Effect of Residual Stress on the Vibration of Welded Joints

Abstract

We have studied in this paper on the problem of effect of residual stress on the vibration of welded joints. For the sake of simplicity we have used the so-called "H-type constrained specimen" as shown in Fig. 1 which was made from structural plain cabon steel SS41 of 10mm thick.
At first we examined the relief of residual stress due to vibration. Specimen, which was fixed at oneend, was vibrated at constant amplitude and constant frequency, and the residual stress was measuredafter 10, 10², 10³, 10⁴ and 10⁵ numbers of vibration respectively. It was known'that the residual stress, initial value of which is about 14-18kg/mm² in center bar of the specimen, decreased with the increase of numbers of vibration, and after 10⁵ numbers of vibration it became about 50% of the initial value for the case of amplitude 10mm. The magnitude of relieaved stress increase with amplitude. The resultsof this experiment are shown in Figs.3, 4and 5.
Nextly we have made the test of free damped vibration of the specimen which was fixed at one end. The frequency and logarithmic decrement of each specimen are shown in Table 3. It is known from this that the frequency decreases with increase of residual stress and the logarithmic decrement is vice versa. At last we have made the test of forced vibration at various number of frequency, and the amplitude of welded specimen was known to be lower than the specimen without weld at the resonance point.