Torsional Fatigue Behaviour of Aluminum/Composite Tubes

2007

Experiments were carried out to study the bending fatigue characteristics of a hybrid aluminum/composite drive shaft. A hybrid shaft was fabricated using a wetted filament winding method by winding glass and carbon fibers onto an aluminum tube with different winding angles, numbers of layers, and stacking sequence. The flexural moment fatigue life relationships were obtained and the failure modes of the hybrid shaft were studied. The results show that the fatigue life for a winding angle of 45 is larger than it is for 90 , for both glass and carbon fibers. For [AE45] 3 , carbon fiber/epoxy laminates enhance the fatigue strength of aluminum tube up to 40% and the hybrid specimen does not fail until 10 7 cycles under 14.7 N.m applied bending moment. In the hybridized specimens the percentage containing carbon and glass fiber are significantly affected by the fatigue life of the hybrid shaft at high and low level load. The results of a fatigue test on a macroscopic level indicate that the cracks initiating in the zones free of fibers or in the outer skin of resin, increase with increasing number of cycles until failure of specimen. On the other hand the micro damage shows that the delamination completely took place between the composite layer and the surface of the aluminum tube before the catastrophic failure of a hybrid specimen. In addition, the aluminum tube failure was perpendicular to the applied bending load and this phenomena is the same as for the aluminum shaft under a bending fatigue test. Furthermore, there is no fiber breakage observed from the rotating bending fatigue test.

U.P.B. Sci. Bull, 2017

Most of fatigue machines used for industrial or laboratory applications are limited to perform a single fatigue test and its components are commonly servo-hydraulic or pneumatic actuators of high torque capability, leading to high costs. In the present paper is shown a torsion fatigue machine which works from 0.3 to 10 N-m of torque and it is used to investigate the fatigue torsion endurance for industrial materials, such as: steels, aluminum alloys, cast irons and polymers. This machine employs servomotors mounted with a linear motion mechanism to develop fatigue tests under torsion. The control and programming of angular motion is carried out by the freeware "Robotis" software, allowing an easy control for angular rotation. In this work is presented the general methodology for the setup of torsion tests: calibration of rotation motion, numerical simulation and the experimental results of torsion tests. Furthermore, this machine allows working at different load ratios R by applying an initial static angle before the initiation of torsion testing.

Engineering Fracture Mechanics, 2014

Experimental results were obtained from fatigue tests of thin-walled 7075-T6 and 2024-T3 aluminium tubular specimens with a circular hole. The loading conditions included axial, torsion, combined in-phase and out-of-phase axial-torsion, and axial with intermittent torsion cycles. Crack nucleation was observed on planes of maximum shear stress for both notched and smooth (un-notched) specimens. Macroscopic crack growth in notched specimens occurred along planes experiencing the maximum range of nominal principal stress (i.e. mode I crack growth) whereas smooth specimen cracks grew on maximum shear planes. This is explained in terms of different damage evolution mechanisms in smooth and notched specimens. Cracks grew faster in torsion compared to axial loading, as well as in in-phase loading compared to out-of-phase loading. This is attributed to the T-stress in torsion tests and crack branching with a torturous crack path in out-of-phase tests. Intermittent torsion cycles decreased fatigue life and accelerated axial crack growth rate. These effects and the differences in crack growth behaviour between different loadings are discussed.

2007

A static torque and power transmission capacities of a hybrid aluminium/composite drive shaft, fabricated by a wetted filament winding method, were investigated. Special mechanisms for static torsion and power transmission test setups were designed and fabricated. The following different fibre types were used: carbon, glass, one epoxy, and hardener. The static and dynamic characteristic of the hybrid aluminium/composite drive shaft with respect to the fibre types stacking sequences winding angle and number of layers were investigated. From the experiments, it was found that the static and dynamic torque capacity for a winding angle of 458 is higher than 908 for both glass and carbon fibres. From the power transmission test, it was also found that the percentage between the static torque and dynamic torque is approximately 7-15 per cent. In addition, in the static torsion test, the aluminium tube yielded first at the central region of the shaft, followed by crack propagation in the composite shaft along the fibre direction, which eventually caused the delamination of the composite layers from the aluminium tube. On the other hand, in the power transmission test, different locations of failure were observed along the gauge length of the specimen. The shaft's being laminated with a stacking sequence of [90/ þ 45/245/90] and [þ45/245/90/90] resulted in the same behaviour in the torque-angle and the twist relation. The power transmission capacities were close to each other and this in turn satisfied the lamination theory. The finite-element method was used to analyse the hybrid shaft under static torsion and ANSYS finite-element software was used to perform the numerical analysis for the hybrid shaft. A full scale hybrid specimen analysis was done. Elasto-plastic properties were used for the aluminium tube and linear elastic for composite materials. Good agreement was obtained between the finite-element predictions and experimental results.

