A Mathematical Model for Temperature Induced Loosening due to Radial Expansion of Rectangle Thread Bolted Joints

Abstract

This paper proposed a mathematical model to investigate the radial expansion induced loosening of rectangle thread bolted joints that were subjected to cyclic temperature variation, which could cause slippage between contact pairs of engaged threads and bolt bearing. Firstly, integral equations were derived for the shear stress components caused by expansion difference, as well as the bearing and thread friction torque components, which depended on the temperature variation. Secondly, the relationship of displacement components was developed based on quasi-static hypotheses. Then, treating the rotation of bolt as plastic elongation, the bolt tension's evolution was obtained by using a one-dimensional bolted joint model. Numerical results showed that the temperature variation decreased the bearing and thread friction torque components, which could lead bolted joint to loosen. Finally, the effects of some associated factors on the progress were discussed.

Experimental investigation on self-loosening of a bolted joint under cyclical temperature changes

“…Since, in the following cycles, radial shear forces of the threated part may reach their limits later than that of the beginning cycle. 10 Second reason is that occurring of local plastic deformations and elastic deformations in the bolted joint can cause slackening of the joint and main part of this loosening corresponds to the beginning cycle. The preload can decrease more due to relaxation and embedding in the first cycle.…”

“…As aforementioned, a mathematical model of loosening under cyclical temperature changes of a rectanglethreaded bolt was studied in reference. 10 Based on the reference, the rectangle-threaded bolt and nut specimens were, therefore, modeled according to ISO965 standard and manufactured by use of rolled method for the test, as shown in Figure 4. The bolt, nut, and plates were made of stainless steel (SS400), and nine pairs of specimens were used for the experiment to analyze selfloosening phenomena.…”

“…The preloads of the joint for the test are chosen in terms of the amplitude of the temperature changes based on the reference. 10 The preloads are applied by use of torque wrench (Manufacturer: Tohnichi, model: 450QL3, according to the specification of the torque wrench, the accuracy is 6 3%) and 10.8, 21.5, and 32.5 Nm torques are given to set up the preloads, respectively. The average values of the test results are used to evaluate the loosening phenomenon of the bolted joint in results section.…”

“…Coman and Constantinescu 9 have done a research about the temperature effects on joint strength. Hou et al 10 have made a mathematical model of radial expansion for the self-loosening of a rectangle-thread bolted joint under repeated temperature variations with some assumptions such as:…”

Invisible mechanical lap joints for metal–polymer laminates

“…Mechanical fastening (Figure 1(a)) requires drilling holes through the laminates matching the diameter of the screws (or rivets) that will be utilized to clamp the two sheets together. The resulting joints are easy to dismantle at the end of service life, although this feature may be responsible for unintentional self-loosening caused by mechanical 6 and/or thermal 7 loading. Another limitation in the use of fasteners is the protrusions above and below the laminate surfaces, which are not acceptable in many applications.…”