Loosening under Transverse Cyclic Loads: Procedure and Results

In this test, a load is repeatedly applied transverse to the bolt to check for looseness prevention. It is generally known that rotation looseness occurs when the repeated load is at least twice the preload.

Test frequency

Cycle load: 1 Hz

Test photographs

test photographs

Test conditions

(1) Two combinations of the initial axial force F0 and 20%/70% of the bolt yield axial force
Fy = 340 × 84.3 = 28662 N (1) 20% of Fy = 5732 N (2) 70% of Fy = 20063 N

load W and 50/80% of the bolt yield axial force Fy (3) 50% of Fy = 14331 N (2) 80% of Fy = 22930 N

(3) Combinations of the tensile load and initial axial force

test chart
Conditions/
combination
Initial axial
force F0
Repeated load W Comments
②ー④ 20063 N 22930 N No loosening
①ー③ 5732 N 14331 N The possibility of loosening
①ー④ 5732 N 22930 N Loose

Test nut

HLN: Hardlock Nut
Standard rim WN: Hex nut (one type) + hex low nut (three types)
SN + SW: Hex nut (one type) + spring washer
SN: Hex nut (one type)

As it is understood that rotational looseness does not easily occur if an adequate initial preload is set, it can also be seen that even with a low initial preload, rotational looseness does not easily occur with the Hardlock Nut if the concave nut is tightened adequately.

test results