Suggestion of Pipe Coupling Method for Maximum and Uniform Joining Stress

A new method of pipe joining using shape memory alloys (SMAs) is proposed in this study to obtain the maximum and uniform joining stress. Fe-based SMAs, regarded as potential alloys for pipe couplings, is not so widely industrialized as anticipated. The major obstacle is error of pipe size, which causes a gap between deformed SMA joint and pipes to be joined prior to heating. Since the recoverable strain of Fe SMAs is comparable to the gap, most of the strain is wasted as free recovery. In this study, the problem is settled by deforming simultaneously SMA coupling and pipes to be joined with the coupling inserted in the pipes. By doing so, there is always no gap between coupling and pipes prior to heating. The new method makes it possible to apply alloys with a poor shape memory effect (SME) to pipe couplings. Some other expected advantages and disadvantages will be discussed.