Three-Dimensional Displacement Mapping of Carbon Fibre Bicycle Frames using Digital Image Correlation

Author: Juan Laurea

Laurea, Juan, 2018 Three-Dimensional Displacement Mapping of Carbon Fibre Bicycle Frames using Digital Image Correlation, Flinders University, College of Science and Engineering

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The investigation of three carbon fibre bicycle frames using Digital Image Correlation (DIC) was conducted to provide a full-field assessment of these structures. Literature research for this project found finite element analysis (FEA) and strain gauges to be common methods of testing bicycle frames, however, the use of DIC was limited. Therefore, using this measurement tool may offer a new approach to obtaining the lateral and vertical displacement values for bicycle frames. Research showed that using DIC enabled a comprehensive measurements of full field displacements on a bicycle frame, which was not easily achieved with strain gauges and FEA required laboratory testing to confirm its findings.

The bicycle frames tested were designed to suit sprint cycling conditions, hence, a testing rig was created to emulate these parameters. The design was mainly inspired from an international standard (ISO 4210- 6), however, modifications were made to create to suit static testing conditions. These were to implement multiple crank angles (90O – 180O) during the downstroke phase cycling as this area has the highest loads applied, and applying 266 N.m (Korff et al. 2007; Martin et al. 2006).

A testing and post-processing protocol was developed to obtain the displacement values, consistently. There were several investigations involved; one to find locations of high displacement, the second was to observer if the displacement changed as the crank angle changed, and finally, a comparison between bicycle frame designs.

The results found that vertical displacement for all bicycle frames was the same, regardless of the crank angle, however, the development of these displacements was different along each section of the bicycle frame. All three bicycle frames showed high lateral displacement at the seat tube, down tube, and chain stays near the bottom bracket, as the load increased. As well, it was found that lateral displacement changes as crank angle changes.

Comparison between the left-hand side (LHS) and right-hand side (RHS) of a single bicycle frame design (CA01) showed differences in lateral displacement. Moreover, the comparison of two bicycle frames with the same design (CA01 and CA02) also showed considerable differences. These differences in lateral displacement may have be caused by the manufacturing process. Two bicycle frames with different designs, CA01 and AR01, were compared to observe which bicycle frame was stiffer. It was found that the AR01 design deflected less than the CA01 design during testing. Therefore, the AR01 design may be preferable for sprint cycling based in terms of its stiffness properties. AR01 may be stiffer because of its design, how the carbon fibre was layered, or the curing method (Bie et al. 2017; Chang et al. 2017; Rahmani et al. 2014).

Keywords: Digital Image Correlation, Sprint Cycling, Cycling, Displacement Maps, Lateral Displacement, Vertical Displacement, Bicycle Frame

Subject: Engineering thesis

Thesis type: Masters
Completed: 2018
School: College of Science and Engineering
Supervisor: Professor Mark Taylor