Mechanical behaviour of black anodic films on 7175 aluminium alloy for space applications

Goueffon, Yann; Mabru, Catherine; Labarrère, Michel; Arurault, Laurent; Tonon, Claire; Guigue, Pascale

doi:10.1016/s0026-0576(10)80037-6

Cited by 6 publications

(9 citation statements)

References 13 publications

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“…A previous study (Goueffon et al, 2009b) showed that films with initial porosities of 40% and 50% were crazed after colouring and sealing steps. Actually, the differential thermal dilatations in the sealing bath, associated to a poor limit tensile stress of highly porous films, were proved to lead to formation of cracks perpendicular to the interface during the process.…”

Section: Process Of Black Anodizingmentioning

confidence: 96%

“…As the anodic films elaborated at 20 and 25°C (40% and 50% initial porosity) are crazed after the whole black anodizing process (Goueffon et al, 2009b), a finite element simulation was used to evaluate mechanical behaviour of a crazed thin film on its substrate during thermal cycling. The software SAMCEF was used to perform isotropic thermo-elastic calculations with 2-dimensional plane strain hypotheses.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…So the dehydration of black anodic films occurring during thermal cycles is amplified by the vacuum. This phenomenon results in additional tensile stresses in the film (Goueffon et al, 2009b) favourable to cracks development. After several days in a vacuum of 10 À6 Pa at ambient temperature, the cracks width increases (Fig.…”

Section: Influence Of the Pressure On The Adhesion Of The Filmmentioning

confidence: 99%

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Flaking of black anodic films in space environment: Ageing and numerical simulation

Goueffon

Aldebert

Mabru

et al. 2012

Mechanics of Materials

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Black coatings can be used for managing passive thermal control on spacecraft and for avoiding stray light in optical equipment. Inorganic black anodizing of aluminium alloys is a solution to obtain films with a low outgassing and a sufficient thermal stability for this kind of application. Flaking of these coatings has sometimes been observed after thermal cycling on 2XXX and 7XXX aluminium alloys. This phenomenon could generate particulate contamination on satellites optics and may affect mission lifetime. In this work, the influence of thermal cycling on the adhesion of the films was investigated thanks to both a qualitative method (peel-test) and a quantitative method (scratch-test). It has been shown that differential dilatations and dehydration of the film result in stresses inside the film. A finite element model was developed to identify the mechanisms of crack propagation and bifurcation inside the film and thus explain the reasons of flaking. Especially, it has been shown that cracks can bifurcate and propagate in the film along the interface under thermal solicitation resulting in a mixed opening/shearing mode loading at the crack tip.

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Section: Process Of Black Anodizingmentioning

confidence: 96%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Influence Of the Pressure On The Adhesion Of The Filmmentioning

confidence: 99%

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Flaking of black anodic films in space environment: Ageing and numerical simulation

Goueffon

Aldebert

Mabru

et al. 2012

Mechanics of Materials

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“…Due to attractive combinations of (relatively) high strength and low density, 7000 series aluminium alloys (such as the 7175-T7351 alloy considered in the present work) have numerous naval, aerospace, and military applications [4][5][6] and have consequently received a great deal of attention in the literature. In the work of Benoit et al, for example, the microstructure of two 7000 series alloys was analysed, in addition to fundamental mechanical response parameters such as yield stress, ultimate tensile strength, elongation at fracture, and fracture initiation energy [4].…”

Section: Introductionmentioning

confidence: 99%

“…Linear relationships could however be recovered when dislocation spacing is considered in formulations. Goueffon and co-workers examined coefficients of thermal expansion in anodised 7175 films for space applications using 10mm thick beam bending experiments (values of 13.0+/-1.0x10 -6 K -1 were suggested [6]), with values being relatively independent of the porosity of the film [11].…”

Section: Introductionmentioning

confidence: 99%

Investigations into Taylor-Quinney coefficient determination for a 7000 series aluminium alloy using a novel small specimen test technique

