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Untightening torque

Untightening torque. Can we use the untightening / tightenigng torque ratio to estimate the efficiency of HEICO-LOCK ?. Action in the bolt. What is the tightening torque. T= Force x distance. Force. distance. Torque calculation. Kellermann & Klein

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Untightening torque

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

  2. Action in the bolt

  3. Whatis the tightening torque • T= Force x distance Force distance

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

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

  6. Tighteningenergy ratio Source : GrupoAztec

  7. Tighteningenergy ratio Source : Bolt Science 56% ② 12% 32%

  8. Tighteningenegergy 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 withwedgelockeffect components ① TIGHTENING : Friction under the bolthead: The bolt/nutslides on the serrated surface of the HL washer UNTIGHTENING : Friction : The upperwasherslides on the lower, at the camside. Cam surface couldbeconsidered to flat surface

  10. Specific friction withwedgelockeffect components • µa > µi

  11. consequence ① • The torque, taken by the friction between the camswhenuntighteningismuchlowerthan the torque taken by the friction under the bolthead on the serratedside. • The Untightening / Tightening ratio, depends on friction coefficients on 2 differents surfaces

  12. Clamp loadincreasewhenuntightening ②

  13. Clamp loadincreasewhenuntightening Tension / clamp loadincrease

  14. Clamp loadincreasewhenuntightening • Depending on: • Cam angle α • Cam height

  15. Clamp loadincreasewhenuntightening • Depending on: • Clamp length Case B Case A The elongation of the boltwhen passing the campeakisequal in value (few 1/10mm), but the %ismuchhigher on short clamp length (case B) than long bolt (case A).

  16. Consequence ② • Differentproductcould have : • differentα • differentcamheight • the clamp loadincreasecouldbe a bit different • the wedgeeffectrequiresα>β. Wecannotdeductanybetter or worseeffect. • Only the residual clamp loadprooves the efficiency.

  17. Consequence ① ② • Underhead frictions, are differentTightening / Untightening • The torque need to beat the friction varies • Clamp loadincreasecouldvary 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’tgiveany information on the wedgeeffectefficiency. Tests available: • Occular : tighten and thenuntighten. whenturningleft, itshouldslidebetween the cams.When passing the campeak, a « click » shouldbefeelt or heard. • Junker test by simulatingyour joint. • Real life montage and test.

  19. THANK YOU FOR YOUR ATTENTION

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