Modeling a Bearing with Changeable Stiffness Based on Shape Memory Alloys for Vibration Control of Rotating Machinery

Shape memory alloys have great potential in applications involved in the control of vibration in many structures. In rotating machines, the critical operating speeds are functions of the system equivalent stiffness. This work focus in the thermoelastic temperature induced martensitic transformation in SMA, capable of altering between two crystallographically reversible stages, martensite and austenite. The phase change of shape memory alloy can result in very significant modifications in the material’s modulus of elasticity. Hence, it seek to develop a concept of adaptive bearing with SMA elements embedded in bars format, with the intention of affecting the equivalent stiffness of the bearing and thus change the intrinsic critical speed of the rotating machine, resulting in a configuration with various elements of a conventional bearing (rolling element or fluid film bearing, pedestal) arranged in series with the bars. Phase transformation is induced by Joule heating, requiring thermal and electrical isolation of the bars made of SMA. Uses different amounts, sizes and geometries of bearing elements and models mathematically a rotating system with flexible shaft, centralized rigid disc, and bearings with changeable stiffness, in order to investigate the dynamic response of the system, as well as changes in the amplitude and natural frequency.