Visit to Virginia Tech, Blacksburg, Virgingia, USA and Revolve, Calgary, Canada

The overall aim of this work is the investigation of the use of shape memory alloys in rotating machinery. It has emerged from work so far that it is possible to construct a bearing support whose stiffness can be modified by the application of an electric current. This is a highly desirable property as it implies that the vibrational response can be modified, and therefore controlled. With the appropriate loops, this lead to a so-called 'Smart Machine'.Working with colleagues at University of Glasgow, two distinct systems have so far been developed to address this problem. The approach followed at Swansea has been to support the actual bearing in a pair of elastomer O-rings, whose stiffness is a function of their compressive stress. The effective stiffness of the support is controlled by varying the loading on a pair of elastomer O-rings which support the rolling element bearings. The stiffness of the O-rings is strongly influenced by the (static) loading on the elastomer and the load is applied by two sets of SMA wires as shown. Ohmic heating is used to control the temperature of the SMA wires and this is monitored by means of thermocouples. The SMA wires, shown as a single wire in figure 3, actually comprise a multiloop of wire, so arranged in order to provide sufficient compressive pre-load for the elastomer O-ring. This is a simple geometry which is employed merely to prove the concept.Experimental results to date show very promising results, with natural frequencies being shifted by more than 50% as current is applied.To take this work forward it would be highly beneficial to discuss with members of the group at Virginia Tech, many of whom have extensive experience with SMA application.The subsidiary part of this visit, to a bearing manufacturer in Calgary is in the same general are of 'Smart Machines', albeit a somewhat different application.