For fatigue design of welded hollow structural sections connections, the “hot spot stress method” in CIDECT Design Guide 8 is widely used. This method forms the basis of various national and international design standards. This thesis sought to address some contemporary design issues where the existing approaches cannot be directly applied. Modified design approaches were proposed for various practical design details. For galvanizing of welded tubular steel trusses, sufficiently large holes to allow for quick filling, venting and drainage must be specified. These holes, quite often specified at the hot spot stress locations, will inevitably affect connection fatigue behaviour. In Chapter 1, six rectangular hollow section (RHS) connections were tested under branch axial loading. The stress concentration factors (SCFs) obtained from the experimental investigation were compared with those calculated using the formulae in CIDECT Design Guide 8. It was shown that the predictions based on the current formulae were unsafe. Hence, finite element (FE) models were developed and validated by comparison with the experimental data. A subsequent parametric study was conducted, including 192 FE models with different hole locations and non-dimensional parameters [branch-to-chord width (β), branch-to-chord thickness (τ), and chord slenderness (2γ) ratios]. SCF formulae for RHS connections with vent/drain holes at different locations were established based on the experimental and FE data. In Chapter 2, by modifying the 192 parametric models in Chapter 1, FE analysis was performed to examine the existing SCF formulae in CIDECT Design Guide 8 for RHS T-connections under branch in-plane bending. The parametric study showed that the existing SCF formulae can lead to unsafe predictions. Critical hot spot stress locations were thus identified. The effects of both branch in-plane bending and chord loading were studied. New design formulae that take the vent and drain holes into account were proposed. The design rules in CIDECT Design Guide 8 assumes sufficient chord continuity on both sides of connection. Therefore, the existing formulae cannot be directly applied to RHS-to-RHS connections situated near a truss/girder end. Chapter 3 sought to develop new approach for calculation of SCFs in such connections. 256 FE models of RHS-to-RHS X-connections, with varied chord end distance-to-width (e/b0) and non-dimensional parameters were modelled and analyzed. The analysis was performed under quasi-static axial compression force(s) applied to the branch(es) and validated by comparison of strain concentration factors (SNCFs) to SNCFs obtained from full-sized connection tests. For all 256 connections, SCFs were determined at five critical hot spots on the side of the connection near the open chord end. The SCFs were found to vary as a function of e/b0, 2γ and β. Existing formulae in CIDECT Design Guide 8 to predict SCFs in directly welded RHS-to-RHS axially loaded X-connections were shown to be conservative when applied to a connection near an open chord end. SCF reduction factors (ψ), and a parametric formula to estimate ψ based on e/b0, 2γ and β, were derived. For RHS-to-RHS connections situated near a truss/girder end, reinforcement using a chord-end cap plate is common; however, for fatigue design, formulae in current design guidelines [for calculation of SCFs] cater to: (i) unreinforced connections, with (ii) sufficient chord continuity beyond the connection on both sides. Chapter 4 sought to develop definitive design guidelines for such connections. The parametric models in Chapter 3 were modified to simulate such connections. Existing SCF formulae in CIDECT Design Guide 8 were shown to be inaccurate if applied to cap plate-reinforced end connections. SCF correction factors (ψ), and parametric formulae to estimate ψ based on e/b0, β, τ and 2γ, were derived. The same methodology was used in Chapter 5 to study the SCFs in square bird-beak (SBB) and diamond bird-beak (DBB) tubular steel X-connections situated at the end of a truss or girder. A comprehensive parametric study, including 256 SBB and 256 DBB connection models, covering wide ranges of chord end distance-to-width (e/b0) and non-dimensional parameters, was performed. Two sets of correction factor (ψ) formulae for consideration of the chord end distance effect were derived, for SBB and DBB X-connections, respectively. / Graduate

The improvement of static properties of combined rivet and adhesive bonded joints have been proven by several authors [1, 2]. On the other side, dynamic properties of joints (for example fatigue and corrosion) significantly affect final function of structures during their service life. In this thesis, the combine joints created by blind rivets and hyper elastic sealant are solved. Complex description of dynamic properties of this particular combined joining technology has not been publicised, yet. Description of sealant layer influence on stress concentration in rivet hole regions is one of the main goal of this work. The next stage of the thesis is focused on the influence of above mentioned sealant layer on fatigue properties of combined blind rivet and solid countersunk rivet joints. Stress strain analysis of rivet and combined joints done by FE analysis and by experimental optical measurement of strain field proved that hyper elastic sealant layer has a positive effect on decreasing of stress peaks in rivet hole regions. This findings are in direct compliance with fatigue measurement of combined joint (AAPL). The influence of applied sealant in this combined joints improved fatigue properties by twenty percentage increasing of stress to failure in comparison with rivet joints.

