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Fatigue behaviour of laser-sintered PA12 specimens under four-point rotating bending

Lookup NU author(s): Dr Javier Munguia ValenzuelaORCiD, Professor Kenneth DalgarnoORCiD

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Abstract

AbstractPurpose – The purpose of this paper was twofold: first, to determine if rotating bending could be used as an effective way of determining thefatigue behaviour of laser-sintered nylon, and second, to examine whether the fatigue behaviour of laser-sintered PA12 showed any significantanisotropy.Design/methodology/approach – Specimens were measured to obtain dimensional accuracy, density and surface roughness levels. Then, uniaxialtensile and rotating-bending fatigue tests were performed. A purpose-built test-jig has been used to subject hourglass-shaped specimens to reversedbending at two frequencies: 50 and 30 Hz. Additionally, thermal and microstructural analyses were performed to understand the underlyingmechanisms of failure.Findings – The experiments suggest PA12 specimens will fail in fatigue following the conventional fatigue mechanisms observed in previousresearch with ductile polymers. Although high-frequency loading caused a heat build-up in the specimen, temperatures stabilised between 20 and30°C, suggesting that rotating-bending fatigue at frequencies of up to 50 Hz is a valid way of determining the fatigue behaviour of laser-sinteredPA12 specimens. Stresses below 20 MPa led to fatigue lives above 1 million cycles. Some anisotropic behaviour was observed in the fatigue testresults, with specimens made orientated with the Z axis showing the lowest fatigue lives on average, but an endurance limit of approximately 15MPa seems to be common for all specimens regardless of their build orientation.Practical implications – The observed endurance limit of 15 MPa did not depend significantly on the orientation at which a part was built –meaning that it may be possible to guarantee a service life for a part which does not depend on part orientation within a build. Clearly, good-qualitycontrol will also be required to ensure performance, but this has important implications for the design of laser-sintered PA12 parts for realistic serviceconditions.Originality/value – To our knowledge, this is the first paper to present rotating-bending fatigue data for laser-sintered PA12 parts, and the firstto identify an endurance limit which is independent of part orientation.

Publication metadata

Author(s): Munguia J, Dalgarno K

Publication type: Article

Publication status: Published

Journal: Rapid Prototyping Journal

Year: 2014

Volume: 20

Issue: 4

Pages: 291-300

Online publication date: 02/06/2014

Acceptance date: 06/03/2013

ISSN (print): 1355-2546

ISSN (electronic): 1758-7670

Publisher: Emerald Group Publishing Limited

URL: http://dx.doi.org/10.1108/RPJ-07-2012-0064

DOI: 10.1108/RPJ-07-2012-0064

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