡¦s CSP and VCSEL assembly are employed to simulate the thermal cycling fatigue. Results indicate that the fatigue lifes of solder predicted by using the proposed equations have good agreement with those measured from experimental tests.

[pt] O método EN baseia-se na quantificação do dano causado pela deformação decorrente do histórico de carregamento. O objetivo desse modelo consiste em estimar o número de ciclos para iniciar uma trinca por fadiga. Diferente do método SN o número de variáveis envolvidas nesse modelo é menor. Entretanto, requer um número maior de constantes, que nem sempre podem ser obtidas experimentalmente. Esse fato levou a formulação de diversos modelos que se propõem a estimar as constantes de Coffin-Manson, que na maioria dos casos levam a previsões de vida não conservativas, como visto em outros trabalhos. Contudo a maioria dos casos existentes na literatura não abordam o efeito de regiões de concentração de tensão e a influência de carregamentos com amplitudes variáveis. A metodologia usada nessas pesquisas consiste em avaliar a influência desses aspectos através da comparação entre a vida em fadiga experimental e a estimada segundo as constantes de Coffin-Manson medidas e estimadas segundo diferentes modelos. Esse estudo avalia o dano à fadiga segundo 2 tipos de concentradores de tensão e quatro históricos de carregamentos de amplitude variável. Considerando os modelos de Manson, Muralindhran-Manson, Bäumel-Seeger and Meggiolaro-Castro os resultados mostram que a vida em fadiga prevista usando os parâmetros de Coffin Manson obtidos segundo o método de Meggiolado-Castro e por Baumel-Segger são os que mais se aproximam das vidas estimadas baseada nas constantes experimentais. Nos demais casos nota-se que a regra de concentração de tensão exerce uma maior influência no resultado e levam a vidas à fadiga não conservativas. / [en] The strain-life designed is based on the damaged caused by the strain as a result of a loading history. The purpose of this approach is estimating the number of cycles to initiate a fatigue crack. Compared with the stress life method the EN needs a lower number of variables. However, it needs a large number of parameters that are not directly measurable properties of a material and conduct the necessary number of tests to obtain them is not always an option. This fact leads to the formulation of different models to estimate Coffin- Manson s constants, which in most of the cases can result in a non-conservative fatigue life prediction, as seen in several papers. However, in these studies, it is not considered a specimen with a stress concentration factor neither under a variable amplitude loading history. The methodology used in this research is evaluating the influence of these aspects by comparing the fatigue life experimental with the estimated by using the Coffin Manson s experimental constants and the fatigue life calculated with different models to estimate the Coffin-Manson s parameters. This study evaluated the fatigue damage based on four load histories and two types of samples with different stress risers. Considering the models of Manson, Muralidharan-Manson, Bäumel-Seeger, and Meggiolaro-Castro the results indicated that the fatigue life predicted using the Coffin Manson s parameter obtained by Meggiolaro-Castro and Baumel-Segger s model are more similar to the life calculated with the experimental constants. The other models are more influenced by the stress concentration s rule and can lead to not conservative fatigue life.

Two subjects are included in this thesis; one is to construct the Coffin-Manson equation of the unleaded SnAgCu solder according to the experimental results provided by the Metal Research Laboratory (MRL) of Industrial Technologies Research Institute (ITRI). The results of CSP thermal cycle fatigue and SOJ pull tests and the corresponding stress and strain distributions solved from FEM analyses have been used to derive the Coffin-Manson equation for the SnAgCu solder. The other subject is to investigate the effect of CTE mismatch on the fatigue life of solder balls in the opto-electronic packaging. The solidified shapes of the different solder balls after undergoing the re-flow process are predicted by employing the Surface Evolver package program. The FEA meshes of the solidified solder balls in opto-electronic packaging are built according to the output results of the Surface Evolver program. The maximum equivalent plastic shear strain range of the solder after under one thermal cycle process is calculated by employing the MARC finite element package. The fatigue lives of solder balls under different arrangements are estimated according to the proposed Coffin-Manson equation. The effect of solder ball parameters, i.e. solder volume, solder offset distance, solder DNP and solder material on the reliability of different solder balls has also been explored in this thesis.

