1955 Volume 24 Issue 1 Pages 35-41
In this report, we give the mathematical analysis for the mechanism of Low Temperature Stress Relieving method and confirmed the virtues of this method, using comparatively small pipes.
For the former object, we adopted the test pieces shown in Fig. 1. After welding, the stress-strain relations of each member are expressed by eqs. (1) & (2), where H is the inherent strain. When both side members are heated to temperature T, the central member will be deformed plastically as eq. (3), where g is the plastic strain. After cooling, T becomes zero. Then we have the relations expressed by eq. (6). In the residual stress of the central member is equal to the yielding stress of the material and the material can be assumed to be perfect plastic body, we have the relation σc1≅σc2. Then we get g??αT. From this relation stresses of each member after cooling can be expressed by eq. (7). In Fig. 2, we showed experimental and theorititcal results.
Fig. 4. shows the heating and cooling apparatus for pipes. Test results are summarized in Figs. 7-11 for seam welded pipes and in Figs. 12-16 for butt welded pipes. From these curves we know Low Temperature Stress Relieving method can be sufficiently applied to welded pipes in place of annealing at the point of stress-relieving.
By measuring the residual stresses at the outside and inside of the pipe, we know the occurence of bending monents by these treatment.
