Microhardness and Macrostructures of Friction Stir Welded T-joints

The results of research regarding the friction stir welding process of T-joints are presented in this paper. Experimental welding of two and three aluminium plates were performed in order to obtain T-joints. Microhardness measuring and macrostructural examinations of welded T-joints of aluminium alloy are processed. All phases of the welding process are monitored by visual control

An experimental study on lap joining of multiple sheets of aluminium alloy (AA 5754) using friction stir spot welding

Friction stir spot welding (FSSW) process is widely used in the automobile industry for a range of applications such as battery components, standard wire connectors and terminals. This manuscript addresses two grand challenges in the arena of FSSW, hitherto, unaddressed in the extant literature: (i) lap joining of thin sheets (0.3 mm thickness) of AA 5754 alloy and (ii) lap joining of more than two sheets using FSSW. To accomplish this task, a novel pinless convex shaped tool was designed to alter the stress state while gradually advancing the tool which led to achieving stress state necessary for obtaining defect free lap joints. The weld joints were inspected by optical microscopy, SEM imaging and analysed by nanoindentation tests and Vickers microindentation tests for assessment of the quality of the weld interface (WI). Process parameters of FSSW such as torque on the tool and axially applied load were used to analytically obtain the average local measure of peak normal and axial stresses as well as the coefficient of friction in the contact zone. In samples welded at low rotational speeds, strain-hardening mechanism was seen dominating in contrast to samples welded at higher rotational speeds, which showed thermal softening. As a direct consequence of this, the samples welded at low rotational speeds showed much higher hardness at the weld surface than the samples welded at higher speeds. A strong transition of strain hardening to thermal softening was noticeable beyond an applied strain rate of 400 s-1

Experimental Study on the Perforation Process of 5754-H111 and 6082-T6 Aluminium Plates Subjected to Normal Impact by Conical, Hemispherical and Blunt Projectiles

This paper presents an experimental investigation on the perforation behaviour of 5754-H111 and 6082-T6 aluminium alloys. The mechanical response of these materials has been characterized in compression with strain rates in the range of . Moreover, penetration tests have been conducted on 5754-H111 and 6082-T6 plates of thickness using conical, hemispherical and blunt projectiles. The perforation experiments covered impact velocities in the range of . The initial and residual velocities of the projectile were measured and the ballistic limit velocity obtained for the two aluminium alloys for the different nose shapes. Failure mode and post-mortem deflection of the plates have been examined and the perforation mechanisms associated to each projectile/target configuration investigated. It has been shown that the energy absorption capacity of the impacted plates is the result of the collective role played by target material behaviour, projectile nose shape and impact velocity in the penetration mechanisms.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2011-24068) for the financial support received which allowed conducting part of this work

Directed energy deposition of AA7075 - effect of TiC nanoparticles on microstructure

AA7075 alloy is a high-strength aluminum alloy with properties enhanced by heat treatments. However, like most high-strength aluminum alloys, AA7075 is non-weldable, as it suffers from hot cracking when it is welded or additively manufactured with fusion techniques. A proposed way to reduce the hot cracking tendency is by refining the microstructure by adding nucleation enhancers. In this study, AA7075 powder feedstock was functionalized with 1.7 and 3.4 vol.% TiC nanoparticles, printed with laser-directed energy deposition (DED), subjected to T6 heat treatment, and characterized with optical and electron microscopy, electron backscatter diffraction (EBSD), and hardness measurements. Although TiC was not homogeneously distributed in the aluminum matrix, the addition of TiC successfully suppressed hot cracking by inhibiting dendritic growth produced by increased and more uniform nucleation, which resulted in refined equiaxed grains, and thus enhanced the printability of the material.publishedVersionPeer reviewe

Influence of riveting parameters on joint strength

Teoretická část bakalářské práce uvádí základní principy a způsoby nýtování. Navazují na to s tím související typy nýtů a materiály, ze kterých jsou vyráběny. Dále jsou uvedeny výhody a nevýhody nýtování a faktory, které ovlivňují pevnost nýtových spojů. V experimentální části bakalářské práce je pozorován vliv nýtovacích parametrů na pevnost spoje. Experimentální část se též zabývá volbou experimentálního plánu a s ním související postup a vyhodnocení výsledků.The theoretical part of the bachelor's thesis lists the basic principles and methods of riveting. This is followed by the related types of rivets and the materials which they are made of. The advantages and disadvantages of riveting and the factors that influence the strength of rivet joints are also listed. In the experimental part of the thesis, the effect of riveting parameters on joint strength is observed. The experimental part also deals with the choice of the experimental plan and the related procedure and evaluation of the results.632 - Katedra materiálů a technologií pro automobilyvelmi dobř

Simulation of Impact of the Battery Box of the Vehicle SCX 3.5

Import 23/08/2017Předložená práce se zabývala numerickou simulací reálné zkoušky, jejímž účelem bylo zkoumat celistvost bateriového boxu vozidla SCX 3.5 v případě bočního nárazu do vozidla. V první části této práce byla provedena rešerše na téma teorie potřebné k řešení. Ve druhé části byl vytvořen výpočtový model a provedena vlastní numerická simulace, a to prostřednictvím metody konečných prvků v prostředí komerčních programů MSC Patran a MSC Marc Mentat. V poslední části byla popsána samotná realizace skutečné zkoušky. Závěrem této práce bylo provedeno zhodnocení výsledků numerické simulace.Submitted thesis dealt with a numerical simulation of a real test, whose purpose was to examine a structural integrity of the battery box of the vehicle SCX 3.5 in case of side impact to the vehicle. In first part of this thesis there was conducted a background research on topic of theory necessary for a solution. An analysis model was created and numerical simulation itself was realized in second part, in a user environment of commercial software MSC Patran and MSC Marc Mentat. In last part, an execution of the real test was described. In conclusion of this thesis there was done an evaluation of results of the numerical simulation with the results of the real test.330 - Katedra aplikované mechanikyvýborn