[pt] Foram determinados experimentalmente fatores de concentração de tensões teóricos para placas e eixos com entalhes simétricos e circunferenciais em U sujeitos à combinação de esforços de flexão e tração, para as placas e, flexão e torção para os eixos. Os fatores obtidos foram plotados em gráficos para comparação com fatores determinados aplicando-se o princípio da superposição. Foram utilizadas as relações geométricas D / d = 1,5; 1,25; 1,10 e r/d = 0,30; 0,25; 0,20 para as placas. Para os eixos utilizaram-se apenas as relações 0/d = 1,3 e r/d = 0,25. Também foram obtidos fatores de concentração de tensões para os esforços puros e seus valores comparados com resultados já publicados. Os resultados para as placas foram obtidos a partir da fotoelasticidade bidimensional. Foi empregado o método fotoelástico tridimensional de congelamento de tensões para os eixos. Neste caso, os modelos foram cortados em finas fatias para separação das tensões. Para o estudo tridimensional foi utilizado um material desenvolvido no laboratório de Fotomecanica da PUC-RJ. / [en] Theoretical stress concentration factors were determined experimentally for bars and shafts with symmetrical and circunferential U – shaped grooves subjected to combinations of bending – tension loads for the bars and bending – torsion loads for the shafts. The stress concentration factors obtained were plotted to compare with the factors determined by application of the superposition effects. The geometric relations used for the bars were Dd = 1,5; 1,25; 1,10 and rd = 0,30; 0,25; 0,20. The geometric relations used for the shafts were Dd = 1,3 e rd = 0,25. The stress concentration factors were also determined for single loaded specimens and they were compared wuth data already published. The stress concentration factors for the bars were determined by the two – Dimensional photoelastic method. In the case of the shafts they were determined by the three – Dimensional photoelastic Method of stress Freezing. In this method, the models developed in the laboratory of Photomechanics of the Universidade Católica.

[pt] A determinação do fator teórico ou geométrico de concentração de tensões em um cilíndrico oco de paredes espessas com furo lateral oblíquo é o objeto deste estudo. É analisada a influência do ângulo de ineliação do furo lateral sobre o fator teórico de concentração de tensões. Foi usado na análise, o método fotoelástico. Os cilindros foram fabricados com uma mistura de araldite CY-205, anidrido ftálico e anidrido maleico. O carregamento é feito, introduzindo-se no cilindro um pino fabricado com o mesmo material. É usada a técnica do congelamento das tensões. Para determinar as tensões, o cilindro é cortado em fatias que são analisados em um polariscópio. São apresentadas conclusões, formuladas a partir dos resultados obtidos na experiência. Com este trabalho, novos dados são acrescidos ao problema de concentração de tensões, ampliando os recursos para aqueles que se dedicam ao projeto de máquinas. / [en] The study deals with the problem of concentration of stress introduced by the oblique hole in th thick wall cylinder. The influence of the angle of the axes of hole and cylinder in the stress concentration factor is studied by the method of three-dimensional photoelasticity. The cylinder was manufactured from the CIBA CY-205 epoxy resin cured by mixture of phtalic and maleic anhydrides, loaded by the inner pin and studied by the stress freezing method. The results are presented, which forms of dimensionless diagrams, which permits designer to calculate stresses using the simple Lame’s formula.