[pt] Esta pesquisa teve como objetivo avaliar a vida-fadiga de dois ferros fundidos nodulares modificados metalurgicamente, sendo uma classe predominantemente ferrítica e outra.perlítica. Inicialmente, amostra dos dois ferros fundidos nodulares ferrítico e perlítico foram fundidas adotando-se moldação em areia na geometria padrão Y-block. Em seqüência, corpos de prova para ensaios mecânicos e de fadiga foram usinados das amostras ferríticas e perlíticas. Após os ensaios de tração e dureza, realizaram-se análises metalográficas qualitativas e quantitativas em ambos os materiais, com o intuito de se determinar suas características metalúrgicas, tais como contagem, distribuição e classe dos nódulos de grafita, bem como quantidade da matriz ferrítica e perlítica. Dando continuidade a etapa experimental, as curvas tensão versus número de ciclos para a falha do ferro fundido nodular ferrítico e do ferro fundido nodular perlítico foram levantadas por meio de ensaios de flexão rotativa. A vida útil em fadiga dos dois materiais foi relacionada com as suas características metalúrgicas. Quanto a resistência à fadiga, as amostras do ferro fundido nodular perlítico tiveram um melhor comportamento sob carregamento cíclico do que as amostras do ferro fundido nodular ferrítico. Tal comportamento superior foi atribuído a maior microdureza da matriz e a presença da estrutura olho-de-boi. Finalmente, as curvas experimentais tensão versus número de ciclos para a falha dos ferros fundidos nodulares ferrítico e perlítico foram modeladas pela equação de Coffin-Manson, que se mostrou eficiente no tratamento de dados experimentais da vida em fadiga de ambos os materiais. / [en] The objective of the present work was to evaluate the fatigue life of two nodular cast irons with metallurgical modifications and resulting in ferritic and perlitic different classes of material. Initially, samples of both materials were cast in sand moulds adopting the standard Y-block geometry. In the sequence, tensile and fatigue specimens were machined from the ferritic and perlitic samples. After the tensile and hardness tests, the microstructure of the both materials were analyzed by qualitative and quantitative metallography, aiming to characterize their metallurgical aspects as content, distribution and class of graphite nodules, as well as the contents of the ferritic and perlitic matrix. Following the metallurgical characterization, rolating bend fatigue tests were performed in order to estabilish the stress-life curves of the ferritic and perlitic nodular cast irons. Regarding the fatigue resistance, the specimens machined from the perlitic nodular sample showed a longer fatigue life than that related to the ferritic nodular specimens. The longer fatigue life of the perlitic nodular specimens was associated with a higher microhardness of the perlitic matrix and the preserve of the bull`s-eye structure. Finally, the experimental stress-life curves of the ferritic and perlitic nodular cast irons were modeled adopting the Coffin-Manson law, which was considered efficient in fitting experimental fatigue life data of both materials.

Prognostics and health management (PHM) is a major tool enabling systems to evaluate their reliability in real-time operation. Despite ground-breaking advances in most engineering and scientific disciplines during the past decades, reliability engineering has not seen significant breakthroughs or noticeable advances. Therefore, self-awareness of the embedded system is also often required in the sense that the system should be able to assess its own health state and failure records, and those of its main components, and take action appropriately. This thesis presents a radically new prognostics approach to reliable system design that will revolutionise complex power electronic systems with robust prognostics capability enhanced Insulated Gate Bipolar Transistors (IGBT) in applications where reliability is significantly challenging and critical. The IGBT is considered as one of the components that is mainly damaged in converters and experiences a number of failure mechanisms, such as bond wire lift off, die attached solder crack, loose gate control voltage, etc. The resulting effects mentioned are complex. For instance, solder crack growth results in increasing the IGBT’s thermal junction which becomes a source of heat turns to wire bond lift off. As a result, the indication of this failure can be seen often in increasing on-state resistance relating to the voltage drop between on-state collector-emitter. On the other hand, hot carrier injection is increased due to electrical stress. Additionally, IGBTs are components that mainly work under high stress, temperature and power consumptions due to the higher range of load that these devices need to switch. This accelerates the degradation mechanism in the power switches in discrete fashion till reaches failure state which fail after several hundred cycles. To this end, exploiting failure mechanism knowledge of IGBTs and identifying failure parameter indication are background information of developing failure model and prognostics algorithm to calculate remaining useful life (RUL) along with ±10% confidence bounds. A number of various prognostics models have been developed for forecasting time to failure of IGBTs and the performance of the presented estimation models has been evaluated based on two different evaluation metrics. The results show significant improvement in health monitoring capability for power switches. Furthermore, the reliability of the power switch was calculated and conducted to fully describe health state of the converter and reconfigure the control parameter using adaptive algorithm under degradation and load mission limitation. As a result, the life expectancy of devices has been increased. These all allow condition-monitoring facilities to minimise stress levels and predict future failure which greatly reduces the likelihood of power switch failures in the first place.