Rouse

Hyde

Kazakeviciute

2018

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Thermo-mechanical coupling is a critical component in the thermodynamics of irreversible processes and is related to the dissipation of thermal energy during plastic straining. The Taylor-Quinney coefficient may be thought of as a ratio between thermally dissipated energy and plastic work, thereby giving insight into the thermomechanical coupling term. The inclusion of this parameter in a meaningful way is complicated by the various dependencies that the Taylor-Quinney coefficient may be subject to (e.g. loading rate and temperature). Determination of these dependencies is usually achieved through extensive experimentation, wherein temperature variations are monitored (with reference to an unloaded control sample) in a test piece during mechanical loading. There are practical limitations in full size testing methods however, not least relating to the location of full sized control and loaded samples in an environment chamber/furnace while simultaneously maintaining (control sample) temperature uniformity and high resolution temperature measurement (in the loaded sample). The present work details a method based on a novel small specimen testing technique that is currently under development at the University of Nottingham. A small ring of 7175-T7351 aluminum alloy (approximately 10mm in diameter and 2mm in thickness) is loaded between two pins at room temperature, with the local specimen temperature field monitored during monotonic deformation using an infra-red thermal camera. Experimental results are compared for different pin loading rates (namely 0.1mm/s, 1mm/s, and 10mm/s), with particular emphasis placed on localised temperature variations in areas of expected high plasticity. Differences of approximately 0.6°C were observed between 0.1mm/s and 1mm/s tests, with higher temperatures recorded in the latter. Higher temperatures were also noted at small specimen locations associated with localised plasticity. Fundamental thermal material properties are reported for the 7175 alloy in order to facilitate future analysis and heat equation solution efforts (working towards Taylor-Quinney coefficient determination).

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The Estimation of Taylor-Quinney Coefficients Using Small Ring Specimens

2022

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Background The use of the Taylor-Quinney coefficient for introducing a thermal dissipation term into material models relies on understanding its dependencies. These are usually determined through extensive experimentation, wherein temperature variations are monitored in a test piece during mechanical loading. Objective This study aims to reduce the cost and time necessary to determining the dependencies of the Taylor-Quinney coefficient by proposing a novel small specimen inverse testing method and demonstrating its use on aluminium alloy 7175. Methods The method proposed is based on mechanical testing of a novel small ring specimen in parallel with FEA simulations. In the experiments, small rings of 7175-T7351 aluminium alloy, 20 mm in outer diameter, were loaded between two pins for different pin displacement rates (namely 1, 1.5 and 2 mm/s) at room temperature and the local specimen temperature field was monitored using an infra-red thermal camera. Fully coupled thermal-mechanical simulations of the tests were performed using a range of Taylor-Quinney coefficients, and the resulting temperature evolutions compared to the experimental results in order to determine appropriate coefficient values for the material. Results The method presented shows good repeatability and allows for clear observation of thermal dissipation. Taylor-Quinney values ranging 0.51-0.59 are reported for the 7175 alloy, in line with values reported in the literature for similar alloys. Density, specific heat capacity and thermal conductivity, fundamental thermal material properties necessary for the simulations, are also reported for the alloy. Conclusions The method detailed shows promise for determining Taylor-Quinney coefficients in a wide range of experimental conditions and is proposed as a cheap and fast alternative to full-scale specimen testing of Taylor-Quinney coefficients. Taylor-Quinney values obtained for 7175 aluminium are shown to be much lower than the value of 0.9 often proposed for materials.

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Mechanical behaviour of black anodic films on 7175 aluminium alloy for space applications

Abstract: OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is a publisher-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 4371To link to this article:

Cited by 6 publications

References 13 publications

Flaking of black anodic films in space environment: Ageing and numerical simulation

Flaking of black anodic films in space environment: Ageing and numerical simulation

Investigations into Taylor-Quinney coefficient determination for a 7000 series aluminium alloy using a novel small specimen test technique

The Estimation of Taylor-Quinney Coefficients Using Small Ring Specimens

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