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Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.

Hsieh CC, Wang PS, Wang JS, Wu W - ScientificWorldJournal (2014)

Bottom Line: The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process.A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency.The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan.

ABSTRACT
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ -ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

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The waveform of the TX-VSR (a) resonant: 375 Hz and (b) subresonant: 362 Hz.
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fig7: The waveform of the TX-VSR (a) resonant: 375 Hz and (b) subresonant: 362 Hz.

Mentions: Figure 4 shows the spectrum map created using an eccentric circulating vibrator. It indicates maximum amplitude of vibration at a resonant frequency of 60.9 Hz. According to Meta-Lax technology [10], the subresonant point is within a former 10 Hz of the maximum amplitude of vibration and resonant frequency of 1/3. In this study, the former 10 Hz of resonance decayed rapidly on the spectrum map so the amplitude of vibration of 1/3 (59.3 Hz) was selected as a subresonant point. Figure 5 shows the spectrum map created using a magnetic telescopic vibrator with the resonant point occurring at a frequency of 375 Hz. Here, the resonant frequency of 1/3 was selected as 362 Hz. In comparing the two spectrum maps, the resonant and the subresonant frequencies for a magnetic telescopic vibrator were about 6 times greater than those created using an eccentric circulating vibrator. Figure 6 shows the waveform of the resonant and subresonant frequencies of an eccentric circulating vibrator. In this instance, the vibrator was set on the working table and the table and samples were vibrated by an eccentric circulating vibrator. As a result, the measured waveform was affected by the loss of energy transfer and the energy absorption of the samples, meaning that the waveform was not the sine wave. Figure 7 indicates the waveform of the resonant and subresonant frequencies of a magnetic telescopic vibrator. In this experiment, this waveform is indicated as a continuous knock wave. The peck voltage of the opposite amplitude of vibration (Vpp = ±0.42 mV) is the same on the waveform of the resonant frequencies for the two vibration systems. However, the peck voltage of the opposite amplitude of vibration at a subresonant frequency is about equal to the opposite amplitude of vibration of the resonant frequency of 1/3 (±0.14 mV~0.16 mV). On the other hand, a vibration waveform of high frequency occurs near the primary wave of an eccentric circulating vibrator in comparison to four vibration waveforms. It means that the samples sustained a microvibration in addition to the original vibration. The resonant waveform of the magnetic telescopic vibrator displayed the same result. Liao [11] pointed out that the microvibration of a high frequency wave can cause a great amount of microdeformation and has a greater effect on residual stress relief. However, the high frequency wave of the subresonant frequency is not obvious in a magnetic telescopic vibrator. All output energies were transferred into vibration energies and that the plastic deformation of samples was unapparent. The effect of the residual stress relief was therefore limited.


Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.

Hsieh CC, Wang PS, Wang JS, Wu W - ScientificWorldJournal (2014)

The waveform of the TX-VSR (a) resonant: 375 Hz and (b) subresonant: 362 Hz.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3926365&req=5

fig7: The waveform of the TX-VSR (a) resonant: 375 Hz and (b) subresonant: 362 Hz.
Mentions: Figure 4 shows the spectrum map created using an eccentric circulating vibrator. It indicates maximum amplitude of vibration at a resonant frequency of 60.9 Hz. According to Meta-Lax technology [10], the subresonant point is within a former 10 Hz of the maximum amplitude of vibration and resonant frequency of 1/3. In this study, the former 10 Hz of resonance decayed rapidly on the spectrum map so the amplitude of vibration of 1/3 (59.3 Hz) was selected as a subresonant point. Figure 5 shows the spectrum map created using a magnetic telescopic vibrator with the resonant point occurring at a frequency of 375 Hz. Here, the resonant frequency of 1/3 was selected as 362 Hz. In comparing the two spectrum maps, the resonant and the subresonant frequencies for a magnetic telescopic vibrator were about 6 times greater than those created using an eccentric circulating vibrator. Figure 6 shows the waveform of the resonant and subresonant frequencies of an eccentric circulating vibrator. In this instance, the vibrator was set on the working table and the table and samples were vibrated by an eccentric circulating vibrator. As a result, the measured waveform was affected by the loss of energy transfer and the energy absorption of the samples, meaning that the waveform was not the sine wave. Figure 7 indicates the waveform of the resonant and subresonant frequencies of a magnetic telescopic vibrator. In this experiment, this waveform is indicated as a continuous knock wave. The peck voltage of the opposite amplitude of vibration (Vpp = ±0.42 mV) is the same on the waveform of the resonant frequencies for the two vibration systems. However, the peck voltage of the opposite amplitude of vibration at a subresonant frequency is about equal to the opposite amplitude of vibration of the resonant frequency of 1/3 (±0.14 mV~0.16 mV). On the other hand, a vibration waveform of high frequency occurs near the primary wave of an eccentric circulating vibrator in comparison to four vibration waveforms. It means that the samples sustained a microvibration in addition to the original vibration. The resonant waveform of the magnetic telescopic vibrator displayed the same result. Liao [11] pointed out that the microvibration of a high frequency wave can cause a great amount of microdeformation and has a greater effect on residual stress relief. However, the high frequency wave of the subresonant frequency is not obvious in a magnetic telescopic vibrator. All output energies were transferred into vibration energies and that the plastic deformation of samples was unapparent. The effect of the residual stress relief was therefore limited.

Bottom Line: The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process.A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency.The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 402, Taiwan.

ABSTRACT
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ -ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

Show MeSH