Calculation of the effective bearing contact radius for precision tightening of bolted joints

Abstract

Torque control is usually the only method for tightening bolts in some precision assembly applications. However, the scatter of the torque-tension relationship may significantly decrease the accuracy of the preload, which conflicts with the high requirement for mechanical accuracy in such precision assemblies. An important, but often ignored, factor affecting the accuracy of the torque-tension relationship is the effective bearing contact radius. In this article, a threedimensional finite element model of a typical bolted joint was developed to obtain the actual bearing pressure distribution, based on which the effective bearing contact radius can be further calculated. Then, a parametrical study was conducted to systematically investigate the effects of various geometrical, material, and frictional factors on the effective bearing contact radius. Based on the numerical results, a comprehensive and quantitative evaluation of the relative accuracy of each traditional method of calculating the effective bearing contact radius was made. In particular, it was found that the effective bearing contact radius, calculated based on the assumption of uniform bearing pressure distribution, was always relatively accurate regardless of the geometrical, material, and frictional conditions considered. This study will be helpful in increasing the accuracy of preload, thus ensuring mechanical accuracy and quality for precision assemblies.

Analisa Akurasi Penggunaan Strain Gauge Dan Transducer Pada Kunci Momen

“…Keamanan, keandalan, dan kualitas sambungan baut ditentukan sebagian besar oleh besarnya dan stabilitas beban penjepit atau preload. Untuk mencapai preload yang diinginkan, berbagai metode pengencangan telah dikembangkan, seperti pengaturan torsi, pengaturan sudut torsi, pengaturan peregangan, dan pengaturan yield point [5].…”

Friction-Induced Vibrations during Tightening of Bolted Joints—Analytical and Experimental Results

“…With the motor transferring the torque to the head into the bearing of the screw, the latter will be rotated and increase the pretension force onto the clamped parts [24][25][26][27]. The frictional contact area underneath the bearing is approximated by [28]…”

Improvements to torque versus tension relationship considering nut dilation effects

“…Almost all assumed pressure distributions would result in a centre of pressure at the vicinity of the midpoint and as a result would not make much of a difference to the final formula. 16 Gong et al 17 attempted to calculate the effective bearing contact radius using 3D finite-element modelling and it was found that the assumption of uniform bearing pressure distribution by Nassar et al 16 matched the FE model within 2% of error.…”

“…16 Gong et al. 17 attempted to calculate the effective bearing contact radius using 3D finite-element modelling and it was found that the assumption of uniform bearing pressure distribution by Nassar et al. 16 matched the FE model within 2% of error.…”