Elastic tensor stiffness coefficients for SLS Nylon 12 under different degrees of densification as measured by ultrasonic technique

Amado‐Becker, Antonio; Ramos‐Grez, Jorge; Yanez, Maria; Vargas, Y.; Gaete, L.

doi:10.1108/13552540810907929

Cited by 43 publications

(22 citation statements)

References 27 publications

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“…Pairwise t ‐testing between the Young's moduli of the different orientations with a confidence level of 0.05 indeed shows that no statistically significant difference exists. Therefore, following these results, the elastic mechanical response of LS‐PA12 can be assumed to have isotropic constitutive parameters, confirming the findings of Amado‐Becker et al and Wegner and Witt . Due to the fact that the shear moduli were approximated using Huber's law (Equation ), no check of Lamé's constraints is made.…”

Section: Resultssupporting

confidence: 87%

“…Research on the quasi‐static mechanical response of LS‐PA12 parts shows that the mechanical response is typically governed by either isotropic, transverse isotropic, or orthotropic constitutive equations on a macroscopic scale, with the principal axes of the model oriented parallel to the three principal axes of the machine, as is shown by numerous authors . In this regard, Ajoku et al found orthotropic properties in terms of Young's modulus, ranging from 1817 to 2047 MPa for the different axes of the model, using a 3D‐Systems Vanguard LS machine .…”

Section: Introductionmentioning

confidence: 92%

“…Jollivet et al found similar values for an orthotropic model using an EOS Formiga LS machine . On the other hand, Amado‐Becker et al employed an ultrasonic technique to determine the elastic constitutive model of LS‐PA12 samples, identifying the samples as isotropic . Cooke et al found transverse isotropy in the Young's modulus of LS‐PA12 samples, produced with a Sinterstation HiQ platform using a statistically relevant population of 144 test samples .…”

Section: Introductionmentioning

confidence: 99%

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Variability, heterogeneity, and anisotropy in the quasi‐static response of laser sintered PA12 components

Faes

Wang

Lava³

et al. 2016

Strain

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Additive manufacturing (AM) receives an increasing industrial interest thanks to its advantages in the economic production of highly complex and small-series components. Especially laser sintering (LS) is in this context of particular interest for the production of plastic components, as it is generally deemed the most robust AM technology for polymer parts and therefore is expected to enable AM for functional components in the near future. However, to date, designers are often confronted with a severe lack of knowledge on the possible mechanical behavior of AM components. More specifically, the unit-to-unit variability, heterogeneity (within-part variation), and anisotropy of the mechanical properties very often prove to be substantial and therefore require more elaborated studies in order to take these effects into account in the engineering of reliable components. Moreover, typical experimental results that are used for the determination of the elastic stiffness tensor are subject to variability, caused by the influence of the difference in thermal history between produced parts. This work therefore focuses first on the identification and quantification of the variability and heterogeneity in the quasi-static response of laser sintering-polyamide 12 (LS-PA12) components. Second, also the anisotropy in this quasi-static response is studied. For the first part, uniaxial tensile tests are performed and the variability on the quasi-static properties is quantified by means of statistical analysis. Also, the elastic stiffness tensor is identified based on these tests. Next, the heterogeneity in the tested specimens is investigated by means of digital image correlation. Finally, in order to study the anisotropy in the quasi-static properties, the Virtual Fields Method is applied to determine the variability in the elastic stiffness tensor of the LS-PA12 material. A variability with a coefficient of variance of up to 6.5% on Young's modulus was measured. It was also found that the production planning has an important influence on the homogeneity of the mechanical properties of the produced parts. Finally, the Virtual Fields Method showed that, contrary to most literature on the topic, the elastic properties of LS-PA12 material is best described using an isotropic material model.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Variability, heterogeneity, and anisotropy in the quasi‐static response of laser sintered PA12 components

Faes

Wang

Lava³

et al. 2016

Strain

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“…By improving SLS printing technology, the printed elasticity modulus can be enhanced so as to close to ‘real’ elasticity modulus. According to the results of [ 51 ], elastic properties of elements obtained via SLS 3D printing technology can be improved by using higher energy density, considering only the laser beam power variation.…”

Section: Discussionmentioning

confidence: 99%

Experimental and Numerical Study on Withdrawal Strength of Different Types of Auxetic Dowels for Furniture Joints

