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Untightening torque Can we use the untightening / tightenigng torque ratio to estimate the efficiency of HEICO-LOCK ?

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Presentation on theme: "Untightening torque Can we use the untightening / tightenigng torque ratio to estimate the efficiency of HEICO-LOCK ?"— Presentation transcript:

1 Untightening torque Can we use the untightening / tightenigng torque ratio to estimate the efficiency of HEICO-LOCK ?

2 Action in the bolt

3 What is the tightening torque T= Force x distance distance Force

4 Torque calculation Kellermann & Klein Torque = ( p/2π + 0,583 d μf + D/2 μt) *F F= clamp Force P= pitch Rotzler

5 Tightening energy ratio Source : Cetim ② Thread friction ~ 40% Underhead friction ~ 50% Tension ~ 10% A high friction in the thread adds high torsion TOTAL ENERGY SUPPLIED BY THE TIGHTENING TORQUE

6 Tightening energy ratio Source : Grupo Aztec

7 Tightening energy ratio 12% 32% 56% Source : Bolt Science ②

8 Tightening enegergy Ratio summary : – 50% underhead of the bolt / nut friction – 40% thread friction – 10% generate tension /clamp load Only the clamp load serves the join. ① ②

9 Specific friction with wedge lock effect components TIGHTENING : Friction under the bolthead: The bolt/nut slides on the serrated surface of the HL washer UNTIGHTENING : Friction : The upper washer slides on the lower, at the cam side. Cam surface could be considered to flat surface ①

10 µa > µi Specific friction with wedge lock effect components

11 consequence The 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 ①

12 Clamp load increase when untightening ②

13 Tension / clamp load increase

14 Clamp load increase when untightening Depending on: – Cam angle α – Cam height

15 Clamp load increase when untightening Depending on: – Clamp length Case A Case B The 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 Different product could have : – different α – different cam height  the clamp load increase could be a bit different  the wedge effect requires α>β. We cannot deduct any better or worse effect.  Only the residual clamp load prooves the efficiency. Consequence ②

17 Underhead frictions, are different Tightening / Untightening – The torque need to beat the friction varies Clamp load increase could vary due the geometry of the washers – The torque need to increase the clamp load and pass the peak varies ②①

18 Consequence Untightening / 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. ②①

19 THANK YOU FOR YOUR ATTENTION


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