A New Tightening Technique for Threaded Fasteners

Abstract

A new technique for tightening threaded fasteners was proposed aiming to assure the quality and the reliability in the tightening operations. The technique is based on the torque difference and the relative rotation angle in tightening and loosening process, and no preliminary experiment is required. Repeated tightening (and loosening) experiments were performed for different types of lubricant to verify the applicability of this technique. Experimental results show that the preload provided to the joint can be estimated with high accuracy and precision by this technique, and the possibility to boost the reliability of tightening control is confirmed.

Development of a New Testing Machine for Torque/Clamp Force Testing for Threaded Fasteners in Accordance with ISO 16047 -Characteristics of a Load/Torque Cell System Using Piezoelectric Force Sensors-

“…(4), where two factors κ and ε for each torque are manually tuned by trial and error. Although the diagram could represents different shape in every experiment due to the effect of friction, the compensated values show very good agreement with the measurements by strain gages including the unstable change normally observed (6), (8) …”

“…Therefore, the piezoelectric force sensor is chosen as the sensor element constituting the load/torque cell system for its high sensitivity in pC/N unit and high compressive stiffness in kN/µm unit. Figure 2 shows the relationship among the applied torque T, the thread torque T th , and the baring surface friction torque T b in tightening and loosening process drawn theoretically under the assumption that the coefficients of friction are constant throughout the process (6) .…”

“…Experimental and analytical considerations have been performed to seek the root causes that may generate the measuring error. Figure 1 shows an example of the conventional testing machine (apparatus) used for tightening experiments in a laboratory (6) . This machine has the load/torque cell system using Fig.…”

Preloads Generated with Repeated Tightening in Three Types of Screws Used in Dental Implant Assemblies

“…The absolute values for preload in implant prosthetic and abutment screws vary considerably among studies, and this may be due to differences in how preload is measured. 28 Experiments have calculated preload from rotational angle, 27 from compression in the implant assembly, 22,29 or from screw elongation. 30 The apparatus used here maintained a gap between the abutment and the implant head, and so more directly measured tension in the abutment screw compared with the other methods.…”

Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study

“…Although direct measurement is preferable, it is not practical because it requires the use of strain gauges or load cells. However, indirect methods can be used to estimate preload by measuring the torque, angle of rotation of the screw head, or both (Hagiwara & Ohashi 1994). Torque control is the most used method.…”