2020

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Studies on the application of the auxetic metamaterials and structures in furniture joints are very limited. However, they have huge potential for use in ready-to-assemble furniture. This study aimed to design and produce different types of auxetic dowels in 3D printing technology, and experimentally and numerically analyze the withdrawal strength of these dowels. In the scope of the study, 24 auxetic dowels with different types and size of inclusions, a different diameter of holes, and a non-auxetic reference dowel were designed and produced with appropriate muffs. Dowels were 3D printed from polyamide (PA12). Poisson’s ratios, withdrawal strength, contact pressures, and friction coefficients of dowels were determined theoretically by means of numerical analyses and real static compression tests. After the pre-production of dowels, the dowels with triangular inclusions have not been found to have sufficient strength and stiffness. Withdrawal strength of dowels decreased as the size of inclusions is decreased, or dowel hole diameter is increased. Furthermore, contact pressures and stresses in auxetic dowels were considerably lower than non-auxetic dowels under the withdrawal force.

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“…Predictions from Timoshenko beam theory agree with the experimentally determined phase velocities, with a consistent 10% underestimation of the predicted absolute values at all frequencies. We attribute this discrepancy to either the residual powder present in the pores resulting from sintering process, or the uncertainty in the material properties of the phantom, which were not nearer specified by the manufacturer, for example introduced through the laser sintering process itself [ 51 ]. While the original Timoshenko theory does not explicitly model porosity, porosity was included through a linear effect on the density and a cubic effect on the elastic modulus [ 52 ].…”

Section: Discussionmentioning

confidence: 99%

Towards assessing cortical bone porosity using low-frequency quantitative acoustics: A phantom-based study

et al. 2017

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PurposeCortical porosity is a key characteristic governing the structural properties and mechanical behaviour of bone, and its quantification is therefore critical for understanding and monitoring the development of various bone pathologies such as osteoporosis. Axial transmission quantitative acoustics has shown to be a promising technique for assessing bone health in a fast, non-invasive, and radiation-free manner. One major hurdle in bringing this approach to clinical application is the entanglement of the effects of individual characteristics (e.g. geometry, porosity, anisotropy etc.) on the measured wave propagation. In order to address this entanglement problem, we therefore propose a systematic bottom-up approach, in which only one bone property is varied, before addressing interaction effects. This work therefore investigated the sensitivity of low-frequency quantitative acoustics to changes in porosity as well as individual pore characteristics using specifically designed cortical bone phantoms.Materials and methods14 bone phantoms were designed with varying pore size, axial-, and radial pore number, resulting in porosities (bone volume fraction) between 0% and 15%, similar to porosity values found in human cortical bone. All phantoms were manufactured using laser sintering, measured using axial-transmission acoustics and analysed using a full-wave approach. Experimental results were compared to theoretical predictions based on a modified Timoshenko theory.ResultsA clear dependence of phase velocity on frequency and porosity produced by increasing pore size or radial pore number was demonstrated, with the velocity decreasing by between 2–5 m/s per percent of additional porosity, which corresponds to -0.5% to -1.0% of wave speed. While the change in phase velocity due to axial pore number was consistent with the results due to pore size and radial pore number, the relative uncertainties for the estimates were too high to draw any conclusions for this parameter.ConclusionsThis work has shown the capability of low-frequency quantitative acoustics to reflect changes in porosity and individual pore characteristics and demonstrated that additive manufacturing is an appropriate method that allows the influence of individual bone properties on the wave propagation to be systematically assessed. The results of this work opens perspectives for the efficient development of a multi-frequency, multi-mode approach to screen, diagnose, and monitor bone pathologies in individuals.

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Elastic tensor stiffness coefficients for SLS Nylon 12 under different degrees of densification as measured by ultrasonic technique

Cited by 43 publications

References 27 publications

Variability, heterogeneity, and anisotropy in the quasi‐static response of laser sintered PA12 components

Variability, heterogeneity, and anisotropy in the quasi‐static response of laser sintered PA12 components

Experimental and Numerical Study on Withdrawal Strength of Different Types of Auxetic Dowels for Furniture Joints

Towards assessing cortical bone porosity using low-frequency quantitative acoustics: A phantom-based study

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