Development Self-Locking Bolts using Shape Memory Alloy

In many situations, the bolts of a mechanical design are seen as having a secondary importance, when in fact they have fundamental aspects of its operation, once they are used within the loading limits established by the manufacturer. If not, the bolts may have three major types of failure: fracture under high load, self-loosening and untightening. In order to solve or minimize these problems associated with bolts, new materials have been studied, such as Shape Memory Alloys (SMA). Such alloys belong to the class of active materials and have the surprising ability to recover an "apparently plastic" strain through a subsequent heating above a critical temperature. In this context, a possible alternative to minimize or even eliminate the mentioned drawbacks would be manufacturing these elements from SMA. In this regard, the main objective of this work was to manufacture bolts from SMA and carry out their thermomechanical characterization. These characterizations aimed to analyze the behavior of SMA bolts from the viewpoint of Shape Memory Effect (SME), Superelasticity (SE), and Transverse Cyclic Shear (TCS). To analyze the effects of many variables on the response variables, some of the tests were carried out according to a specific Design of Experiments (DOE).