Pretension in Fastners

Pretension load play very important role in industrial assemblies in order to avoid accident by loosening of assemblies. The aim is to determine maximum limit of pretension load without thread failure using universal testing machine. The vibration test rig is developed for measuring the loosening performance of nut bolt assemblies. The samples of ISO Metric bolts of different size such as M8 M10 M12 M16 and M20 bolt having 1.25 1.5 1.75 2 and 2.5 mm pitches respectively are used for testing. The maximum stresses developed and deformations occur due to pretension load applied on nut bolt assembly are obtained by finite element method using ANSYS Workbench version 14. The validations of results are carried out by using analytical method.