Practical issues of activating self-repairing bolted joints

Abstract

An investigation of self-sensing and self-repairing bolted joints is presented. The goal of the self-sensing and self-repairing joint is to reduce the likelihood of failure due to self-loosening and to reduce the cost of maintenance of critical bolted joints. The concept combines piezoelectric-based health-monitoring techniques with shape memory alloy (SMA) actuators to restore tension in a loose bolt. The objective of this study is to enhance the practicality of the self-healing bolted joint. One of the primary issues is the actuation of the SMA actuators. The relatively large mass of the shape memory washer and low resistance because of the washer’s short length make resistive heating particularly difficult. A series of models was developed to assess the viability of resistive heating and provide an estimate for the power requirements for effective actuation. Modeling and experimental testing have shown that an external heater can be used to actuate a shape memory alloy actuator with conventional power sources. By making the shape memory alloy washer substantially easier to actuate, this method provides a convenient alternative to resistive heating, and aids the practical implementation of the concept of self-sensing, self-repairing joints.

Design for adaptability (DFAD)—a new concept for achieving sustainable design

“…The first example is shown in Fig. 5 as a block diagram for an engine mount with a self-tightening bolt/washer combination [5,6]. The potential of a product to self-adjust for looseness will clearly extend the useful life of many mechanical products.…”

“…In some cases, this process will involve remanufacture, and in other cases the utilization of self-healing materials and approaches such as a self-tightening bolt developed by Antonious et al [5] and Peairs et al [6]. The premise is that adaptation is a feedback process with inputs, actuators, and control algorithms, among other components, and that a product can be designed to respond effectively to changing inputs to increase useful life.…”

“…For example, inputs to the DFAD model of a given product may be mechanical (looseness), and market-driven (styling), among others. Actuators may be smart materials such as self-tightening bolts [5,6] to adjust for looseness, or a specific remanufacturing capability to facilitate changing the fenders and grille of a ''healthy'' vehicle to respond to styling changes. Control algorithms associated with adaptability may be based on look-up tables, fuzzy logic, or standard linear control algorithms to allow the product to ''respond'' to changing inputs in a stable, effective, and efficient manner and allow for evaluation of the performance of the product to do so.…”

Adaptive Structures for Structural Health Monitoring

“…A device-level example is given here, while a materials approach is given in Chapter 9 of this volume. The basic idea is presented here in terms of a bolted joint having the ability to assess its current preload and, if too loose, to tighten itself up (Peairs et al, 2004b;Antonios et al, 2006). The idea is fairly simple: a bolted joint is monitored using, in this case, the impedance-based SHM system.…”

Bolt loosening analysis and diagnosis by non-contact laser excitation vibration tests

“…However, bolted joint failures, including self-loosening, shaking apart, slippage, stress cracking due to fatigue, and breaking due to corrosion [1], are frequent, and it has been suggested that most failures of bolted joint are caused by loosening [2]. For this reason, bolt loosening has become an important research area in mechanical engineering in efforts to prevent failures in a variety of mechanical applications.…”