Search Results

In this paper, an emphasis is put on describing the elastic and plastic deformation behavior of the bolted joint. The bolt material is assumed to be plastic hardening. A nonlinear combined stress model is established for a typical bolted joint for the purpose of studying its behavior under a yield tightening. The combined effect of axial and torsional stresses in the tightened threaded fastener is considered. A new approach for yield tightening under ideal plastic bolt was proposed, and the effects of the thread and bearing frictional coefficients on the clamp load prediction are evaluated. The prediction precision of deformation behavior of the bolted joint under yield tightening for the strain hardening bolt material are studied experimentally.

An experimental study is presented in order to determine the effect of tightening speed on clamp load distribution in a gasketed steel joint. Two gasket materials are considered, namely, Styrene Butadiene Rubber and Flexible Graphite. Flange tightening is achieved using a multiple spindle fastening system that has speed and torque controls; the fastening system is also capable of performing simultaneous tightening of all fasteners using other advanced control modes such as torque-turn or torque-to-yield strategies. Two tightening patterns are investigated, namely, simultaneous tightening of all bolts and individual tightening of one bolt at a time following a star pattern. The tightening speed in this study ranges from 1 rpm to 100 rpm. Clamp load loss due to the combined effects of gasket creep relaxation and elastic interaction is investigated.

A nonlinear model is established for the clamp load analysis of tightened bolted joints that are subjected to a separating service load that is cyclic in nature. The analysis takes into account the strain hardening of the bolt material to determine its behavior beyond the elastic limit. The bolt tension versus elongation curves during the tightening are established. The clamp load loss is determined due to the permanent set in the fastener after a cyclic separating force has been removed. The fastener material with strain hardening plastic behavior is used for modeling the behavior of the bolted joint system. The effect of some non-dimensional variables on the amount of clamp load loss is investigated. Analytical results are presented for a range of stiffness ratios that simulate both soft and hard joint applications.

An experimental procedure is presented in order to study the simultaneous tightening of automotive wheel lugnuts and to enhance the clamp load uniformity and repeatability. Two different tightening strategies are investigated, namely, the torque-only and the torque-angle control methods. The effect of the tightening speed, initial threshold torque level, and the torque steps is investigated. The study is conducted on two different wheel materials, namely, steel and aluminum. Lugnut tightening is accomplished by using a five-spindle DC fastening system in either a torque-only or torque-angle control mode. The achieved clamp load in each lugnut is monitored by using inserted force washers (load cells). The torque tension data is analyzed and discussed for both steel and aluminum wheels, in order to select the optimum tightening process that achieves the desired uniform clamp load in the wheel lugnuts assembly.