ASTM D5649 Torque Strength of Adhesives Used on Threaded Fasteners

Scope:

The standard ASTM D5649 describes the test method to determine the securing or locking effect of adhesives that are applied onto threaded fasteners. It can also assess the degree of cure and the effect of the environment on the torque strength. Thread locking and sealing adhesives are applied on the threads of fasteners, to prevent their lateral movement or slip in service, which can compromise joint integrity. The torque strength is a measure of the ability of the cured adhesive to resist applied torque without breaking. The ASTM D5649 test involves torque testing of an adhesively bonded bolt and nut assembly. The breakaway and prevailing torques, at specified rotation speed and rotation angles, are measured for each adhesive and threaded fastener assembly. The breakaway torque refers to the torque at which the adhesive bond breaks allowing the first movement between the nut and bolt. The torque measured at various angles thereafter is referred to as the prevailing torque

Procedure:

The ASTM D5649 procedure is conducted in a test apparatus that can clamp the bolt head of the adhesive bonded bolt and nut assembly and turn the nut at a prescribed speed and torque. The torque at the first movement of the nut is noted as the breakaway torque. Further rotation to unscrew the nut is measured at various angles such as 90°, 180°, 270°, and 360°, in addition to other angles. The corresponding torque values are noted. It is customary to report a single value for prevailing torque, which may correspond to a specified angle or maximum or average values. An electronic torque measurement or direct reading torque wrench is acceptable.

Specimen size:

In ASTM D5649 testing, the bolt and nut sizes to be tested can be as agreed between the supplier and user of the adhesive. Non-plated nuts and bolts must be degreased and kept clean and dry before the application of the adhesive. Electroplated nuts and bolts may not require additional cleaning.

Result:

The breakaway and prevailing torques are reported in inch pounds.

Conclusion:

The standard ASTM D5649 describes the test method to determine the securing or locking effect of adhesives that are applied onto threaded fasteners.