FIELD: machine building.
SUBSTANCE: invention relates to machine building, to methods for determining coefficient of friction in thread. Chain of parts is assembled to create load F stretching the bolt rod and to maintain the value of this load approximately constant during rotation of the bolt rod. Tension spring is included in this chain of parts. This chain of parts also includes a cable and swivels, which enable to rotate the bolt rod with low friction forces. Bolt rod is stretched by means of a special device; the tension force of the bolt rod is measured by means of a dynamometer. First, required lubricant or other composition is applied on bolt rod. Nut is screwed on the bolt rod. Bolt is inserted into the hole in the fixed stop. Tip is screwed on the end part of the bolt rod until it stops. This tip is equipped with a device for fastening with a swivel. Chain of parts is assembled. Bolt rod is stretched by force of required value. Nut is secured against turning, i.e. when the bolt rod is rotating, the nut shall not rotate. Torque is applied to bolt rod, magnitude of which is measured. Torque is gradually increased to the moment when the bolt rod starts to spin in the nut. Such measurements are carried out both in case of screwing nut (distance from tip to nut decreases) (measuring moment of screwing Mscr), and in case of unscrewing of nut (distance from tip to nut increases) (unscrewing moment Muns). For statistics, such measurements are carried out several times. So, when screwing f=tg{arctg[2×Mscr/(F×d2)]–ψ}×cos(γ). When unscrewing f=tg{arctg[2×Muns/(F×d2)]+ψ}×cos(γ). fred=f/cos(γ) (This is the reduced coefficient of friction in the thread), for metric thread γ=α/2=30°; ψ is the lead angle of the thread (radians).
EFFECT: possibility of conducting research to determine coefficient of friction in thread for objects without two support surfaces.
1 cl, 2 dwg, 3 tbl