No description available.

Fatigue testing of stretch sensors often focuses on high amplitude, low-cycle fatigue (LCF) behavior; however, when used for orthopaedic, athletic, or ergonomic assessments, stretch sensors are subjected to low amplitude, high-cycle fatigue (HCF) conditions. As an added layer of complexity, the fatigue testing of stretch sensors is not only focused on the life of the material comprising the sensor, but also on the reliability of the signal produced during the extension and relaxation of the sensor. Research into the development of a smart sock that can be used to measure the range of motion (ROM) of the ankle joint during athletic practices and competitions using stretch sensors is ongoing at Mississippi State University. The current smart sock prototype utilizes StretchSense™ StretchFABRIC capacitive dielectric elastomer sensors. These sensors are no longer manufactured, and FlexSense stretch sensors are being investigated as a potential replacement. To assess the reliability of the signal of the StretchFABRIC sensors currently used in the prototype, two sensors were subjected to 25,000 cycles of fatigue, under with simultaneous capture of the capacitance. The capacitances of the fatigued sensors were then compared to the capacitance of an unfatigued StretchFABRIC sensor during participant trials. Participants completed four static movements and six dynamic gait trials using either the fatigued or unfatigued sensor. Following completion of the initial static and dynamic movements, the movements were repeated using the opposite sensor. Comparison of the fatigued sensor to the unfatigued sensor revealed an upward drift in the capacitance of the fatigued sensor for all trials. Two FlexSense sensors were then subjected to either 450,000 or 250,000 cycles of fatigue with simultaneous capture of the signal from the sensor. To assess the signal, the peak capacitance recorded during the fatigue test was compared to the peak stretch percentage produced by the sensor. The peak displacement remained tight about the mean, while the peak stretch percentage exhibited a high level of scatter. From a materials standpoint, the sensors conformed to the Rabinowitz-Beardmore model of polymer fatigue where an initial monotonic overload of the material is followed by a transition to cyclic stability of the material.

Sélectionner des traitements de surface pour l’industrie nécessite de prendre en compte : les propriétés à conférer au substrat, la nature et la géométrie de celui-ci et les caractéristiques du milieu extérieur. Certaines combinaisons de ces paramètres rendent difficile la sélection d’un traitement unique, d’où le recours à des multitraitements de surface. Dès lors, se posent les questions suivantes : - Utiliser des multitraitements de surface peut se faire en scindant les différentes requêtes en sous-ensembles, de manière à ce que chaque traitement réponde à l’un d’eux. Dans quel ordre ces requêtes doivent-elles être introduites par rapport au substrat ? - Comment sélectionner les traitements de surface répondant à chaque requête individuelle ? - Comment classer des multitraitements en termes d’adéquation au problème posé ? Dans ce travail, les première et troisième questions sont abordées, en explorant les requêtes concernant habituellement les dispositifs de moulage de l’aluminium : - Résistance aux contraintes d’origine thermique. - Résistance à la corrosion par les métaux fondus. - Résistance au frottement. L’analyse de la bibliographie relative aux traitements de surface utilisés dans ces systèmes a été analysée et des « architectures »-types ont été identifiées (chapitre 3). On prévoit, par exemple, un traitement conférant la résistance à la fatigue superficielle, ainsi qu’un revêtement étanche et résistant à l’aluminium fondu. Une barrière thermique est parfois préconisée. Pour chacune des architectures, des traitements de surface individuels peuvent être sélectionnés. Un « facteur de performance » permettant de classer les solutions par rapport au problème de la fatigue thermique a été construit (chapitre 4) et discuté dans deux situations : - Lorsqu’un revêtement est présent, et que les contraintes d’origine thermique (différence de dilatation thermique couche-substrat) menacent de le rompre lors de l’immersion dans un milieu corrosif à haute température. Des essais de corrosion dans de l’aluminium fondu ont été réalisés sur un acier revêtu par du nitrure de chrome dopé à l’aluminium, synthétisé par déposition physique en phase vapeur (chapitre 5 – collaboration : Inasmet). - Lorsque des variations thermiques rapides menacent de rompre le substrat et la (les) couches. Des essais de fatigue thermique ont été réalisés sur de l’acier à outils pour travail à chaud non traité, boruré ou recouvert d’un multitraitements (zircone yttriée / NiCrAlY / boruration / acier). Le revêtement en zircone yttriée a été obtenu par projection par plasma. L’essai de fatigue thermique a été modélisé et le facteur de performance, discuté (chapitre 6). Au chapitre 7, les architectures-types ont été introduites dans une méthodologie de sélection des multi-traitements de surface, qui a été appliquée dans deux cas : - Celui des moules de fonderie, devant résister à la fatigue thermique et à la corrosion par l’aluminium fondu. Le facteur de performance a été extrapolé à d’autres situations qu’aux chapitres 5 et 6. Les solutions habituellement proposées pour résoudre ce problème sont retrouvées. - Celui de deux pièces en acier frottant l’une contre l’autre en présence d’aluminium fondu. To select surface treatments, one must account for the required functional properties, the substrate features and the solicitations the substrate must endure. Certain combinations of these parameters make it difficult to select a single surface treatment, a reason why several successive treatments are preferred. To select them, one needs to determine: - How to divide the several requests into groups and how to stack up these groups from the substrate to the outer surface, so that each treatment deals with one specific group of requests/properties. - How to select individual layers for each group of properties. - How to rank the multi-treatments in terms of relevance for a given application. In this work, one tries to answer the first and the third questions, by studying the case of aluminium foundry, in which the industrial devices frequently face the following solicitations: - Thermal stress (thermal fatigue, thermal expansion mismatch). - Presence of corrosive molten metal. - Sliding wear. In the literature, several “standard” architectures are proposed (chapter 3), like a diffusion layer reducing superficial fatigue plus a corrosion barrier layer. A thermal barrier coating is also sometimes proposed. For each of these architectures, one can select individual treatments. To rank them, one devised a “performance index” for thermal stress (chap.4), which is discussed for two cases: - For large differences between layer and substrate thermal expansion coefficients, when both are put into contact with a high temperature corrosive medium, the layer may be damaged. One discusses this case by examining the corrosion caused by molten aluminium for a steel substrate coated by anticorrosive chromium nitride doped with aluminium. The layer is produced by physical vapour deposition (chap. 5 – cooperation: Inasmet). - Repeated fast surface temperature transients can also damage the substrate and/or the layer by thermal fatigue. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multilayer. In the last case, top coat is yttria stabilised zirconia, followed by a nickel superalloy and then a borided layer (undercoat). One synthesized the zirconia coating by plasma spray and one modelled the thermal fatigue (chap. 6). In chap. 7, architectures from chap. 2 are introduced in a multi-treatment selection routine, which is applied in two cases: - Foundry moulds for molten aluminium, withstanding both thermal fatigue and corrosion. The devised performance index is extrapolated beyond the tests of chap. 5 and 6 to treatments for this industrial application, thereby quantifying their respective merits. - A foundry device exposed to molten metal and sliding wear.

