Factors affecting the tightening characteristics of bolts

Bray, A.; Levi, Raffaello

doi:10.1007/bf02326286

Cited by 16 publications

(3 citation statements)

References 2 publications

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“…Hagiwara and Ohashi [9] presented a new tightening technique for threaded fasteners. Bray and Levi [10], Jiang et al [11], and Sakai [12] carried out some experimental studies on the fastener torque tension relationship. Further, Chiang et al [13] examined the relationship between the tightening torque and the fastener tension for bolted assemblies.…”

Section: Introductionmentioning

confidence: 99%

Surface roughness effect on the torque-tension relationship in threaded fasteners

Nassar

Sun

2007

Proceedings of the Institution of Mechanical Engineers, Part J:

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An experimental study is presented in order to investigate the effect of surface roughness on the torque-tension relationship in threaded fasteners. Three levels of surface roughness are considered for the fastener underhead and the joint surface; namely, low, medium, and high levels of surface roughness. The study is conducted for two joint materials, two fastener classes, and for coarse and fine threads. In this study, the torque-tension data are expressed in terms of the value of the nut factor as well as its scatter. The effect of the number of tightening on surface roughness and on the torque-tension relationship is investigated as well. The surface roughness is measured before tightening, and after each loosening using a WYKO optical profiling system. An M12 fastener is used in this study. Both fine and coarse threads and fastener material Classes 8.8 and 10.9 for M12 fasteners are used in this study. The torque-tension data is analysed for both steel and aluminium joints. The safety and reliability of bolted assemblies are mainly determined by the level and the stability of the clamp load provided by the initial tightening of the threaded fastener. The value of initial clamp load, which is achieved by a specific level of tightening torque, is highly sensitive to the friction torque components. This study provides an insight into the reliability of the existing engineering practices for estimating the clamp load level from the tightening torque. Hence, the findings of the study would help enhance the reliability and the safety of bolted assemblies, especially in critical applications.

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Section: Introductionmentioning

confidence: 99%

Surface roughness effect on the torque-tension relationship in threaded fasteners

Nassar

Sun

2007

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Therefore, the relationship between applied torque and the axial load of the bolt should be first studied. The mechanical behavior of bolted joints during loosening and fastening was investigated [ 42 , 43 , 44 , 45 ]. The research results show that the torque applied to a bolted connection consists of three components [ 43 , 46 ]: (1) the torque to stretch the bolt; (2) the torque to overcome the friction in the threads of the bolt; and (3) the friction between nut face and bearing surface.…”

Section: Bolt Looseness Monitoring Experiments Using Smart Washermentioning

confidence: 99%

A Fiber Bragg Grating (FBG)-Enabled Smart Washer for Bolt Pre-Load Measurement: Design, Analysis, Calibration, and Experimental Validation

Chen

Huo

et al. 2018

Sensors

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A washer is a common structural element that is directly used along the loading path of a bolted connection. Pre-load on a bolted connection directly impacts its load bearing capacity and pre-load monitoring is an important aspect of structural health monitoring (SHM). With the change of the pre-load on a bolted connection, the loading force on the washer will change and, therefore, the outer diameter and outer circumferential length of the washer will change. Taking advantage of the high sensitivity and the small size of a Fiber Bragg Grating (FBG) sensor, we propose an innovative smart washer encircled by an FBG sensor that can directly measure the circumferential strain change and, therefore, the pre-load on the washer. For protection, the FBG is embedded in a pre-machined groove along the circumferential surface of the washer. A theoretical approach is used to derive the linear relationship between the applied load and the circumferential strain of the washer. To validate the functionality of the FBG-enabled smart sensor for in situ bolt pre-load monitoring, a simple but effective testing apparatus is designed and fabricated. The apparatus involves a bolt, the FBG-enabled washer, a metal plate, and a nut. The bolt has an embedded FBG along its axial direction for precise axial strain and, therefore, force measurement. With the calibrated axial force measuring bolt, in situ experiments on the FBG-enabled smart washers are conducted. Experimental results reveal the linear relationship between the pre-load and the wavelength of the FBG sensor encircling the washer. Both analytical and experimental results demonstrate that the proposed novel approach is sensitive to the bolt pre-load and can monitor in real time the bolt looseness in the entire loading range.

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“…Among the mentioned detachable joints, bolted joints are the most important elements in aerospace structures. However, the existence of geometrical discontinuity in bolted joints due to essential hole‐drilling operation causes stress concentration and thus increases the tendency of fatigue crack to initiate and grow under cyclic loading . On the other hand, easy disassembling that simplifies repairs and permits replacing of damaged components makes these types of joints favourite for extensive use in aerospace structures.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigations on the Effects of Torque Tightening on the Fatigue Strength of Double‐lap Simple Bolted and Hybrid (Bolted/Bonded) Joints

Esmaeili

Zehsaz

Chakherlou

2014

Strain

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In this paper, the effects of bolt torque tightening on the fatigue strength of double‐lap simple bolted and hybrid (bolted/bonded) joints have been studied experimentally. To do so, two types of joints, that is, double‐lap simple and hybrid (bolted/bonded) joints, were studied. For each type of joints, three sets of specimens were prepared and subjected to the tightening torque of 1, 2.5 and 5 Nm, and then, fatigue tests were carried out at different cyclic longitudinal load levels. Experimental tests results showed that the hybrid joints have better fatigue performance in comparison with the simple bolted joints. In addition, the investigation revealed the positive role of tightening torque on the fatigue life of both simple and hybrid joints.

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Factors affecting the tightening characteristics of bolts

Cited by 16 publications

References 2 publications

Surface roughness effect on the torque-tension relationship in threaded fasteners

Surface roughness effect on the torque-tension relationship in threaded fasteners

A Fiber Bragg Grating (FBG)-Enabled Smart Washer for Bolt Pre-Load Measurement: Design, Analysis, Calibration, and Experimental Validation

Experimental Investigations on the Effects of Torque Tightening on the Fatigue Strength of Double‐lap Simple Bolted and Hybrid (Bolted/Bonded) Joints

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