When we want to incorporate FEA techniques in ouranalysis, we should consider ways to simplify our model. A bike frame has avery small thickness relative to its surface area. Therefore, we can analyzethe geometry using shells. 9 v# J6 n& m9 ~: k5 f+ O; x5 ^In SOLIDWORKS, shells are very easy to set up. With thehelp of the Shell Manager,surfaces can be given a thickness, material, offset type, and more within oneconvenient table.& P1 }4 N9 ~ x4 i Y4 `$ U- N
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Analysis (computational) times are much lower for shellsthan solid geometry.4 n: _9 N* L: |
Furthermore, laminar edges (coincident surfaces) aretreated as bonded, so there is no need to worry about knitting your surfacesbefore starting your analysis.$ h2 E6 `1 a( I: w& @( v
[attach]365869[/attach]Tapered vs. Non-Tapered Head TubeThere is quite a lot of hype about ‘tapered head tubes’ inthe performance cycling world [where the bottom profile of the head tube tapersout], but how much of a difference does it actually make? To find out, I ran astatic analysis to see if there was any noticeable effect on the frame’sstiffness. 1 l0 s; [" E+ x1 `% yThe main forces applied to the bike are torsional andlateral forces. Therefore, we can limit our analysis to torsional and lateralstiffness.0 o4 O6 c! u) ^8 a: w1 J: k/ r
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These are simplified definitions for a body with onedegree of freedom. This can be applied to our case by analyzing the resultantdeflection in the direction of the applied force as long as one force isapplied at a time for each analysis.! e/ k! j# G7 Z
First, let’s look at the torsional stiffness. In order tocalculate torsional stiffness (for the Head Tube) we can create a resultantplot of the circumferential deflection about the Head Tube Axis (HT AXIS).* u5 O7 f7 c) o( n) T# ]9 F
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By taking advantage of the extra spaceon the non-drive side, I was able to increase the lateral stiffness of theframe by 11%.
In the next part, I will furtherimprove the performance of the frame design by using CFD (computational fluiddynamics) analysis to optimize for aerodynamic performance.
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Thank you for reading, stay tuned forthe next part!
Summary of results
Design Aspect
Change In Stiffness (%)
6 b) Z h/ O2 W( d u8 {" |
Non-Circular Profile
37 (Torsional)
% F/ [9 H+ c" G+ Y! A4 `: b
Tapered Head Tube
21.5 (Torsional)
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Non-Symmetric Chain Stay
11 (Lateral)
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Seat Stay (+/- 1 mm thickness)
<<1 (Torsional/Lateral)
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Top Tube Taper (1 1/10)
3 (Torsional): k1 m8 E, a; f1 f' y) {9 E
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這篇文章給人印象深刻的不是分析，而是自行車架的3D草圖。不要抱怨軟件如何如何，還是多檢討自己吧。