[pt] A concentração de tensões nas extremidades de cilindros montados com interferência é muito pouco conhecida. Neste trabalho estudou-se a concentração de tensões na extremidade do cilindro oco. Foram analisadas várias relações de diâmetros e diferentes posições do cilindro interno, utilizando o método fotoelástico tri-dimensional. Os modelos foram construídos usando resina epóxi e anidridos ftálico e maleico como endurecedores. Após o congelamento das tensões retirou-se fatias para análise no polariscópio. Para o cálculo das tensões foi usado o método da diferença das tensões cisalhantes. Os resultados são apresentados em gráficos e analisados. / [en] The stress concentration at end of thickwall cylinders with interference assemblage is unknow yet. In present work the stress concentration has been analized for several diametral relations and differents positions of inner cylinder. The photoelastic method has been used the models was constructed with epoxy resin using phthalic and maleic anhydride as curing agent. After stress freezing procedure the model was sliced to polariscope analysis. For stress calculations the shear difference method was used. The results are plotted and analized.

Woven structures are steadily emerging as excellent reinforcing components in dualphase composite materials subjected to multiaxial loads, thermal shock, and aggressive reactants in the environment. Metallic woven wire mesh materials display good ductility and relatively high specific strength and specific resilience. While use of this class of materials is rapidly expanding, significant gaps in mechanical behavior classification remain. This thesis works to address the mechanics of material knowledge gap that exists for characterizing the behavior of a metallic woven structure, composed of stainless steel wires on the order of 25 microns in diameter, and subjected to various loading conditions and stress risers. Uniaxial and biaxial tensile experiments, employing Digital Image Correlation (DIC) as a strain measurement tool, are conducted on woven wire mesh specimens incised in various material orientations, and with various notch geometries. Experimental results, supported by an ample analytic modeling effort, indicate that an orthotropic elastic constitutive model is reasonably capable of governing the macro-scale elasticity of the subject material. Also, the Stress Concentration Factor (SCF) associated with various notch geometries is documented experimentally and analytically, and it is shown that the degree of stress concentration is dependent on both notch and material orientation. The Finite Element Method (FEM) is employed on the macro-scale to expand the experimental test matrix, and to judge the effects of a homogenization assumption when modeling metallic woven structures. Additionally, plasticity of the stainless steel woven wire mesh is considered through experimental determination of the yield surface, and a thorough analytic modeling effort resulting in a modified form of the Hill yield criterion. Finally, mesoscale plasticity of the woven structure is considered, and the form of a multi-scale failure criterion is proposed and exercised numerically.

The topic of this thesis is the investigation of the local states of stress resulting from the introduction of av-notch in a coaxial circle on the pressurized surface of a circumferentially clamped plate subject to axisymmetric loading. The understanding of the fracture behavior of a component experiencing such a condition is of particular interest to the aerospace and defense industries where circular plate components are often utilized. In such applications, it is imperative that the designer be able to predict the loading conditions facilitating dynamic fracture. As a step towards solving such problems, the quasi-static analogy is studied. Specifically, the purpose of this research is to examine and model the precise effects a stress raiser will have on the fracture behavior and strength reduction of a circular plate machined from Ultem 1000. Parametric FEM simulations were employed to determine the correlation between notch geometry and the resulting maximum stress and stress distribution in the notch root vicinity. Stress concentration factor (SCF) relationships were developed which characterize the effect individual geometric parameters have on the notch root stresses. Mathematical models were developed to provide the elastic stress concentration factor for any combination of geometric parameters within the range studied. Additionally, the stress distributions along the notch root and ahead of the notch were characterized for a variety of geometric configurations. Test coupons were employed to not only characterize the mechanical behavior of the material, but also characterize the correlation between simple and axisymmetric loading, respectively. The development of a predictive approach for designers of such circular components to be able to accurately determine the fracture behavior of these components was the motivating factor of this study.

