7 Tightening energy ratio 12%32%56%Source : Bolt Science②
8 Tightening enegergy Ratio summary :50% underhead of the bolt / nut friction40% thread friction10% generate tension /clamp loadOnly the clamp load serves the join.①②
9 Specific friction with wedge lock effect components ①TIGHTENING :Friction under the bolthead:The bolt/nut slides on the serrated surface of the HL washerUNTIGHTENING :Friction :The upper washer slides on the lower, at the cam side. Cam surface could be considered to flat surface
10 Specific friction with wedge lock effect components µa > µi
11 consequence①The torque, taken by the friction between the cams when untightening is much lower than the torque taken by the friction under the bolt head on the serrated side.The Untightening / Tightening ratio, depends on friction coefficients on 2 differents surfaces
15 Clamp load increase when untightening Depending on:Clamp lengthCase ACase BThe elongation of the bolt when passing the cam peak is equal in value (few 1/10mm), but the % is much higher on short clamp length (case B) than long bolt (case A).
16 Consequence Different product could have : different α ②Different product could have :different αdifferent cam heightthe clamp load increase could be a bit differentthe wedge effect requires α>β. We cannot deduct any better or worse effect.Only the residual clamp load prooves the efficiency.
17 Consequence①②Underhead frictions, are different Tightening / UntighteningThe torque need to beat the friction variesClamp load increase could vary due the geometry of the washersThe torque need to increase the clamp load and pass the peak varies
18 Consequence①②Untightening / Tightening ratio doesn’t give any information on the wedge effect efficiency.Tests available:Occular : tighten and then untighten. when turning left, it should slide between the cams. When passing the cam peak, a « click » should be feelt or heard.Junker test by simulating your joint.Real life montage and test.
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