Evaluation of new spot variant approach for joining of dissimilar materials

Lightweight structures are typically applied in structurally optimized components integrating multi-lightweight materials. One major limitation for further development and wider use of these structures is the difficulty to join the materials with significant dissimilar physical properties, especially metals to polymeric based materials. The joining of metal to polymer is one important demand from modern mechanical design that still strives to find reliable and energy efficient manufacturing solutions for this field of application. The existing solutions are not able to meet all the demands, namely regarding load-bearing structures where thicker components are needed. In this scenario, a new solution for hybrid joining of advanced lightweight engineering material, was recently invented at Aalto University, and it will be tested in the variant of spot joining. The new solution envisages the joining of thick structural components enabling multi-directional mechanical resistance. The current work aims to evaluate a new approach for the spot variant and to understand the process better. New laboratorial conditions were developed for the implementation of the joining method. Tentative work started with some slot variant tests, but focus was put on the spot variant. The results obtained from the mechanical testing of the spot variant indicate a 50 percent and 85 percent increase in the tensile shear and cross tension tests respectively

Design of a wearable active ankle-foot orthosis for both sides

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Biomateriais, Reabilitação e Biomecânica)Portugal is the west European country with the highest rate of stroke-related mortality, being that, of those who suffer cerebrovascular accidents, 40% feature an impairment which can manifest itself through motor sequelae, namely drop foot. An ankle-foot orthosis is often recommended to passively accommodate these motor problems; however, active/powered exoskeletons are also a suitable solution for post-stroke patients. Due to the high complexity of the human ankle joint, one of the problems regarding these active devices is the misalignment occurring between the rehabilitation device and the human joint, which is a cause of parasitic forces, discomfort, and pain. The present master dissertation proposes the development of an adjustable wearable active ankle-foot orthosis that is able to tackle this misalignment issue concerning commercially available lower limb orthotic devices. This work is integrated on the SmartOs – Smart, Stand-alone Active Orthotic System – project that proposes an innovative robotic technology (a wearable mobile lab) oriented to gait rehabilitation. The conceptual design of a standard version of the SmartOs wearable active orthosis was initiated with the analysis of another ankle-foot orthosis – Exo-H2 (Technaid) – from which the necessary design changes were implemented, aiming at the improvement of the established device. In order to achieve a conceptual solution, both the practical knowledge of the Orthos XXI design team and several design methods were used to ensure the accomplishment of the defined requirements. The detailed design process of the standard SmartOs wearable active orthosis prototype is disclosed. With the purpose of validating the design, the critical components were simulated with the resources available in SolidWorks®, and the necessary CAD model’s adaptations were implemented to guarantee a reliable and safe design. The presented design is currently set for further production in Orthos XXI, followed by the mandatory mechanical tests.Portugal é o país da Europa ocidental com maior taxa de mortalidade por acidente vascular cerebral (AVC), sendo que, dos que sofrem acidentes vasculares cerebrais, 40% apresentam uma deficiência que pode manifestar-se por sequelas motoras, nomeadamente o pé pendente. Uma ortótese do tornozelo é recomendada frequentemente para acomodar passivamente esses problemas motores; no entanto, exoesqueletos ativos são também uma solução adequada para pacientes pós-AVC. Devido à alta complexidade da articulação do tornozelo humano, um dos problemas associados a esses dispositivos ativos é o desalinhamento que ocorre entre o dispositivo de reabilitação e a articulação humana, que é uma causa de forças parasitas, desconforto e dor. A presente dissertação de mestrado propõe o desenvolvimento de uma ortótese ativa do tornozelo ajustável e vestível, que seja capaz de resolver esse problema de desalinhamento relativo aos dispositivos ortóticos de membros inferiores disponíveis comercialmente. Este trabalho está integrado no projeto SmartOs - Smart, Stand-alone Active Orthotic System - projeto que propõe uma tecnologia robótica inovadora (wearable mobile lab) direcionada para a reabilitação da marcha. O projeto conceptual de uma versão padrão da ortótese ativa vestível do projeto SmartOs foi iniciado com a análise de outra ortótese do tornozelo – Exo-H2 (Technaid) - a partir da qual foram implementadas as alterações de projeto necessárias, visando o aprimoramento do dispositivo estabelecido. Para se chegar a uma solução conceptual, tanto o conhecimento prático da equipa de projeto da Orthos XXI como os diversos métodos de projeto foram utilizados para garantir o cumprimento dos requisitos definidos. O processo do desenho detalhado da versão padrão da ortótese ativa SmartOs será também divulgado. Com o objetivo de validar o projeto, os componentes críticos foram simulados com os recursos disponíveis no SolidWorks® e as adaptações necessárias do modelo CAD foram implementadas para garantir um projeto fidedigno e seguro. O projeto apresentado está atualmente em preparação para produção na empresa Orthos XXI, depois do qual se seguem os ensaios mecânicos obrigatórios