Metallurgical bonded aluminium-copper bi-metal tube has a future prospect as an alternative material to copper in the heat, ventilation and air-conditioning (HVAC) industries. The application of aluminum-copper bi-metallic material is seems practical in maintaining the quality of existing products. However, the mechanical strength and fatigue properties of the bi-metal tubes are unknown. In this study, metallurgical, mechanical and fatigue properties of the copper phosphorous alloy and aluminium-copper bi-metal tubes were characterized through metallographic analysis, tensile, bending and fatigue tests. The results show that there observed a weak and brittle Al-Cu intermetallic compound at the interlayer between Al and Cu. Tensile fracture surface observation revealed that separation of Cu from Al occurred at the interlayer. The bending properties of the tubes were influenced by the amount of volume fraction of Cu in the materials. Three point bending fatigue test results showed that a critical buckling stress is presents for tubes with diameter less than 12.7mm. The aluminium-copper bi-metal tubes show degradation of fatigue strength almost 55% as compared to that of Cu alloy tube.

Procedia Engineering, 2012

The article deals with determining of fatigue lifetime of structural materials during by multiaxial cyclic loading. The theoretical part focuses on fatigue and criterions for evaluation of the multiaxial fatigue lifetime. The experimental part deals with modeling of combined bending-torsion loading and determining the number of cycles to fracture in region low-cycle fatigue and also during of the loading with the sinusoidal wave form under in phase = 0°. Based on the experimental results the fatigue design curves are compared to fatigue data from base metal and weldments.

2000

The present study focused on the estimation of load and non-load shares of pavement maintenance and rehabilitation expenditures. The information provides the basis for the allocation of pavement-related expenditures in a highway cost allocation study. A comprehensive database was developed in the study, and an aggregate performance approach was used based on econometric models. This approach utilizes the marginal effect of traffic loading to quantify the load and non-load shares of pavement routine maintenance and rehabilitation expenditures. The study revealed that the share of pavement damage attributable to load and non-load factors depends on several factors such as the type of improvement (routine maintenance or rehabilitation), pavement type, and other variables. For routine maintenance, the load and non-load shares were found to be 25-75 for flexible pavements, 36-64 and 60-40 for Jointed Concrete Pavements (JCP) and Continuously Reinforced Concrete (CRC) pavements, and 30-70 for composite pavements. The load and non-load fractions of rehabilitation expenditures used to repair pavement damage were found to be 30-70 for flexible pavements, 80-20 for JCP, and 40-60 for composite pavements. It is expected that the results of this study will facilitate the apportionment of pavement routine maintenance and rehabilitation expenditures in a fair and equitable manner.

Cadernos Cedes, 2024

Este artigo trata do uso de um livro didático digital acessível construído na perspectiva do desenho universal para a aprendizagem. O estudo quantitativo e qualitativo foi realizado em escolas públicas de quatro redes da Baixada Fluminense com a participação de 21 crianças com deficiências, seus professores de turmas comuns e do atendimento educacional especializado, assim como os colegas de turma. A análise, à luz da teoria histórico-cultural, problematiza os conceitos como inovação pedagógica, mediação pedagógica e uso de recursos tecnológicos na escola.

Contemporary Political Theory, 2021

Epistemologies have power. They have the power not only to transform worlds, but to create them. And the worlds that they create can be better or worse. For many people, the worlds they create are predictably and reliably deadly. Epistemologies can turn sacred land into ‘resources’ to be bought, sold, exploited, and exhausted. They can turn people into ‘labor’ in much the same way. They can not only disappear acts of violence but render them unnamable and unrecognizable within their conceptual architectures. Settler systems of epistemic and conceptual resources and the relations among them are constructed to preclude certain forms of knowledge. This is not an accident; it is a central goal of colonial violence. Colonization and land dispossession would not be possible without the violent disruption of Indigenous knowledge systems and ongoing organized attempts to disrupt their survival. Violently disrupting the relationships of people to land is as much an epistemic project as it is a material one, and these two projects are inherently linked. The task of theorizing epistemic oppression is not only about epistemic oppression. Epistemic oppression is a story that gives language to a phenomenon in order to get past it, to carry on with the maintaining and reviving the forms of Indigenous and diasporic knowledge that colonialism has worked tirelessly to corrupt and silence.

Acta Archaeologica Academiae Scientiarum Hungaricae, 2020

One of the important cemetery and settlement of the Celts lies in a plateau on the southern side of the Öreg Rába river, in the vicinity of Győr-Ménfőcsanak. The first burials were found in 1967 during a short rescue excavation, however it made Ménfőcsanak a key La Tène site in the Carpathian Basin. Excavations investigated on a larger scale in the area of a previously known cemetery in 1993–94. The burial rite of the necropolis was mainly inhumation and only two graves were cremated and two biritual graves. Celtic warriors with swords and richly furnished females with fibulae, coral, amber, and glass beads jewelry were also buried in this part of the cemetery. Few graves were limited by rectangular enclosing trenches. According to find analyzing this part of the cemetery dates to the LT B period, and that is why Ménfőcsanak became an important archaeological site in terms of burials in the history of the Celtic “migrations” in the fourth century BC.