Investigating the behavior of laser-sintered Nylon 12 parts subject to dynamic loading
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di Moztarzadeh Warwick Manufacturing Group, University of Warwick, Coventry CV4 7AL, UK
Jem Rongong and Neil Hopkinson Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD, UK (Received 28 February 2014; accepted 17 June 2014)
Laser sintering allows producing end-use parts directly from computer files with no tooling required. For these parts to be used in industrial applications, their mechanical properties throughout in-service applications must be examined. The aim of this article is to provide an understanding of the dynamic performance of laser-sintered Nylon 12 parts. To investigate the viscoelastic properties of the material, dynamic thermal mechanical analysis has been performed in different frequencies and temperatures. Tension–tension cyclic behavior of samples has been studied and creep is shown to have a great impact in such behavior in addition to fatigue. Stress relaxation plots are provided and compared with the cyclic loading plots validating the fact that samples experience a combination of creep and fatigue in tension–tension loading. Hysteresis loops indicate brittle crack propagation in the samples experiencing fatigue.
I. INTRODUCTION
Production of lightweight structures to reduce fuel consumption and increase energy efficiency, while maintaining safety and comfort standards, has long been a challenge for automotive and aerospace industries. Different approaches1 such as using materials of less weight but similar performance – polymers and composites – or altering the current parts by high-stiffness, reduced weight designs have been attempted by industries. The challenge for utilizing alternative designs is a manufacturing process with the capability of fabricating complex structures with reduced need for postprocessing to get the end products.1 Additive manufacturing (AM) has attracted the interest of researchers over the past decade, as a layerwise technique enabling manufacturers to produce parts with high geometric complexity in reduced time and with no tooling requirement. Some of the materials and processes used are mature enough that AM techniques have been transformed from producing prototypes with poor and unrepeatable properties to producing end-use parts with properties comparable with the ones from conventional techniques. Laser sintering (LS) is an AM process where a laser scans the surface of a layer of powder to sinter the particles to fuse and form a new part. Unlike other AM processes, a)
Address all correspondence to this author. e-mail: h.amel@sheffield.ac.uk DOI: 10.1557/jmr.2014.150 1852
J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
Downloaded: 14 Mar 2015
LS allows building of parts from a wide range of materials including polymers, metals, and various types of composites, while possessing the advantages of AM. However, to use this process in automotive applications the mechanical properties of the parts must be satisfactory and must meet the standard requirements. Tensile properties are the most widely provided pr
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