| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 105 === The purpose of this study was to investigate the effect of vibratory waveform, structure and temperature factor on vibration residual stress elimination. After selecting SS400 low carbon steel as the substrate and welding, using the Vibratory Stress Relief (VSR) technology and chose the wavelet frequency. Finally used the Cr target-cosα measurement method before and after the vibration to analyzed residual stress, and the LabVIEW program presented on the waveform analysis.
The results revealed a positive relationship between the secondary wave frequency of the high frequency wave and the residual stress elimination rate. When the frequency of the secondary wave was high (1450.9Hz, 1468.6Hz), the residual stress can be effectively eliminated, also the high frequency wave increased 22.9% elimination rate than the lower frequency.
The maximum residual stress elimination rate in the fillet welds was the back center of the workpiece which was caused by the structural change, reaching 39.5%. Without structural changes, the elimination rate for the plate was 38.6%. There was a great elimination rate gap in the fillet welds on the back of the base material, but in contrast, the central part had a large elimination rate 32.6%, also found that the residual stress at left and right sides of the base material had not been eliminated, this phenomenon was due to the wave interference.
The residual stress elimination of the vibration system with temperatures is better than that of the unheated vibration system. The elimination effect is the best at 100 °C, which reached 43.6%, compared with the unheated plate workpiece, the elimination rate improved up to 38.8%. The eliminations between applying 100 °C and 200 °C, the former was better because of air cooling will re-accumulate stress. In addition, heating in different parts of the weld, the elimination rate will tend to homogenize with the growing temperature.
From the experimental results, it is seen that the frequency of the secondary wave decrease after vibration. With a large secondary wave frequency drop, the elimination rate of the residual stress is higher, there found a linear relationship between the dropping frequency and the elimination of residual stress. The elimination can be explained by the deformation of the defective atom caused by vibration.
Finally, it was found that the effect of eliminating can be determined by the applied waveform, and the effect of stress relief can be judged by the change in the waveform before and after the vibration.
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