Research on bolt pre-tightening and relaxation mechanism under transverse load

Abstract

In order to predict the bolt’s stress distribution under the pre-tightening state and the loosening process under the transverse load, a 3D model considering the bolt thread structure was established by finite element method (FEM). In this study, the looseness effect of transverse load amplitude, the friction coefficient of the bolt head load bearing surface and the thread contact surface are mainly studied. The result indicated that the stress under bolt pre-tightening is mainly concentrated on the contact part of the bolt’s head and bar. At the contact area of the load threads at one end and the transition part between the bolt bar and the thread, the stress and axial direction of the thread part are offset. Under the transverse displacement load, the sliding of the bolt can be divided into three stages: full contact, viscous contact, and full slip. The numerical model of bolt relaxation obtained in this paper can provide reference for the application, checking and prediction of threaded fasteners.

Experimental and numerical analysis of preload in Extended Hollo-Bolt blind bolts

“…Ganeshmurthy and Nassar [13] identified two zones in the torque-preload relationship for nonparallel contact joints; the first zone ends at about 15% of the total torque and it is justified by the fact that the wedge angle is consumed by the rotated bolt head at the beginning of tightening. Gao et al [29] also reported nonlinear behaviour in the turn-preload curves up to a value of 15% of the applied turning angle. The mechanism for this effect is not completely understood, however, its effects are generally neglected as this occurs at low tightening levels.…”

Application of SLAM in bolt tightening monitoring process based on intelligent data algorithm analysis

“…The results show that the bolt preload can significantly improve the mechanical properties of the joints, but at high temperatures, the bolt preload relaxes due to material expansion, resulting in the degradation of the joint performance. In the literature [14], the effect of transverse load on the bolt preload and preload relaxation mechanism was analyzed through experiments and numerical simulations, and the stress distribution and deformation of the bolt under different preload and load cases were explored. The results indicate that the transverse load causes the bolt preload to relax and stress concentration to increase, which impacts the bolt's connection performance.…”

Analisis Pergantian Alat Pengencang Baut-U 4 Spindel Menjadi 1 Spindel di Station Rear axle PT.Daimler Commercial Vehicles Manufacturing Indonesia

“…Penelitian ini memperlihatkan pemberian beban melintang akan mengurangi gaya pre-tightening dan putaran baut serta menyajikan model numerik pelonggaran baut-Untuk prediksi pengencangan baut berulir. Kelemahan dari jurnal ini adalah peneliti tidak menjelaskan mekanisme relaksasi baut secara jelas, namun hanya menjelaskan bahwa ketika baut sudah memasuki fase Full Slip Stage maka semakin besar koefisien geseknya dan semakin besar terjadinya relaksasi dari pengencangan awal atau Looseness [4]. Mery Silviana(2017), melakukan penelitian untuk mengetahui kekuatan sambungan batang tarik pelat baja dengan sambungan baut variasi tebal pelat 8mm dan 10 mm dan diameter baut Ø1/4'' , Ø3/8'', dan Ø1/2''.Metode yang dilakukan adalah dengan melakukan uji tarik menggunakan mesin pembebanan tarik (Universal Testing Machine) lalu di bandingkan dengan hasil perhitungan secara teoritis.Hasil dari penelitian tersebut menunjukan bahwa sambungan pada pelat tebal 8 mm sedikit lebih kuat dibandingkan dengan pelat 10 mm,dan perbandingan nilai kekuatan sambungan dari eksperimen dan perhitungan teoritis menunjukkan perhitungan secara teoritis lebih kecil dari hasil eksperimen ini dikarenakan dalam metode perhitungan ini memang hanya menggunakan tegangan ijin sedangkan secara aktual eksperimen faktor pembebanan lebih berpengaruh kekuatan batang tarik.Kekurangan penelitian ini adalah peneliti menyimpulkan perencanaan menggunakan metode ASD (Allowable Stress Design) dianggap tidak efisien namun tidak menampilkan proses perhitungannya sehingga belum jelas apakah terdapat kesalahan pada perhitungan atau pemilihan benda uji pelat dan diameter baut [5].…”