Durch die zunehmende technologische Entwicklung des Getriebe-, Gelenkwellen-, Werkzeugmaschinen-, Kraftfahrzeug-, sowie Landmaschinenbaus steigen die zu übertragenden Leistungen und Drehmomente enorm. Dies führt zu einem wachsenden Bedarf an formschlüssigen Profilwellenverbindungen und deren erhöhter Lebensdauer und Genauigkeit. Hierbei bilden die Zahnwellenverbindungen (ZWVen) mit Evolventenflanken nach DIN 5480 /N1/ den Regelfall für eine Vielzahl der Anwendung. Abhängig von Festigkeitsüberlegungen, Herstellungsverfahren und Platzbedarf treten in der Praxis nahezu ausschließlich die folgenden zwei Grundtypen auf. Es handelt sich dabei zum Ersten um die Zahnwelle (ZW) mit freiem Auslauf.Die zweite Geometrievariante ist die Zahnwelle mit gebundenem Auslauf, die eine nach DIN 471 /N2/ genormte Sicherungsringnut (SRN) enthalten kann. Zahnwellenverbindungen dienen zur Übertragung großer, wechselnder und stoßartiger Drehmomente ohne zusätzliches Verbindungselement durch die Profilierung der Welle und Nabe. Axiale Verschiebbarkeit unter Last, Profilverschiebungsmöglichkeit, einfache Montage und Demontage sowie die Herstellung mit hochleistungsfähigen umformenden und spanenden Massenfertigungsverfahren, die die Herstellungskosten verhältnismäßig niedrig halten, sind technisch bedeutsame Eigenschaften, die zum ansteigenden Einsatz von ZWVen führen (z.B. /N1/, /Vil84/, /Koh86/ und /Wes96/). Starke Kerbwirkung und erhebliche Überdimensionierung benachbarter Gestaltungszonen sind die wesentlichen Schwachpunkte der Profilverbindungen. Eine große Anzahl (ca. 80 %) von Ausfällen im Maschinenbau ist auf Schäden an Achsen und Wellen infolge konstruktiv bedingter Kerben zurückzuführen (z.B. /N3/ und /Hai89/). Speziell im Bereich der hochbeanspruchten Profilwellen-Verbindungen kommt es auf Grund der starken Querschnittsveränderungen und der häufig angewandten Ausläufe und Formelemente, z. B. Zahn- und Keilwellen zu Kerbwirkungen, die erhebliche örtliche Spannungskonzentrationen sowohl im Zahnfußbereich und Zahnlückenauslauf als auch im Bereich der Verbindung selbst verursachen. Diese Beanspruchungskonzentrationen sind fast in der Hälfte aller Zahnwellenbrüche die häufigste Ursache für Dauerbrüche (Ermüdungs- bzw. Schwingungsbrüche) und für Schäden (bleibende Verformung, Anriss, Gewaltbruch) infolge Maximalbelastung. Hier trifft die Lastüberhöhung am Welle-Nabe-Verbindungsrand mit dem Steifigkeitssprung des Verzahnungsendes auf der Welle zusammen /Die93/. Die erwähnten Schadensfälle belegen, dass der heutige Kenntnisstand über eine beanspruchungsgerechte Auslegung von Zahnwellen noch recht lückenhaft ist. Deshalb sind neue Erkenntnisse über Form- bzw. Kerbwirkungszahlen bei Einzel- und Mehrfachkerben von scharf und weniger scharf gekerbten Zahnwellen mit Auslauf für eine treffsichere Festigkeitsberechnung erforderlich und stellen damit die Hauptschwerpunkte dieser Arbeit dar. Das vorliegende Forschungsprojekt, welches sich erstmals mit der Ermittlung der Beanspruchungen in torsions-, und biegebelasteten Zahnwellen mit freiem und gebundenem Auslauf befasst, wurde im Rahmen der Forschungsvereinigung für Antriebstechnik e.V. (FVA) unter der Nummer T 467 und dem Forschungsthema „ Ermittlung der Kerbwirkung bei Profilwellen für die praktische Getriebeberechnung von Zahnwellen“ initiiert und untersucht.

