Experimental study on torque-preload conversion of prestressed screw steel anchor

doi:10.16265/j.cnki.issn1003-3033.2022.11.1462

Abstract

Abstract:

In order to effectively improve the pre-tightening force of prestressed thread steel bolt and reduce the anchor bolt broken anchor loss phenomenon, the transformation relationship between bolt torque and pre-tightening force and the dangerous points of a bolt in the nut assembly process were analyzed theoretically. The factors affecting pre-tightening force and the causes of bolt fracture were obtained. The bolt torque-pre-tightening force conversion test tooling was developed. The bolt pre-tightening process applied to the total torque, thread pair torque, and tray bearing surface torque were detected, respectively. The rolling friction-reducing gasket of the anchor rod was developed. Through theoretical analysis and field application, the relationship between torque and preload was obtained, and the influence of friction loss of pallets on preload was reduced. The tension-compression separation nut was developed. The force cloud diagram and torque-preload transformation relationship were obtained through numerical simulation and laboratory tests, and the influence of thread pair deformation and poor stress environment on preload was reduced. The results show that the rolling friction-reducing gasket can reduce the friction between the nut and the supporting surface of the tray, improve the torque-preload conversion efficiency, and increase the preload by more than two times. By applying the tension-compression separation nut, the concentrated load bearing of the tension-compression composite of the traditional bolt thread pair is optimized to the uniform load bearing of the tension-compression separation type, which significantly alleviates the stress of the dangerous surface and dangerous point of the bolt, realizes the coordinated deformation of the thread pair, and reduces the phenomenon of broken anchor.

Key words: prestressed thread steel bolt, torque-prestress, bolt fracture risk point, rolling antifriction gasket, tension-pressure separation nut

HOU Junling, LI Chuiyu, ZHAO Neng, ZHANG Dunxi, DU Chenghang. Experimental study on torque-preload conversion of prestressed screw steel anchor[J]. China Safety Science Journal, 2022, 32(11): 55-64.

Figures/Tables 18

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总扭矩/ (N·m)	支承面扭矩/ (N·m)	螺纹副扭矩/ (N·m)	预紧力/ kN
75	35	40	18.9
145	75	70	30.9
215	115	100	49
300	170	130	65.3
385	220	165	80.8
465	265	200	96.85
555	325	230	103.35
625	370	255	107.3

总扭矩/ (N·m)	支承面扭矩/ (N·m)	螺纹副扭矩/ (N·m)	预紧力/ kN
65	5	60	31.5
150	35	115	62.5
245	55	190	97.5
340	90	250	131.8
390	100	290	140

总扭矩/ (N·m)	支承面扭矩/ (N·m)	螺纹副扭矩/ (N·m)	预紧力/ kN
65	15	50	38.1
135	20	105	74.6
225	55	170	115
300	65	235	156.4
405	85	320	204.5