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
Force
distance

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

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

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 components①
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

10. Specific friction with wedge lock effect components
µa > µi

11. consequence ①
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

12. Clamp load increase when untightening②

13. Clamp load increase when untightening
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. Consequence Different product could have : different α②
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.

17. Consequence ① ②
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

18. Consequence ① ②
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.

19. THANK YOU FOR YOUR ATTENTION