M. Tech. (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The purpose of this research was to develop optimal numerical solutions that can be employed during the design of cross bored thick-walled compound cylinders. The geometric design parameters of a cross bored compound cylinder that were optimized include shrinkage pressure, cross bore size, shape, location, and obliquity. Finite Element Analysis (FEA) modeling software called Abaqus version 2019 was used to generate numerical solutions. A total of 48 different part models were created and analyzed in this work. The generated FEA results from these models were validated using analytical solutions developed from Lame’s theory. The effects of shrinkage pressure on hoop stresses and Stress Concentration Factor (SCF) were studied to determine the optimal conditions. The optimum shrinkage pressure obtained was henceforth used for further analysis in this work. In addition, using one factor at time optimization technique, an optimization process was carried out to determine the optimal combination of the cross bore configuration geometry that gives minimum SCF. These parameters of cross bore configuration geometry include different sizes of either circular or elliptical-shaped cross bore, positioned at radial, offset, and/or inclined. The analyses of the effects of shrinkage pressure ranging from 4.4733 to 223.662 MPa on 11 different part models, established that the shrinkage pressure of 89.464 MPa generated the minimum SCF magnitude of 3.02. After analyzing 8 different circular cross bore size ratios ranging from 0.1 to 0.8, at the radial position, it was established that the hoop stress increases with an increase in a cross bore size. The smallest cross bore size ratio of 0.1 gave the lowest hoop stress and minimum SCF of 3.02. Whereas the highest stress was developed at the cross-size ratio of 0.8 with an SCF magnitude of 6.75. The minimum magnitude of SCF translates to a reduction of the pressure carrying capacity of the compound cylinder by 67% than a similar plain compound cylinder. Generally, offsetting of the circularly shaped cross bore from the radial position, led to a reduction of the magnitude of SCFs. For instance, from the 8 offset positions analyzed, the minimum SCF occurred at the offset position of 0.006 m with a magnitude of 2.50. This SCF magnitude indicated a reduction of pressure carrying capacity of 60% in comparison to a similar plain compound cylinder. Evaluation of 12 different diameter ratios of elliptical-shaped cross bore ranging from 0.5 to 10, at the radial position, established the lowest SCF magnitude of 1.33 that occurred at a diameter ratio of 5. Henceforth, this optimum diameter ratio was used for further analysis. This aforesaid SCF magnitude translated to a reduction of the pressure carrying capacity of the compound cylinder by 24.81% when compared to a similar plain compound cylinder. Besides, offsetting of elliptically shaped cross bore generally decreased the magnitudes of SCFs. Therefore, for elliptically shaped cross bore, the lowest SCF occurred at radial position with magnitude of 1.33. A general comparison between the effects of circular and elliptical cross bore, established that the elliptical-shaped cross bores generated both lower hoop stresses and SCFs than those of circularly shaped cross bores. On the other hand, oblique elliptical offset cross bores along the Z-axis of the compound cylinder led to an increase in SCFs. As the oblique angle increased from 0 0 to 75 0, the SCFs also increased progressively, however, there was a significant increase in SCF when the inclination angle increased from 60 0 to 75 0. The lowest and highest SCF magnitude was 1.52 and 1.92 at 15 0 and 6.19 at 75 0, respectively. Overall, the optimum geometric configuration of a cross bore in a thick compound cylinder was found to be elliptically shaped, offset at radial position which is an obliquity angle of 0 0 having a diameter ratio a/b of 5.

Neste trabalho está apresentada uma alternativa para o cálculo do fator de concentração de tensões (FCT) em juntas tubulares soldadas do tipo Y. Redes Neurais Artificiais (RNA) foram utilizadas para representar a distribuição de tensões ao longo da junta tubular para os casos de carregamento força axial no plano e momento fletor no plano. As RNA podem aprender a partir de um conjunto de dados sem a necessidade de uma expressão matemática entre as variáveis dependentes e independentes; representa uma vantagem sobre o procedimento normalmente utilizado, ou seja, as equações paramétricas. O modelo proposto representa um avanço no projeto de juntas tubulares, uma vez que evita a necessidade de se conhecer uma expressão matemática para representar a distribuição de tensões na junta e fornece um método mais preciso para avaliar a distribuição de tensões ao longo da junta soldada. O conjunto de dados utilizado foi formado a partir de simulações numéricas das juntas soldadas através do MEF, nas quais foi considerada a geometria do cordão de solda. / An alternative approach to calculate stress concentration factors (SCF) in Y-type welded tubular joints is presented. Artificial Neural Networks (ANN) were used to represent the stress distribution along the tubular joints in both in-plane axial force and in-plane bending moment load cases. ANN can learn from a database without establishing a mathematical expression between dependent and independent variables, which is an advantage over the usual parametric equations approach. The proposed model represents an improvement in the tubular joints design, since it avoids the previous knowing of a mathematical expression to represent the stress distribution in the joint and provides an accurate method to evaluate the stress distribution along the welded fillet joint. The database herein used was completed with FE simulations of tubular joints which consider the geometry of the weld fillet.