A strength prediction of joints by Fe-Mn-Si-Cr shape memory alloy through strain monitoring during pre-processes including diameter expansion and tightening by heating

Abstract

To guarantee the functionality of the pipe joint in different service environments, the evaluation of its strength is critical. Typically, the assessment is performed after completing the pipe joint assembly. However, it is pretty inconceivable to examine each pipe joint’s strength in the environment for actual installations. Therefore, a strength prediction of pipe joints is required as similar to the bolted-flange systems. Due to the unique manufacturing process of the pipe joint made of shape memory alloys (SMAs), the strength prediction before the installation becomes possible by means of its pre-processing. This work chooses the pipe joint made of the iron-based shape memory alloy (Fe-SMA), which is very promising in the joint families in SMAs because of its low weight. In the diameter expanding process of the Fe-SMA hollow cylinder with different methods, both the circumferential and axial strains are measured. After heating, the cylinder tightens round bar or pipes made of SUS304 due to the shape memory effect. A measurement of the circumferential strain during thermal tightening is also made for each diameter expansion method. After that, it is attempted to identify the axial push-out strength and bending strength of the joints by measuring strain during the diameter expansion and thermal tightening processes. The results demonstrate that both the axial push-out strength and bending strength of pipe joints can be predicted in prior to the installation through the measured strain during the diameter expansion and heating processes.