Sélectionner des traitements de surface pour l’industrie nécessite de prendre en compte :les propriétés à conférer au substrat, la nature et la géométrie de celui-ci et les caractéristiques du milieu extérieur. Certaines combinaisons de ces paramètres rendent difficile la sélection d’un traitement unique, d’où le recours à des multitraitements de surface. Dès lors, se posent les questions suivantes :<p>- Utiliser des multitraitements de surface peut se faire en scindant les différentes requêtes en sous-ensembles, de manière à ce que chaque traitement réponde à l’un d’eux. Dans quel ordre ces requêtes doivent-elles être introduites par rapport au substrat ?<p>- Comment sélectionner les traitements de surface répondant à chaque requête individuelle ?<p>- Comment classer des multitraitements en termes d’adéquation au problème posé ?<p>Dans ce travail, les première et troisième questions sont abordées, en explorant les requêtes concernant habituellement les dispositifs de moulage de l’aluminium :<p>- Résistance aux contraintes d’origine thermique.<p>- Résistance à la corrosion par les métaux fondus.<p>- Résistance au frottement.<p>L’analyse de la bibliographie relative aux traitements de surface utilisés dans ces systèmes a été analysée et des « architectures »-types ont été identifiées (chapitre 3). On prévoit, par exemple, un traitement conférant la résistance à la fatigue superficielle, ainsi qu’un revêtement étanche et résistant à l’aluminium fondu. Une barrière thermique est parfois préconisée.<p>Pour chacune des architectures, des traitements de surface individuels peuvent être sélectionnés. Un « facteur de performance » permettant de classer les solutions par rapport au problème de la fatigue thermique a été construit (chapitre 4) et discuté dans deux situations :<p>- Lorsqu’un revêtement est présent, et que les contraintes d’origine thermique (différence de dilatation thermique couche-substrat) menacent de le rompre lors de l’immersion dans un milieu corrosif à haute température. Des essais de corrosion dans de l’aluminium fondu ont été réalisés sur un acier revêtu par du nitrure de chrome dopé à l’aluminium, synthétisé par déposition physique en phase vapeur (chapitre 5 – collaboration :Inasmet).<p>- Lorsque des variations thermiques rapides menacent de rompre le substrat et la (les) couches. Des essais de fatigue thermique ont été réalisés sur de l’acier à outils pour travail à chaud non traité, boruré ou recouvert d’un multitraitements (zircone yttriée / NiCrAlY / boruration / acier). Le revêtement en zircone yttriée a été obtenu par projection par plasma. L’essai de fatigue thermique a été modélisé et le facteur de performance, discuté (chapitre 6).<p>Au chapitre 7, les architectures-types ont été introduites dans une méthodologie de sélection des multi-traitements de surface, qui a été appliquée dans deux cas :<p>- Celui des moules de fonderie, devant résister à la fatigue thermique et à la corrosion par l’aluminium fondu. Le facteur de performance a été extrapolé à d’autres situations qu’aux chapitres 5 et 6. Les solutions habituellement proposées pour résoudre ce problème sont retrouvées.<p>- Celui de deux pièces en acier frottant l’une contre l’autre en présence d’aluminium fondu.<p><p>To select surface treatments, one must account for the required functional properties, the substrate features and the solicitations the substrate must endure. Certain combinations of these parameters make it difficult to select a single surface treatment, a reason why several successive treatments are preferred. To select them, one needs to determine:<p>- How to divide the several requests into groups and how to stack up these groups from the substrate to the outer surface, so that each treatment deals with one specific group of requests/properties.<p>- How to select individual layers for each group of properties.<p>- How to rank the multi-treatments in terms of relevance for a given application.<p>In this work, one tries to answer the first and the third questions, by studying the case of aluminium foundry, in which the industrial devices frequently face the following solicitations:<p>- Thermal stress (thermal fatigue, thermal expansion mismatch).<p>- Presence of corrosive molten metal.<p>- Sliding wear.<p>In the literature, several “standard” architectures are proposed (chapter 3), like a diffusion layer reducing superficial fatigue plus a corrosion barrier layer. A thermal barrier coating is also sometimes proposed.<p>For each of these architectures, one can select individual treatments. To rank them, one devised a “performance index” for thermal stress (chap.4), which is discussed for two cases:<p>- For large differences between layer and substrate thermal expansion coefficients, when both are put into contact with a high temperature corrosive medium, the layer may be damaged. One discusses this case by examining the corrosion caused by molten aluminium for a steel substrate coated by anticorrosive chromium nitride doped with aluminium. The layer is produced by physical vapour deposition (chap. 5 – cooperation: Inasmet).<p>- Repeated fast surface temperature transients can also damage the substrate and/or the layer by thermal fatigue. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multilayer. In the last case, top coat is yttria stabilised zirconia, followed by a nickel superalloy and then a borided layer (undercoat). One synthesized the zirconia coating by plasma spray and one modelled the thermal fatigue (chap. 6).<p>In chap. 7, architectures from chap. 2 are introduced in a multi-treatment selection routine, which is applied in two cases:<p>- Foundry moulds for molten aluminium, withstanding both thermal fatigue and corrosion. The devised performance index is extrapolated beyond the tests of chap. 5 and 6 to treatments for this industrial application, thereby quantifying their respective merits.<p>- A foundry device exposed to molten metal and sliding wear.<p><p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished